Effects of Physical Exercise Breaks on Executive Function in a Simulated Classroom Setting: Uncovering a Window into the Brain

Abstract

Acknowledging the detrimental effects of prolonged sitting, this study examined the effects of an acute exercise break during prolonged sitting on executive function, cortical hemodynamics, and microvascular status. In this randomized crossover study, 71 college students completed three conditions: (i) uninterrupted sitting (SIT); (ii) SIT with a 15 min moderate-intensity cycling break (MIC); and (iii) SIT with a 15 min vigorous-intensity cycling break (VIC). Behavioral outcomes, retinal vessel diameters (central retinal artery equivalents [CRAE], retinal vein equivalents [CRVE], arteriovenous ratio [AVR]), cortical activation, and effective connectivity were evaluated. Linear mixed models identified significant positive effects of exercise conditions on behavioral reaction time (RT), error rate, and inverse efficiency score (β = -2.62, -0.19, -3.04: ps < 0.05). MIC and VIC conditions produced pre-to-post-intervention increases in CRAE and CRVE (β = 4.46, 6.34), frontal activation, and resting-state and task-state causal density (β = 0.37, 0.06) (ps < 0.05) compared to SIT; VIC was more beneficial for executive function and neurobiological parameters. The effect of AVR on average RT was mediated through task-based causal density (indirect effect: -0.82). Acutely interrupting prolonged sitting improves executive function, microvascular status, and cortical activation and connectivity, with causal density mediating the microvascular-executive function link.

Keywords: brain Health; cerebrovascular health; effective connectivity; microvascular health; sedentary behavior; young adults.

Figure 1

The schematic illustration of the three experimental conditions (i.e., SIT versus MIC versus VIC). (Notes. The primary outcomes of assessments 1–3 were also separately shown at the bottom of the figure; SIT, condition of 115 min uninterrupted sitting [control]; MIC, experimental condition 1 with 15 min moderate‐intensity cycling; VIC, experimental condition 2 with 15 min vigorous‐intensity cycling; fNIRS, functional near‐infrared spectroscopy; A1, assessment 1; A2, assessment 2; A3, assessment 3; CRAE, central retinal artery equivalent; CRVE, central retinal vein equivalent; AVR, arteriole‐to‐venule ratio; HbO, oxyhemoglobin; HbR, deoxyhemoglobin; GCA, Granger causality analysis).

Figure 2

a,b) Visualization of the functional near‐infrared spectroscopy setup and recording, c) the spatial registration of the fNIRS channels, and d) the test procedures of the modified dual Stroop task. (Notes. Figure 2a, equipment worn in the actual experimental environment; Figure 2b, coordinates of sources, detectors, and channels; Figure 2c, location of sources and detectors; Figure 2d, modified dual‐task Stroop task paradigm. In Figure 2c, the pink circle represents the source, while the blue circle represents the detector. In Figure 2c, the yellow, orange, green, blue, and purple lines separately represent channels in the medial frontal [C10, C12, C14], superior frontal [C2, C7‐9, C11, C13, C15‐17, C19, C31‐32, C34, C37, C39‐40], middle frontal [C1, C3‐6, C18, C20‐23], precentral [C24, C26, C33, C38, C47‐48], and parietal [C25, C27‐30, C35, C36, C41‐46, C49] regions. In Figure 2d, three blocks of modified dual‐task Stroop task were well represented: the baseline Stroop block ran first, and then the Color‐Dual Stroop block and the Lexical‐Dual block ran in a counterbalanced order. Each block comprised a practice sequence and 3 test sequences, with 12 trials in each sequence.). (Abbreviations. S, source; D, detector; C, channel).

Figure 3

Results of behavioral assessments. (Notes. a1, comparisons of experimental conditions [SIT, MIC, VIC] of reaction time; a2, comparisons of assessment timepoints [pretest, posttest] of reaction time; a3, comparisons of Stroop conditions [baseline, color‐dual, and lexical‐dual Stroop] of reaction time; b1, comparisons of experimental conditions of error rate; b2, comparisons of assessment timepoints of error rate; b3, comparisons of Stroop conditions of error rate; c1, comparisons of experimental conditions of inverse efficiency score; c2, comparisons of assessment timepoints of inverse efficiency score; c3, comparisons of Stroop conditions of inverse efficiency score. Data are shown as the mean and 95% confidence intervals. Statistical comparisons were conducted using estimated marginal means with post‐hoc comparisons of linear mixed models. Asterisks indicate significance levels: *p < 0.05, **p < 0.01.). (Abbreviations. SIT, uninterrupted sitting; MIC, moderate‐intensity cycling; VIC, vigorous‐intensity cycling).

Figure 4

Granger causality analysis of the task‐based causal density of oxyhemoglobin. (Notes. Figure a1‐a6, p values of Granger causality analyses [a1‐2, pre‐intervention and post‐intervention of SIT; a3‐4, pre‐intervention and post‐intervention of MIC; a5‐6, pre‐intervention and post‐intervention of VIC. The black dot indicated the existence of a connectome between two ROIs [from the X axis to the Y axis], with the dot size indicating the value of p value. Figure b1‐6 and F‐statistics of Granger causality analyses [b1‐2, pre‐intervention and post‐intervention of SIT; b3‐4, pre‐intervention and post‐intervention of MIC; b5‐6, pre‐intervention and postintervention of VIC]. The color [from red to blue] and size [from the smallest to the largest] of dots indicated the values of F‐statistics [from 0.00 to 0.05]. ROI 1, medial frontal region; ROI 2, left superior frontal region; ROI 3, left middle frontal region; ROI 4, left precentral region; ROI 5, left parietal region; ROI 6, right superior frontal region; ROI 7, right middle frontal region; ROI 8, right precentral region; ROI 9, right parietal region; ROI, region of interest; SIT, condition of 115 min uninterrupted sitting [control]; MIC, experimental condition 1 with 15 min moderate‐intensity cycling; VIC, experimental condition 2 with 15 min vigorous‐intensity cycling.]

Figure 5

Directional connectomes among the brain regions of interest. (Notes. The directional connectomes among the brain regions of interest were acquired from Granger causality analysis for task‐based causal density of oxyhemoglobin. a1‐2, connectomes of pre‐intervention and post‐intervention of SIT; a3‐4, connectomes of pre‐intervention and post‐intervention of MIC; connectomes of pre‐intervention and post‐intervention of VIC. ROI 1, medial frontal region; ROI 2, left superior frontal region; ROI 3, left middle frontal region; ROI 4, left precentral region; ROI 5, left parietal region; ROI 6, right superior frontal region; ROI 7, right middle frontal region; ROI 8, right precentral region; ROI 9, right parietal region.); ROI, region of interest; SIT, condition of 115 min uninterrupted sitting [control]; MIC, experimental condition 1 with 15 min moderate‐intensity cycling; VIC, experimental condition 2 with 15 min vigorous‐intensity cycling).

Figure 6

Mediation model. (Notes. Independent variable, retinal arteriovenous ratio; dependent variable, average reaction time; mediator, task‐based causal density of oxyhemoglobin).