The properties and function of the neuromuscular system change with advancing age. The effects on the performance capabilities of older adults are profound. We have found, for example, that finger movements are less steady in older adults compared with young adults. More recently, we have also demonstrated the impact of emotional state on neuromuscular function. We found that a stressor increased cognitive and physiological measures of arousal and impaired the ability of young men and women to exert a constant force during a submaximal pinch grip. It is likely that the same effect occurs in older adults. This led us to ask the question, does an increase in arousal further impair the steadiness of a submaximal pinch grip in older adults? Because baseline differences in steadiness are due to changes in the activation of muscle by nervous system, we hypothesize that an increase in arousal produces a greater deterioration of pinch-grip steadiness in older adults compared with young adults due the changes in motor unit function that occur with advancing age. We propose three specific aims to test this hypothesis: (1) to quantify the level of arousal evoked in young, middle-aged, and older adults in response to noxious stimulus using physiological and psychological measures; (2) to assess the fluctuations in force during a submaximal pinch grip performed by young, middle-aged, and older adults in the presence and absence of a noxious stimulus; (3) to examine the association between the changes in arousal fluctuations in pinch-grip force. We will quantify the moment-to-moment effect of the stressor on men and women with cognitive and physiological measures of arousal. The outcome variable will be the coefficient of variation for force during a submaximal pinch grip. We expect to find that the stress proposal will increase arousal to the same extent in all three groups of adults and that the impairment in steadiness will be proportional to the increase in arousal. These outcomes will result in a constant difference in steadiness between young and old adults, which will produce a much greater impairment in the simple motor task with an increase in arousal for the older adults. The findings will expand our understanding of the daily challenges experienced by older adults and will provide the foundation for a more extensive R01 application.

R03AG020339

2002-02-01

2004-01-31