PERFORMANCE ENHANCEMENT AT THE FIFTH IOC WORLD CONGRESS ON SPORT SCIENCES Carl D Patona MSc and Will G Hopkinsb PhD aSports Studies, Waikato Polytechnic, Hamilton, New Zealand; bDepartment of Physiology, University of Otago, Dunedin 9001, New Zealand. Sportscience 3(3), sportsci.org/jour/9903/cdpwghIOC.html, 1999 (2253 words) Reviewed
by Louise Burke PhD, Australian Institute of Sport, Belconnen 2616, Australia
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Effects of Altitude on Sea-Level Performance Five presentations dealt with the effect of adaptation to real or simulated altitude on performance at or near sea level. Two presenters reported on the effects of the traditional approach: living and training high. The other three combined exposure to real or simulated altitude (to get any benefits of altitude adaptation) with training at or near sea level (to avoid reduction in training intensity). Living and training high didn't seem to help 28 elite male and female Chinese kayakers. One week after 4 weeks at 1800 m, they averaged a 5% reduction in strength on a bench-pull test, a 1% reduction in power in 1- and 2-min tests on a kayak ergometer, a 4% reduction in speed for a 500-m time trial on the water, but a 0.7% enhancement in speed in a 5000-m time trial. A control group of 5 kayakers showed little or no changes. [Sun, p.115] In another Chinese study, 10 middle-distance runners living and training high (1900 m) apparently showed a 10% increase in maximum oxygen consumption relative to a control group of 9 runners living and training at sea level. Unfortunately the language barrier prevented us from coming to terms with some unusual aspects of this study. For example, there was a fall rather than the expected rise in the concentration of the hormone erythropoetin, after 1 and 4 weeks at altitude. This finding is in direct contrast to other studies and simply doesn't make sense. [Feng et al., p.90] In a pilot study of intermittent exposure to simulated altitude at the Australian Institute of Sport, 4 rowers breathed 12% oxygen through a mask for 5-min periods interspersed with 5-min periods of normal air, for a total of 90 min a day. The rowers performed a combined incremental-maximal rowing test immediately before and after 14 days of such exposure. The rowers ended up doing slightly worse than 4 performance-matched rowers in a control group, but because of the small sample size, the researchers cannot exclude the possibility that the treatment had a substantial positive or negative effect. A longer period of exposure at a higher simulated altitude, and with testing a week after the exposure, might also have produced a different outcome. [Clark et al., p.85] In another study from the Australian Institute of Sport, 10 members of the women's national road cycling squad lived and trained for 7 d at 1600 m, then slept high (2700 m) and trained low (600 m) for another 10 d. In an incremental test immediately after the camp maximum oxygen consumption decreased by 3%, but other changes in the test (peak power, lactate threshold) appeared to be unremarkable. On the other hand, power output in a high-intensity sprint test the next day was up by 10%. Sure, there was no control group, but it looks like this particular camp produced a massive enhancement of anaerobic capacity rather than endurance. [Fornasiero et al., p.90] Finally, the latest results from Finland. Twelve endurance male and female athletes trained at sea level (150 m) for 25 d while living high for 12-16 hours per day in 15% oxygen (equivalent to 2500 m). These athletes showed a 3% increase in maximum oxygen consumption a week later, whereas a control group of 10 similar athletes showed a slight drop. There were no data on field tests or competitive performance. [Rusko et al., p.179] Most researchers accept that creatine supplementation benefits performance of repeated bursts of all-out exercise. An important issue now is the effect of creatine on performance in specific sports. Two presenters addressed this question. There were also papers on the possible effects of creatine loading and on aspects of the loading regime. Creatine keeps volleyball players jumping! In a double-blind placebo controlled study, 5 d of supplementation with creatine (5 g with 5 g of glucose, 4 times per day) in 9 players resulted in a 7% enhancement in jump height in the third of three sets of 5 jumps. [Sax and Cummins, p.88] Creatine probably helps in a basketball tournament, eventually! Daily supplementation (0.1 g per kg of body mass in a sports drink, 4 times a day) for 5 d benefited several components of high-intensity performance by the third day of a 3-d simulated tournament in a double-blind crossover study of 6 elite female and 4 elite male players. Only the males appeared to benefit in a repeated jumping activity. Creatine had several negative effects on performance in the first game of the tournament relative to the last game, especially on goal shooting. The presenter concluded in his talk (but not in the abstract) that creatine may be more beneficial if loading occurs over several weeks; athletes would then have longer to adapt to any increase in body or limb mass. [Fausett and Hopkins, p.248] Creatine didn't seem to have any substantial effect on the muscle damage or muscle soreness that occurs following eccentric contractions. Interestingly, the anti-inflammatory drug Ibuprofen also had little effect in this randomized double-blind study of 26 females. [Fell et al., p.89] What is the best way to load up with creatine? The usual 4 doses of 5 g per day for 5 days resulted in substantially more uptake into muscle when glucose was taken at the same time. A subsequent daily dose of 2 or 5 g maintained the store over the following six weeks. Of interest to creatine researchers was the finding that muscle creatine was not completely back to normal six weeks after loading, so the washout period in crossover studies needs to be at least this long. Changes in creatine in red blood cells also showed a poor relationship to changes in muscle, so researchers still have to do muscle biopsies to track changes in muscle creatine. [Preen et al., p.247] Colostrum is the first milk produced by a lactating mammal. It contains various growth factors and antibodies, so it might be good for athletic health and performance. At an Australian conference last year a group from Adelaide presented a study of apparently non-athletes comparing performance in a group who supplemented for 8 weeks with colostrum powder (60 g per day) with a group who supplemented with whey powder. The measure of performance was work done in two incremental runs to maximum effort separated by 20 min of rest. The colostrum group performed substantially better than the whey group in the second of the two tests. (See the abstract.) At the IOC conference they presented another study with a similar double-blind placebo-controlled design, but with elite female rowers as subjects. The supplementation period was 9 weeks. The performance test consisted of three 4-min submaximal stages followed by a 4-min maximal effort on a rowing ergometer, which was then repeated 15 min later. Unfortunately the study ended up with only 3 subjects in the experimental group and 5 subjects in the control group. In spite of these small numbers, there was a statistically significant improvement in performance in the colostrum group relative to the whey group in both maximal stages of the test. But there is a problem. The difference in performance between the two groups amounted to only 10.5 m, over what must be at least 1000 m in the last 4-min stage (the authors don't state the distance). That's an improvement of 1.0% or less, which is important enough for a top rower, sure, but our calculations show that the reliability of the test would have to be unusually high for such a difference to be statistically significant with such a small number of subjects. [Buckley et al., p.246] Several presenters dealt with the growing use of so-called safe nutritional supplements and strategies by elite athletes. Corrigan (p.145) highlighted the problem caused by classification of several supplements as "natural remedies" by the American health food industry lobby. This classification allows remedies containing substances such as DHEA, androstenedione and ephedrine to be sold as over-the-counter supplements in health-food stores. He pointed out that these substances could cause serious side effects and would almost certainly cause an athlete to fail a drug test. Worst of all is the fact that many of the remedies either fail to list key ingredients or provide no ingredients list at all, which may account for some of the positive tests reported recently for substances like nandrolone. Corrigan went on to discuss several supplements (DHEA, ginseng, ma huang, insulin, chromium) that are marketed as performance enhancers. The take home message: if it sounds too be good to be true, it probably is. In a session chaired by Louise Burke and Ron Maughan (uninformative abstract on p.257), a panel of renowned sport scientists each had a maximum of four minutes and four slides to review evidence for specific performance-enhancing supplements and diets.
Lactate Threshold Partially Tracks Performance To be really useful, a lab test should closely track a sport-specific field test (or competitive performance). How good is a lactate-threshold test in this respect? Dave Martin of the Australian Institute of Sport presented a poster showing that two months of early season training produced similar changes (7-10%) in a measure of the lactate threshold (the Dmax) and a 30-min lab-based time trial in six male road cyclists of the Australian National Squad. In a discussion at his poster he told us that further improvements in time-trial performance in selection trials did not show up in the lactate test, because the cyclists push themselves harder in a competitive situation. We speculated that peak power (but possibly not Dmax) in the lactate test might have tracked performance in the time trial, if cyclists had similar motivation to perform well in the test. [Martin et al., p.107] What is the smallest enhancement of performance that would make a difference to an athlete's chances of getting the gold? According to a recent study it's about half the typical variation in an athlete's performance between events (Med Sci Sports Exerc 31, 472-484, 1999). Fine, so how big is that variation? At this meeting one of us (Will) presented an analysis of international track-and-field competitions in which the variation for the top athletes was about 1% for running, 2% for jumping, and 3% for throwing. Gender and time between competitions had little effect. That means sport scientists and coaches need to be concerned about changes in performance of as little as 0.5-1.5%, depending on the event. [Hopkins, p.126] We also presented a similar analysis of Olympic triathlons, in which we showed that variation of total time for the top triathletes was about 1.5%. We also showed that changes in performance in the swimming, cycling, and running phases are largely uncorrelated, and that no gains can be made in the transitions between phases. Conclusion: to increase the chance of winning, a top athlete will need to make a gain of at least 0.8% in overall time. That gain may be possible only from one phase for any given preparation or race strategy. [Hopkins and Paton, p.13] ©1999 |