The effects of aerobic, resistance, and combination training on insulin sensitivity and secretion in overweight adults from STRRIDE AT/RT: a randomized trial

Abstract

Most health organizations recommend a combination of aerobic training (AT) and resistance training (RT), yet few studies have compared their acute (within 24 h of the last exercise bout) and sustained (after 14 days of no exercise training) effects alone and in combination on glucose metabolism. The present study (Studies Targeting Risk Reduction Interventions through Defined Exercise-Aerobic Training and/or Resistance Training) compared the effects of AT, RT, and the combination (AT/RT) on insulin action at both acute and sustained phases. Subjects (N = 196) were 18-70 yr old (mean age = 50 yr), overweight (mean body mass index = 30 kg/m2), sedentary with moderate dyslipidemia, and were randomized into one of three 8-mo exercise groups: 1) RT: 3 days/wk, 8 exercises, 3 sets/exercise, 8-12 repetitions/set; 2) AT: equivalent to ∼19.2 km/wk (12 miles/wk) at 75% peak O2 consumption; 3) AT/RT: the combination of AT and RT. One hundred forty-four subjects completed the intervention. Eighty-eight subjects completed all pre- and postintervention testing visits. Insulin sensitivity, glucose effectiveness, and disposition index were measured via a frequently sampled intravenous glucose tolerance test with subsequent minimal model analyses. AT/RT resulted in greater improvements in insulin sensitivity, β-cell function (disposition index), and glucose effectiveness than either AT or RT alone (all P < 0.05). Approximately 52% of the improvement in insulin sensitivity by AT/RT was retained 14 days after the last exercise training bout. Neither AT or RT led to acute or chronic improvement in sensitivity index. In summary, only AT/RT (which required twice as much time as either alone) led to significant acute and sustained benefits in insulin sensitivity

Trial registration: ClinicalTrials.gov NCT00275145.

Figures

Fig. 1.

The values are post- minus pretraining (means ± SE). These parameters are all derived from the intravenous glucose tolerance test (IVGTT) with minimal model analyses. Top left: insulin sensitivity (Si; units are mU·l−1·min−1). Top right: acute insulin response to glucose infusion (AIRg; units are mU·l−1·min−1) = area under the insulin curve during first 10 min of test. Bottom right: glucose effectiveness (Sg; units are per minute), which is defined as the ability of glucose to cause its own uptake. Bottom left: disposition index (DI; no units for this term as the units for Si and AIRg cancel each other out) = AIRg × Si and is considered a measure of β-cell function. All P values refer to significant differences between the group indicated [aerobic training (AT) or resistance training (RT)] vs. the combination AT/RT based on post hoc tests for significant difference between groups. That is, AT/RT was significantly different from both AT and RT for Si, Sg, and DI.

Fig. 2.

Retention of the improvement in Si 14 days after the last exercise training bout. Of the 23 subjects in AT/RT with Si measured before training and 24-h after the last training bout, only 16 of these subjects also had IVGTT data at the 14-day detraining time point. To determine the percentage of the improvement in Si that was sustained after 14 days of no exercise, we used only subjects who had IVGTT data at all three time points. Just over one-half of the effect was sustained after 14 days. This amount trended toward significance (P = 0.092). The other two groups (AT and RT) did not have a significant improvement in Si at 24 h, and there was no change at 14 days. Values are means ± SE; N, no. of subjects.

Fig. 3.

IVGTT raw data figures for each group for glucose values and insulin values over the 180 min of the IVGTT. Left: the three graphs are of the glucose values during the IVGTT for the AT (top), RT (middle), and AT/RT (bottom) groups. Right: the three graphs are of the insulin values during the IVGTT for the AT (top), RT (middle), and AT/RT (bottom) groups. Insets for each graph show expanded views for the 19-min (just before the insulin infusion at 20 min) through 80-min time periods. These insets emphasize the much larger decrease in glucose values (for the graph insets on the left) for the postexercise training vs. pretraining curves, over this time period, observed in the AT/RT group compared with AT and RT only groups. The insets on the right (insulin graphs) show virtually no difference in insulin responses for the AT- and RT-only groups compared with a noticeable reduction in the insulin curve observed after training vs. before training in the AT/RT group. Values are means ± SE.