Effect of the volume and intensity of exercise training on insulin sensitivity

Abstract

Physical activity enhances insulin action in obese/overweight individuals. However, the exercise prescription required for the optimal enhancement is not known. The purpose of this study was to test the hypothesis that exercise training consisting of vigorous-intensity activity would enhance insulin sensitivity more substantially than moderate-intensity activity. Sedentary, overweight/obese subjects (n = 154) were randomly assigned to either control or an exercise group for 6 mo: 1) low-volume/moderate-intensity group [ approximately 12 miles walking/wk at 40-55% peak O2 consumption (Vo2 peak)], 2) low-volume/high-intensity group ( approximately 12 miles jogging/wk at 65-80% Vo2 peak), and 3) high-volume/high-intensity group ( approximately 20 miles jogging/wk at 65-80% Vo2 peak). Training volume (miles/wk) was achieved by exercising approximately 115 min/wk (low-volume/high-intensity group) or approximately 170 min/wk (low-volume/moderate-intensity and high-volume/high-intensity groups). Insulin action was measured with an insulin sensitivity index (SI) from an intravenous glucose tolerance test. In the control group, there was a decrement (P < 0.05) in SI. In contrast, all the exercise groups significantly (P < 0.05) increased SI; the relative increment in the low-volume/moderate-intensity and high-volume/high-intensity groups ( approximately 85%) were greater than in the low-volume/high-intensity group ( approximately 40%). In conclusion, physical activity encompassing a wide range of intensity and volume minimizes the insulin resistance that develops with a sedentary lifestyle. However, an exercise prescription that incorporated approximately 170 min of exercise/wk improved insulin sensitivity more substantially than a program utilizing approximately 115 min of exercise/wk, regardless of exercise intensity and volume. Total exercise duration should thus be considered when designing training programs with the intent of improving insulin action.

Walking and inflammatory markers in individuals screened for type 2 diabetes

“…The finding that walking activity status was not associated with fasting insulin levels is in contrast to other studies (Houmard et al 2004, Mayer-Davis et al 1998). …”

Differential relationship between physical activity and progression to diabetes by glucose tolerance status: the Inter99 Study

“…Physical activity can reduce muscle insulin resistance [20,21]; however, studies have also shown that physical activity is associated with a lower intrahepatic fat content [22], and that intrahepatic fat content is associated with hepatic insulin sensitivity [23,24]. Consequently, a differential effect of physical activity on progression to diabetes in individuals with i-IFG and i-IGT could be expected.…”

Exercise intensity and insulin sensitivity: how low can you go?

“…Recently, Houmard et al [25] investigated whether vigorous-intensity exercise training would improve insulin action to a greater degree than moderate-intensity training. The participants in this study [25] comprised 154 sedentary, overweight men and women with pre-diabetes (i.e.…”

“…The participants in this study [25] comprised 154 sedentary, overweight men and women with pre-diabetes (i.e. dyslipidaemia considered as a pre-diabetic state).…”

“…However, exercise prescriptions that incorporated~170 min/week improved SI significantly more than a programme of~115 min/week, independently of exercise intensity. These workers concluded that exercise duration should be considered when designing exercise training interventions, with the intent of improving insulin sensitivity [25], and based upon an examination of the other dose-response variables, suggested that the theoretical minimal activity to maintain optimal health is about 10-20 km/week of walking or jogging (2,930-4,186 kJ) or other energy expenditure equivalent [26]. Other investigators [27,28] have also reported that low-intensity exercise is just as effective as more intense exercise for improving insulin sensitivity in people with mild insulin resistance.…”