Author(s): BOCCIA, G., GROSSIO, L., SALVAGGIO, F., RAINOLDI, A., Institution: UNIVERSITY OF TURIN, Country: ITALY, Abstract-ID: 2145

INTRODUCTION:
We aimed to evaluate the convergent validity of the 5-times single-leg sit-to-stand test (STS) against maximal voluntary torque (MVT) and rate of torque development (RTD) of the knee extensors.
METHODS:
Forty-eight physically active participants performed the classical bilateral 5-times STS and the single-leg STS with both lower limbs. Mechanical power was estimated using the equation proposed by Alcázar et al. (2018). Ground reaction forces (GRF) were recorded during the STS tasks, and peak force, peak rate of force development (RFD), and mean push-off time across repetitions were extracted. Isometric knee extension MVT and RTD (50, 100, 150 ms and peak) were assessed bilaterally (96 limbs) to establish convergent validity. Validity was examined using Pearson correlation coefficients. Inter-limb asymmetry magnitude and direction were computed for single-leg STS, MVT, and RTD; agreement in asymmetry direction was assessed using Cohen’s kappa. Sample variance and coefficient of variation (CoV) were calculated to quantify performance dispersion in single-leg and bilateral STS tests.
RESULTS:
Single-leg STS mechanical power demonstrated moderate-to-strong convergent validity with knee extensor RTD at 100 ms (r = 0.54, p < 0.0001) and moderate convergent validity with MVT (r = 0.39, p < 0.0001). Peak GRF during single-leg STS was strongly associated with knee extensor MVT (r = 0.75, p < 0.0001), whereas GRF-derived RFD showed a moderate-to-strong association with knee extensor RTD at 150 ms (r = 0.54, p < 0.0001). Inter-limb asymmetry in single-leg STS performance was not correlated with knee extensor MVT or RTD asymmetry (all p > 0.12), and agreement in asymmetry direction was negligible for both RTD (κ = 0.01) and MVT (κ = −0.13). Performance dispersion was greater for the single-leg STS (variance = 6.5 s; CoV = 30%) compared with the bilateral STS (variance = 2.3 s; CoV = 22%).
CONCLUSION:
The moderate association between single-leg STS performance and RTD shows acceptable convergent validity. Thus, this test can be implemented as a functional indicator of explosive force capacity. The greater variability observed in the single-leg STS compared with the bilateral version suggests a superior ability to discriminate performance differences among healthy individuals. However, single-leg STS performance does not provide valid information regarding the magnitude or direction of inter-limb asymmetry in knee extensor neuromuscular function.