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Wednesday, November 18, 2009

The Magic of Interval Training

The evidence continues to mount that interval training is very effective in a number of ways. For those not familiar with interval training, it involves short bouts of intense exercise (usually running, cycling or rowing) interspersed with longer periods of light exercise. An example involving running would be to warm up thoroughly first, then run a quarter-mile (~400m) at 85-90% of max speed, then walk or jog an eighth-mile (~200 m), repeating the run/walk cycle for 8-10 repetitions followed by a warm-down. There are many variations of interval training, and some involve even shorter bursts of intense exercise (e.g. 200m runs).

A recent article in the Journal of Strength and Conditioning Research (Tanisho and Hirakawa, vol 23, no. 8, 2009, pages 2405-2410) reinforces the efficacy of interval training. The subjects were 18 Japanese male lacrosse players who trained 3 days/wk for 15 weeks on an exercise cycle. The continuous-training (CT) group pedaled continuously for 20-25 minutes, while the intermittent-training group (IT) alternated 10-second max-speed pedaling with 20-second easy pedaling, for a total of 10 intervals (total time = 5 minutes). There was also a control group that did no training. Interestingly, the IT group improved almost as much (10%) in the maximal oxygen uptake test (gold standard of aerobic fitness) as the CT group (12%). However, only the IT group improved in maximal power output. The IT group was also the only one to improve in fatigability, measured as the ability to maintain cycling power output over 10 intervals of 10-second max-speed pedaling interspersed with 40-second recovery periods.

One would have to conclude that the interval training produced amazing results. The 5-minute interval training sessions produced almost as much increase in aerobic capability as 20-25 minutes of endurance training. Yet the interval training also produced significant gains in maximum power and in resistance to fatigue from repeated intense exertions bouts. IT was a truly remarkable and time-efficient form of training.

This type of training is clearly advantageous for most team sports, which generally involve short bursts of intense activity interspersed with mild-to-moderate activity. The effectiveness of the interval training supports the concept of Specificity of Training, by which training is most effective when it reflects important aspects of the sport in which improvement is sought. Distance running is not effective for most team-sport athletes because it has been shown to actually reduce max power output, needed for jumping and sprinting. Thus long runs are only recommended for athletes in endurance sports.

A word of caution is in order. No-one should engage in an exercise program without first determining whether a doctor's clearance is needed first. See our Exercise Risk Questionnaire. Even if you are cleared for general exercise, you may not be ready yet for interval training, which should only be undertaken by people who are already well-conditioned. It is an intense form of exercise that puts considerable strain on the heart, lungs, muscles, and bones. Running intervals can easily cause muscle pulls or other musculoskeletal injuries, so very thorough pre-interval warmups are necessary. Cycling and rowing intervals involve less impact and peak force on the musculoskeletal system than running and are thus less likely to produce injury. However, any interval training must be approached with caution. The key points are to start with a well-conditioned individual, warm up very thoroughly, and start at a moderate level of difficulty, increasing the intensity of intervals over a period of several weeks.

Tuesday, November 17, 2009

An Effective Stretch for Hamstring Flexibility

An article in the Journal of Strength and Conditioning Research (Vol. 23, no. 2, 2009, pages 660-667) described the comparison of various hamstring stretching techniques done for 30 seconds, 5 days per week. There were 100 subjects ranging in age from 21 to 57. The most effective stretch over the 8 weeks for lengthening the hamstrings was a straight-leg passive stretch. For this stretch, a protruding corner of a wall, a tall piece of furniture or other object is needed. The subject lies on the floor with the crotch at the corner and, with both knees completely straight, keeps the inner surface of one leg on the floor next to the wall and raises the other leg as close to vertical as possible, resting the heel against the other wall forming the protruding corner. This position is held for 30 seconds. Then the subject repositions to stretch the other leg similarly. In each subsequent session, the subject tries to bring the stretched leg more vertical by getting closer to the wall. The passive stretch was more effective than an active stretch in which the subject's hip flexor muscles, rather than a wall, were used to pull the leg toward vertical.

The study must not have included extremely flexible people like dancers and gymnasts who, while keeping one leg flat on the ground, can easily raise the other straight leg beyond 90 degrees. However, such athletes can hold a passive straight-leg position beyond 90 degrees by either having a partner hold the leg or by using a strap to hold the leg in position themselves.

Monday, November 16, 2009

Vitamin D and Your Health

The information in this article is from the November 2009 issue of the Nutrition Action Health Letter, published by the Center for Science in the Public interest.

While several different studies have linked higher blood levels of Vitamin D to lower levels of various cancers, some studies have shown no effect at all. Therefore, larger clinical trials with many more participants are needed to definitively show that Vitamin D decreases the risk of cancer.

The ability of Vitamin D to reduce heart attack and stroke risk is more firmly established. The vitamin works by suppressing potentially harmful hormones and reducing inflammation in the walls of arteries. It also appears to lower blood pressure. And because of its bone-building effects, Vitamin D (at least 700 IU per day) reduces the risk of bone fracture and has reduced the risk of falls by 20%, possibly by improving the ability of muscles to take preventive action when a fall in imminent. Another apparent benefit of Vitamin D is that, when taken with calcium, it slows the rise of blood sugar, thus reducing the risk of Type II diabetes.

Considering its apparent benefits, the Center recommendas 700 to 1,000 IU of vitamin D a day, which is much higher than the standard multivitamin dose of 400 IU. Supplements are particularly important for people living at northern latitudes as, in winter, the angle of the sun in cities north of Atlanta and Los Angeles is such that even direct sun exposure does not bring about the manufacture of appreciable amounts of Vitamin D.

Wednesday, November 11, 2009

Health Benefits of Cocoa

Evidence keeps coming on the benefits of chocolate. A Spanish study of 47 subjects aged 55 and older showed that those who drank skim milk with cocoa powder had less inflammation of their blood vessels and an increased HDL level. Inflammation of the vessels is implicated in arterial disease, so reduced inflammation is a positive change. HDL ("good cholesterol") removes cholesterol from the blood vessel walls - so the more, the better. The lower the ratio of total cholesterol to HDL, the lower the risk of heart disease. A ratio of lower than 3.0 is ideal. This study reinforces previous evidence that moderate chocolate consumption helps keep arterial walls healthy. But be careful about which chocolate or cocoa you buy. Dark chocolate is best, and you should look for brands that list chocolate liquor or cocoa mass as the first ingredient. If you buy a brand that lists the percent cocoa mass, look for at least 50%. It's also wise to avoid brands that add milk fat, which unnecessarily raises the saturated fat and cholesterol content of the bar.

Tuesday, November 10, 2009

A Recent Study on Plyometric Exercise

A recent article in the Journal of Strength and Conditioning Research (Volume 23, no. 2, 2009, pages 495-506) analyzed the combined results of 56 studies of plyometric (bounce) training to determine what exercises were most effective in improving jump height. Increases in the neighborhood of 7% were observed after good plyometric training programs. The combination of squat jumps (jumping up from a static squatting position), countermovement jumps (starting from a standing position, then quickly dipping into a bent-knee position before jumping up) and drop jumps (jumping down to the ground from a box, then jumping up) provided the most improvement in jump height. Adding weight to the body using a vest or other means was not better than jumping with bodyweight alone. Also, weight training in combination with plometric exercise did not result in more improvement than plyometrics alone. Programs of 10 or more weeks were more effective than shorter programs. Programs of more than 20 total sessions of 50+ jumps per session were better than shorter programs of lower volume. Box height (e.g. 6" vs 12") for drop jumps didn't matter. The most experienced athletes improved the most. Improvement was seen even in subjects of low initial fitness level.

A word of caution is in order. Most of the subjects in these studies were of college age and many had been physically active before their studies. Plyometric exercise can result in high forces on muscles and tendons, and injury risk is higher than with slow, steady exercises. Plyometric programs should only begin at a very low level, particularly for those people who have been relatively inactive and those above 35 years of age. More gentle plyometric exercises for the beginner include gentle, submaximal hops and jumps. Running itself is a plyometric exercise, especially when running faster in short intervals interspersed with walking or jogging. Tendons and ligaments take a very long time to build up strength, much more than muscles do, so patience is the key word. The intensity and volume of plyometric workouts should only be increased very gradually, and more advanced exercises, like drop jumps, should only be added after a relatively high jump-strength level is attained.

Thursday, November 5, 2009

1-2 Alcoholic Drinks Per Day May Thwart Dementia

A study was described in the Tufts Health and Nutrition Letter of October 2009 relating alcohol consumption to dementia (deterioration of mental ability). The study, by Dr. Kaycee Sink of Wake Forest University found that of 3,069 test subjects, all of whom were over age 75, those who drank 1-2 alcoholic beverages per day were 37% less likely than non-drinkers to develop dementia within 5 years. However, of those subject who already showed some mental impairment, those drinking 3 or more alcoholic beverages per day were almost twice as likely as non-drinkers to develop dementia. Health authorities caution that non-drinkers should not start drinking to improve their health risk profile. However, 1-2 drinks per day also decreases risk of heart disease. The drawbacks of even this level of drinking are that alcohol tends to reduce a man’s testosterone level and any alcohol at all increases a woman’s risk of breast cancer.

Monday, November 2, 2009

A Healthy Lifestyle Can Trump Prescription Drugs

All of the people described below are real, but their names are not menioned to protect their privacy.

We're often amazed when someone who has always been involved in sports and fitness seeks a prescription drug solution to a health problem without making a serious attempt to solve the problem by natural means. One example is a man who had competed at the national level in an endurance sport, and later coached the sport for many years while still competing individually at a more modest level. He also ran regularly to keep in shape and competed seriously in some distance running events. As he got into his late 40’s he developed some musculoskeletal problems and switched to mainly low-impact endurance activities for fitness. However, he enjoyed rich foods and, while of slim build, developed a modest but noticeable pot belly. He mentioned that his cholesterol level had been high and he was currently on regular Lipitor treatment. He also talked about how he had gotten into cooking and described some of the high-fat dishes he had been preparing. He was spotted several times eating piles of French fries and giant cookies he bought regularly at his workplace cafeteria. Our thought was, “Why doesn’t he just try to eat a healthy diet somewhat lower in calories and saturated fat?” A loss of 10-15 pounds along a lower intake of saturated fat would very likely normalize his cholesterol level. But no - drugs were an easier solution. That is probably why Lipitor is the most prescribed drug in the U.S. (

A man recognized as an international authority on exercise and sport was asked if he was watching his sodium intake. He responded, “No, but my blood pressure was high and I’m on blood pressure medication.” Again we were surprised that this man opted for the drug solution instead of watching his diet. He had been a competitive athlete from grade-school through college and remained very physically active for decades. Why didn't he just watch his sodium intake?

A third man exercises avidly and competes seriously in various endurance sports. Training for fitness and competition is almost a religion to him. However, he readily admits his diet is terrible and includes lots of soda and salted snacks. Despite the great amount of endurance exercise he does, he was diagnosed with metabolic syndrome ( characterized by excess fat around the waist, low HDL level, high blood pressure, high triglyceride level, and insulin resistance. As a result, his doctor put him on a multi-drug regimen, which he will probably remain on indefinitely. We couldn’t help but think that if he reduced his caloric intake a bit and lowered his intake of simple sugars and salty foods, his symptoms would likely disappear. But somehow, he wouldn’t even consider that.

A man in his mid-forties who had been quite strong in the weight room, later added distance running into his fitness program, and successfully completed a marathon. At that time he was in great cardiovascular and muscular condition. However, he sustained a calf injury and stopped running regularly. Another injury limited the weight lifting exercises he could do. Overall, his exercise program became irregular. Over a period of months he developed a good-sized potbelly that was quite obvious despite being partially hidden by a wide leather weightlifting belt. He mentioned that his cholesterol level had become elevated and he had gotten on regular Lipitor treatment. We knew he would probably not need the drug if he just lost his potbelly.

Admittedly, the medical establishment treats Lipitor and other statins as wonder drugs and there have been few reported side-effects beyond muscle weakness and pain in some individuals. However, our feeling is that the natural way, if effective, is always preferable. Even with statin drugs, we don’t really know what the negative side effects might be over several years. Other drugs used to treat lifestyle-related health problems have widely-known negative side effects (e.g. blood pressure drugs:

Our conclusion: Try natural solutions to health problems when they have been proven effective. It just takes some effort and self-discipline. We are by no means condoning unproven and possibly dangerous treatments such as shark cartilage for cancer or bowel cleansing to cure a wide variety of ailments. For serious illnesses, it is best to follow standard medical treatment backed by clinical trials. Yet for health problems related to lifestyle, such as obesity, high blood pressure, high blood sugar, high total cholesterol and low HDL, a regimen of healthy diet and exercise is usually the best solution. Being healthy is often just a matter of will.