Time Matters: Acute Physiological and Psychological Effects of Different Exercise Durations in Prediabetes

Abstract

Background: Exercise is a key non-pharmacological strategy for improving metabolic and psychological health in individuals with prediabetes. While the effects of exercise intensity are well documented, the acute impact of exercise duration on metabolic biomarkers and perceived stress remains unclear. This study examined the immediate effects of four different exercise durations on serum cholesterol, Irisin levels, and perceived stress in sedentary adults with prediabetes. Methods: Twenty-two adults with prediabetes completed a laboratory-based crossover trial consisting of four treadmill exercise sessions of increasing duration: 15 minutes (Visit 1), 30 minutes (Visit 2), 45 minutes (Visit 3), and 60 minutes or maximum tolerable duration (Visit 4). All sessions were performed at moderate intensity following an isocaloric breakfast. Blood samples were collected immediately before and after each session to measure total cholesterol and Irisin concentrations. Perceived Stress Scale (PSS-10) scores were recorded pre- and post-exercise. Paired t-tests assessed within-visit changes, and repeated measures ANOVA compared changes across durations. Results: Total cholesterol decreased significantly after each exercise duration (Visit 1: −23.2 mg/dL, p=0.001; Visit 2: −16.6 mg/dL, p<0.001; Visit 3: −12.4 mg/dL, p=0.001; Visit 4: −21.2 mg/dL, p=0.006). Irisin levels increased after all sessions, with significant rises in Visits 2–4 (p<0.05) and a non-significant increase during the shortest duration (Visit 1: p=0.120). Repeated measures ANOVA showed no significant differences in delta cholesterol or delta Irisin across visits (p>0.05). PSS-10 scores did not change significantly within individual visits but improved significantly from Visit 1 to Visit 4 (p=0.02), indicating cumulative psychological benefit. Conclusion: Acute bouts of exercise, even as short as 15 minutes, produce meaningful reductions in cholesterol, while longer durations elicit stronger Irisin responses and gradual improvements in perceived stress. These findings highlight the effectiveness of varying exercise durations in improving metabolic health in prediabetic adults and support flexible, tolerance-based exercise prescriptions.