Jan 29, 2015News from the Lab
Research presented at the 2008 ACSM Annual Meeting offers new information about fueling during activity, the performance benefits of caffeine, the efficacy of some popular supplements, and more. Our nutrition expert shares her notes from the convention.
By Dr. Janet Rankin
Janet Rankin, PhD, is a Professor in the Department of Human Nutrition, Foods, and Exercise at Virginia Tech. Her teaching and research specialty is sports nutrition.
Does consuming protein during exercise improve performance and endurance? What does the latest research say about certain new supplements on the market or in the pipeline–are they safe, and do they work? What kind of physical toll does an Ironman competition, one of the most grueling events in all of sports, take on its participants? In May, I attended the 55th Annual Meeting of the American College of Sports Medicine (ACSM) in Indianapolis and came back with interesting insights into those questions and many others. Every year, the ACSM meeting provides a forum for some of the country’s leading nutrition researchers to present their studies, discuss research methods, and share ideas.
In this article, I’ll summarize several of the most interesting sports nutrition findings presented at this yearís meeting. Iíll also explain how the research results can help you provide better nutritional counseling to athletes in your own setting.
The debate over whether athletes should consume protein during and immediately after exercise is not new. Some researchers have found that carbohydrates on their own provide maximum performance and endurance benefits, and others have found that adding protein to the carbs offers optimal fueling. In one of the most interesting sessions at this year’s conference, Martin Gibala, PhD, Associate Professor of Kinesiology at McMaster University, reviewed recent research to shed new light on the question.
Gibala noted that at least three papers published since 2003–from the labs of John Ivy, PhD, of the University of Texas and Michael Saunder, PhD, of James Madison University–support adding protein to carbohydrate consumed during exercise. These studies have found increases in endurance performance ranging from 13 to 36 percent when protein is added to an athlete’s supplement. However, Gibala also referenced three recent papers (including one from his own lab) that found no boost in performance due to protein consumption. So what’s going on here?
In trying to sort out the conflicting results, Gibala noted that all three studies showing a benefit of protein used “non-energy matched” treatments: The athletes who consumed protein along with the carbs actually received more energy (measured in calories) than the athletes who consumed carbohydrate alone. In addition, endurance was measured in these studies using a time-to-exhaustion performance test.
Meanwhile, in the three studies showing no benefit to adding protein, athletes in both the protein and protein-free groups usually did receive energy matched treatments, with carbohydrate doses at the higher end of the recommended range. And the performance gauge used in these studies was a time trial, not an exhaustion test.
Based on that analysis, it may be fair to conclude that energy intake–not necessarily the presence of protein–is the key to optimal fueling during exercise. If that’s true, a similar performance or endurance benefit can be achieved by consuming a high amount of carbohydrate (roughly one gram per kilogram of body weight per minute), or alternatively, less carbohydrate with some added protein.
Gibala also took the analysis a step further, discussing the possible biochemical effects of ingesting protein during exercise. He said there is not enough evidence to conclude that protein replaces critical cellular compounds required during aerobic metabolism, or that protein directly affects central fatigue or muscle glycogen use. He also cited a lack of evidence that protein serves as an important energy substrate during exercise.
However, Gibala said he remains intrigued by the possibility that consuming protein during exercise may improve protein balance during recovery and thus aid in the repair of exercise-induced damage. A small body of research suggests that protein ingested during exercise reduces markers of muscle damage, such as serum creatine kinase, but Gibala worries that these markers can be misleading, so he said future research should focus on actual muscle function to assess recovery.
Although future studies may identify a specific benefit to consuming protein during activity, particularly for endurance athletes, the current evidence hasn’t revealed any special advantage. The best available information suggests that endurance athletes should focus on consuming enough energy, whether it comes from carbohydrate alone or a carb-protein blend.
PUMPED UP ABOUT CAFFEINE
Several studies presented at the ACSM meeting gave further support to the benefits of caffeine for athletes. Rather than just confirming old research, much of which focuses on caffeine’s effects on prolonged running, they branched out into three sports where the drug has not been extensively studied: cycling, shot put, and soccer.
For the latter, researchers in New Zealand asked premier-level soccer players to ingest six milligrams of caffeine per kilogram of body weight or a placebo one hour before performing a 90-minute simulated soccer test. Every 15 minutes during intermittent running, the players performed a passing skill test and a timed 15-meter sprint.
Interestingly, even though previous research has shown caffeine to improve running performance, there was no measurable effect on these athletes’ sprinting speed. However, the caffeine group did experience a statistically significant increase in passing accuracy. They did not attempt to explain exactly why this occurred, but it was likely due to central nervous system stimulation allowing for superior focus on the task.
The second study looked at shot putters, whose performance depends on brief, intense muscle power. Male and female collegiate throwers were asked to chew a piece of gum that contained either a placebo or 100 milligrams of caffeine–a fairly low dose–a few minutes before six throws of the shot.
When throwing, those who had chewed the caffeine-laced gum experienced a moderate performance boost. The average first throw of an athlete who chewed the caffeine gum was 9.63 meters, while that of an athlete who chewed the placebo gum was 9.05 meters. The average of all six throws was higher for the caffeine-consuming athletes as well.
While both these studies measured the value of caffeine consumed prior to exercise, the third focused on its role in recovery. Presented by Australian researcher John Hawley, PhD, the study followed up on previous research suggesting that caffeine influences glycogen metabolism.
To begin, body glycogen was drained from a group of trained athletes through a standard procedure involving prolonged exhaustive cycling and a low-carbohydrate meal. The next day, the athletes cycled again, followed by ingestion of either carbohydrate alone (four grams per kilogram of body weight) or the same amount of carbohydrate with eight milligrams of caffeine per kilogram of body weight.
Analysis of muscle biopsies from both groups after the second bout of cycling showed similar glycogen replacement after one hour, but 34 percent higher glycogen replacement among the caffeine-ingesting athletes after four hours. Analysis of key compounds involved in muscle metabolism suggests caffeineís effect on cellular calcium could explain the difference.
It’s notable that each of these studies demonstrates a performance benefit of caffeine despite using widely varying doses. The lowest dose, used in the study on throwers, could easily be obtained from beverages, while the higher doses would probably have to come from caffeine pills or another type of supplement. None of these studies sought to determine the minimum effective dose, so while the results are meaningful, further research is still needed. (For a link to a previous Training & Conditioning article on caffeine and its effect on athletic performance, see the “Resources” at the end of this article.)
Studies involving caffeine’s benefits can certainly grab the attention of anyone looking for an edge, but remember to proceed with caution: Competitive athletes may be tempted to “overdo it” with energy drinks, gels, and over-the-counter pills, which can put them at serious risk for health problems. Itís critical to remind athletes caffeine is a powerful stimulant that can increase heart rate and blood pressure, cause anxiety and sleep disturbance, and raise heat stress risk. Those who are interested in using caffeine as an ergogenic aid should be advised to stick with low doses–a cup of coffee or a soft drink for starters–which may provide the desired result without the potentially harmful side effects.
OF MICE AND MEN
Rarely does a supplement come along offering both a consistent ergogenic benefit and a demonstrable metabolic mechanism. Quercetin may fit into that category, and as a result it’s emerging as a supplement to watch. However, it has mostly been tested on rodents thus far, and its relative effect on humans is one of the main unanswered questions.
Quercetin is the major flavonol found in many fruits and vegetables. Its health benefits have been studied for years, and there’s some evidence it can help prevent cancer and other chronic diseases. More recently, it has been fed to mice and people to evaluate its effects on the immune system and athletic performance.
Most of this research has been performed by J. Mark Davis, PhD, Professor of Exercise Science at the University of South Carolina, and David Nieman, PhD, Professor in the Department of Health, Leisure, and Exercise Science at Appalachian State University. The two presented a symposium at the ACSM meeting and summarized several of their recent studies.
Davis’s lab has found that seven days of quercetin supplementation in mice increased endurance performance and helped build mitochondria, the “powerhouses” of cells, which generate most of the adenosine triphosphate (ATP, a key form of cellular energy) required by muscle tissue, the liver, and the brain. Quercetin feeding also increased voluntary activity by about 40 percent as measured with running wheels in the mouse cages. Davis says the heightened exercise capacity is likely due to increased ATP production through synthesis of more mitochondria. He also points to quercetin’s stimulating effect on the brain, caused by opposition of adenosine receptors (the same mechanism that accounts for caffeine’s stimulating effect).
Nieman described a major ongoing study in which quercetin is being provided to 1,000 people–not just athletes–to evaluate its effects. No specific results were presented at this time, but with the amount of interest generated by the rodent studies, it’s likely that more research involving humans will be conducted in the near future.
Lest we jump too quickly on the quercetin bandwagon, the presenters noted that studies using humans have so far yielded much less impressive results than those using rodents. Nieman has published a number of studies evaluating the effects of ingesting 1,000 milligrams of quercetin per day on performance and immune response in trained endurance athletes, and he has not yet found many significant benefits. In one notable exception, he reported that the incidence of upper respiratory tract infections after three days of strenuous exercise was reduced with quercetin supplementation.
One hypothesis to explain the discrepancy in results between animals and humans centers on training status. Nieman’s research used very highly trained athletes, who may have already maximized their aerobic performance and immune response through training, such that no further improvement could be observed by introducing quercetin. Support for this idea was presented by Stephen Chen, a member of Davis’s laboratory, who has studied quercetin supplementation in non-athlete college students and found that 1,000 milligrams per day for a week improved maximal aerobic capacity modestly (3.9 percent) and cycling endurance more significantly (13.2 percent).
If positive effects can be reliably proven in humans, quercetin supplementation will likely become popular. To date, no evidence of side effects from larger doses (for instance, 1,000 milligrams per day) has been found. Our average quercetin intake through diet is only about 25 milligrams per day, primarily coming from foods like apples and onions, though individuals who eat a diet rich in fruits and vegetables may consume significantly higher amounts.
BUFFERING THE BURN
Some athletes who compete in short, intense running or cycling events have experimented with bicarbonate ingestion in the hope of neutralizing the lactic acid that accumulates during heavy exercise. Their rationale is that buffering the acid delays muscle fatigue. However, bicarbonate use results in nausea and intestinal distress for some athletes, leading them to search for alternatives.
A fairly new compound, beta alanine, may provide similar acid-buffering benefits without the side effects. This amino acid, which occurs naturally in many proteins, increases the synthesis of a natural buffer inside the cell called carnosine. Several published studies have reported a carnosine increase of about 60 percent in muscle cells after four weeks of ingesting beta alanine, and researchers have observed a corresponding increase in maximum power during a graded cycle test and a muscle isokinetic endurance test to exhaustion.
New research presented at the ACSM meeting further demonstrates the value of beta alanine for resistance exercise. In one study, experienced resistance training athletes ingested 4.8 grams of beta alanine or a placebo for 30 days while following their regular resistance workout schedule. The athletes who took the beta alanine performed better in a resistance exercise test consisting of six sets of squats with 12 repetitions at 70 percent of one-rep max.
A second study, presented by a group from San Diego State University, tested the effect of one large dose of beta alanine (15 grams), consumed with a beverage containing three percent sucrose 30 minutes before and at intervals throughout a 60-minute endurance cycling session. In a time trial conducted immediately after the cycling bout, there was no performance effect from the beta alanine consumption. However, this was not entirely unexpected, since the average duration of the time trial was about 10 minutes–a length of time in which acid accumulation would probably not cause fatigue for this type of exercise.
Only a modest amount of research has been published on the ergogenic value of beta alanine, so strong conclusions cannot yet be drawn. However, results so far suggest it may offer benefits to athletes competing in sports that rely heavily on anaerobic glycolysis, where lactate accumulation can be a serious problem. Furthermore, studies using another buffer, sodium bicarbonate, typically show improvements in performance during maximum-effort bouts lasting between one and seven minutes. For these reasons, beta alanine warrants further inquiry.
BEHIND THE IRONMAN
Have you ever wondered how much energy is used during an Ironman race? These grueling events typically include a 2.4 mile swim, a 112 mile bicycle ride, and a marathon run, and not surprisingly, fueling and maintaining hydration are major challenges for the competitors. Measuring fuel utilization and dehydration rates would certainly be useful in this setting, but unfortunately, the data-capturing process is quite difficult and requires invasive, complex, and expensive procedures.
Walter Hailes and colleagues from the University of Montana and Appalachian State University recently collaborated to study a 39-year-old male athlete at the Ironman World Championship triathlon. The athlete consumed water that was chemically “labeled” with two non-radioactive isotopes–oxygen and hydrogen. Researchers measured the difference in loss rate of each of these labels by testing the athlete’s urine, and used the results to estimate total energy expended. In addition, muscle biopsies, blood samples, and body weight measurements were taken before and after the race.
The results were fascinating. The subject used an amazing 9,290 kilocalories over the course of the race, and experienced a 68 percent reduction in thigh muscle glycogen. He showed no evidence of hyponatremia (low blood sodium, a potentially dangerous condition in endurance competitions), but had a 7.5 percent loss of body weight (caused mainly by dehydration) and an 18 percent drop in blood plasma volume.
Unfortunately, the experimenters did not report the food and fluid consumption of the athlete to determine exactly what role nutrition played during the race. However, estimated total water turnover during the event was 16.6 liters, so he must have consumed a great deal of fluid to offset his dramatic water loss. If the athlete had consumed no fluid during the race (and yet somehow managed to finish), he would have lost roughly 21 percent of his body weight by the time he crossed the finish line.
This case study gives perspective to the challenges of Ironman competition, and provides a rarely seen glimpse into the intense effort it requires of the body. It also demonstrates that even elite athletes can usually benefit from counseling and recommendations on nutrition and fluid intake to help limit the loss of muscle glycogen, achieve optimal hydration status, and ultimately improve performance.
To see full references for the research discussed in this article, go to: www.training-conditioning.com/references.
To read a past Training & Conditioning article focusing on caffeine and its impact on athletic performance, go to: www.training-conditioning.com/2007/03/the_latest_buzz.html.