Abstract / Summary
Abstract Purpose Prolonged sedentary behavior (SB) negatively impacts musculoskeletal and cardiovascular health, yet the underlying mechanisms and timeframe for these changes remain unclear. Methods This study examined the acute effects of prolonged SB on the electromyographic activity of the vastus medialis, vastus lateralis, and rectus femoris muscles while assessing the relationship between body composition and myoelectric activity. Twenty-one healthy young adults (11 women; 22.5 ± 1.6 years) remained seated for 180 min, with surface electromyography capturing Root Mean Square (RMS), Median Frequency (MDF), and Linear Envelope (LE) at regular intervals. Results Results showed a significant RMS increase in the vastus medialis and rectus femoris after 60 min and in the vastus lateralis after 80 min of sitting. MDF declined significantly in the rectus femoris by 20 min, indicating early fatigue, while LE progressively increased, suggesting compensatory adaptations. At the quadriceps level, MDF decreased from 60 min onward, accompanied by increased activation, indicating progressive neuromuscular fatigue. Correlations between body composition and electromyographic variables suggest that individual physiological characteristics influence neuromuscular responses to SB. Conclusion These findings demonstrate that prolonged SB induces muscle fatigue within 60 min, reinforcing the need of interrupting SB periodically. Future research should explore SB interruption protocols and their impact on clinical and aging populations to support evidence-based prevention guidelines.