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Tuesday, February 23, 2010

Longer-Interval Run Training Shows Beneficial Cholesterol Effect

The two major fractions of blood cholesterol are low-density-lipoprotein (LDL) cholesterol and high-density-lipoprotein (HDL) cholesterol. LDL increases the risk of heart-disease because it is readily deposited in arterial walls and can result in a blood clot that shuts off the blood supply to the heart muscle. In contrast, LDL removes cholesterol from arterial walls. The ratio of total cholesterol (TC) to HDL cholesterol is a risk-index for heart-disease. The higher the ratio, the greater the risk. The average ratio is 4.5, but doctors recommend it be below 4.0 and preferably below 3.0.

Endurance exercise has been shown to improve the TC/HDL ratio, but interval training (sprint running interspersed with rest periods) has not been shown effective in this regard. However, a recent study by Musa et al. (Journal of Strength and Conditioning Research, vol 23, no 2, 2009, pages 587-592) showed that interval training using longer running intervals (500 meters ~ half-mile) can be effective for improving the ratio.

Experimental Procedure
20 college age males ran 4 half-mile intervals at high intensity (90% of max heart rate) seperated by rest periods equal in time (3-5 min) to the running intervals, 3 times a week for 8 weeks. Their TC/HDL ratio improved by 18%, reducing their risk of heart-disease by an estimated 37%. The training also improved their 2.4 km (1.5 mi) running time by 9%.

Bottom Line
Interval training using running distances of 0.5 miles and rest periods equal to run time can effectively enhance blood cholesterol profiles, reducing risk for heart-disease. Thus, for individuals healthy enough to withstand the strain of high-intensity running, longer-distance interval training can have a valuable place in a physical fitness program.

Friday, February 19, 2010

Potential Health Problems Related to Fructose Intake

An article in The January/February 2010 issue of the Nutrition Action Health Letter, a publication of the Center for Science in the Public Interest highlights some potential health problems associated with fructose intake. Aside from the detrimental effects of any added sugar (e.g. empty calories, heart disease, obesity, diabetes, tooth decay) the article points up some problems specific to fructose (not only high-fructose corn syrup):

  • The liver converts virtually all fructose, but not glucose, into fat.
  • Fructose raises blood triglyceride level, an independent risk factor for heart disease
  • Fructose may increase visceral fat (fat around the internal organs) another risk factor for heart disease
  • Fructose intake may raise the risk of gout, a painful joint condition
  • Fructose may suppress the effectiveness of leptin, the body’s appetite-curbing hormone

Drinks and food products sweetened with high-fructose corn syrup are the greatest sources of fructose in the U.S. diet. Whole fruits, the sugar of which is mainly in the form of fructose, is not generally a problem because the amount of fructose in one apple or orange is limited. However, fruit juice is more of a problem because several individual fruits may go into one glass of juice. So it is best to keep eating whole fruits but limit intake of sodas, juice drinks, juices, and syrups.

Smoking Rises Among U.S. Adults

The U.S. government Centers for Disease Control has reported that, for the first time since 1994, the percentage of adults who smoke has increased over the previous year - from 19.8% to 21.0%. For men, the rate is 23.1% and for women it is 18.3%. The increase ended a steady decline in smoking from about 40% in the 1960s. The highest rate is among people aged 25-44 and the lowest by far is among people over 65 (many smokers likely die before reaching that age). American Indians and Inuits (Eskimos) have the highest rate of any group while Asians have the lowest rate by far. As to education, more than 40% of those with a GED degree smoke, while less than 6% of those with graduate degrees do. The smoking rate is more than 50% higher for people below the poverty line than those above it. The U.S. states with the highest percentages of smokers are West Virginia, Indiana, and Kentucky, while the states with the lowerst percentages of smokers are Utah, California, and New Jersey.

Perhaps the economic recession and its associated stress have driven people to smoke, or at least driven those who had quit back into smoking. The entertainment industry doesn't help any, as leading men and women are frequently depicted smoking, as if this makes them sexier or tougher. The upward trend is unfortunate because, according to the CDC, "cigarette smoking is the leading cause of preventable death in the United States, accounting for approximately 443,000 deaths or 1 of every 5 deaths in the United States each year." In addition, smoking drains a considerable amount of money from family budgets, worsening financial pressures.

We must continue to seek other ways of dealing with stress than smoking. Exercise is a great stress-reducer. It is very difficult to think about one's problems while lifting a heavy weight, pushing oneself on a treadmill, keeping up with a strenuous exercise class or playing with one's team against tough competition. In addition, exercise leads to feelings of relaxation and well-being. There are several approaches to quitting smoking. Our web site provides a listing of the methods proven most effective.

Thursday, February 18, 2010

Dynamic Stretching Proves Best For Jump Training

For many years, static stretching was recommended as superior to dynamic stretching for improvement of flexibility. Static stretching involves slowly stretching a muscle to the point of mild discomfort, then holding the position for 15 or more seconds. Dynamic stretching involves moving the body into and immediately out of the stretched position, repeating the cycle for several repetitions. However, while static stretching may be more effective than dynamic stretching for improving range of motion, static stretching performed immediately before explosive activities (e.g. jumping, sprinting) has been found to impair performance.

Experimental Procedure
A study by Hough, Ross, and Howatson, described in the Journal of Strength and Conditioning Research (vol 23, no 2, 2009, pages 507-512) compared the effects of static vs. dynamic stretching on jump performance immediately after stretching. Eleven college-age males jumped on different days after either 1) not stretching, 2) performing static stretching, or 3) performing dynamic stretching. The stretching routines both targeted the ankle extensors (calf), hip extensors (butt), hamstrings (rear thigh), hip flexors (front thigh-torso junction), and quadriceps (front thigh). On the static stretch day, someone held the subjects' limbs in each stretch position for 30 seconds. On the dynamic stretch day, the subjects moved into and out of each stretched position 5 times slowly and 5 time quickly, without bouncing. Jump testing (3 max height jumps from a self-selected bent-knee position) was performed 2 minutes after the stretching.

Experimental Results
There were significant differences in jump height between all 3 stretching conditions. After static stretching, the subjects jumped 4.2% less vertical distance than when they didn't stretch at all. However, after dynamic stretching, the subjects jumped 4.9% greater distance than when they didn't stretch. The static stretching did not decrease muscle electrical activity, so its detrimental effect may be due to reduced muscle stiffness. However, the dynamic stretching increased muscle electrical activity, which may account for its positive effect on jump performance.

Bottom Line
Performance of explosive activities like jumping and sprinting can be enhanced by dynamic stretching immediately before the activity. Yet static stretching detracts from explosive performance.

Other research has shown that the negative effect of static stretching on explosive performance is short-term. Therefore, because static stretching is effective for improving flexibility, it can safely be performed following athletic performance or exercise routines without interfering with the following day's athletic performance. This is particularly relevant to sports like gymnastics, that require great flexibility .

Wednesday, February 10, 2010

An Effective Method for Improving Sprint Speed

Resisted sprinting has become a standard training method for sprinters and other athletes who rely on their sprint speed (e.g. football players). There are various way to provide resistance to sprinting, such as small parachutes pulled by sprinters, push and pull sleds and carts, and long elastic cords. Evidence for the effectiveness of resisted sprinting, especially in combination with strength training, was provided in a recent article by Ross et al. in the Journal of Strength and Conditioning Research (vol 23, no 2, 2009).

Experimental Method
25 college-age male athletes (American football, soccer, track and field), were divided among the following 3 training groups, all of which trained for 7 weeks:

  1. Resisted Sprint Training: Did 8-12 sets of 40-60-meter sprints on a treadmill with 2-3 minutes rest in between. A proprietary device pulled back on the sprinters with up to 25% of their bodyweight. 25-40% of the sprints in each training session were resisted and the rest were unresisted.
  2. Strength Training: Did a split routine of 10 weight-resisted exercises two days per week and 9 other exercises two days per week plus a core circuit each workout. Each exercise was done for 3-4 sets of 6-10 repetitions. There were 26-30 total sets per workout in addition to the core circuit.
  3. Combined-Training: Did both the Resisted Sprint Training and Strength Training programs described above, on different days.

Experimental Results
  • Only the Combined-Training group improved significantly in 30-meter sprint time.
  • The Resisted-Sprint Training group improved somewhat in 30-m sprint time, but the change did not quite reach statistical significance.
  • Only the Combined-Training group improved significantly in treadmill sprint peak power.
  • All 3 training groups significantly improved their maximum barbell squat (6.6-8.4 kg) without any statistically significant difference among the improvements of the groups.

Bottom Line:
Resisted Sprint Training, especially in combination with Strength Training, is effective in improving sprint time, even among athletes who are already practiced in their sports.

Tuesday, February 2, 2010

Weight-Training with Slow vs. Normal-Speed Repetitions

Weight-training with slow and super-slow repetitions has been promoted in some quarters as superior to normal-speed weight training. An article by Tanimoto et al. in the Journal of Strength and Conditioning Research (vol. 23, no. 8, 2009) tested this hypothesis.

Experimental Method:
Twenty-four young men performed 3 sets of barbell squat exercise,  twice a week for 13 weeks, and were equally distributed among the following 3 groups:

     - Control Group: no organized exercise
     - Slow-Repetition Group: 3 sec descending, 3 sec ascending, no rest between reps
     - Normal-Speed-Repetitions: 1 sec descending, 1 sec ascending, 1 sec between reps

The two lifting groups each did 8 reps with the most weight they could handle for that number of reps and the assigned speed (metronome-timed). Because slow reps are more difficult, the weight used was about 60% of max for the slow group and about 85% of max for the fast group.

Both training groups significantly improved both their max squatting strength (Slow: 34%, Fast: 28%) and their lean thigh muscle volume (Slow: 2.5%, Fast 3.6%). However the groups did not differ significantly in their percent gains in these two parameters. The authors concluded that slow resistance-training is just as effective as normal-speed training for improving muscle strength and size, and has the additional advantage of being safer because of lower musculoskeletal forces and less elevation of blood pressure.

One area in which the groups differed was in their muscle electrical activity while riding a bicycle at a typical speed and resistance. The slow-trained group developed a more unusual pattern of muscle activation and force application. The authors felt this indicated that slow-speed strength-training may have some unfavorable effects on dynamic physical activities, like those typical of sports. However, they felt that, because of the safety advantages of slow-speed weight-training, the method can be combined for sport training with some fast and exposive lifts (e.g. cleans), “cheating technique”, and plyometrics (e.g. jumping).