Effects of 8-wk exercise snacks on muscle oxygenation and cardiometabolic, mitochondrial, and subclinical atherosclerosis markers in sedentary women

'Exercise snacks' (ExS) are brief, structured bouts of physical activity designed to counteract the metabolic effects of sedentary behavior. This pilot study examined whether ExS improves metabolic markers, body composition, fitness indicators, peripheral blood mononuclear cells (PBMC) mitochondrial dynamics, autophagy, and subclinical atherosclerosis. Twenty-two women [11 physically active (PA), 11 sedentary; International Physical Activity Questionnaire-classified] were enrolled. Sedentary participants completed daily 12-min ExS sessions for 8 wk. Assessments included body composition, blood biomarkers, muscle oxygenation, cardiorespiratory fitness, grip strength, PBMC mitochondrial dynamics/autophagy markers, and neutrophil-endothelial interactions. Age-adjusted comparisons revealed that sedentary women (34 ± 9 yr) had similar body composition to PA participants (26 ± 5 yr). Cholesterol, low-density lipoprotein, and antioxidant capacity were reduced in sedentary women (P < 0.05). ExS reduced insulin (P < 0.01). Sedentary women displayed higher resting and maximal heart rates, lower estimated [Formula: see text], and reduced muscle reoxygenation versus PA (P < 0.05), all of which improved after ExS, though resting heart rate remained elevated versus PA (P < 0.01). Grip-strength was comparable between sedentary and PA women and increased after ExS (P < 0.01). Neutrophil-rolling velocity was decreased in sedentary versus PA (P < 0.01) and restored by ExS (P < 0.05). Expression of mitochondrial dynamics-related genes (mitofusins, OPA1, and FIS1) was lower in sedentary versus PA (P < 0.05) without changes in protein levels. Autophagy and mitophagy-related genes (Beclin1, LC3b, p62, and Pink/Parkin) were downregulated in sedentary versus PA (P < 0.05), whereas only LC3b mRNA and BECLIN1 protein increased after ExS (P < 0.01). Our findings indicate that ExS can improve cardiometabolic health, functional fitness, PBMC mitochondrial markers, and neutrophil-rolling velocity in sedentary women.NEW & NOTEWORTHY Brief daily 'exercise snacks' improved metabolic health, cardiorespiratory fitness, and muscle oxygenation in sedentary women. These changes were accompanied by modulation of PBMC mitochondrial dynamics, autophagy-related markers, and neutrophil-endothelial interactions. Our findings provide mechanistic support for time-efficient exercise as a feasible strategy to counteract sedentary-induced cardiometabolic dysfunction.