Medicine & Science in Sports & Exercise:
D-30 Free Communication/Poster - Macronutrient Metabolism II - Carbohydrates: JUNE 2, 2011 1:00 PM - 6:00 PM: ROOM: Hall B
Stevens, Michelle M.1; Gribok, Andrei2; Rumpler, William2; DiPietro, Loretta FACSM1
1The George Washington University School of Public Health and Health Services, Washington, DC. 2The United States Department of Agriculture, Beltsville, MD.
(No relationships reported)
Glucose tolerance declines progressively with aging, and this can be attributed primarily to factors secondary to aging, such as changes in body composition, low levels of physical activity, and insufficient insulin secretion. Indeed, impaired B-cell compensation to aging- and disuse-related insulin resistance may accelerate the risk of developing post-challenge hyperglycemia and consequent type 2 diabetes and cardiovascular disease in older age.
PURPOSE: To examine the impact of post-meal exercise on post-prandial and 24-h glycemic control in older people at risk for type 2 diabetes.
METHODS: Older (67±6 yrs) subjects (N=7) underwent three 48-h stays in a whole-room calorimeter, and these visits were spaced 4 weeks apart. The first 24-h served as a control day, whereas on the second day, subjects underwent one of three randomly-ordered exercise protocols: 1) 45-min of treadmill walking (3 METs) at 10:30 AM; 2) 45-min of treadmill walking (3 METs) at 4:30 PM; or 3) 15-min of treadmill walking (3 METs) performed 30 min after each meal. Over the 48-h study period, subjects consumed weight-standardized meals (50% carbohydrate/30% fat). Energy expenditure was measured continuously by respiratory (O2 and CO2) exchange and glucose concentrations determined by a continuous glucose monitoring system (CGMS).
RESULTS: Post-meal exercise significantly lowered 24-h average (121±15 vs. 111±11 mg·dL-1; p<0.05) and 3-h post-dinner (146±27 vs. 133±26 mg·dL-1; p<0.01) glucose concentrations, but not 3-h post lunch (120±18 vs. 115±21 mg·dL-1) concentrations. We observed no significant effects of 45-min of sustained walking performed in the morning or in the afternoon on improved post-prandial or 24-h glycemic control.
CONCLUSIONS: Short bouts of exercise performed after each meal (during the period of absorption) may be more effective in improving post-meal and 24h hyperglycemia than larger sustained bouts performed in the morning or afternoon, as muscle contractions per se will stimulate glucose uptake independent of any defects in endogenous insulin secretion. This may be especially so following the evening meal.
Supported by NIH/NIA Grant R21 AG031550.