SAN FRANCISCO--Elite athletes sometimes push themselves so hard while training that their performance begins to suffer. Now a physiologist has measured the toll this overtraining can take on athletic ability, the immune system, and mood. Experts say that the finding, reported here today at the Experimental Biology '98 meeting, could lead to a useful test for catching athletes before they overtrain.
Symptoms of overtraining include fatigue, anxiety, elevated resting heart rate, increased susceptibility to illness, and decreased athletic performance. But there's no definitive way to detect overtraining before it's too late to reverse the symptoms. "Every person has a different threshold for overtraining," says Erin Lehmer, an exercise physiology student at Fort Lewis College in Durango, Colorado.
Lehmer sought physiological markers of overtraining that could be quantified before performance tapers off. She asked a group of five endurance athletes--marathoners, cyclists, and a triathlete--to crank up their training by 30% for a month. Plasma concentrations of glutamine--an amino acid that fuels white blood cell proliferation--dropped 11%, indicating a dive in immune function. Total white blood cell counts also fell, and the study subjects all reported getting sick. Anaerobic power decreased almost 8%, and overall scores on a mood assessment test fell 18%. A control group training at a less intense pace had no changes and remained healthy.
The study identifies factors that could help diagnose this syndrome in its early stages. "People have trouble even identifying what overtraining is," says Bryan Bergman, an exercise physiologist at the University of California, Berkeley. Glutamine's potential for signaling overtraining is particularly exciting, he says, because "if you have markers you could take on a regular basis, then you could test elite athletes and rest them when they approach that line."