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Thursday, December 30, 2010

Eating Nuts Provides Several Health Benefits

An article in the January 2011 Harvard Health Letter listed several health benefits of eating nuts. Although the calories in nuts come mainly from fat, the type of fat is largely of the unsaturated healthful variety. The article cited a study done at the Beth Israel Deaconess Medical Center showing that walnuts eaten at breakfast made subjects feel more full before lunch, potentially reducing caloric consumption. Other health benefits include favorable effects on blood cholesterol, blood pressure, and inflammatory factors. Studies on large populations have linked high nut consumption with lower heart disease rates. Nuts also contain little or no carbohydrate so they do not cause spikes in blood sugar and may even blunt blood sugar spikes caused by carbohydrates eaten along with the nuts. Peanuts, almonds, and pistacios have the highest protein content, while brazil nuts, cashews, hazelnuts, and walnuts have intermediate protein content, and pecans and macadamias have the lowest protein content. Walnuts have the additional benefit of being high in omega-3 fatty acids, which are widely considered the most healthful kind.

Wednesday, December 22, 2010

Is Resisted Sprint Training Effective?

Coaches in sports requiring  high acceleration and all-out sprint speed have increasingly endorsed sprint training resisted by a variety of means including weighted vests, towed weighted sleds, long elastic cords, or straps for towing another individual. Yet there have been few studies examining the effectiveness of such training. A recent study by Clark et al. in the Journal of Strength and Conditioning Research evaluated the effectiveness of two types of resisted sprint training.

Experimental Procedure
There were 3 groups of  collegiate lacrosse players that trained twice a week for 7 weeks as follows:
  • Weighted Sled: 7 of the subjects trained while towing 10% of their bodyweight in a sled
  • Weighted Vest: 6 of the subjects wore vests containing 18.5% of their bodyweight
  • Unresisted: 7 of the subjects did not use any resistance device during their training
For all groups, each training session consisted of 7-10 sprint intervals of 20-60 yards (18.3-54.9 m) separated by rest intervals of 3-4 minutes. Both before and after training, all subjects were tested as to their sprint-speed over 40 yards (36.6 m) after a 20-yard (18.3 m) running start.

For the subjects as a whole, there was significant reduction (-1.1%) in the time taken to sprint 40-yards. However, there was no significant difference in improvement between any of the training groups. However, the percentage of improvement of the unresisted training group (-2.0%) was greater than for the weighted sled group (-0.1%) or the weighted vest group (-1.2%).

Bottom Line
The fact that the number of subjects in each group was relatively low made it difficult to obtain statistically significant differences in improvement between groups. However, it does appear that the resisted training was no more effective than unresisted training for improving 40-yard sprint speed following a running start. Because the timed portion of the sprints followed a running start in this study, the results do not address the effectiveness of resisted sprint training for improving the initial acceleration phase of a sprint.

Insurance Institute for Highway Safety Top Safety Picks for 2010

BMW 5 series
(except 4-wheel drive and V8)
Infiniti M37/M56
(except M56x 4-wheel drive)

Honda Civic
4-door models (except Si)
with optional ESC
Kia Forte sedan
Mitsubishi Lancer sedan
(except 4-wheel drive)
Subaru Impreza
(except WRX):
sedan | wagon
Volkswagen Golf
4-door models
Volkswagen GTI
4-door models
Ford Fiesta
built after July 2010:
sedan | hatchback

Audi A4 sedan
Chrysler 200
4-door models


Kia Sorento
built after March 2010

Jeep Patriot
with optional side torso airbags

Tuesday, December 21, 2010

Are There Hidden Causes of the Overweight Epidemic?

In the December 20, 2010 issue of Newsweek magazine, Sharon Begley, the magazine’s science columnist, wrote that there are some little-known factors that may contribute to the continued increase in the prevalence of overweight and obesity. Her main argument is that it must be more than a matter of exercising more and eating better because, among animals that have contact with human beings, such as pets, lab animals and rodent pests, 23 of the 24 species studied since 1940 have shown significant increases in the percentages of overweight and obese animals, a statistic that could have occurred by chance only once in 8 million. Yet changes in diet and exercise don’t appear to be the reason, as these factors haven’t changed much for these animals over the years.

Begley cites some possible reasons other than diet and exercise for the weight gain of animals and, by extension, us:
  • The type of bacteria in our gut - more efficient bacteria wring more calories out of our food than do less efficient bacteria. In this case, efficiency is not our friend.
  • Lack of sleep, which increases the appetite-stimulating hormone ghrelin, and decreases the hormone leptin that suppresses our appetite when we’ve eaten enough.
  • Environmental chemicals such as BPA that stimulate fat-cell production.
  • Home heating, which lessens the need for the body’s calorie-consuming heat production.
  • Home air conditioning, which lessens the appetite-suppressing effect of environmental heat.
  • Infection with adenovirus-36, which causes obesity in  lab animals and is correlated with obesity in humans.
In addition, I feel that there may be another contributor to obesity:
  • The lack of internal parasites due to modern sanitary practices. If parasites eat some of our food, less of it can be packed on as fat. If they partake of our bodies, then energy must be consumed for repair. This assumes the kind of parasites that are relatively harmless other than consuming some of our food or body tissue.
Bottom Line
There is no doubt that our health benefits from exercising regularly and eating a healthy diet without excess calories. However, we must continue to look for other contributing factors in order to effectively deal with and counteract the continued rise in overweight and obesity that threatens to undermine the gains we’ve made in improving our health and increasing our lifespan.

Friday, December 10, 2010

For Pure Flexibility, Static Stretching Beats Dynamic Stretching

This blog contains several articles that have shown that static stretching impairs physical performance in jumping, running, and team sports, when the stretching is done immediately prior to the effort. Dynamic stretching has not been shown to cause a similar impairment and may even enhance performance. Yet, this finding does not mean that dynamic stretching is superior to static stretching for all purposes. Indeed, a study published by Covert et al. in the Journal of strength and Conditioning Research (vol. 24, no. 11, pp. 3008-3014, 2010) indicates that static stretching is better for improving pure flexibility.

Study Procedures
Over a 4-week period, 16 men and 16 women, aged 20-27 were randomly divided into the following 3 groups:
Static Stretching: Held a stretched position of the hamstring muscles for 30 seconds 3 times a week
Dynamic Stretching: Got into a stretched position of the hamstring muscles then performed small bounces into and out of that position at a rate of 1 per second for 30 seconds, 3 times a week
Control: Did not stretch
Hamstring flexibility was measured as the number of degrees short of 180 degrees that the knee could be extended to while the subject lay on a table with the thigh in a vertical position. Thus, a smaller number of degrees indicated better flexibility.

The differences between changes in hamstring flexibility among all three groups were statistically significant
The control group declined by a mean of 3.3 degrees in hamstring flexibility
The static stretching group improved a mean of 11.9 degrees in hamstring flexibility
The dynamic stretching group improved a mean of 3.8 degrees in hamstring flexibility

Bottom Line
Either form of stretching improves flexibility. However, static stretching improves flexibility significantly more than does dynamic stretching. For sports in which flexibility in not very important, dynamic stretching is best. However, for sports which require a lot of flexibility (e.g. gymnastics, wrestling, high-hurdles) some static stretching is advisable. But because static stretching impairs performance when done immediately prior to the sport activity, it is best to do such stretching immediately following a training session, when the muscles are well warmed up. The impairment in performance caused by static stretching has not been found to carry over to the following day, so post-exercise static stretching should not impair a subsequent day's performance.

How Safe are Whole-Body Airport Scans?

In it’s December 13, 2010 issue, Newsweek published a chart comparing the radiation a person receives from the new full-body x-ray scanners in airports to other sources of radiation. The radiation levels are listed below:

Airport whole-body scan                            0.01 MREM
x-ray of extremity                                     0.10 MREM
Dental x-ray                                             0.50 MREM
Cosmic radiation, sea level                      24.00 MREM/year
Terrestrial radioactivity                             28.00 MREM/year
Mammogram                                          40.00 MREM
Cosmic radiation, Denver                         50.00 MREM/year
Radon in average home                         200.00 MREM/year
CT scan of abdomen and pelvis           1,500.00 MREM
Level causing radiation sickness      100,000.00 MREM

If the results are to be believed, and Newsweek usually carefully checks its sources, then the airport whole-body scans appear to be low-risk. That is not to say that they are without risk, because any radiation may bring some risk with it. Also, the comparison to environmental radiation exposure per year can be misleading because, when you go through a scanner, you receive the full dose of radiation in a few seconds, and the rate of exposure could be a factor in causing undesirable changes to body cells. For example, the sea-level cosmic radiation exposure per year translates to only 0.0000007 MREM per second. Nevertheless, the exposure from an airport scanner appears far less than that from a dental x-ray, which most of us accept as part of our health maintenance. An additional factor is that the genitals, which are particularly vulnerable to radiation, are usually shielded when health-related x-rays are taken. Since the “underwear bomber” prompted the scans in the first place, the genitals can not be shielded in such scans. At this point, the scans appear safe, but each individual must decide whether or not a body pat-down is preferable to a scan.

Wednesday, December 8, 2010

Men's Health Fit?

There was an article in Men’s Health Magazine’s November 2010 issue entitled, “Are You Men’s Health Fit?”. The article highlighted four elite athletes from different sports and presented seven physical fitness tests, stating that, if you can achieve the highest level on each test, you are “Men’s Health Fit“. Below are the tests along with the Men’s Health standards and my comments.

1. Test - Timed Plank:
The body, face down, is held in a straight line with the toes and forearms on the ground.
  • Below average: Plank with elbows directly below shoulder’s held for less than one minute
  • Average: Plank with elbows directly below shoulder’s held for one minute
  • Above average: Plank as above but with feet on a bench (of unstated height) held for one minute.
  • Men’s Health Fit: Plank with feet on floor and elbows below eyes held for one minute.
2. Squat while holding a wooden stick overhead with hands spaced 1.5 times shoulder width:
  • Below average: You can’t bend your knees to 90 degrees without leaning forward
  • Average: You can only bend your knees past 90 degrees if your heels come off the floor
  • Above average: You can do a full squat while keeping your heels on the floor and not leaning forward
  • Men’s Health Fit: You can do the above while holding a 45-lb bar instead of the stick.
My Comments:
This is a test of flexibility of the calf muscles, shoulder, and back rather than a physical fitness test. It’s hard to see how the ability to do this would relate to sports performance or any physical challenge other than Olympic weightlifting, which requires this specific kind of flexibility.

3. Barbell dead lift:
  • Below average: less than bodyweight
  • Average: 1-1.25 times bodyweight
  • Above average: 1.25-1.5 times bodyweight
  • Men’s Health fit: more than 1.5 times bodyweight
My Comments:
To define levels in terms of proportion of bodyweight lifted is naïve because, for physiological and biomechanical reasons, smaller people can lift more in proportion to their bodyweight. The following standards from show how body size affects standards:

                                     Deadlift as Proportion of Bodyweight
Bodyweight (lb)    untrained     novice    intermediate   advanced   elite
        148                 .85             1.58           1.82           2.57       3.26
        181                 .82             1.51           1.74           2.42       3.03
        220                 .75             1.39           1.60           2.18       2.66

Based on the table, the standards given by Men’s Health are low for anyone who trains with the deadlift exercise.

4. Standing broad jump:
  • Below average: less than 6 feet
  • Average: 6-7 feet
  • Above average: 7-8 feet
  • Men’s Health fit: more than 8 feet
My Comments:
There are few published adult norms for the standing long jump. However, a study by Santilla et al. in Medicine and Science in Sports and Exercise (vol. 38, no. 11, pp. 1990-1994, 2006) presents the following as military standards in Finland.
  • Poor: less than 6’7” (2.0 meters)
  • Satisfactory: 6’7” (2.0 meters)
  • Good: 7’3” (2.2. Meters)
  • Excellent: 7’ 11” (2.4 meters)
The “Men’s Health Fit” standard seems a reasonable approximation of “excellent“. However, the “below average” standard should be higher and the lower limit of the “average” range should be higher. One problem is that jumping ability is largely related to the percentage of fast-twitch fibers in one’s leg and hip muscles, which is determined mainly by heredity. Thus, only a limited degree of improvement can be expected from training.

5. Pushups:
  • Below average: less than 15
  • Average: 16-29
  • Above average: 30-44
  • Men’s Health fit: 45 or more
My Comments:
The magazine’s pushup standards are quite low. The following standards for males aged 20-29 were published by the American College of Sports Medicine (see our website for the full table):
  • 25th percentile: 24
  • 50th percentile: 33
  • 75th percentile: 44
  • 90th percentile: 57
The Army standards (age 22-26) are even tougher because soldiers know they will be tested every 6 months and many of them train for the test:
  • 60 points (just passing): 40
  • 75 points: (average): 53
  • 90 points (excellent): 66
6. Chinups (undergrip) pausing 1 sec at top:
  • Below average: less than 3
  • Average: 3-7
  • Above average: 8-10
  • Men’s Health fit: more than 10
The Marine Corps scores the pullup segment of its physical fitness test for men aged 17-26 as follows:
  • 3rd class (passing): 9
  • 2nd class (good): 12
  • 1st class (excellent): 15
The Men’s Health standards are low in comparison to the Marine Corps standards. Of course, Marines are tested regularly for the number of pullups they can do, so they train at the exercise.

7. Mile Run:
  • Below average: 12 or more minutes
  • Average: 9-12 minutes
  • Above average: 6-9 minutes
  • Men’s Health fit: under 6 minutes
My Comments:
Adult norms for the 1-mile run are not readily available. However, the following 1.5 mile run standards for males aged 20-29 were published by the American College of Sports Medicine (see our website for full table):
  • 25th percentile: 13:53 (9:15 mile pace)
  • 50th percentile: 12:18 (8:12 mile pace)
  • 75th percentile: 10:42 (7:08 mile pace)
  • 90th percentile: 9:09 (6:06 mile pace)
The Army standards (age 22-26) are even tougher at the low end because soldiers know they will be tested every 6 months and most of them train for the test:
  • 60 points (just passing): 16:36 (8:18 mile pace)
  • 75 points: (average): 15:15 (7:38 mile pace)
  • 90 points (excellent): 13:54 (6:57 mile pace)
Since these standards are for the 1.5 and 2.0 mile run, the same populations would run the mile run at an even faster pace. While the pace needed to be “Men’s Health Fit” would be considered excellent by either standard, the magazine’s standards for average and above average are far too slow.

It’s difficult to ascertain how Men’s Health Magazine decided which tests were important and where it got its standards, many of which seem arbitrary. They’re low for the deadlift, pushups, and chinups, and low for the lower fitness levels in the standing broad jump and mile run. Since there are no references for the standards in the article, one might think that they were developed by group consensus among the magazine’s staff members.

One factor that the article ignores is that there are different types of athletes who, because of their body types and natural talents, excel at different sports. Elite athletes are very specialized creatures. Strength and power athletes do not generally do very well on tests of whole-body endurance while endurance athletes often do poorly on strength and power tests. Thus, it is likely that the four athletes highlighted in the article would excel at some tests and do poorly on others. It is misleading to imply that one has to do well on all types of fitness tests to be a good athlete.

By calling the highest level on each test the “Men’s Health Fit” standard, the magazine seems to be sending the message that it has very tough standards, even leading one to surmise that the magazine’s staff members are all super-fit. It would be very interesting to see how its staff would do on the tests. It would be surprising if any of them could score “Men’s Health Fit” on all the tests.

Wednesday, November 24, 2010

More Evidence in Favor of Post-Activation Potentiation (PAP)

We have previous discussed post-activation potentiation (PAP) by which an explosive athletic performance is improved by doing heavy resistance exercise beforehand (see  A recent study provides further evidence of the effectiveness of this technique.

Matthews, Comfort and Crebin performed a study on ice hockey players from the English National League.

Experimental Procedure
On two different days, 11 players were timed for their maximal 25-meter sprint-speed on ice both before and 4 minutes after doing the following:
  1. resting
  2. sprinting while towing another skater
  • When the players rested between sprints, they showed no significant improvement in time between their first and second sprints.
  • When the players skated against resistance following the first sprint, their second sprint took a significant 2.6% less time than their first one.
Bottom Line
This study supports others that have found improvement in explosive athletic performance when heavy resistance exercise is performed first. The resistance exercise should call upon the same muscles used in the athletic performance. Using resisted skating in this study was a good way to achieve this goal.

Thursday, November 18, 2010

Estimating the Caloric Cost of Running or Walking

A recently published article by Loftin et al. in the Journal of Strength and Conditioning Research (vol. 24, no. 10, pp. 2794-2798, 2010) measured the caloric consumption per mile of 19 normal-weight walkers, 11 overweight walkers, and 20 marathon runners. The subjects were about evenly divided among males and females.

  • Caloric consumption was more related to lean body mass than to total body mass
  • Men burned more calories per mile than women
  • Men and women did not differ in calories consumed per mile per unit body mass
  • In terms of calories per mile per unit body mass, marathon runners burned significantly more than normal-weight walkers who burned significantly more than overweight walkers
The following equation was developed from the experimental data to predict an individual’s caloric consumption per mile:

Men weighed in kilograms:
Calories per mile = (0.789 x kg body mass) + 43.5

Men weighed in pounds:
Calories per mile = (0.3586 x lb body mass) + 43.5

Women weighed in kilograms:
Calories per mile = (0.789 x kg body mass) + 35.8

Women weighed in pounds:
Calories per mile = (0.3586 x lb body mass) + 35.8

Bottom Line
The equation can be useful for those interested in estimating the caloric cost of their walking or running workout.

The Drawback of Exercising on Unstable Surfaces

Stability training, mainly in the form of lifting weights while standing on unstable surfaces, became somewhat popular with the advent of the Bosu Ball, which is a hemispheric ball about 2+ feet across mounted on a flat plastic base. The idea is that the instability of the surface brings muscles into play that are required for maintaining stability; muscles that would be minimally involved when exercising on a stable surface.

A study by Chulvi-Dedrano et al. in the Journal of Strength and Conditioning Research (vol. 24, no. 10, pp. 2723-2730, 2010) tested force production and muscle electrical activity during deadlifts on a stable surface and on two different unstable surfaces.

31 young adult subjects did the following:
  1. Isometric deadlift in which the lifter pulled upward maximally for 5 seconds against an immovable bar
  2. Dynamic deadlift in which a barbell weighing 70% of the individual’s maximal isometric deadlift was lifted for 5 repetitions 
Lifting force was measured during the isometric efforts. Muscle electrical activity of the lower back muscles (paraspinals) was measured during both the isometric and dynamic lifts to indicate how hard the muscles were working. Both of the lifts were done on the following 3 surfaces:
  1. Stable floor
  2. Bosu Ball
  3. T-Bow (a curved board that can rock laterally as one stands on it)
  • In the isometric deadlift, both the force produced and the muscle electrical activity were significantly higher on the stable surface than on either unstable surface.
  • In the dynamic deadlift, muscle electrical activity was significantly higher on the stable surface than on either unstable surface
Bottom Line
This study backs up other ones that have shown that exercising on unstable surfaces does not provide as much stimulus as stable-surface training to the main muscles (prime movers) used to effect the exercise movement. It has previously been shown that more weight can be handled when lifting on stable than unstable surfaces, providing greater stimulus to the muscles. In view of these factors, training on unstable surfaces is not best for increasing the size or strength of the major muscles. However, since such training does bring stability muscles into play, it can be effectively used as a supplement to training on stable surfaces, especially for athletes who engage in sports in which maintaining stability is of major importance (e.g. hockey, figure skating, snow-boarding, gymnastics). The major part of the resistance workout should still be on stable surfaces.

Tuesday, November 2, 2010

Minimalist or “Barefoot” Running Shoes

For decades, running shoes were rated by Runner’s World magazine and other organizations largely on their ability to absorb shock. As a result, manufactures made heels and soles increasingly thick to rank highly in the ratings. This led to shoes that were quite bulky and thickly padded. In a countermovement to this trend, and inspired by a track coach who included barefoot running is his training programs, Nike came out with the first of the modern minimalist shoes, the Free, in 2004. This lightly-padded shoe was only intended for occasional use, not full weekly mileage.

Proponents of minimalist running shoes say that, because of their light cushioning, people running in them alter their gait to lessen shock. Such changes include landing on the midfoot or forefoot rather than the heel, shortening the stride, increasing stride frequency, and lowering peak impact force. This is claimed to reduce this risk of tibial stress fracture, plantar fasciitis, and other overuse injuries, and to strengthen the feet. Biomechanical testing has verified that Africans who grow up running barefoot strike the ground with only a third of the impact experienced by U.S. runners in shoes. Lightweight shoes also lower the energy cost of running, so a runner can go at a faster pace at the same level of exertion, which translates into faster race times.  However, running experts have cautioned that any switch from heavily cushioned standard running shoes to minimalist shoes must be gradual in order to allow the muscles, bones, and tendons of the foot and leg to adapt.

The minimalist running shoe movement accelerated significantly with the publication of the 2009 book, “Born to Run,” which revealed that the Tarahumara Indians of northern Mexico get fewer injuries than U.S. runners even though they wear very thin rubber sandals and run extremely long distances. Manufacturers other than Nike came up with their own versions of minimalist shoes. Vibram, an Italian company, introduced its Five Fingers model, in which each toe is individually gloved. It weighs a scant 5.7 oz and has a heel thickness of only 7.2 mm (compared with up to 38 mm on heavily padded “cushion” or “motion control” shoes). This model is now the leader of the minimalist shoe market.

Other running shoe companies have jumped on the minimalist bandwagon. Saucony came out with its Kinvara model, which has somewhat more protection than the free and is intended for regular, rather than occasional, use. New Balance will debut its Minimus in February, which the company says will give a free-foot feel but still have cushioning in key spots. Merrel will put out its Barefoot Collection in February with a sole from Vibram and a very light upper. Also in February, Nike will supplement it Free line with its Lunar Eclipse lightweight stability trainer. Addidas will introduce a light, fast, everyday shoe in the Fall of 2011. Other companies that do not plan to introduce minimalist shoes have been making their existing models lighter and more flexible. Yet there is concern within some shoe companies that runners may switch to minimalist shoes too rapidly and subject themselves to injury.

An important factor in how long it takes to adapt to a minimalist shoe is the difference in thickness between the forefoot and heel padding. It can range from zero for a shoe with no difference between the thickness of heel and forefoot padding, to a 12 mm greater thickness of heel than forefoot padding. If one has been accustomed to running in a heavily padded shoe with a large difference between the padding thickness of heel and forefoot, the adaptation time to a minimalist shoe should be considerable.

As of now, there have been no published articles comparing the injury rate of runners wearing minimalist shoes vs. those training in standard shoes. However, many of the runners who have switched to minimalist shoes swear by them. Yet few market watchers expect such shoes to ever capture a major share of the running shoe market. Currently, no more than 10% of running shoes sold could be called minimalist.

Bottom Line
While few studies have been done on minimalist shoes, evidence suggests that such shoes do alter running gait so as to reduce the degree of foot-strike impact and also allow the foot to flex in a natural manner while in contact with the ground. However, since most Americans have grown up walking, running, and playing sports  in supportive shoes with heels more thickly padded than forefeet, the adaptation to relatively flat and lightly padded shoes can be difficult and potentially injurious. Additionally, such shoes offer little protection against foot injury that can occur when stepping on a rock, tack, or other object. Those who are willing to accept the risk of trying such shoes should do so with caution and increase the weekly mileage they run in them very gradually. It remains to be seen whether the benefits of minimalist shoes outweigh their risks.

Friday, October 29, 2010

Dynamic Stretching Beats Static Stretching for Team Sports

Static stretching involves attaining a stretch to the point of mild discomfort and holding the position for at least 10 seconds. Dynamic stretching involves rapid repeated alternation between a stretched and a relaxed position.

A recent article by Amiri-Khorasani et al. in the Journal of Strength and Conditioning Research (vol. 24, no. 10, pp. 2698-2704, 2010) showed that static stretching detracts from performance on a physical agility test, while dynamic stretching tends to improve it.

Nineteen professional soccer players were divided into more-experienced and less-experienced subgroups. Their performance on an agility test, which involved 14-15 seconds of changing direction and zigzagging as fast as possible around a number of cones, was tested after each of the following:
  • No stretching
  • Static stretching
  • Dynamic stretching
  • Combined static and dynamic stretching
  • The subjects were 4-5% slower after static and combined static/dynamic stretching than they were with either no stretching or dynamic stretching alone.
  • Among the less-experienced players, dynamic stretching resulted in about 3% faster course times than no stretching.
  • Among the more experienced players, there was no difference between the course times after dynamic stretching and no stretching.
Bottom Line
The evidence indicates that dynamic stretching is superior to static stretching for the kind of agility needed for most team sports. This is probably due to a reduction after static stretching in the spring-like stiffness of muscle. The results support those of other studies that have shown a detrimental effect of static stretching on strength, jumping ability and sprint speed. It is not clear why the experienced players in this study showed no advantage of dynamic stretching over no stretching at all. However, since these were professional soccer players, it seems safe to conclude that the effects on amateur athletes would parallel those on the less experienced professional players. Thus, their performance would likely be enhanced by dynamic stretching.

Tuesday, October 26, 2010

Plyometric Training for Improved Sports Performance

Plyometric training has been popular among strength and physical conditioning coaches for a number of years. Yet many people who exercise on their own are not familiar with this method. Simply put, plyometric exercise involved rapid stretch and shortening of a muscle. This occurs in such movements as hopping, jumping, and bouncing. For example, when you jump vertically, you naturally first do a countermovement in which you bend your knees quickly while stretching your quadriceps (front thigh) muscles, then rapidly contract those muscles to straighten the knees and propel the body upwards. Thus, repeated vertical jumps are one kind of plyometric exercise.

There are various gradations of plyometric exercise, and it is considered prudent to start with low-stress ones before progressing to more difficult ones. One of the most stressful plyometric exercises is depth-jumping, in which one jumps down from a box and, after contacting the ground, immediately jumps vertically. This is considered dangerous for anyone who does not already have a strong lower body and has not progressed from low-stress, through moderate-stress, to high-stress plyometric exercise. Various sources have recommended being able to squat with 1.5 times one’s bodyweight before taking on a serious plyometric exercise program. However, it is generally considered safe for people in good health without orthopedic problems to perform low-stress plyometric exercises like low bounces, hops, and jumps.

A recent study by Chelly et al. in the Journal of Strength and Conditioning Research (Vol 24, no. 10, pp. 2670-2676, 2010), showed how effective plyometric training can be.

A group of experienced young male soccer players, average age 19 years, trained as follows:
  • August - preseason training consisting of light resistance exercise and calisthenics
  • September through March (the competitive season) - The players trained 5 days per week for 90 minutes by doing skill and tactical drills along with 30 minutes of continuous play. On one day per week they engaged in a competitive soccer game against another team.
The subjects were divided into 2 groups:

Group 1 only did the training program above.
Group 2 did the training program above plus from January-March they also did the following plyometric training twice per week:
  • Week 1: 5 sets of jumping over ten 40-cm (24“) hurdles spaced 1 meter (39.4”) apart
  • Week 2: 7 sets of jumping over ten 40-cm (24“) hurdles spaced 1 meter (39.4”) apart
  • Week 3: 10 sets of jumping over ten 40-cm (24“) hurdles spaced 1 meter (39.4”) apart
  • Week 4: 5 sets of jumping over ten 60-cm (36“) hurdles spaced 1 meter (39.4”) apart
  • Week 5: 4 sets of depth-jumps from a 40-cm (24“) box
  • Week 6: 4 sets of depth-jumps from a 40-cm (24“) box
  • Week 7: 4 sets of depth-jumps from a 40-cm (24“) box
  • Week 8: 4 sets of depth-jumps from a 40-cm (24“) box

Extensive testing on speed, power, and jump height was performed before and after the training.


The group that did regular soccer training did not show significant improvement in any of the pre-post tests.

The group that did plyometric training in addition to their regular soccer training showed the following statistically significant improvements:
  • Thigh muscle volume: +2.5%
  • Cycle ergometer absolute power: +4.5%
  • Cycle ergometer power relative to body mass: +5.9%
  • Jump height without a countermovement: +8.3%
  • Jump height with a countermovement: +2.5%
  • 40-meter sprint first step velocity: +18.2%
  • 40-meter sprint velocity over first 5 meters: +10.0%
  • 40-meter sprint velocity between 35 and 40 meters: +9.8%

Bottom Line
Although not all studies of plyometric training have produced improvements of this magnitude, it appears that the evidence supports inclusion of plyometric exercise in physical training programs for sports involving sprinting and/or jumping.

NOTE: This description of experimental results is for informational purposes only and does not constitute a recommendation. Anyone engaging in an exercise program should obtain proper medical authorization before doing so.

Monday, October 18, 2010

A Method for Improving Explosive Physical Performance


Post-activation potentiation (PAP) is not a training method. Rather, it is a method for improving performance in an explosive activity (e.g. jumping, sprinting) by doing heavy exercise with relevant muscles (e.g. squats) shortly before the performance. Several studies using either weight-resisted or isometric exercise have shown a positive effect on performance. One such study, by Berning et al. is described in the Journal of Strength and Conditioning Research (vol. 24, no. 9, 2010, pp. 2285-2289).


  • Group 1 - Thirteen trained young men who had been squatting at least twice a week for at least one year.
  • Group 2 - Eight untrained young men
The subjects in both groups were first tested for the maximum amount of weight they could parallel squat for a single repetition. That involved squatting down with a barbell on the shoulders from a standing position until the thighs were parallel to the ground, then standing up again. On other days, each group did the following:
  • On one day they did 5 minutes of low intensity cycling followed by maximal vertical jump testing.
  • On another day they did 5 minutes of low intensity cycling, then a functional isometric squat followed by maximal vertical jump testing. For the functional isometric squat, a barbell containing 1.5 times the subjects’ maximal weight for the parallel squat was placed on supporting rods in a squat rack. A second set of rods was positioned about 4” higher than the first set. The lifter got under the bar so that it rested on his shoulders then drove the bar vertically against the upper set of rods as hard as possible for 3 seconds before placing the bar back to the lower set of rods. The positioning of the rods was such that the subject lifted from a half-squat position. The subjects could lift much more weight than they could in a full squat because of the more advantageous leverage in the half-squat than the full-squat.
  • Among the untrained men, the functional isometric squat performed before the jump test did not provide any advantage.
  • Among the trained men, the functional isometric squat performed before the jump test led to significantly higher jump height, and the effect was retained when they were again tested 5 minutes after the lift. The magnitude of improvement in jumping was about 5% (2.4 cm ~ 1”).
Bottom Line

Post-activation potentiation (PAP) is a phenomenon with a fair degree of experimental support. It can be applied to any athletic activity in which a maximal explosive effort can be conveniently preceded by a heavy squat with a barbell, or even an isometric squat against an immovable object. Such athletic activities include but are not limited to high-jump, long-jump, track sprint, Olympic weightlifting, and Highland Games contests. It remains to be seen if the method can be applied to other athletic activities such as baseball hitting, football kicking, or wrestling. The method does not appear applicable to sports involving exertion over a relatively long period of time such as soccer, basketball, or hockey.

NOTE: This description of experimental results is for informational purposes only and does not constitute a recommendation. Heavy barbell squats should only be performed by experienced lifters. The supportive muscles, tendons, and ligaments involved must be developed using a consistent training program over an extended period of time. Anyone wishing to engage in strenuous physical activity must first determine if it is safe to do so. A physician’s clearance is always the best means of determining if you are healthy enough to exercise. Our exercise risk factor questionnaire can help you estimate your risk.

Wednesday, September 22, 2010

You May Not Be Getting Enough of These Nutrients

An article in the September 2010 issue of the Nutrition Action Health Letter contains a cover story entitled, “Getting Enough? What you don‘t eat can hurt you.” The article states that many of us are not getting enough potassium, magnesium, Vitamin D, or Vitamin B-12, with possible negative health consequences.

  • A third of Americans have high blood pressure, which increases the risk of heart attack and stroke. Over age 65, two-thirds of us have high blood pressure. More than half of those afflicted don’t have it under control.
  • Potassium can help regulate blood pressure. Major studies have shown that people with higher potassium intake have lower blood pressure.
  • A low potassium level is a predictor of stroke. A study of 43,000 subjects showed that those consuming the most potassium had 38 percent fewer strokes that those who consumed the least. The beneficial effect of potassium is the greatest for those who consume the most sodium. It is thought to work by increasing the flexibility of arteries and widening the tiny blood vessels.
  • While blood pressure typically rises as one gets older, 4 weeks on a low sodium, high potassium diet can totally reverse the effect of age on blood pressure. The DASH Diet (Dietary Approaches to Stop Hypertension), which minimizes added salt and includes 11 daily servings of fruit and vegetables as well as 2 servings of low-fat dairy products and low quantities of saturated fats, refined sugar, and refined grains, provides plentiful potassium while keep sodium down to recommended levels.
  • Potassium citrate is the form of potassium found in fruits and vegetables and it is considered more effective for blood-pressure reduction and safer than potassium supplements (usually potassium chloride), which can cause heart problems if taken in excess. Potassium citrate also reduces the risk of kidney stones by 50% and may help prevent bone loss.
 Vitamin D

  • This nutrient seems more important than calcium for protecting bones and preventing osteoporosis, a  bone-thinning disease that causes bone fractures in 25% of men and 50% of women over age 50.
  • Among Navy recruits, supplementation of 2,000 mg of calcium along with 800 IU of vitamin D per day reduced stress fractures by 20%.
  • Evidence suggests that Vitamin-D also protects against colon cancer, heart atacks, stroke, diabetes, falls, autoimmune disease, and all-cause mortality.
  • The article recommends taking a Vitamin-D supplement, as it is difficult to get the recommended amount from food. The recommended dosage is 400 IU per day for people under 60 and 800-1000 IU per day for people over 60.
  • Recommended calcium intake is 1000 mg/day for people under 50, and 1200 mg/day for people over 50.
  • Many Americans have Type II diabetes, including 25% of people over 60.
  • Diabetes greatly increases the risk of stroke, heart disease, blindness, kidney failure, nervous system damage, and limb amputations.
  • While excess body fat, lack of exercise, and poor eating habits are the major risk factors for Type II diabetes, a lack of magnesium can be a contributing factor. Large studies have shown that high magnesium intake is associated with reduced incidence of diabetes.
  • Fruits, vegetables, whole grains, nuts and beans are plentiful in magnesium. 
Vitamin B-12
  • Low levels of Vitamin B-12 are associated with poorer memory and mental ability. Yet the ability to absorb this vitamin from food decreases as we age.
  • A low Vitamin B-12 level in combination with a high levels of folic acid is strongly associated with cognitive impairment.
  • The article recommends taking a multivitamin containing at least 6 micrograms of Vitamin B-12 or a B-12 supplement containing up to 100 micrograms of B-12, and being careful not to get too much folic acid from vitamins and fortified cereals.

Monday, September 20, 2010

Static Stretching Can Impair Distance Running Performance

At times it can be difficult to find sports science articles that have true relevance to athletes. But here's one that can have real impact. A study by Wilson et al. (Journal of Strength and Conditioning Research, vol 24, no. 9, pp. 2274-2279, 2010) provides strong evidence that static stretching before a distance-running event can impair performance among young, male athletes.

Static stretching involves stretching a muscle to the point of mild discomfort and holding the stretch for 10-30 seconds. We have previously highlighted previous evidence that static stretching can impair jumping performance. It has also been shown to reduce maximal leg-press strength, 20-meter sprint speed, and knee-extension torque. Yet this is the first study to examine the effect of static stretching on endurance performance.

Experimental Procedure
10 male collegiate competitive distance-runners and triathletes who ran at least 20 miles per week and were in excellent aerobic condition were tested on 2 different days, at least a week apart, after the following:
  1. 16 minutes of stretching consisting of the following 5 stretches each performed 4 times for 30 seconds of holding:: 1) sit on floor with knees straight and reach with both hands to and beyond the toes, 2) stand with balls of feet on a block, letting bodyweight stretch calves, 3) for both left and right, stand on 1 leg and pull the opposite heel toward the butt 4) for both left and right, lunge deeply, and 5) cross the left leg over the right one, and pull the right thigh towards the torso, repeating for other side
  2. Quiet Sitting
After stretching or not stretching, the subjects underwent the following treadmill tests:
  1. Run at 65% of maximal aerobic capacity (VO2max) for 30 minutes while energy-cost is measured.
  2. After 2 minutes of rest and rehydration, run as far as possible in 30 minutes (subjects could control treadmill speed and see a time display, but not see a speed or distance display).
Experimental Results
On the no-strech day, the athletes performed significantly better as follows:
  • They covered an average of 6.0 km in 30 minutes on the no-stretch day compared to 5.8 km on the stretch day
  • They required an average of 425 calories on the stretch day vs. 405 calories on the no-stretch day to do the 30-minute submaximal run.

Bottom Line
Static stretching before running hurt the athletes' distance-running performance. After stretching they required more energy to run the same speed in the submaximal test, while in the maximal-distance 30-minute test they were not able to run as far. These differences can easily affect the chance of winning a race. The negative effect of static stretching appears to be due to a reduction in the spring-like stiffness of the leg muscles resulting in lower efficiency. Thus, it does not appear advisable to do static stretching before distance-running events. While dynamic stretching has not been subject to similar testing, it is a possible alternative. The evidence suggests that the best warmup before a distance-running event may be walking followed by jogging followed by short-distance runs at speeds increasing to race-pace.

Monday, August 30, 2010

Heart Attack Deaths in the U.S. Have Dropped Sharply

In the Harvard Health Letter, vol 35, no. 10, August 2010, and article appeared entitled, "Is the heart attack going out of style?". It stated that, based on Medicare data, the U.S. heart-attack hospitalization rate declined by 23% from 2002 to 2007. Also, a study based on 3 million members of a northern California health plan showed a 24% drop in heart attack hospitalizations between 1999 and 2008. While an increasing number of people are diagnosed with heart disease, fewer are dying from it - heart attack deaths have been declining in the U.S. for the past 40 years.

The article conjectures that, "Maybe decades of efforts to eat right and exercise more, stop smoking, lower LDL cholesterol levels, and control blood pressure are working." This appears only partially true. Yes, fewer Americans smoke, and Lipitor, a medication for reducing LDL and total cholesterol, is the most prescribed drug in the U.S. Many people are also taking blood pressure medication. Yet, there is little evidence that people are "eating right" as fast-food consumption and obesity continue to increase. Also, various national campaigns, such as the American College of Sports Medicine's Healthy People 2000, have failed dismally to get people to exercise more. Thus, it appears that the reduction in heart attacks is less due to anything that requires will power than to modern medicine. Another possible factor is reduced stress, as the economy was doing well over the study period. It remains to be seen what the recession and high unemployment rate will do to the heart attack rate. Hopefully, and emphasis on family and personal fulfillment and relationships will help keep stress to a minimum, even in the face of economic difficulties.

The reduction in heart attacks is encouraging, yet it would be even better if people became healthier through lifestyle changes such as exercise and good nutrition.

Wednesday, August 4, 2010

Mixed-Intensity Interval Training vs. Steady-Speed Running

Evidence continues to pile up concerning the advantages of interval training. A study by James Clark in the Journal of Strength and Conditioning Research (vol. 24, no. 7, pp. 1773-1781, 2010) compared interval training comprised of runs of varying lengths and intensities to steady-speed running as to which produced greater improvements in maximal oxygen uptake (VO2max), the gold standard of aerobic fitness.

Study Procedure
The subjects were 32 female league and college competitive soccer players who were divided into 2 groups that trained as follows for 8 weeks:

1) Mixed-Intensity Interval Training (MIIT): The workout consisted of repetitions of the following 6-minute exercise cycle:
  • 30 sec of jogging
  • 30 sec running at 90-100% of max effort
  • 60 sec of jogging
  • 60 sec running at 80-90% of max effort
  • 90 sec of jogging
  • 90 sec running at 70-80% of max effort
      The subjects did 2 cycles (12 min) the first week and increased to 6 cycles (36 min) by the eighth week.

2) Steady-Speed Training (SST): They ran steadily at a "moderate to hard" pace (heart rate corresponding to 60-80% of that at maximal oxygen uptake). Run time was 40 minutes the first week and increased to 60 minutes by the eighth week.

The mixed-intensity interval training group improved in maximal oxygen uptake by over 25% while the steady-speed training group improved less than 17%, a statistically significant difference.

Bottom Line
The mixed-intensity interval training improved aerobic fitness more than did steady-speed running, and required less time per workout. In addition, while it was not tested, it is likely that the sprinting segments of the interval training produced more improvement in sprinting ability, which is essential for soccer and other sports requiring bursts of speed. Thus, it appears that mixed-intensity interval training is advantageous for athletes in various team sports. Steady-speed running is still important for distance runners, who generally work out at various intensities during a training week.

NOTE: This description of experimental results is for informational purposes only and does not constitute a recommendation. Anyone engaging in an exercise program should obtain proper medical authorization before doing so.

Tuesday, July 27, 2010

Grouping Exercises Saves Times While Providing Equal Benefits

The benefits of the multiple mini-circuit method of performing resistance exercise have been described previously in this blog. It involves doing a set of each of 2-5 exercises in a grouping, then repeating the cycle 3 or more times before going on to the next exercise grouping. The advantages include:
  • A lot of exercise can be done in a given time period.
  • Each muscle group has adequate recovery time.
  • Heart rate remains high, affording some aerobic conditioning.
  • The body becomes accustomed to intermittent high-intensity exertions, relevant to many sports.
A recent article by Robbins at al. in the Journal of Strength and Conditioning Research (vol. 24, no. 7, pp. 1782-1789, 2010) provides research support for this exercise method.

Study Method
18 physically trained men performed the following two exercises:
  • Bench Pull - lie face down on a bench and perform a rowing movement to raise a barbell lying under the bench
  • Bench Throw - Perform an explosive bench press movement throwing the bar upwards, using a specially designed machine that catches the barbell so it does not fall back down on the lifter
On one day they first did 3 sets of bench pulls followed by 3 sets of bench throws for a total of about 20 minutes of exercise. On another day, they alternated sets of bench pull and bench press, accomplishing 3 sets of each, for a total of about 10 minutes of exercise.

Even though the alternating sets took half as much time as performing 3 sets of one exercise followed by 3 sets of the other exercise, the subjects were able to handle as much weight for as many repetitions of each exercise in both types of routines. In addition, measures such as bench press throw height, peak power, peak velocity, and muscle electrical activity were the same for both routines.

Bottom Line
While saving a lot of time, performing exercises in groupings worked the muscles as well as doing all sets of each exercise before going on to the next exercise. Thus, the grouping method enables a full workout to be performed in much less time or allows more work to be done in a given amount of time.

NOTE: Our descriptions of exercise programs are for educational purposes and do not constitute recommendations. Anyone embarking on a physical exercise program must be in good enough health to safely do so. Fitness to exercise can best be determined by a physician's clearance.

Monday, July 12, 2010

Spending More Time Outdoors Benefits Health

The increased availability of in-home entertainment systems such as TV's, computers, sound systems, and video games along with perceived discomforts and even dangers of spending time outdoors has prompted Americans to spend more time indoors. The U.S. government has estimated that the average American spends 90% of his/her time indoors. But that may be deleterious to our health. A recent article in the Harvard Health Letter (July 2010) details the following benefits of spending more time outdoors:
  1. Your Vitamin D levels will go up - Sunlight hitting your skin begins the process of the body's manufacture of biologically active Vitamin D. Fifteen minutes of sun exposure on bare skin can result in the manufacture of far more Vitamin D than you can get in any supplement pill. An increasing number of studies have shown the association of high Vitamin D levels with various health benefits including protection against osteoporosis, cancer, depression, heart attack and stroke. The northern latitudes get less direct sun exposure than southern latitudes and some forms of cancer are more common in the northern vs. the southern states. As we age, our ability to manufacture Vitamin D from sun exposure drops considerably. People with darker skin also generate less Vitamin D from a given amount of sun exposure. While there is an ongoing controversy about whether sun exposure without sunscreen causes more benefit from Vitamin D production than danger from skin cancer, the Harvard Health Letter recommends some limited daily unprotected sun exposure along with protection against the sun when outdoors for long periods or during the middle of the day in summer.
  2. You will get more exercise - Physical exercise has been shown to have a very wide range of health benefits. People tend to be more sedentary when spending time indoors. When outdoors, people tend to spend more time in physically active pastimes such as walking, biking, gardening, and playing sports. Children are more active outdoors as well. A study using GPS units found that children were more than twice as active when outdoors than indoors.
  3. Your mood will improve - The kind of light you get outdoors tends to elevate mood, and light-therapy has been used to treat people who tend to become depressed during the long winter months. The increased physical activity associated with spending more time outdoors also has a mood-enhancing effect. Exercising in a natural setting has even more positive effect on mood and self-esteem, as a British study has shown.
  4. Your focus may improve - A study has shown that children with Attention Deficit Hyperactivity Disorder do better on a test of concentration after walking through a park than when walking through residential or downtown neighborhoods.
  5. You may heal faster - A University of Pittsburg study showed that surgical patients experienced less pain and stress and needed less medication when exposed to natural light. Even a window view of a natural setting seemed to promote recovery better than a view of buildings.
It's clear that the evidence in favor of spending more time outdoors is quite solid. So find an outdoor activity you enjoy and get out there.

Friday, July 2, 2010

Can Mental Imagery Improve Physical Strength?

Mental imagery involves envisioning oneself performing a physical activity without actually doing it. It is currently used by many high-level athletes to enhance their physical performance. While the method is well-accepted for maintaining focus and consistency of technique, its use has recently been examined for improving strength as well.

Study Method
In a study by Lebon, Collet and Guillot in the Journal of Strength and Conditioning Research (vol. 26, no. 6, pp. 1680-1687, 2010) male college athletes who had not been weight training were put on a program of bench-press and leg-press training 3 times per week for 4 weeks. The only difference between the training groups was that the imagery group visualized doing each exercise during the between-set rest periods while the control group performed another thought task.

Both groups improved in strength and the number of repetitions they could perform with 80% of the maximal weight they could lift during pre-training tests. However, the imagery group improved 26% in leg press strength vs. 21% in the control group. Repetitions with 80% of pre-training max increased 92% in the imagery group vs. 79% in the control group. Both between-group differences were statistically significant. There were no differences between training groups as to changes in bench-press performance and neither group showed any significant increases in muscle-size.

Bottom Line
It is known that the strength gains resulting from the first few weeks of training are largely due to neuromuscular adaptations rather than muscle-size increases. Mental imagery may enhance the neuromuscular component of strength change and thus the most applicable to novice lifters. It is not clear why the method was effective for the leg press but not the bench press.

Wednesday, June 23, 2010

Is Elliptical Training as Good as Running for Improving Fitness?

Elliptical trainers have become very popular in gyms as well as in the home. Their popularity is due to a lack of impact on the body while providing resistance to both the lower and upper body musculature. The movement pattern looks similar to running but does not involve pounding of the feet on the ground. An added advantage is the relative silence of an elliptical device compared to a treadmill, which produces considerable noise from foot strikes and its motor.

An important question is whether the elliptical trainer provides as good an aerobic workout as a treadmill or running outside. A study by Brown et al. in the Journal of Strength and Conditioning Research (volume 24, number 6, pp. 1643-1649, 2010) was designed to answer that question.

Experimental Procedure
9 male and 9 female college-aged subjects worked out for 15 minutes on different days on both a treadmill and an elliptical trainer at a difficulty level they self-selected as “somewhat hard.” The subjects were instrumented to collect information on their rate of oxygen utilization, pulse rate and other relevant variables.

The only statistically significant differences between exercise on the elliptical machine and the treadmill were that the elliptical machine produced higher:
  • heart rate
  • percentage of maximal rate of oxygen utilization
  • Ratio of carbon-dioxide produced to oxygen used
However, there were no significant differences in total energy expenditure or total oxygen consumption.

Bottom Line
The similarities between the responses to exercise on the elliptical trainer and treadmill were far more important than their differences. They both produced very similar aerobic stimulus to the body when the subjects worked out at a moderate level of difficulty, which is typical. Therefore, for general health, one can use an elliptical trainer with confidence. However, since running is a very basic human activity that is essential for sports and reacting to emergencies, run training is still generally more useful. Someone who trains exclusively on an elliptical machine and reaches a high level of fitness will not perform as well when faced with a running challenge, and muscle soreness will surely result. Yet, elliptical training is a good way to maintain cardio-respiratory function for injured athletes and others who cannot tolerate lower body impact. It can also provide variety in training for those who run regularly.

Tuesday, June 22, 2010

How to Avoid Weightlifting-Related Shoulder Injuries

Terms used in this article:
  • Rotator cuff: Muscles (supraspinatus, infraspinatus, teres minor, subscapularis) that stabilize the shoulder joint and rotate the arm at the shoulder
  • Internal shoulder rotation: Standing with your upper arm against your torso with your elbow at a right angle, rotate your upper arm inward until your hand touches your abdomen.
  • External shoulder rotation: From the position you just attained by internally rotating your shoulder, rotate your upper arm outward so that your hand moves away from your abdomen, as you would when throwing a Frisbee.
  • Trapezius muscle: Extends from the back of your head and neck down your central upper back and serves to raise the shoulders and draw them backwards.
  • Range of motion: The number of degrees through which a joint can be rotated.

A recent article by Kolber et al. in the Journal of Strength and Conditioning Research (Vol 24, no 6, pp. 1696-1704, 2010) reviewed existing scientific research articles on shoulder injuries brought on by weightlifting. It noted that 25-35% of people who engage in resistance training sustain an injury severe enough to require medical attention and that 36% of such injuries are to the shoulder. The vulnerability of the shoulder is related to the high number of exercises that involve the shoulder, the great stresses the exercises place on the shoulder, and the unfavorable positions in which some exercises place the shoulder. In addition, many lifters do not warm up properly, select a balanced set of exercises, use proper lifting technique, or modify/eliminate exercises that cause pain. Major muscles are frequently worked to the exclusion of minor ones, leading to muscle imbalances. Shoulder muscles commonly injured include the pectoralis major, biceps, deltoid and rotator cuff group.

The Most Common Signs of Shoulder-Dysfunction Among Weightlifters:
  • Reduced internal shoulder rotation range of motion
  • Excessive external shoulder rotation range of motion
  • Underdeveloped external rotation strength relative to internal rotation strength
  • Underdeveloped external rotation strength relative to arm abduction (raising) strength
  • Underdeveloped lower trapezius strength relative to upper trapezius strength
  • Instability of the anterior (front) shoulder
  • Tightness of the posterior (rear) shoulder
Common Pain-Producing Exercises
The following exercises in which the upper arm is raised to the side and parallel to the floor while the forearm is vertical put the shoulder in a fully externally rotated position and are considered hazardous:
  • Behind the neck pull-down
  • Behind the neck overhead press
  • Overhead stack machine press in which the hands move rearward as the weight is lifted
Other exercises, although generally safe, also associated with shoulder pain:
  • Bench press
  • Incline chest fly
  • Supine chest fly
  • Dip
  • Biceps curl
The following may help to prevent weightlifting-related shoulder injury:
  • Discontinue any exercise that causes pain.
  • If an exercise hurts, try variations that do not hurt (e.g. bench press with rolled up towel on chest to limit movement).
  • Balance every push exercise with a pull exercise in the opposite direction.
  • Balance exercises involving major body movements (e.g. bench press, pull-down) with those that stabilize and rotate the shoulder.
  • Exercises that strengthen external shoulder rotation are particularly important (e.g. do the external rotation movement described above, resisted by weight stack cable or elastic band).
  • Do strength exercises for the lower trapezius (e.g. rowing motions with elbows high and shoulders drawn fully back).
  • Do flexibility exercises to increase internal shoulder rotation.
  • Do flexibility exercises to stretch the rear shoulder (e.g. Stand with upper arm parallel to the ground. Grip elbow with other hand and pull arm horizontally across the chest).

Friday, June 4, 2010

Should You Skip Breakfast to Burn More Fat During a Workout?

An Associated Press article suggesting that, because skipping breakfast before a workout burns more fat, such a practice may be effective for body fat loss. Yet, the study on which the article is based provides absolutely no evidence that such a practice would result in a stable loss of body fat. Sure, if your body is depleted of stored carbohydrates in the form of muscle and liver glycogen, you will burn more fat during exercise. However, a close look at the article reveals that the fat burned is in the muscle, and not around the waist or other parts of the body where people generally want to lose fat. Thus, exercising in a fasted state merely depletes intramuscular fat that is replenished upon eating. So there is no net body fat loss unless one consumes fewer calories than are used, which requires dietary control. So we can’t escape from the truism that the only way to lose weight is to burn more calories than you take in.

The following are additional reasons not to exercise in a fasted state:
  • You will feel less energetic and more lethargic
  • The quality of your workout will diminish
  • Your motivation to exercise will be reduced
  • You will cannibalize muscle to convert protein into needed carbohydrates
The only advantage to running in a fasted state might be for long-distance runners who wish to train their bodies to preferentially burn fat, thereby sparing muscle and liver glycogen to avoid “hitting the wall” late in a race. However, training with long-distance runs accomplish the same goal.

Wednesday, June 2, 2010

Caffeine May Interfere With Muscle Building

An online article in the Journal of Sports Science and Medicine by Wu and Lin (vol 9, pp 262-269, 2010) indicates that going heavy on the caffeine before resistance training may be counterproductive.

Experimental method
Ten men performed a workout consisting of 3 sets of 8 exercises. Each set consisted of 10 repetitions of 75% of the weight that could be lifted only once. On one day, the workout was performed an hour after caffeine ingestion and on another day an hour after ingesting a non-caffeinated placebo. The amount of caffeine was 6 mg/kg or about 475 mg for a 175 lb man. That’s about the amount of caffeine in one-and-a-half 16 oz Starbucks Grande coffees or four-and-a-half 8 oz cups of home-brewed coffee. Blood was analyzed at various times for levels of insulin, testosterone, cortisol, growth hormone, glucose, free fatty acid and lactic acid.

As has been observed in previous studies, blood levels of free fatty acids were higher in those who ingested caffeine than in those who did not. That is why caffeine is considered an ergogenic aid (performance enhancer) for endurance sports. Long distance runners often take in caffeine to promote the burning of fats in preference to carbohydrates, allowing the limited store of carbohydrates in the muscle and liver to last longer, sparing the athlete from “hitting the wall’ later in the race.

A result not noted in previous studies was that blood concentration of human growth hormone (HGH) was significantly lower when the subjects had previously ingested caffeine than when they hadn‘t. Since HGH is a muscle-building hormone, caffeine ingestion prior to resistance training can be considered counterproductive.

There were no significant differences in blood levels of insulin, testosterone and cortisol between caffeine and no-caffeine conditions.

Bottom Line
It appears prudent to avoid caffeine consumption for at least 3 hours prior to a resistance training session in order to maximize results. Since the time it take for the body to rid itself of half of ingested caffeine is approximately 5 hours in healthy adults, then excessive caffeine consumption is not recommended, even several hours before a workout.

Limiting Your Fruit and Vegetable Pesticide Exposure

The Environmental Working Group, a nonprofit organization whose purpose is to promote public health, reviewed nearly 100,000 reports on fruit and vegetable pesticide residue from the U.S. Food and Drug Administration and the Department of Agriculture. After being washed with a USDA high-pressure water system, many of the fruits and vegetables still contained high pesticide residues. The following were the worst.
  • Celery
  • Peaches
  • Strawberries
  • Apples
  • Domestic blueberries
  • Nectarines
  • Sweet bell peppers
  • Spinach, kale and collard greens
  • Cherries
  • Potatoes
  • Imported grapes
  • Lettuce
 In contrast, the following were found to have little or no pesticide residue.
  • Onions
  • Avocados
  • Sweet corn
  • Pineapples
  • Mango
  • Sweet peas
  • Asparagus
  • Kiwi fruit
  • Cabbage
  • Eggplant
  • Cantaloupe
  • Watermelon
  • Grapefruit
  • Sweet potatoes
  • Sweet onions
Bottom Line
Obviously, buying organic fruit and vegetables is the simplest and most direct way to avoid pesticide exposure. Unfortunately, organic produce is usually a lot more expensive than the non-organic variety and most people balk at the price difference. A reasonable compromise is to limit consumption of the most pesticide-tainted fruits and vegetables and preferably buy them in organic form, while buying other fruits and vegetables in non-organic form. The Environmental Working Group states that switching to the organic version of just the produce from the worst-offender list would reduce total dietary pesticide consumption by 80%.

Tuesday, May 25, 2010

Grouping Weightlifting Exercises for Time-Efficiency

The usual recommended rest period between sets of a weightlifting exercise is 1-5 minutes. Short rest periods are most often used by bodybuilders, while longer rest periods are often used by athletes looking to achieve maximum strength in specific lifts, such as those engaged in powerlifting or Olympic weightlifting competition. Most athletes and recreational lifters rest 2-3 minutes between sets.

Since the rest period between sets can account for the great majority of total workout time, some strength and conditioning coaches and athletes favor doing exercises in groups of 2-5, doing a set of each of the exercises in the group, then repeating the cycle 3 or more times before going on to the next group. The exercises within a given group involve different muscles. There is typically little time between sets but, because of the grouping system, more substantial time between sets of the same exercise. Such a routine has been called "multiple mini-circuits." The advantages of this type of program are that:
  • A lot of exercise can be done in a given time period
  • Each muscle group has adequate recovery time
  • Heart rate remains high, affording some aerobic conditioning
  • The body becomes accustomed to intermittent high-intensity exertions, relevant to many sports
The time-efficiency of such a workout is substantial. A typical weightlifting set takes about 30 seconds. If the trainee moves directly from one exercise to the next, there is generally only 30-40 seconds between the end of one set and the beginning of another. Thus, after becoming accustomed to this type of workout, a trainee can typically do 40-50 exercise sets in one hour, without sacrificing weight lifted or repetitions accomplished. In comparison, someone doing sets of the same exercise consecutively, with 2-3 minutes of rest in between, typically completes only 18-24 sets within an hour. Thus, performing exercise in groups allows one to either do twice as many exercises in a given amount of time or to take half the time to do the same number of exercises.

The exercises within a group use different movements and involve different muscle groups. A group might consist of:

  1. Push: bench press
  2. Pull: stack row
  3. Leg: squat
  4. Torso: leg raise
3-5 such groupings make for a comprehensive total-body workout. Done twice per week, this leaves time for a lot of other conditioning activities such as sport drills, plyometrics, distance running, speed work, and agility training.

The results of a research study by Robbins et al. (Journal of Strength and Conditioning Research, vol 24, no 5, pp 1237-1245, 2010) supports this type of training. In the study, following a warmup, 16 males performed 3 sets of bench press and 3 sets of bench pulls 2 different ways:
  1. 3 consecutive sets of bench pull beginning 4 minutes apart, followed by 3 consecutive sets of bench press beginning 4 minutes apart, for a total workout time of 20 minutes.
  2. 3 pairs of alternating sets of bench pull and bench press beginning 2 minutes apart for a total workout time of 10 minutes.
Note that both routines provided 4 minutes between sets of the same exercise. Analysis of the study results showed the two workouts similar in effect on the muscles. Both were similar in muscle electrical activity, the amount of weight lifted, and the number of repetitions performed in each set. The study also gave support for grouping more than 2 exercises together, as full recovery was not achieved with 4 minutes between sets of the same exercise.

Medical Disclaimer
This description of exercise practices and experimental results is for informational purposes only and does not constitute a recommendation. Anyone engaging in an exercise program should obtain proper medical authorization before doing so.

Wednesday, May 19, 2010

Avoiding or Lessening the Effects of a Stroke

An article in the May 2010 issue of the NIH (National Institutes of Health) News in Health describes how to avoid a stroke or, if you have one, how to recognize it and take immediate action to completely avoid, or at least lessen any lasting effects.

A stroke is a failure of normal blood flow to the brain, which can damage and destroy brain cells. There are two types of stroke:
  • Ischemic Stroke - the arteries feeding the brain are blocked, usually by a blood clot
  • Hemorrhagic stroke - broken or leaking blood vessels fail to supply oxygen to brain cells
Ischemic stroke accounts for about 80%, and hemorrhagic stroke about 20% of cases. Unfortunately, the treatment for the two types of stroke are opposite, so treating for the wrong kind of stroke can actually increase the damage to brain cells.

Signs of an ischemic stroke include sudden weakness or numbness of the face, arm, or leg, especially if it occurs on one side of the body, and/or difficulty in walking, talking, seeing and thinking. If you have any of these symptoms, it is important to be taken to an emergency room immediately (don’t drive yourself) because clot-busting drugs, if taken within 3 hours of the onset of symptoms, can stop brain damage. Unfortunately, only 2% of stroke victims actually get this effective treatment within the optimal time window. If given too late, the drug can actually increase damage. It is also important to get prompt treatment even if symptoms disappear quickly, because mini-strokes, also called transient ischemic attacks (TIAs), are a sign that a major stroke may occur soon afterwards.

The most common symptom of hemorrhagic stroke is a very sudden and painful headache, and prompt surgery may be required to repair a damaged blood vessel feeding the brain.
Some cases of partial or complete paralysis on one side of the face are not caused by stroke but by Bell’s Palsy, a nerve disorder that is, in most cases, temporary. However, only a medical professional can distinguish between Bell’s Palsy and a stroke. In both illnesses, immediate treatment produces the best outcome, so an emergency room visit is required in either case.

A healthy lifestyle can lessen your risk of a stroke. By exercising, eating healthfully (especially limiting foods high in saturated fat, cholesterol, and sodium), not smoking, and keeping your weight under control you can dramatically reduce your risk of a stroke. Our web site has more specific details on avoiding a stroke.
Bottom Line
To greatly reduce your risk of a stroke, follow a healthy lifestyle. But if you do develop stroke symptoms, seek immediate medical attention to avoid permanent damage and long-term disability.

Monday, May 17, 2010

Making the Best Use Your Time in the Gym

I'm frequently amazed by how much time many people waste in the gym. This particularly applies weight lifters, because it is difficult to waste time when you’re on a cardio machine or in a group exercise class, both of which provide largely non-stop exercise. But lifting allows you to go at your own pace, so it is very easy to get lazy or distracted. You may have even been given the incorrect advice that a work-to-rest ratio of one to five is the right way to exercise.

I recently saw a gym patron talking on a cell phone most of the time and doing a minimum of lifting between conversations. I’ve seen many others standing around chatting for long periods. Then there are the people who do a set of exercise and sit on the bench or machine for 3-5 minutes before doing another set, oblivious to other people who are waiting to use the device. I even saw one gym patron reading magazine articles between sets. And personal trainers, who have great influence over their trainees, often chat extensively with their clients. That might be effective for promoting a client-trainer relationship, but it’s certainly not the best for physical conditioning.

Long rests between lifting sets is recommended for a very limited number of competitive strength athletes, such as Olympic weightlifters, who spend hours in the gym in their quest to maximize the weight they can lift and need long rest periods for full recovery and to focus on technique. However, such time-intensive programs are not effective for bodybuilders or athletes in most sports that require a good balance of strength, muscular endurance, and overall conditioning. It takes an inordinate amount of time to do a comprehensive workout when there is a lot of time between exercise sets. Most of us have lives outside of the gym and must work out efficiently to get the desired benefits within a limited amount of time. Even high-level athletes often must commit so much time to the practice of their sport that they do not have many hours in the week left to spend in the gym on training.

One way to do a comprehensive workout in a limited time is to work out in groups of 2-5 exercises. For example, you can first go through the following group 3 times: 1) an upper-body push exercise, 2) an upper-body pull exercise, 3) a lower-body push exercise, and 4) a torso exercise. After the first group is done, a second and then a third group of exercises are performed. While a beginner should rest as needed between sets, as one becomes conditioned , the only rest needed between sets is the time required to walk between stations and adjust the weight. Using this method, a well-conditioned lifter can accomplish more than 40 sets of exercise in one hour. Some advantages of this system are:
  • There is enough rest between sets of the same exercise to allow optimal recovery time for that muscle group.
  • Both strength and muscular endurance are developed
  • The heart rate stays up, providing some aerobic benefit
  • More calories are burned per hour.
  • The routine provides whole-body conditioning essential to most sports
  • The workout leaves more time to work on speed, power, agility, and endurance, as well as practice of one's sport.
Bottom Line
Time spent in the gym talking, sitting, standing around, or reading does not contribute to one’s physical development. A great majority of gym time should be spent exercising unless the gym is the center of one's social life. A routine based on cycling through groups of 2-5 exercises provides a lot of muscle work in a limited amount of time, and provides the added benefit of total body conditioning.

Thursday, May 13, 2010

The Bagel Dilemma

What could be more simple than a bagel? It would appear to have simple ingredients like flour and water and, when flavored, ingredients like cinnamon, raisins, sesame seeds, onion, and garlic. All seem fairly wholesome. What could be a better snack or source of energy when a meal is several hours away or an exercise session is planned within 2-4 hours?

Just to check on the ingredients in fresh bagels available to me, I did a web search on their ingredients, and found the following counts for plain bagels:

  • Stop and Shop: calories 290, sodium 520 mg, sugars 4 mg
  • Finagle a Bagel: calories 290, sodium 410 mg, sugars 8 mg
  • Dunkin Donuts calories 320, sodium 660 mg, sugars 6 mg
  • Bruegger’s: calories 300, sodium 530 mg, sugars 7 mg
  • Starbucks: calories 300, sodium 460 mg, sugars 8 mg
I have nothing against the calories. We all need them to survive. And when carbo loading for athletic activity, healthy calories are what we’re looking for. It’s the sodium that’s the problem. Based on average caloric intake and recommended sodium limits, we should be taking in very roughly about one milligram of sodium per calorie consumed. That means that any food containing significantly more milligrams of sodium than calories should be considered a high-sodium food. Thus, all of the bagels listed above are high in sodium. If a plain bagel can’t be low to moderate in sodium, what can? Anything you put on top of the bagel is likely to be high in sodium as well. One slice of cheese contains about 300 mg, 2 slices of cold-cuts have 600-800 mg. But the real dilemma is, if even a plain bagel is high in sodium, how can we possibly keep our sodium levels under control?

The best we can do is to carry our own snacks and energy foods that have healthy ingredients and low to moderate sodium levels. That means either using fresh fruits or buying products whose ingredient labels pass muster. And when we prepare dinner, we can use as many fresh ingredients as possible and use processed products like sauces and salad dressings that have reasonable sodium levels listed on their labels. Fruit juices are not recommended as a major energy source because of their high sugar content. The same goes for chocolate milk, which has recently been touted as a good recovery drink. Skim or 1% milk isn’t a bad alternative if one prefers a liquid rather than solid snack. A glass of 1% milk contains 102 calories, 107 mg of sodium, and 13 mg of natural sugars.

Tuesday, May 11, 2010

The Difficulty of Eating Lunch Without Getting Socked by Sodium

Recommendations for daily sodium intake have been made by various health organizations such as the National Academy of Sciences' Institute of Medicine. They generally agree on a range of 1,500 to 2,300 mg/day for normal people but lower limits for those with congestive heart failure, liver cirrhosis, or kidney disease. One teaspoon of salt contains 2,300 gm of sodium.

Unfortunately, without ever picking up a salt shaker, it is very difficult to keep within the recommended sodium limits range if one either eats in restaurants or uses processed foods at home.

While people frequently eat dinner at home, and thus may control the amount of sodium they take in by using fresh ingredients, many of us find it convenient to eat lunch in a fast-food or table-served restaurant. Some examples from popular restaurants below show how difficult it is to find a restaurant meal that does not contain excess sodium.

  • Big Mac®: 1040 mg
  • Premium Grilled Chicken Ranch BLT Sandwich: 1190 mg
  • Premium Bacon Ranch Salad with Grilled Chicken: 1010 mg

 Burger King
  • Whopper®with cheese: 1450 mg
  • Angus Steak Burger®: 1260 mg
  • TenderGrill™ Chicken: 1180 mgs
  • BK Big Fish®: 1450 mgs
  • Double w/Everything and Cheese: 1440 mg
  • Homestyle Chicken Fillet Sandwich: 1120 mg
Dunkin’ Donuts
  • Egg and cheese on a bagel: 1160 mg
  • Bagel and cream cheese: 910 mg
Panera Bread
  • Chipotle chicken sandwich on artisan French: 2370 mg
  • Cuban chicken Panini: 1900 mg
  • Turkey artichoke Panini on focaccia: 2340 mg
Pizza Hut
  • Half of a 12” medium cheese pan pizza: 2120 mg
  • 2 slices of large 14” meat lover’s pan pizza: 2360 mg

  • Chicken burrito in 13” tortilla with rice, black beans, tomato salsa, guacamole and lettuce: 2100 mg
  • Steak burrito in 13” tortilla with rice, red beans, tomato salsa, cheese, guacamole and lettuce: 2160 mg
Bottom Line
These amounts of sodium are way over the top. And don’t think that table-served restaurants are any better. They vary widely as to the amount of salt added to their food, but most use a lot of salt. Why? Because most people like the taste. It’s obvious that any large restaurant chain would do extensive taste tests to see what people like best. So high salt foods must be what people prefer. Salt levels in food are thus market-driven. However, it is difficult to tell whether we have just gotten used to high-salt foods because of their prevalence or whether we have some instinctive salt craving that dates back to hunting and gathering days, when salt in the diet was difficult to obtain. Whatever the case, medical authorities widely agree that we are getting too much of it. Pending possible legislation to limit the sodium count in foods, the best we can do is to prepare our own food from fresh ingredients as much as possible and to consult nutritional information at restaurants or on their web sites to make selections without excessive sodium content, however difficult that is. It would also be helpful if large companies received e-mail or other messages from consumers asking to reduce the sodium content in their foods.