Dietary intervention and training in swimmers

To ascertain if muscle damage occurred in swimmers as a result of high-intensity training and to find if fluid and dietary manipulation could affect muscle damage, we studied 40 members of the University of Florida swimming team using creatine kinase (CK) and lactic dehydrogenase (LDH) as markers of muscle damage during a 6-month period of intensive training. During this time, training intensity, fluid intake during exercise and dietary supplementation were all modified one by one to examine their individual effects. During a control period of 4 weeks, all swimmers drank water before and during (120 min) workouts. CK in men at the end of this period averaged 315, SD 122 (normal less than 170 IU.l-1). Half of the swimmers were then given 500 ml of a glucose-electrolyte solution (GES) (Na 21 mmol.l-1, Cl 13 mmol.l-1, K 2.5 mmol.l-1, PO4 5 mmol.l-1 and glucose 6%) before workouts and twice at intervals during the workout, while half continued to drink the same volume of water. One week after division into fluid groups, the workout intensity was increased by about 10%. Another week later CK had increased to 500, SD 180 IU.l-1 in swimmers drinking water, but fell to 280, SD 105 IU.l-1 in those drinking GES (P less than 0.05). The second phase of the study began after a 4-week control period during which all athletes drank water before and during workouts. The swimmers were divided into four matched groups.(ABSTRACT TRUNCATED AT 250 WORDS)