Exercise training amount and intensity effects on metabolic syndrome (from Studies of a Targeted Risk Reduction Intervention through Defined Exercise)

Abstract

Although exercise improves individual risk factors for metabolic syndrome (MS), there is little research on the effect of exercise on MS as a whole. The objective of this study was to determine how much exercise is recommended to decrease the prevalence of MS. Of 334 subjects randomly assigned, 227 finished and 171 (80 women, 91 men) had complete data for all 5 Adult Treatment Panel III-defined MS risk factors and were included in this analysis. Subjects were randomly assigned to a 6-month control or 1 of 3 eight-month exercise training groups of (1) low amount/moderate intensity (equivalent to walking approximately 19 km/week), (2) low amount/vigorous intensity (equivalent to jogging approximately 19 km/week), or (3) high amount/vigorous intensity (equivalent to jogging approximately 32 km/week). The low-amount/moderate-intensity exercise prescription improved MS relative to inactive controls (p <0.05). However, the same amount of exercise at vigorous intensity was not significantly better than inactive controls, suggesting that lower-intensity exercise may be more effective in improving MS. The high-amount/vigorous-intensity group improved MS relative to controls (p <0.0001), the low-amount/vigorous-intensity group (p = 0.001), and the moderate-intensity group (p = 0.07), suggesting an exercise-dose effect. In conclusion, a modest amount of moderate-intensity exercise in the absence of dietary changes significantly improved MS and thus supported the recommendation that adults get 30 minutes of moderate-intensity exercise every day. A higher amount of vigorous exercise had greater and more widespread benefits. Finally, there was an indication that moderate-intensity may be better than vigorous-intensity exercise for improving MS.

Figure 1

Flowchart of randomization graduates, dropouts and reasons for dropout. ^a 2 out of 3 due to preexisting injuries. ^b 4 out of 12 due to preexisting injuries. ^c 3 out of 3 due to preexisting injuries. Note: 56 graduates were excluded from the present analysis due to missing data for one or more of the ATPIII-defined metabolic syndrome criteria.

Figure 2

The effects of exercise amount and intensity on mean changes in MS Z-score (panel A) and ATPIII Score (panel B) are shown. Error bars show SE. Two-way ANOVA for a main group effect was significant (p<0.0005). Post hoc tests for group differences are shown. ANOVA results for gender effect (p=0.70) and gender by group interaction effect (p=0.085) were not significant.

Figure 3

The effects of exercise amount and intensity on mean changes in MS Z-score (panel A) and Insulin Sensitivity (panel B) are shown for men and women separately. Error bars show SE. Two-way ANOVA results for a main group effect were significant (p<0.0005) and the post hoc tests for specific group differences are the same as shown in Figure 2. The test for gender by group interaction was not significant (p=0.085). The test for a main gender effect (p=0.70) was also not significant. ^aUnits for insulin sensitivity index were mU/L/min.

Figure 4

The number of subjects with 0, 1, 2, 3, 4, or 5 of the ATPIII criteria and with ATPIII defined metabolic syndrome for Controls (panel A), Low Amount/Moderate Intensity (panel B), Low Amount/Vigorous Intensity (panel C), and High Amount/Vigorous Intensity (panel D) are shown. The percentage change in ATPIII prevalence was +19% in Controls, −44% in the Low Amount/Moderate Intensity, −12% in the Low Amount/Vigorous Intensity, and −44% in the High Amount/Vigorous Intensity groups.

Figure 5

Prevalence of risk factors in all exercisers (n=130) before and after exercise training. * p≤0.05 indicates significant change from pre to post. WC = waist circumference; HDL-C = HDL-cholesterol; TG = triglycerides; FBG = fasting blood glucose; MS = metabolic syndrome based on ATPIII-defined criteria.