Effect of exercise intensity on skeletal muscle AMPK signaling in humans

Abstract

The effect of exercise intensity on skeletal muscle AMP-activated protein kinase (AMPK) signaling and substrate metabolism was examined in eight men cycling for 20 min at each of three sequential intensities: low (40 ± 2% Vo2 peak), medium (59 ± 1% Vo2 peak), and high (79 ± 1% Vo2 peak). Muscle free AMP/ATP ratio only increased at the two higher exercise intensities (P < 0.05). AMPK α1 (1.5-fold) and AMPK α2 (5-fold) activities increased from low to medium intensity, with AMPK α2 activity increasing further from medium to high intensity. The upstream AMPK kinase activity was substantial at rest and only increased 50% with exercise, indicating that, initially, signaling through AMPK did not r..