"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 inidcators, PBMC mitochondrial dynamics, autophagy, and subclinical atherosclerosis. Twenty-two women (11 physically active [PA], 11 sedentary; IPAQ-classified) were enrolled. Sedentary participants completed daily 12-minute ExS sessions for 8 weeks. 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 years) had similar body composition to PA participants (26±5 years). Cholesterol, LDL, 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 VO2max, and reduced muscle re-oxygenation vs PA (p< 0.05), all of which improved after ExS, though resting heart rate remained elevated vs 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 vs PA (p< 0.01) and restored by ExS (p< 0.05). Expression of mitochondrial dynamics-related genes (mitofusins, OPA1, FIS1) was lower in sedentary vs PA (p< 0.05) without changes in protein levels. Autophagy and mitophagy-related genes (Beclin1, LC3b, p62, Pink/Parkin) were downregulated in sedentary vs PA (p< 0.05), while 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.
