Recent studies have shown that the 5'AMP-activated protein kinase (AMPK) is an important signaling intermediary leading to exercise-induced activation of muscle glucose utilization. We determined the effects of exercise on isoform-specific AMPK activity (α1 and α2) in human skeletal muscle. Needle biopsies of vastus lateralis muscle were obtained from seven healthy subjects at rest, after 20 and 60 min of cycle ergometer exercise at 70% of VO₂max, and 30 min following the 60 min exercise bout. In comparison to the resting state, AMPK α2 activity significantly increased at 20 and 60 min of exercise, and remained at a higher level with 30 min of recovery. In contrast, AMPK α1 activities were at basal levels at 20, 60 min of exercise and 30 min of recovery. The same subjects exercised for 20 min at 50% of VO₂max. Exercise at this intensity did not change α2 activity, and similar to exercise at 70% of VO₂max, there was no significant change in all activity. These results suggest that the α2-containing AMPK complex, rather than α1, may be involved in the metabolic responses to exercise in human skeletal muscle, and that the exercise intensity more than 50% VO₂max may be required to activate AMPK α2. Studies should be performed to develop an exercise program that efficiently activates AMPK α2 -and thereby results in improved glucose metabolism.

DESCENTE SPORTS SCIENCE Vol.22/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE