Introduction: Conditioned pain modulation (CPM) is the concept that pain inhibits pain and has potential rehabilitation implications for exercise prescription. The purpose of this study was to determine whether changes in pressure pain perception after a thermal conditioning stimulus (i.e., CPM) was attenuated with aging and whether CPM predicted pain relief after exercise (exercise-induced hypoalgesia (EIH)) in healthy young and older adults.
Methods: Twenty young (21.9 ± 3.3 yr, 10 men) and 19 older (72.0 ± 4.5 yr, 10 men) adults participated in three sessions: one familiarization and two experimental (EIH and CPM) sessions. Pressure pain perception was assessed using a weighted Lucite edge placed on the right index finger for 1 min. EIH was determined by measuring pressure pain perception before and after prolonged submaximal isometric contraction of the elbow flexors. CPM was assessed by measuring pressure pain perception at the finger while the foot was immersed in neutral water versus painful ice water.
Results: Young, but not older, adults reported a decrease in pressure pain at the finger while their foot was immersed in the ice water bath compared with the neutral bath (i.e., CPM, trial–age: P = 0.001). Pressure pain ratings decreased after exercise (P = 0.03) that was perceived as painful (peak arm pain, 7.0 ± 3.3) for both young and older adults. Regression analysis showed that after controlling for age and baseline pain, CPM predicted EIH (model adjusted R2 = 0.23, P = 0.007).
Conclusions: CPM was attenuated in older adults, as measured with a noxious pressure stimulus after a thermal conditioning stimulus, and adults with greater CPM were more likely to report greater EIH.
1Department of Physical Therapy, Marquette University, Milwaukee, WI; and 2Department of Physical Therapy, Concordia University Wisconsin, Mequon, WI
Address for correspondence: Kathy J Lemley, P.T., M.S., Department of Physical Therapy, Concordia University Wisconsin, 12800 North Lake Shore Drive, Mequon, WI 53097; E-mail: firstname.lastname@example.org.
Submitted for publication October 2013.
Accepted for publication May 2014.