Age-related maximal voluntary isometric force production characteristics of six muscle groups in women ranging in age from 25 to 74 years

The purpose of the study was to determine the age related maximal voluntary isometric force production characteristics in women ranging in age from 25 to 74 years. The subjects (N = 143) were grouped into ten five-year age groups with 13 to 16 subjects in each group. Variables representing parameters of force, time, instantaneous rate of force increase, average rate of force production and impulse were used to characterize muscle function. A Daytronic linear voltage differential transducer interfaced with an IBM microcomputer was used to measure muscle function in six muscle groups including the finger flexors, thumb extensors, forearm extensors, forearm flexors, dorsi flexors and plantar flexors. Twelve force-time recordings (2 days x 2 instructions x 3 trials) were obtained for each muscle group. Anthropometric techniques were employed to obtain measures of physique and body composition. The statistical techniques employed included: repeated measures analysis of variance, zero-order correlational analysis, dependent t-tests, one way analysis of variance and analysis of covariance. The repeatability of the data was highest for maximal force and lowest for the time-based variables. The rate instruction trials elicited higher maximal rates of force increase, shorter times to maximal force and maximal rate, lower total impulse and maximal forces when compared to the strength trials. The intercorrelations among the variables within and between parameters were diverse yet fairly similar among age groups. The average rate and rate parameters were more highly intercorrelated than the other parameters. The age related decline in muscle function was dependent upon the force-time variable and muscle group considered. Age group differences were noted for variables within all force-time parameters; however, only 2 of 11 time based variables were statistically significant. The most marked decline in maximal force was observed in the plantar flexors (45%), and the earliest significant decline was noted in the finger flexors and forearm flexors (45-49 years). The differences in muscle function across age could not be entirely explained by body size and composition differences. Hence, it appears that the quality, as opposed to solely the quantity, of senescent muscle tissue is compromised.U of I OnlyETDs are only available to UIUC Users without author permissio