Reliability of a new instrument for measuring maximum rising strength

Objective: To assess the intrarater test-retest reliability of a newly developed instrument for measuring maximum rising strength (MRS) in comparison with that of maximum knee extension strength (KES). Design: Three replications of isometric MRS and KES were measured on three test occasions separated by 1 wk in 97 healthy men and women aged 23-90. MRS was measured in seated subjects using a dynamometer fixed on the ground and connected by an adjustable nonelastic cord to a padded belt. Results: The intraclass coefficients (ICCs) of MRS were 0.92 and 0.93 at 60 and 70 degrees of knee flexion, respectively, and 0.98 when the mean of three highest peak values of MRS at 600 and the three highest peak values at 70 degrees knee flexion on each session were considered vs. 0.95 for KES. A significant increase in MRS and KES strength was found between the first and the third sessions (+ 7 to 8%) (P < 0.001). No side effects of strength measurements were noticed. Conclusion: Despite a significant learning effect, MRS measurement is reliable in men and women of a wide range of ages. Whether this instrument will be useful for targeting individuals with early sit-to-stand difficulties requires further investigation.