| Summary |
The purpose of this thesis was to examine the effects of different intensities of exercise training on insulin sensitivity. Cardiorespiratory fitness and body composition were also examined. Eleven men and 11 women (average age, 52.5 years) who were previously sedentary, trained at 3 different exercise intensities. Training consisted of a ramp phase (0-3 months) and 6 months of exercise training at low intensity (40-55% of VO2 max, 1200-1400 Kcal/wk) n=6, medium intensity (65-80% VO2 max, 1200-1400 Kcal/wk) n=3, high intensity (65-80% VO2 max, 2000-2200 Kcal/wk) n=6, and a control group, n=7. Insulin sensitivity was assessed using Bergman's minimal model 3-hour intravenous glucose tolerance test 24-hours post exercise training, 96-hours post exercise training, and 2 weeks post exercise training. Body composition was determined by hydrostatic weighing and cardiorespiratory fitness by a maximum graded exercise test at sedentary, 24-hours post training, and 2-weeks post exercise cessation. Insulin sensitivity significantly improved by 57% from sedentary to 24-hours post exercise training, 33% from sedentary to 96-hours post exercise training, and 22% from sedentary to 2 weeks post training. There were no significant differences between intensities. Cardiorespiratory fitness significantly improved as indicated by maximal treadmill time from sedentary (706.7 ± 20.6 sec) to 24-hour post exercise training (819.6 ± 20.6 sec) and 2-week post exercise training (794.8 ± 20.6 sec). There were no significant changes in body mass or composition The results of this study indicate that all exercise intensities were beneficial at 24-hours post exercise training. At 96-hours post exercise training the medium exercise intensity showed the highest elevation in insulin sensitivity when compared to sedentary versus the low and high exercise intensities. At 2-weeks post exercise cessation, the low and high exercise intensity groups maintained insulin sensitivity, whereas the medium intensity returned to baseline values when compared to the sedentary condition. We concluded 6 months of exercise training improves insulin sensitivity, regardless of the intensity in previously sedentary, middle-aged men and women. However due to the small group sizes, we are cautious about drawing any conclusions when comparing exercise intensities. |
