Effects of Exercise Training on Glucose Homeostasis

Abstract

OBJECTIVE -To determine the effect of a 20-week endurance training program in healthy, previously sedentary participants on measures derived from an intravenous glucose tolerance test (IVGTT).RESEARCH DESIGN AND METHODS -An IVGTT was performed before and after a standardized training program in 316 women and 280 men (173 blacks and 423 whites). Participants exercised on cycle ergometers 3 days per week for 60 sessions. The exercise intensity was progressively increased from 55% VO 2max for 30 min per session to 75% VO 2max for 50 min per session.RESULTS -Mean insulin sensitivity increased by 10% (P Ͻ 0.001) following the intervention, but the variability in the changes was high. Men had larger improvements than women (P ϭ 0.02). Improvements in fasting insulin were transitory, disappearing 72 h after the last bout of exercise. There were also significant mean increases in the glucose disappearance index (3%, P ϭ 0.02) and in glucose effectiveness (11%, P Ͻ 0.001), measures of glucose tolerance and of the capacity of glucose to mediate its own disposal, respectively. The acute insulin response to glucose, a measure of insulin secretion, increased by 7% in the quartile with the lowest baseline glucose tolerance and decreased by 14% in the quartile with the highest baseline glucose tolerance (P Ͻ 0.001). The glucose area below fasting levels during the IVGTT was reduced by 7% (P ϭ 0.02).CONCLUSIONS -Although the effects of structured regular exercise were highly variable, there were improvements in virtually all IVGTT-derived variables. In the absence of substantial weight loss, regular exercise is required for sustained improvements in glucose homeostasis. Diabetes Care 28:120 -126, 2005

Towards the minimal amount of exercise for improving metabolic health: beneficial effects of reduced-exertion high-intensity interval training

“…No other study has investigated the effects of HIT on insulin sensitivity in women. Following a traditional aerobic exercise intervention in a large cohort, insulin sensitivity improved to a greater degree in men when compared with women but (similar to our study) the female participants had a higher baseline level of insulin sensitivity which may have impacted on the subsequent training response (Boule et al 2005). …”

“…Alternatively, it could be that our small sample included several non-responders. Previous studies have comprehensively demonstrated that following a period of exercise training part of the population will not adapt for specific parameters (non-responders), and for insulin sensitivity this has been shown to be the case for up to 40% of the population (Boule et al 2005;Vollaard et al 2009;Bouchard and Rankinen 2001). Therefore, further studies with larger sample sizes will be needed to confirm or refute our initial observations.…”

Early-onset type 2 diabetes in obese white subjects is characterised by a marked defect in beta cell insulin secretion, severe insulin resistance and a lack of response to aerobic exercise training

“…In 2005 a group in Canada reported the effects of exercise training on glucose homeostasis in almost 600 subjects, using a standard IVGTT [30]. While they observed a mean increase of 10% in insulin sensitivity after 20 weeks of aerobic training, between-subject variations in metabolic response to exercise were large, not unlike our study.…”

Influence of sex on total and regional fat loss in overweight and obese men and women

“…19 Together, these results would suggest that men might experience greater improvements in health risk for a given amount of weight loss or reduction in WC. For a similar weight loss, middleaged men and women are reported to have similar improvements in their lipid profile, 20 but may have a greater improvement in glucose metabolism 21 and insulin sensitivity. 4,5 Regardless of whether sex differences exist, it is clear that decreases in visceral adiposity are associated with improvements in health risk.…”