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Nancy Clark Reports on the ACSM Meeting
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Copyright: Nancy Clark MS RD CSSD July 2012
Sports Nutrition News from The American College of Sports Medicine
The American College of Sports Medicine (www.ACSM.org) is the world's largest organization of sports medicine and exercise science professionals. At ACSM's annual meeting in San Francisco, May 30-June 3, 2012, over 6,000 exercise scientists, sports dietitians, physicians and other health professionals gathered to share their research. Here are a few of the nutrition highlights.
• During a 46-mile (75-km) race, cyclists performed just as well when they fueled with banana as compared to sports drink. They drank about 8 ounces of sports drink or ate half a medium banana + water every 15 minutes during the 2.3-hour event. Time to start taping bananas to your helmet?
• Tart cherry juice contains numerous antioxidant and anti-inflammatory agents that can reduce pain and inflammation associated with osteoarthritis. When arthritic women (ages 40-70) drank a 10.5-ounce bottle of tart cherry juice or a placebo twice a day for three weeks, some of the inflammatory markers in their blood decreased. Women with the highest amount of inflammation noticed the most benefits. This is just one example of how food is a powerful medicine.
• Pomegranate juice is another rich source of bioactive compounds that reduce muscle soreness. Healthy men who drank PomWonderful juice for eight days before muscle-damaging exercise experienced less muscle soreness.
• Nitrates in foods such as spinach (and beets) reduce the oxygen cost of exercise and enhance efficiency. Healthy young men who consumed half a liter of spinach juice for 6 days were able to perform better anaerobically. Maybe this is why Popeye was strong to the finish?
• Dietary nitrates in the form of beet juice (called beetroot juice in the UK) have been shown to improve 2.5 mile (4 km) and 9.5 mile (16 km) time trial performance by almost 3% in racing cyclists. During a longer, 50-mile time trial, cyclists who consumed a half-liter of beet juice 2.5 hours pre-ride rode almost 1% faster. This small improvement was not statistically significant, but to a cyclist, the improvement would likely be meaningful.
• Elite rowers who consumed beet juice for 6 days performed better on an erg test. This was particularly noticeable in the later stages of exercise. Pre-exercise beets or borscht anyone?
• Both beta-alanine and sodium bicarbonate can reduce the negative effects of lactic acid in athletes who do very high intensity exercise. In an intense five-minute cycling test, beta-alanine enhanced performance. When combined with sodium bicarbonate, the improvements were even better.
• Most research with caffeine is done with pure caffeine supplements. Does coffee offer the same ergogenic effect? Yes. In research with cyclists and triathletes, the time trial results were very similar with pure caffeine (39.4 minutes) and coffee (39.5 minutes). Instant decaffeinated coffee (41.4 minutes) gave the slowest time. The researchers suggest the small improvement was related to caffeine’s ability to stimulate the central nervous system. This makes exercise seem easier so the athlete can work harder.
• An extensive review of the literature indicates caffeine does not have a dehydrating effect not impair heat tolerance. Hence, a 150-lb (68 kg) athlete need not worry about consuming about 200 to 600 mg caffeine (3-9 mg caffeine/kg body weight) when exercising in the heat. That’s 1 to 3 large cups of Joe.
• While commonly consumed intakes of caffeine do not have a diuretic effect over the course of the 24-hour day, what happens in the short term? In three hours, habitual coffee drinkers who consumed 7 ounces (200 mL) coffee (with 250 mg caffeine) voided 11.3 ounces (316 mL) urine, very similar to the group that consumed plain water and voided 10.4 ounces (290 mL) urine.
• When cyclists were given 1.5 or 3 mg caffeine/lb body weight (3-6 mg/kg) one hour prior to a 24-mile (40-km) time trial, they performed equally well, regardless of the dose. However, the athletes who responded best to pre-exercise caffeine had a specific gene that was missing in the non-responders. That is, when compared according to genotypes, the AA homozygote group was 4.6% faster at 6 mg caffeine/kg as compared to 2.6% improvement in the C allele carriers. Genetic differences influence caffeine’s ability to enhance exercise performance.
• Is Red Bull better than coffee? Doubtful. In a cycling time trial, Red Bull enhanced performance similarly to caffeine. Red Bull's added ingredients offered no additional benefits.
• Female cyclists who trained about 10 hours a week had low spine bone density in the osteopenic range—even though they were only 26 years old! Whether you are male or female, if you spend most of your exercise-time cycling, think about cross training with weight bearing exercise to improve your bone health.
• When getting your body fat measured with a Bod Pod, be sure to follow the instructions to not eat, drink, or exercise for two hours before the measurement. Athletes who did 30 minutes of treadmill exercise prior to Bod Pod testing were 21.3% body fat pre-exercise and 19.6% post-exercise. That 2% drop was not due to a loss of body fat, but rather to inaccuracy related to having an elevated body-temperature!
• When getting your body fat measured, take note: Different methods of body fat measurement give different results. In collegiate gymnasts, the body fat results were:
Omron HBF-510W 26.1% fat ($55 on amazon.com)
Tanita BF-350 21.7% ($899 at Walmart)
Tanita BF-522 21.7% ($366 at amazon.com)
DXA 21.06% (research-based; the “gold standard”)
Omron HBF-306C 18.4% ($30 on amazon.com)
• Trained runners lost twice as much sweat during a one-hour summer race than they had predicted. As a group, they predicted losing about 750 mL sweat in hot, humid conditions but they actually lost about 1,500 ml. Weigh yourself pre/post exercise to learn your sweat rate!
Nancy Clark, MS, RD, CSSD (Board Certified Specialist in Sports Dietetics) counsels both casual and competitive athletes at her office in Newton, MA (617-795-1875). Her Sports Nutrition Guidebook and food guides for new runners, marathoners, and soccer players offer additional information. They are available at www.nancyclarkrd.com and sportsnutritionworkshop.com.