INFLUENCE OF ELEVATED MUSCLE TEMPERATURE ON METABOLISM DURING INTENSE, DYNAMIC EXERCISE

This study examined the effects of elevated muscle temperature on musc le metabolism during exercise. Seven active but untrained men complete d two cycle ergometer trials for 2 min at a workload estimated to requ ire 115% maximal oxygen uptake (VO2) either without pretreatment (CT) or after having their thigh wrapped in a heating blanket for 60 min be fore exercise (HT). HT increased (P < 0.01) muscle temperature (T-m) a nd resulted in a difference in T-m between the two trials before (Delt a = 1.9 +/- 0.1 degrees C, P < 0.01) and after exercise (Delta = 0.6 /- 0.2 degrees C, P < 0.05). HT did not affect rectal temperature or p lasma catecholamines. In addition, these parameters were not different between CT and HT either before or after exercise. No differences in resting intramuscular concentrations of the adenine nucleotides (ATP, ADP, AMP) or their degradation products (inosine 5'-monophosphate, amm onia), lactate, glycogen, creatine phosphate, or creatine were observe d between HT and CT. During exercise, the magnitude of ATP degradation and inosine 5'-monophosphate and ammonia accumulation was higher (P < 0.05) in HT compared with CT. Although preexercise concentrations of glycogen and lactate were not different between the two trials, postex ercise lactate concentration was higher (P < 0.05) and glycogen lower (P < 0.05) in HT compared with CT. In addition, net muscle glycogen us e was higher (P < 0.05) in HT. It is concluded that an elevated T-m pe r se increases muscle glycogenolysis, glycolysis, and high energy phos phate degradation during exercise. These alterations may be the result of an increased rate of ATP turnover associated with the exercise and /or changes in the anaerobic/aerobic contribution to ATP resynthesis.