Title

Effects of exercise at different times of the day on postprandial lipemia and endothelial function

Date of Completion

January 2006

Keywords

Health Sciences, Recreation|Biology, Physiology

Degree

Ph.D.

Abstract

Twelve healthy and recreationally trained men (age = 22.3y ± 2.5, weight = 80.7 ± 12.4, BMI = 25.1 ± 3.1, triglycerides (TAG) = 62.1 ± 24.1mg/dL, glucose = 5.12 ± 0.8mmol/L, insulin = 63.4 ± 51.4pmol/L, and non-esterified fatty acids (NEFA) = 0.22μ ± 0.10μEq/L) participated in this study that examined the effects of previous exercise on metabolic, hormonal and endothelial responses to an oral fat tolerance test (OFTT). Subjects completed three OFTT trials all beginning at 11:15 AM in a balanced, crossover design that included exercise sixteen hours (EX-16), exercise four hours before (EX-4) and no exercise (NE) before the fat load. Blood was collected before and after the meal and hourly for six hours. Ultrasound measurements of the brachial artery were made before and at 2, 4 and 6 hours after the meal. The OFTT consisted of 13 kcal/kg and 1.4 g fat per kg body weight. Dietary intake and exercise were standardized 4 days prior to each intervention. The exercise session consisted of 6 resistance exercises and 30 min of running on a treadmill. ^ Compared to NE, there were, significant (P<0.05) decreases in triglyceride area under the curve (AUC) during EX-16 (-26%) and EX-4 (-15%). Compared to NE, there were decreases in insulin AUC during EX-16 (-7%, P<0.05), and EX-4 (-5%, n.s). Compared to NE, there was a significant decrease in glucose AUC during EX-16 (-7%). Finally compared to there was a significant increase in NEFA AUC during EX-16 (11%) and EX-4 (9%). Values found for percent change in brachial artery flow mediated dilation were small, and with a marked variability within and between trials from pre-OFTT to the 6-hour period. Lipemic variables did not show any large or significant correlation with percent change in dilation for any of the trials. An acute exercise session regardless of the times chosen, (i.e., sixteen hours and four hours before the OFTT), reduced to a similar extent both the total and incremental lipemic responses when compared to the no-exercise condition.^