Exercise-induced changes in insulin action and glycogen metabolism in elderly adults.
OBJECTIVE
Although data suggest that physical activity is associated with decreased insulin resistance, recommendations for exercise training are not specific for age or level of obesity. Therefore, we examined the influence of moderate-intensity (50% of VO2max) exercise training (MI) versus high-intensity (75% of VO2max) exercise training (HI) on insulin-stimulated glucose disposal (ISGD) in elderly individuals.


METHODS
Following medical examinations, 21 overweight (body mass index = 29 +/- 1 kg x m(-2)) elderly (74 +/- 1 yr) subjects were randomized to 1) HI, 2) MI, or a 3) nonexercising control group. Subjects enrolled in HI or MI completed a 12-wk exercise training regimen designed to expend 1000 kcal x wk. ISGD was assessed using a hyperinsulinemic, euglycemic clamp pre- and postintervention. ISGD was corrected for hepatic glucose production (glucose Ra) using a constant rate infusion of [6,6-H2]glucose and determined during the last 30 min of the clamp by subtracting glucose Ra from the exogenous glucose infusion rate. Nonoxidative glucose disposal was calculated using indirect calorimetry. Body composition testing was completed using dual energy x-ray absorptiometry.


RESULTS
ISGD increased by approximately 20% with HI (Delta of 1.4 +/- 0.5 mg x kg(-1) FFM.min(-1)). However, ISGD did not change (Delta of -0.4 +/- 0.1 mg x kg(-1) FFM.min(-1)) with MI and was not different (Delta of -0.2 +/- 0.1 mg x kg(-1) FFM.min(-1)) in the control group. Nonoxidative glucose disposal increased with HI (Delta of 1.4 +/- 0.5 mg x kg(-1) FFM.min(-1)), but there was no change in nonoxidative glucose disposal with MI or in the control group. No change in body weight or percentage of body fat was observed in any group.


CONCLUSIONS
In weight-stable subjects, MI resulted in no change in ISGD, and the improvement in ISGD with HI was completely reliant on improvements in nonoxidative glucose disposal.
Nutrition, Metabolism, and Exercise Laboratory, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
Robert H
RH
Coker
Nicholas P
NP
Hays
Rick H
RH
Williams
Amy D
AD
Brown
Scott A
SA
Freeling
Patrick M
PM
Kortebein
Dennis H
DH
Sullivan
Raymond D
RD
Starling
William J
WJ
Evans
D000368:Aged; D001131:Arkansas; D015444:Exercise / Q000502:physiology*; D005260:Female; D006003:Glycogen / Q000097:blood / Q000378:metabolism*; D006801:Humans; D006946:Hyperinsulinism / Q000097:blood / Q000378:metabolism*; D008297:Male
D006003:Glycogen