The purpose of this study was to examine the test-retest reliability for peak torque (PT), rates of torque development (RTD), and electromechanical delay (EMD) calculated during voluntary and evoked muscle actions in men ages 65 and older. Fifteen older men (mean ± standard deviation (SD) age = 72.3 ± 7.3 years) completed 3 evoked and 3 voluntary isometric muscle actions of the leg extensors during two visits separated by 48 to 72 h. PT and EMD were calculated during voluntary and evoked muscle actions. RTD was quantified as the peak RTD, overall RTD, RTD in time intervals of 0-30 (RTD30), 0-50 (RTD50), 0-100 (RTD100), and 0-200 ms (RTD200) from the onset of torque, and RTD in 10 ms epochs during the first 250 ms after the onset of torque or to peak torque for voluntary and evoked muscle actions. Intraclass correlation coefficients (ICCs), standard errors of measurement (SEMs), and coefficients of variation (CV) were used to quantify the test-retest reliability. Voluntary and evoked PT demonstrated good reliability, whereas EMD can be considered unreliable. The ICCs for voluntary PRTD, RTD30, RTD50, RTD100, RTD200, and overall RTDranged from 0.598-0.799, while for evoked PRTD, RTD30,RTD50, RTD100, and overall RTD, ICCs ranged from 0.943-0.984. Voluntary RTDs in 10 ms epochs had ICCs ranging from 0.179-0.939, while evoked RTD in 10 ms epochs demonstrated ICCs ranging from 0.693-0.975. Except for PRTD and RTD in 10 ms epochs after 50 ms, CVs were higher for voluntary (11-41%) than evoked (7-24%) measures. Systematic decreases occurred from trial one to trial two for several voluntary measures of RTD, while there was only one for the evoked measures of RTD. CONCLUSIONS: There is dissociation in the reliability of voluntary and evoked PT, and RTD, such that the evoked measurements display greater reliability in older men. Voluntary RTDs were most suspect, consistently demonstrating lower ICCs and greater SEMs than evoked RTD. However, if choosing to measure voluntary RTD in older men, the most reliable measurements may be RTD in the first 10 ms, 80-110 ms, or overall RTD. Finally, EMD may be unreliable in older men.
Adviser: Joel T. Crame
