Assessment of Leg Muscle Power Using a Low Step Height Stair Test

Abstract

A stair-climbing power test using an ordinary stair is an inexpensive, practical test that is simple to perform. An individual's lower extremity power is a critical element associated with both mobility and the activities of daily living, while it is also a key determinant of independence for elderly people. However, no report has so far described the efficacy of lower height step stairs to assess the leg muscle power. PURPOSE: To determine the usefulness of the low step height stair-climbing power (LSSCP) test by comparing the results obtained from the LSSCP test with those from a leg power test in young people. METHODS: The subjects of this study included healthy young males (N=17, 20.8±2.9 yrs) and females (N=19, 20.5±2.6 yrs). The LSSCP was measured using lower height step stairs (9 cm step height, 10-stair flights, 72 cm total height). The time spent in stair climbing was measured by a contact mat connected with an electronic timer. The circuit is automatically opened at take off and closed when the subject touches the mat. The subjects were instructed to ascend the stairs as fast as they could. The stair-climbing power was then calculated with the body mass, the time spent in stair climbing, the vertical height travelled, and the gravitational acceleration. The bilateral leg extensor power (LEP) was measured using an isotonic leg power system in a sitting position. The isometric knee extension strength (KES) was measured on each side of the knee using a specially designed dynamometer. Test-test reliability was determined from participants, with the use of the intraclass correlation coefficient (ICC) model. RESULTS: The LSSCP was 338.7±48.3 watts (mean ± SD) for males and 246.1±43.0 watts for females. The LEP was 1411.7±448.7 watts (mean ± SD) for males and 718.5 ± 203.2 watts for females. The LSSCP significantly correlated with both the LEP (both p<0.05) and the KES (both p<0.05) in males and females, respectively. The ICC value of LSSCP was 0.81 for males and 0.95 for females, indicating excellent reliability. CONCLUSIONS: From a practical viewpoint as a field test, the LSSCP test was therefore found to be useful for accurately assessing the functional leg power levels.