Fractional O₂ extraction and fitness among physically active and inactive children during post-exercise recovery

This study aimed to determine the differences in muscle O₂ extraction capacity and physical fitness between physically active and sedentary schoolchildren. 19 students aged 10 to 14 years participated, categorized as physically active or inactive. In addition, a battery of basic physical condition and cardiovascular variables assessments was carried out. Physically active children demonstrated significantly greater efficiency in muscle O₂ extraction and resaturation during post-exercise recovery compared to sedentary counterparts (17.8 ± 8.11s vs 26.1 ± 8.54 s; p = 0.004; η^2p: 0.271). In the physical fitness tests there were only significant differences in the 30s Chair Stand Test (27.8 ± 3.97 vs. 19.4 ± 2.88 reps. P=< 0.001 η^2p: 0.614). These findings underscore the potential of regular physical activity to optimize peripheral vascular response and muscle oxygen utilization during post-exercise recovery in children.