Most research on sedentary behaviour has focused on cardiometabolic outcomes and markers of metabolic dysfunction, while neuromuscular outcomes have received less attention. The objective of the present study was to determine whether sedentary time is negatively associated with laboratory-based measures of lower body muscular strength and postural stability in middle-aged women. Forty-nine women (56.6 ± 4.1 years) participated in the study. Participants wore an ActiGraph GT3X accelerometer for 7 days to quantify sedentary time and physical activity. Following a familiarization session, assessments of lower body muscular strength and postural stability were performed. Peak torque of knee extensors and flexors was assessed using an isokinetic dynamometer. Postural stability was assessed using computerized dynamic posturography and a composite equilibrium score (CES) was calculated. Participants spent 9.4 ± 1.3 h per day (65% of wear time) sedentary and 28.2 ± 17.3 min per day (3.3% of wear time) in moderate to vigorous physical activity (MVPA). Postural stability and relative peak torque of the knee flexors were significantly associated with time spent sedentary (r = -0.35, p = 0.01 and r = -0.31, p = 0.03, respectively). Multiple linear regression analyses showed that after adjusting for MVPA, sedentary time was not significantly related to either CES or peak torque of the knee extensors or flexors. In contrast to our hypothesis, postural stability and leg strength were not independently related to sedentary time. While sedentary behaviour may be an important risk factor for cardiometabolic disease, the present results suggest MVPA may be more important to neuromuscular outcomes.
Keywords: aging; balance; capacité fonctionnelle; force musculaire; functional capacity; postural stability; sedentary; stabilité posturale; strength; sédentarité; vieillissement; équilibre.