The effect of age on dominance-related neuromuscular fatigue characteristics

The purpose of this study was to test the hypothesis that older adults exhibit no differences in central and peripheral mechanisms of fatigue between the dominant (D) and non-dominant (ND) first dorsal interosseous (FDI) muscles, in contrast to greater fatigue-related changes observed in the ND compared with the D FDI of young adults. A secondary purpose tested the hypothesis that older adults exhibit larger differences in central fatigue mechanisms and lesser changes in peripheral measures of fatigue compared with young adults. Variables of interest were voluntary activation, median frequency of electromyographic (EMG) signals and contractile characteristics of the FDI before, during, and after a sustained maximum isometric index finger abduction fatiguing contraction. Twelve young and eleven older right-handed adults were tested. The level of voluntary activation was determined by superimposing doublets of stimulation upon the maximal contractions. Single pulses of electrical stimulation were delivered to the FDI before and after fatigue to elicit twitch responses (force, contraction time and half-relaxation time). Surface EMG signals were recorded from the FDI, and median frequency obtained through frequency analysis. Older adults exhibited no differences in measures reflecting central and peripheral mechanisms of fatigability between the D and ND FDI, in contrast to young adults, where the D FDI exhibited more fatigue-resistant behavior at central and peripheral levels. It appears that age-related changes at central and peripheral levels can lessen differences in fatigue-related changes in measures of muscle function between D and ND FDI muscles in old age. Furthermore, older adults exhibited significantly smaller changes in peripheral measures of fatigability compared to those of young adults, while the central mechanisms of fatigability did not contribute differently to the force-generating capabilities of young and older adults. The larger proportion of Type I muscle fibers thought to be associated with the aging process likely contributed to the fatigue-resistance of older adults. Age-related changes in the FDI muscle likely caused an improved resistance to fatigue at the peripheral level, but no significant difference in the central mechanisms of fatigability when compared to those of young adults.