EFFECT OF ENDURANCE TRAINING ON ACTIVATORS OF GLYCOLYSIS IN MUSCLE DURING EXERCISE

Endurance training attenuates exercise-induced increases in blood lact ate at the same submaximal work late. Three intramuscular compounds th at influence muscle lactate production were measured in fasted nontrai ned (NT) and endurance-trained (T) rats. The T rats were subjected to a progressive endurance-training program. At the end of the program (1 1 wk), they were running 2 h/day at 31 m/min up a 15% grade 5 days/wk. NT and T rats were fasted for 24 h and then anesthetized (pentobarbit al, iv) at rest or after running for 30 min at 21 m/min (15% grade). B lood lactate levels were significantly lower in the T rats than in the NT rats after 30 min of running (2.3 +/- 0.2 vs. 3.9 +/- 0.2 mM). The lower blood lactate concentration was accompanied by lower plasma epi nephrine (2.8 +/- 0.4 vs. 6.0 +/- 0.8 nM), adenosine 3',5'-cyclic mono phosphate (0.36 +/- 0.02 vs. 0.50 +/- 0.03 pmol/mg), glucose 1,6-dipho sphate (26 +/- 2 vs. 40 +/- 5 pmol/mg), and fructose 2,6-diphosphate ( 3.2 +/- 0.2 vs. 4.3 +/- 0.3 pmol/mg) in white quadriceps muscle in T t han in NT rats. Red quadriceps muscle glucose 1,6-diphosphate and aden osine 3',5'-cyclic monophosphate were also lower in T than in NT rats. These adaptations may be responsible in part for the lower exercise-i nduced blood lactate in fasted rats as a consequence of endurance trai ning.