Effect of reduced training and training cessation on insulin action and muscle GLUT-4.
This study examined the impact of a 50% reduction in training frequency or training cessation on insulin action and muscle GLUT-4 protein concentration. Middle-aged individuals were tested before and after 12 wk of exercise training (4 days/wk, 40-45 min/day). Subjects then either maintained training (n = 9), reduced training frequency by 50% (n = 11), or stopped exercising (n = 10) for the ensuing 2 wk. GLUT-4 protein concentration and insulin action (insulin sensitivity index, as determined by the minimal model) increased (P < or = 0.05) by an average of 1.6- and 1.9-fold, respectively, with the 12 wk of training. Insulin action and GLUT-4 did not increase further with the additional 2 wk of training in the maintained training group. Similarly, insulin sensitivity index and GLUT-4 concentration remained at trained levels when training frequency was reduced by 50% for 2 wk. GLUT-4 concentration and insulin action, however, were not different from sedentary values after 14 days of training cessation. These findings indicate that a 14-day 50% reduction in exercise frequency maintains the improvements in GLUT-4 protein concentration and insulin action gained with endurance training in moderately trained middle-aged adults; in contrast, these adaptations are largely lost with training cessation.
Houmard
J A
JA
Human Performance Laboratory, East Carolina University, Greenville, North Carolina 27585, USA.
Tyndall
G L
GL
Midyette
J B
JB
Hickey
M S
MS
Dolan
P L
PL
Gavigan
K E
KE
Weidner
M L
ML
Dohm
G L
GL
D000328:Adult; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007328:Insulin / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009004:Monosaccharide Transport Proteins / Q000502:physiology*; D009132:Muscles / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology*
D007328:Insulin; D009004:Monosaccharide Transport Proteins