Training cessation does not alter GLUT-4 protein levels in human skeletal muscle.

The purpose of this study was to determine whether short-term training cessation resulted in reduced GLUT-4 protein levels. Endurance- (n = 12, ET) and strength-trained (n = 12) individuals (ST) were examined before and after 14 days of training withdrawal. GLUT-4 content was determined from muscle biopsy samples of the gastrocnemius in ET and the vastus lateralis in ST. Insulin sensitivity (oral glucose tolerance test) was significantly (P < 0.05) reduced in ET and ST with training cessation. GLUT-4 content was unaltered (P > 0.05) in both groups (92 and 100% of trained values for ET and ST, respectively). In ET, citrate synthase activity decreased significantly (P < 0.05) with training withdrawal (41.0 +/- 3.6 vs. 30.6 +/- 2.8 mumol.g-1.min-1); in ST no change was evident. The decrement in insulin sensitivity with the cessation of endurance- or resistance-oriented activity is therefore not associated with a reduction in GLUT-4 protein content. Muscle oxidative capacity and GLUT-4 content do not coincide with the removal of endurance training.