Date of Award

Summer 2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Interdisciplinary Ph.D.

First Advisor

Bement, Marie Heoger

Second Advisor

Pan, Lawrence G.

Third Advisor

Hunter, Sandra K.

Abstract

Pain reduction following exercise (exercise-induced hypoalgesia; EIH) is well-established in young adults. Specific to isometric exercise, the greatest EIH follows low intensity contractions held for long duration. The EIH response of older adults is not known; and the mechanisms for EIH are unclear at any age. This dissertation aimed to address these unknowns through a series of three studies. In study one, repeatability of pressure pain reports (pain threshold and pain ratings) was assessed in healthy older adults, including the impact of psychological factors. Pain reports, measured before and after quiet rest, did not change following quiet rest. Higher state anxiety was associated with greater pain. Study two examined the impact of isometric contractions that varied in intensity and duration on pain relief in healthy older adults. Pressure pain was assessed before and after isometric contractions of the left elbow flexor muscles. Unlike young adults, older adults experienced EIH similarly across different isometric exercise tasks and women experienced greater pain reduction than men. Anxiety did not influence EIH. Conditioned pain modulation (CPM; a reduction in pain to a test stimulus in the presence of a noxious conditioning stimulus) has been hypothesized to augment EIH when exercise is painful. In study three, CPM and EIH were assessed in healthy young and older adults. CPM was measured as the difference in pressure pain with the foot immersed in neutral-temperature water versus noxious ice water. While young adults experienced CPM, older adults experienced a range of responses from hypoalgesia to hyperalgesia with foot immersion in the ice water bath. CPM predicted EIH and was associated with state anxiety; however state anxiety was unrelated to EIH. Results for age and sex-related differences in pain perception varied across studies or sessions. The results of this dissertation suggest anxiety influences pain sensitivity, but not magnitude of EIH. Older adults, particularly women, experience reductions in pain following isometric exercise and are less dependent upon task than young adults. CPM may predict EIH response following isometric exercise in both young and older adults and may be a useful tool in clinical decision making for adults experiencing pain

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