Assessment of Unilateral Lower Limb Muscle Power: Are Unilateral Functional Tests Correlated with Nottingham Power Rig in Healthy Adults?

Background: Muscle power is an important physical capability across all age groups and health statuses. Typically, assessing lower limb muscle power requires expensive and sophisticated equipment to ensure reliability and validity of power. Hence, there exists a clear need to identify a simple and effective functional performance test that can serve as a proxy for evaluating muscle power when equipment is unavailable. Thus, this study aimed to identify an easily administered, functional performance test to assess unilateral muscle power. Methods: Correlations between maximal leg extensor power (LEP) were measured using the Nottingham Power Rig, and several functional tests (i) unilateral 5-repetition Sit-To-Stand (5STS), (ii) unilateral 30-second Sit-To-Stand (30STS), and (iii) unilateral Hop For Distance (HFD), as well as (iv) self-reported physical activity assessed by the Short Questionnaire to AsseS Health-enhancing physical activity (SQUASH). Pearson's correlation coefficients were calculated between LEP and the functional tests for both legs, as well as self-reported activity, among 52 healthy participants with a mean age of 31.1 years (ranging 19-49 years). Results: A negligible correlation was found between LEP and SQUASH score. Negligible correlations were found between LEP and unilateral 5STS, unilateral 30STS, and HFD on the dominant leg. Positive low correlations were found between LEP and Unilateral 30STS (r=0.43, p=<0.01) and HFD (r=0.44, p=<0.01) on the non-dominant leg, as well as an inverse low correlation between LEP and unilateral 5STS (-0.42, p=0.01) on the non-dominant leg. Conclusion: All correlations produced were negligible to low, suggesting that the functional tests investigated in this study may not be indicative of lower limb muscle power. Level of evidence: 3b.