Reliability of Measuring Voluntary Strength and Isometric Twitch Properties in the Ankle Muscles of Very Old Adults

The purpose of this study was to assess the reliability of measuring voluntary isometric strength, evoked isometric twitch properties (peak torque, time to peak torque, half-relaxation time), M-wave amplitude, and passive tension in very old adults (73-92 years). Five male and 5 female subjects were tested on two different test occasions that were 1 week apart. Using the intraclass correlation coefficient (ICC) method, the mean reliability coefficient of all measurements on the dorsiflexor (DF) and plantar flexor (PF) muscle groups was .91 ± .05. Similar ICC values were found for DF and PF muscles (.92 ± .04 and .90 ± .05, respectively). Resting PF half-relaxation time was the least reliable measure, with an ICC value of .80, while maximum voluntary strength was the most reliable with ICC values of .98 for DF and .97 for PF. The variation ranged from 0.2 to 12.3%. It was concluded that ankle muscle function (both voluntary and evoked) can be reliably assessed in this very old age group.