AMINO ACIDS AND ATHLETIC PERFORMANCE: A Mini Conference in Oxford
Andy M Stewart PhD
Scottish Institute of Sports Medicine and Sports Science, University of Strathclyde, Glasgow, G13 1PP, Scotland.
Sportscience 3(2), sportsci.org/jour/9902/ams.html, 1999 (1108 words)
Reviewed by Ron Maughan, Department of Biomedical Sciences, University of Aberdeen, Scotland AB25 2ZD
This report is a summary of a one-day conference aboutsupplementing with amino acids, particularly branched chain aminoacids, glutamine, and creatine. The conference was organised by LindyCastell of the Department of Biochemistry, University of Oxford. Itwas the second sports nutrition conference sponsored by Ajinomoto, amanufacturer of an amino acid supplement called Amino Vital.
The day commenced with Eric Newsholme discussing potential rolesof glutamine for cells of the immune system. Glutamine providesnitrogen for the synthesis of nucleotides required in the formationof DNA and RNA during lymphocyte proliferation and macrophageactivation. Newsholme speculated that the high rate of glutamineoxidation provides precision in the mechanisms that regulate suchsynthesis. For moderate levels of physical activity the body is ableto synthesize sufficient glutamine to meet demands, but in highlyactive or traumatized people the concentrations of plasma glutamineis lower than normal. He suggested that supplementing with glutaminemay be important for reducing the risk of infection. Lindy Castellsupported this idea when she presented data showing a decrease in thereported incidence of respiratory infections in athletes givenglutamine (0.1 g per kg body weight) after a marathon. Newsholme alsosuggested glutamine supplementation might reduce exercise-inducedtissue damage and help recovery from hard training.
Damian Bailey presented a study of the role glutamine might playin infection and acute mountain sickness in athletes exposed toaltitude. Twenty-two elite distance runners were randomly assignedeither to normal training or to four weeks of livingand training at reduced pressure(equivalent to 1640 m). Another 32 physically active males wererandomly assigned in a double-blind manner either to normal trainingor to four weeks of intermittent laboratory-based training while theybreathed nitrogen-enriched air equivalent to an altitude of 1640 m.Tests were conducted immediately pre and post intervention. Theincidence, duration, and severity of infectious illnesses increasedand plasma glutamine concentration decreased only in the athletesliving and training at altitude. Greater decreases in plasmaglutamine were evident in the elite athletes. In contrast, plasmaglutamine increased after intermittent altitude training,whereas there were no changes following normal training. Theseresults suggest that the duration of the hypoxic stimulus hasimportant implications for an individualís well-being duringaltitude exposure. Bailey also suggested that the greater the aerobicconditioning the greater the likelihood of infection at altitude, andthat symptoms (headache, nausea, sleep disturbance, lethargy) ofacute mountain sickness seem to be more prevalent in the moreaerobically fit athletes. Preliminary results from a lab-based studysuggest that the degree of arterial desaturation may be related tothe incidence of acute mountain sickness.
Some researchers think that a fall in the plasma concentration ofbranched-chain amino acids (BCAAs) contributes to fatigue inendurance events (see BCAAsin Kreider's review for an explanation), but attempts to enhanceendurance performance with BCAA supplementation have beeninconclusive. Until now, that is. Eva Blomstrand presented resultsindicating a 3-4% enhancement in marathon performance followingconsumption of a sports drink (PRIPPS Energy-2) containing BCAAs.Blomstrand also showed evidence that cognitive ability at theconclusion of a 30-km cross-country run was improved or maintainedfollowing supplementation with the same drink. Suggestive but notstrong evidence of long-term benefits of BCAA feeding on racehorsesand rugby players was also presented.
Jacques Poortmans gave the most controversial talk of the day,with a strong view that creatine supplementation does not work. Headmitted that positive benefits were found in laboratory studies, buthe suggested that any enhancements in performance observed in thefield are due to higher motivation to perform in that environmentthan in a laboratory setting. He also spoke about the side effects ofcreatine supplementation. One of the side effects is a gain in bodyweight, which is actually a benefit if it represents a gain in massof muscle protein. He claimed that an increase in body weight wasevident in less than half of 29 studies he reviewed, but if he wascounting only statistically significant changes in weight, it ispossible that most studies showed gains. The extent to which waterretention and protein synthesis contribute to the weight gainrequires further research: watch for a paper by Francaux andPoortmans in the European Journal of Applied Physiology. Finally, inhis view creatine supplementation does not cause harmful orunpleasant side effects, such as liver problems, muscle cramps, andgastrointestinal disorders.
Overtraining, Underrecovery,or Underperformance?
For the final act of the day, an invited panel discussed theovertraining syndrome, then suggested renaming it theunderperformance syndrome. The panel objected to the termovertraining, because they didn't like the implied emphasis ontoo much training as the cause of not performing well. In the ensuingdebate, some members of the audience agreed with the proposed newterm, while others thought underrecovery was a betterdescription.
Do we need a term to encompass poor performance due to factorsother than training stress? Yes, in my opinion, but only if there isgood evidence that these factors all cause poor performance in thesame way. Will we want to replace overtraining with this term? Not ifwe want to talk about poor performance due to too much training.Whether underrecovery is a better way to describe such poorperformance and whether the term will catch on remains to beseen.
Thanks to Lindy Castell for valuable comments during thepreparation of this report.
Antonio J, Street C (1999). Glutamine: a potentially usefulsupplement for athletes. Canadian Journal of Applied Physiology 24,1-14
Kreider RB (1999). Effects of protein and amino-acidsupplementation on athletic performance. Sportscience 3(1), sportsci.org/jour/9901/rbk.html(5579 words)