Are there interindividual responses of cardiovascular disease risk markers to acute exercise? A replicated 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.</p

Exploring the acute effects of running on cerebral blood flow and food cue reactivity in healthy young men using functional magnetic resonance imaging

Introduction: Acute exercise suppresses appetite and alters food-cue reactivity but the extent exercise-induced changes in cerebral blood flow (CBF) influences the blood-oxygen-level-dependent (BOLD) signal during appetite-related paradigms is not known. This study examined the impact of acute running on visual food-cue reactivity and explored whether such responses are influenced by CBF variability. Methods: In a randomised crossover design, 23 men (mean±SD: 24±4 years, 22.9±2.1kg/m2) completed fMRI scans before and after 60-mins of running (68±3% peak oxygen uptake) or rest (control). Five-min pseudo-continuous arterial spin labelling fMRI scans were conducted for CBF assessment before and at four consecutive repeat acquisitions after exercise/rest. BOLD-fMRI was acquired during a food-cue reactivity task before and 28-mins after exercise/rest. Food-cue reactivity analysis was performed with and without CBF adjustment. Subjective appetite ratings were assessed before, during and after exercise/rest. Results: Exercise CBF was higher in grey matter, the posterior insula and in the region of the amygdala/hippocampus, and lower in the medial OFC and dorsal striatum than control (main effect trial P≤0.018). No time-by-trial interactions for CBF were identified (P≥0.087). Exercise induced moderate-to-large reductions in subjective appetite ratings (Cohen’s d=0.53-0.84; P≤0.024), and increased food-cue reactivity in the paracingulate gyrus, hippocampus, precuneous cortex, frontal pole and posterior cingulate gyrus. Accounting for CBF variability did not markedly alter detection of exercise-induced BOLD signal changes. Conclusion: Acute running evoked overall changes in CBF that were not time dependent and increased food-cue reactivity in regions implicated in attention, anticipation of reward, and episodic memory independent of CBF. </p

Exploring the acute effects of running on cerebral blood flow and food cue reactivity in healthy young men using functional magnetic resonance imaging

Introduction: Acute exercise suppresses appetite and alters food-cue reactivity but the extent exercise-induced changes in cerebral blood flow (CBF) influences the blood-oxygen-level-dependent (BOLD) signal during appetite-related paradigms is not known. This study examined the impact of acute running on visual food-cue reactivity and explored whether such responses are influenced by CBF variability. Methods: In a randomised crossover design, 23 men (mean±SD: 24±4 years, 22.9±2.1kg/m2) completed fMRI scans before and after 60-mins of running (68±3% peak oxygen uptake) or rest (control). Five-min pseudo-continuous arterial spin labelling fMRI scans were conducted for CBF assessment before and at four consecutive repeat acquisitions after exercise/rest. BOLD-fMRI was acquired during a food-cue reactivity task before and 28-mins after exercise/rest. Food-cue reactivity analysis was performed with and without CBF adjustment. Subjective appetite ratings were assessed before, during and after exercise/rest. Results: Exercise CBF was higher in grey matter, the posterior insula and in the region of the amygdala/hippocampus, and lower in the medial OFC and dorsal striatum than control (main effect trial P≤0.018). No time-by-trial interactions for CBF were identified (P≥0.087). Exercise induced moderate-to-large reductions in subjective appetite ratings (Cohen’s d=0.53-0.84; P≤0.024), and increased food-cue reactivity in the paracingulate gyrus, hippocampus, precuneous cortex, frontal pole and posterior cingulate gyrus. Accounting for CBF variability did not markedly alter detection of exercise-induced BOLD signal changes. Conclusion: Acute running evoked overall changes in CBF that were not time dependent and increased food-cue reactivity in regions implicated in attention, anticipation of reward, and episodic memory independent of CBF. </p

A replicate crossover trial on the inter-individual variability of sleep indices in response to acute exercise undertaken by healthy men

Study objective: Using the necessary replicate-crossover design, we investigated whether there is inter-individual variability in home-assessed sleep in response to acute exercise.Methods: Eighteen healthy men (mean(SD): 26(6) years) completed two identical control (8-h laboratory rest, 08:45-16:45) and two identical exercise (7-h laboratory rest; 1-h laboratory treadmill run [62(7)% peak oxygen uptake], 15:15-16:15) trials in randomised sequences. Wrist-worn actigraphy (MotionWatch 8) measured home-based sleep (total sleep time, actual wake time, sleep latency, sleep efficiency) two nights before (nights 1-2) and three nights after (nights 3-5) the exercise/control day. Pearson’s correlation coefficients quantified the consistency of individual differences between the replicates of control-adjusted exercise responses to explore: (1) immediate (night 3 minus night 2); (2) delayed (night 5 minus night 2); and (3) overall (average post-intervention minus average pre-intervention) exercise- related effects. Within-participant linear mixed models and a random-effects between- participant meta-analysis estimated participant-by-trial response heterogeneity.Results: For all comparisons and sleep outcomes, the between-replicate correlations were non-significant, ranging from trivial-to-moderate (r range = -0.44 to 0.41, P≥0.065). Participant-by-trial interactions were trivial. Individual differences SDs were small, prone to uncertainty around the estimates indicated by wide 95% confidence intervals and did not provide support for true individual response heterogeneity. Meta-analyses of the between-participant, replicate-averaged condition effect revealed that, again, heterogeneity (τ) was negligible for most sleep outcomes.Conclusion: Control-adjusted sleep in response to acute exercise was inconsistent when measured on repeated occasions. Inter-individual differences in sleep in response to exercise4 were small compared to the natural (trial-to-trial) within-subject variability in sleep outcomes.</p