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Purpose: This study assessed the effects of the COVID-19 pandemic restrictions/lockdowns on physical activity levels, bodymass, quadriceps strength, and gait biomechanics over 18 months. Methods: Ten healthy men were assessed at baseline (~14 wk before first lockdown) and 17.9 ± 0.3 months later (<1 wk after second lockdown). At both times, physical activity levels, body mass, and quadriceps strength were acquired using the International Physical Activity Questionnaire, a force plate, and a dynamometer, respectively. Gait data were also acquired using a motion capture system and force plates during self-paced walking, from which spatiotemporal parameters, knee angles, and externalmoments were computed. Baseline and follow-upmeasurements were compared using two-tailed paired t-tests (a = 0.05). Results: At follow-up, participants spent less time doing vigorous physical activity (Δ = -76 ± 157 min·wk-1, P = 0.048), exhibited a tendency toward increased sedentary time (Δ = +120 ± 162 min·d-1, P = 0.056), weighedmore (Δ = +2.5 ± 2.8 kg, P = 0.021), and showed a trend toward reduced quadriceps strength (Δ = -0.29 ± 0.45 (N·m)·kg-1, P = 0.071) compared with baseline. At follow-up, participants walked slower (Δ = -0.09 ± 0.07 m·s-1, P = 0.005), had greater knee flexion angles at heel strike (Δ = +2.2° ± 1.8°, P = 0.004) and during late stance (Δ = +2.2° ± 1.8°, P = 0.004), had reduced knee extension moments (Δ = -0.09 ± 0.09 (N·m)·kg-1, P = 0.012) and knee internal rotationmoments (Δ = -0.02 ± 0.02 (N·m)·kg-1, P = 0.012) during late stance. Conclusions: Healthymen exhibited reduced physical activity levels, increased body weight, a tendency toward reduced quadriceps strength, and altered gait biomechanics over the initial 18months of the COVID-19 pandemic--alterations that could have far-reaching health consequences. [ABSTRACT FROM AUTHOR]

Introduction: Data evaluating mortality benefit from replacing sedentary time with physical activity are sparse. We explored reallocating time spent in sedentary behavior to physical activity of different intensities in relation to mortality risk. Methods: Women and men age 50-85 yr from the National Health and Nutrition Examination Survey 2003-2004 and 2005-2006 cycles with follow-up through December 31, 2011, were included. Sedentary time and physical activity were assessed using an ActiGraph accelerometer. Isotemporal substitution models were used to estimate the effect of replacing one activity behavior with another activity behavior for the same amount of time while holding total accelerometer wear time constant. Results: During a mean follow-up of 6.35 yr, 697 deaths from any cause occurred. Replacing 30 min of sedentary time with an equal amount of light activity was associated with 14% reduced risk of mortality (multivariable-adjusted hazard ratio (HR), 0.86; 95% confidence interval (CI), 0.83-0.90). Replacement of sedentary time with moderate to vigorous activity was related to 50% mortality risk reduction (HR, 0.50; 95% CI, 0.31-0.80). We also noted a 42% reduced risk of mortality when light physical activity was replaced by moderate to vigorous activity (HR, 0.58; 95% CI, 0.36-0.93). Conclusion: Replacing sedentary time with an equal amount of physical activity may protect against preterm mortality. Replacement of light physical activity with moderate to vigorous activity is also associated with protection from premature mortality. [ABSTRACT FROM AUTHOR]