Are there interindividual responses of cardiovascular disease risk markers to acute exercise? A replicate crossover study

Purpose: Using a replicated crossover design, we quantified the response heterogeneity of postprandial cardiovascular disease (CVD) risk marker responses to acute exercise. Methods: Twenty men (mean (SD) age, 26 (6) years; BMI, 23.9 (2.4) kg·m^-2) completed four, 2-day conditions (two control, two exercise) in randomised orders. On days 1 and 2, participants rested and consumed two high-fat meals over 9-h. Participants ran for 60-mins (61 (7)% of peak oxygen uptake) on day 1 (6.5-7.5 h) of both exercise conditions. Time-averaged total-area-under-the-curve (TAUC) for triacylglycerol (TAG), glucose and insulin were calculated from 11 venous blood samples on day 2. Arterial stiffness and blood pressure responses were calculated from measurements at baseline on day 1 and at 2.5-h on day 2. Consistency of individual differences was explored by correlating the two replicates of control-adjusted exercise responses for each outcome. Within-participant covariate-adjusted linear mixed models quantified participant-by-condition interactions and individual-response SDs. Results: Acute exercise reduced mean TAUC-TAG (-0.27 mmol·L^-1 h; Cohen’s d = 0.29, P = 0.017) and TAUC-insulin (-24.45 pmol·L^-1 h; Cohen’s d = 0.35, P = 0.022) vs. control, but led to negligible changes in TAUC-glucose and the vascular outcomes (Cohen’s d ≤ 0.41, P ≥ 0.106). Small-to-moderate, but nonsignificant, correlations were observed between the two response replicates (r = -0.40 to 0.15, P ≥ 0.066). We did not detect any individual response heterogeneity. All participant-by-condition interactions were P ≥ 0.137, and all individual-response SDs were small with wide 95% confidence intervals overlapping zero. Conclusion: Large trial-to-trial within-subject variability inhibited detection of consistent inter-individual variability in postprandial metabolic and vascular responses to acute exercise.