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Does a prolonged speech-like task affect sense of effort in Parkinson disease?
Nancy Pearl Solomon, Matthew J. Makashay, and Kevin R. Cannard

Maintaining a constant effort during a submaximal contraction with the tongue has been used to assess sense of effort related to fatigue. In this study, 13 adults with Parkinson disease and concomitant fatigue and 13 neurologically normal nonfatigued adults performed the constant-effort task with the tongue. Multiple trials were collected before and after six 10-min intervals of rapid syllable repetitions. The resulting curves were submitted to curve fitting for a negative exponential function with a positive asymptote. The derived time constant, reflecting the rate of decay, was significantly smaller for the PD group than for the control group. Time constants did not differ significantly before and after the syllable-repetition task. It appears that 1 hour of speech-like exercise was not adequate to induce fatigue in the tongue for either subject group. An alternate interpretation is that the constant-effort task was not sensitive to speech-related fatigue. Interestingly, the time constants determined after 10-20 min of exercise were significantly greater than those at baseline. This result may have reflected a novelty or energizing effect from the fast syllable repetitions. [Research support by NIDCD R03 DC06096; The views expressed in this article are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or U.S. Government.]

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