Feasibility and Reliability of Quadriceps Muscle Power and Optimal Movement Velocity Measurements in Different Populations of Subjects

This study aimed to assess the feasibility and reliability of quadriceps maximal short-term power (P-max) and corresponding optimal movement velocity (upsilon(opt)-velocity at which the power reaches a maximum value) measurements in different populations of subjects. Five groups of subjects, fifty participants in each group, took part in the study: students; patients of the cardiac rehabilitation program; patients after stroke; older adults; and subjects of different ages who performed repetitive measurements with two different bicycles. The correlations calculated for the pairs of scores ranged from 0.93 to 0.99 for P-max and from 0.86 to 0.96 for upsilon(opt) (all with p < 0.001). Intraclass Correlations Coefficients (ICCs) varied from 0.93 to 0.98 for P-max and from 0.86 to 0.95 for upsilon(opt). The standard error of measurement (SEM) varied from 16.9 to 21.4 W for P-max and from 2.91 to 5.54 rotations(rot)/min for upsilon(opt). The coefficients of variation (CVs or SEM%) for P-max and upsilon(opt) in the stroke group were 10.6% and 11.4%, respectively; all other CVs were clearly lower than 10%. The minimal detectable change (MDC) varied from 46.6 to 59.3 W for P-max and from 8.07 to 15.4 rot/min for upsilon(opt). MDC% varied from 9.53% to 29.3% for P-max and from 8.19% to 31.7% for upsilon(opt), and was the highest in the stroke group. Therefore, the precision of measurements of P-max and upsilon(opt) was confirmed by very good indices of absolute and relative reliability. The proposed methodology is precise, safe, not time-consuming and feasible in older subjects and those with diseases.