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PERFORMANCE
ENHANCEMENT AT ACSM 1998: |
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Tips for Better Abstracts · Ergogenic Aids and Strategies · Fuel for Exercise · Training · Performance Symposium |
Bigger than
ever! Over 1900 abstracts, presented at as many as
19 parallel sessions, attended by over 7000 registrants. No wonder I
failed to meet up with several people. Worse still, I missed many
more good talks and posters than I attended, in spite of carefully
planning each day. There were so many posters that I had time for
only a superficial glance at most of them. But does it matter? Maybe
the main purpose of these meetings is to get your data and ideas
straight for eventual publication. Any questions or advice from
onlookers are a bonus. Networking with colleagues is also very
worthwhile.
For this review I've covered the experimental studies of performance enhancement mainly for endurance events and team sports. Mary Ann Wallace has dealt with overtraining and other topics in her report. Fred Hatfield will review the presentations that focused on strength for the next issue of Sportscience News.
The numbers shown below in parentheses (e.g., A123) are the numbers of the abstracts published in the supplement to the May issue of Medicine & Science in Sports & Exercise (Volume 30, Number 5). But first, some suggestions for improving next year's abstracts.
Tips
for Better Abstracts
Show more data in your abstract, enough to convey the size of
your outcome, regardless of its size or significance. And try to show
confidence
limits for the size. A p value on its own isn't much help: for
example, you could have p=1.0 (no observed effect whatsoever), but
the confidence interval could be huge (you haven't a clue what's
really going on). Citing test statistics like F and t is also
pointless: devote the space to means and standard deviations, or
outcome statistics like the effect size, percent differences,
correlations, and relative frequencies.
Avoid abbreviations (A) in your abstract (Ab) or poster (P). Some of you are under the false impression that including As in Abs and Ps is more scientific (S). The aim of a S Ab or P is to transmit (T) information (I). If I can't understand your Ab or P because of the As, or if I get fed up and give up, you have failed to T your I, so it can't be S. Please, cut back on As in Abs and Ps. Shortage of space is no excuse.
Follow the rules for formatting the abstract: spacing, font size, and font style. Then print a final draft and proof-read every keystroke. If your abstract is below par, people might think your research is, too.
Ergogenic
Aids and Strategies
Branched-chain amino acids taken before and during exercise
with carbohydrate didn't enhance performance of a ride to exhaustion
following 60 min of hard cycling (A92). No data were given, but the
researchers used a crossover design with 20 trained cyclists, so they
were in a strong position to detect the smallest worthwhile effect.
It's a blow against the idea that these amino acids could reduce the
concentration of fatigue-inducing serotonin in the brain, by reducing
transport of serotonin's precursor, tryptophan, across the
blood-brain barrier. For a recent study showing a positive effect on
low-intensity exercise to exhaustion in the heat, see Med Sci Sports
Exerc 30, 83-91, 1998.
After a 6-wk training program, distance runners were able to apply biofeedback and relaxation techniques to enhance their economy of running on a treadmill at 70% of peak speed by a whopping 7% (A186). But will it work on race day?
Tablets of sodium bicarbonate slowed 800-m times by 1.7% relative to placebo (tablets of calcium carbonate) in six college runners (A345). Performance averaged over both treatments was 2.3% better than in a trial when the runners took no tablets at all: a placebo effect. Bicarbonate loading also had a negligible effect on performance of 60 min of cycling in seven reasonably well-trained males (A1519). Although these studies had small sample sizes, they had the power of crossover designs, so they should have detected any modest enhancements. But surely bicarbonate works by reducing acidity in muscles, at least for sprints? See our review on the Training & Technology pages.
A "nitrogen-containing supplement" consisting of the glycine and arginine salt of alphaketoisocaproic acid (GAKIC) may be the next ergogenic nutritional for repetitive high-intensity exercise (A397). Like creatine, it's a natural constituent of cells, so it's unlikely to be banned.
Creatine supplementation: no effect on repeated sprint performance after 6 d in soccer players (A794, no data); increases in bench-press strength and lean body mass after 6 weeks in resistance-trained males (A796); increases in multiple sprint performance after 10 d, then a slight decline after 10 wk, in ice-hockey players (A797); non-significant 2% increase in jump height after 6 d in female softball players (A800); improved performance in a shuttle run after 3-5 wk in female soccer players, but no further increase after 13 wk (A1504); 2.4% increase in speed of 50-m intervals in male swimmers (A1506), but not significant in females (no data); reduction in fatigue in a multiple skating task in ice-hockey players (A1767). Conclusion: seems to work acutely for multiple sprints, but anabolic effects of longer-term use are less clear in these abstracts. For more information on creatine, see our review.
Breathe Right nasal strips enhanced performance of a simulated ice-hockey period in eight Division-1 college players (A1769, no data). Apparently it wasn't all a placebo effect, because the change in performance correlated strongly with change in nasal cross-sectional area. There's a report in the literature showing that the strips could work by cooling the blood going to the brain (see the review at this site), so maybe that's what happened here: ice-hockey players get really hot underneath all that protective clothing.
A group of highly trained male cyclists supplementing with antioxidants over a 5-d period tended to train harder and achieve a bigger improvement in maximum oxygen uptake than a placebo group (A1830). The antioxidants presumably worked by reducing muscle damage.
Fuel for
Exercise
Medium-chain triglycerides are an easily digested form of fat
that might provide a beneficial extra source of fuel in
ultra-endurance events. But when ingested by trained cyclists at low
(1.7%) or high (3.4%) concentration with a 10% glucose solution
during more than 3 h of cycling, they did not modify fuel utilization
or enhance performance relative to glucose only (A18; no performance
data). Another group got a negative result in a similar protocol with
4% medium-chain triglycerides in 6% carbohydrate (A475). It looks
like medium-chain triglycerides aren't worth taking after all.
Everyone knows that supplementing with water plus carbohydrate is better than water alone for steady endurance exercise of sufficient duration, but it's also better at maintaining bursts of maximal power during 2 h of cycling in the heat in trained, heat-acclimated cyclists (A22). Moderately trained subjects also performed intermittent exercise (1 min on, 1 min off, total 80 min) better with carbohydrate and water than with water alone (A23).
How short does the endurance exercise have to be before carbohydrate supplementation is ineffective? It didn't enhance performance of a 20-km cycling time trial (lasting about 30 min), relative to placebo (A472). The design was a crossover with 14 subjects in a very reliable test, so that's a definite negative result, folks. Whether carbohydrate is worth consuming during an hour of exercise is still not clear, but better to be safe than sorry. Anything longer than an hour, definitely take carbohydrate!
Carbohydrate even works as a placebo! The effect of a being told carbohydrate was in a sports drink amounted to a 2.7% increase in speed when the drink was consumed during a 40-km cycling time trial (A346). In another study of the placebo effect, fit non-athletes performed 4.6% better in a 60-min cycling test after 24 h of consuming non-caloric placebo meals vs fasting for 24 h (A1139).
What kind of carbohydrate meal should you consume before an endurance event? If you consume carbohydrate during the event, it probably doesn't matter: a pre-exercise carbohydrate meal with a high glycemic index produced a non-significant 0.8% enhancement relative to one with a low glycemic index in a time trial lasting 16 min performed after 2 h of fatiguing cycling (A471). (By the way, it's important to have some sort of meal: a non-caloric placebo meal slowed performance by 2.1%, even though the cyclists supplemented with carbohydrate during the exercise.) In the unrealistic situation of no carbohydrate during more than 2 h of cycling, a meal with a moderate glycemic index worked better than one with a high glycemic index (A879). See the Compeat article in the last issue of Sportscience News for more information on this topic.
Here's a bit more evidence in favor of high-fat diets for ultra-endurance events. Cycling time to exhaustion for highly trained triathletes after 7 d on a moderately high-fat diet (38% of total energy) showed a tendency to be less for five females and more for five males relative to times after a high-carbohydrate diet (73% of energy) (A1141, A1142). But the test lasted for about 2 h for the females, and they didn't burn more fat during the test when they switched to the fat diet. It was a 3-h test at lower intensity for the males, and they did burn more fat when they switched. My guess is the high-fat diet might work for females, too, if the diet is high enough in fat and the event is long and slow enough to make a difference to fuel use. The findings need to be confirmed with a bigger sample size, of course, and there may be individual differences in the response to different diets.
Training
Live-high train-low altitude training for 27 d enhanced 3000-m
times by 1.1% in elite 3000-m runners (A198). For various reasons the
final enhancement is likely to be 2-3 times greater. See our Training
& Technology pages for a
review that deals
with this and other studies.
The duration of interval-training workbouts had unusual effects in a novel study of 40-km time-trial performance in highly trained cyclists (A202): 4-min workbouts at race intensity had the greatest effect (2.8% enhancement), but 30-s intervals at twice the pace were almost as good, while everything else (1-min, 2-min, and 8-min workbouts at appropriate intensities) had a smaller effect or no effect. Stick to 4-min intervals until more research is done.
Hyperoxic interval training didn't enhance several measures of high-intensity performance in competitive female cyclists (A209). So don't start training with an oxygen mask yet.
Performance Symposium
Performance Enhancement: Can Scientists Detect It? That was
the title of a mini-symposium given by John Hawley (chair), Louise
Burke, and me. As first speaker, I claimed that the smallest
worthwhile enhancement is equivalent to the typical variation in
performance of a top athlete (e.g. 1.0% between international track
events). I then outlined the problems of detecting it using real
competitions and lab/field tests. Real competitions are the most
valid but are impractical for most well-controlled studies. Some
tests may be more reliable than real competitions, but a change in
performance in such a test may not mirror a change in a competition.
My conclusion: most claims for lack of enhancement are premature,
because the tests or study designs haven't been good enough to
exclude the possibility of small but worthwhile enhancements.
John reviewed the various types of lab endurance test, from the least reliable (constant-load tests to exhaustion) to the most reliable (time to complete an athlete's usual competitive distance). In what seemed the best test to date--a 2000-m time trial on a Concept II rowing ergometer--top rowers vary by only 0.6% between tests. We've been touting this test-athlete combination as a model system for research on short-term endurance performance, but now we're not so sure. Stephen Seiler has since pointed out that the power developed in rowing and on the ergometer is proportional to the cube of the speed, so percent variations in time to complete 2000 m translate into bigger percent variations in power. This argument applies to all wind-braked ergometers like the Concept II and Kingcycle, but not to treadmills or electrically braked ergometers. We're now doing a big rethink on the relative reliabilities of ergometer-based lab tests.
Louise showed that none of the research on the effect of a pre-exercise meal on performance passed all the reasonable criteria of acceptability (well-trained athletes as subjects, performance measured in a reliable and valid test, athletes allowed to supplement during the test...). She also made the important point that the experimental constraints necessary to get work published in high-impact mechanism-type journals often make the research inapplicable to real athletes in competitions. Is this the root of the ongoing debate about the nature of sport science?
