10.26153/TSW/10976
Dial, Michael
0000-0003-0675-4463
Physical inactivity does not impair the insulin-lowering effects of moderate-intensity exercise, yet it does impair fat metabolism
The University of Texas at Austin
2020
Inactivity
Exercise
Physical inactivity
Glucose
Insulin
Insulin sensitivity
Exercise resistance
The University of Texas at Austin
The University of Texas at Austin
Coyle, Edward F., 1952-
2020-12-22
2020-12-22
2020-08
2020-08-17
August 202
2020-12-22
en
Thesis
https://hdl.handle.net/2152/83983
application/pdf
Acute exercise and physical activity improve insulin sensitivity, glucose tolerance, and postprandial lipemia, although recent research suggests that physical inactivity may attenuate some of these healthy metabolic benefits of exercise. This study aimed to determine how two days of physical inactivity and physical activity affected exercise-induced changes in plasma insulin, glucose, and triglyceride concentrations during an oral glucose tolerance test (OGTT) performed the next morning. Five untrained men (n=2) and women (n=3) completed three five-day trails in a randomized crossover design. Each trial began with two days of normal activity levels, followed by two intervention days. Two days of physical inactivity (3,666 ± 100 steps) without exercise (SIT) were compared to two days of physical inactivity (3,077 ± 141 steps) with a 1-hr bout of moderate intensity cycling at 65% of VO2peak (SIT + EX). Finally, two intervention days of high activity (12,270 ± 408 steps) were performed with a 1-hour bout of moderate cycling (ACTIVE + EX). The following morning, subjects completed a 120-min OGTT, during which plasma was collected and analyzed for glucose, insulin, and triglycerides. No changes were observed in plasma glucose. Compared to SIT, insulin total area under the curve (AUCT) was 39% lower in SIT+EX (p=0.18) and 21% lower in ACTIVE+EX (p=0.48), demonstrating that exercise had an insulin-lowering effect. Plasma triglyceride AUCT in ACTIVE+EX was 26% lower than SIT (p=0.10) and 28% lower than SIT+EX (p=0.03), and fasting plasma triglyceride concentration in ACTIVE+EX was 34% lower than SIT (p=0.06) and 20% lower than SIT+EX (p=0.43). These data indicate that the insulin-lowering effect of physical activity is influenced to a greater extent by an acute bout of moderate exercise (65% VO2peak) than the background daily steps. Conversely, the triglyceride lowering effect of physical activity appears to be contingent upon higher physical activity (daily step count) and not acute moderate-intensity exercise. This also was the case with postprandial whole-body fat oxidation as ACTIVE+EX was 26% higher when compared to SIT+EX. Taken together, insulin sensitivity appears to be improved by prolonged moderate-intensity exercise (i.e. 65% of VO2peak), while postprandial triglyceride concentration and fat oxidation are improved by increasing daily step count (i.e.; from < 4,000 to >11,000 per day).