Association of sedentary behavior, physical activity, and the "weekend warrior" pattern with muscle mass and strength in U.S. adults: cross-sectional NHANES study

Background Prolonged sedentary behavior (SB) and insufficient physical activity (PA) are key risk factors for sarcopenia, but their joint effects remain underexplored. This study aimed to examine the independent and joint associations of SB and PA, particularly the weekend warrior (WW) and regularly active (RA) patterns, on muscle mass and strength. Methods A cross-sectional study was conducted using data from NHANES 2011–2014, including information on SB, PA, appendicular skeletal muscle mass index (ASMI), and grip strength (GS). Participants were categorized as inactive, insufficiently active, and physically active, with the physically active group further classified into WW and RA based on weekly PA frequency. Multivariable weighted linear regression was performed to explore associations, and sensitivity analyses were conducted to validate the robustness of the results. Results Among 4,878 participants (mean age 39.3 ± 11.8 years; 52.0% male), 48.8% reported SB > 6 hours/day, and 20.0% met PA guidelines, with 7.9% classified as WW and 12.0% as RA. In multivariable-adjusted models, SB > 8 hours/day was associated with lower ASMI (β: -0.23; 95% CI [-0.30, -0.15]) and GS (β: -3.59; 95% CI [-4.70, -2.48]), while physically active was linked to higher ASMI (β: 0.34; 95% CI [0.26, 0.41]) and GS (β: 3.02; 95% CI [1.31, 4.73]). Joint analysis showed that meeting PA guidelines mitigated the adverse effects of SB. Compared to the inactive group, RA was associated with higher ASMI (β: 0.39; 95% CI [0.30, 0.48]) and GS (β: 3.28; 95% CI [1.33, 5.22]), while WW was linked to higher ASMI (β: 0.21; 95% CI [0.08, 0.35]) but not GS. Conclusions Prolonged SB was associated with lower ASMI and GS, but meeting PA guidelines mitigated these adverse effects. The WW pattern, characterized by twice-weekly, short-duration, and low-intensity activity, was associated with higher ASMI, with effects comparable to the RA pattern, but had limited benefits for GS.