title: Conditioned pain modulation predicts exercise-induced hypoalgesia in healthy adults.
abstract: BACKGROUND
  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 R = 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.
authors.affiliation: 1Department of Physical Therapy, Marquette University, Milwaukee, WI; and 2Department of Physical Therapy, Concordia University Wisconsin, Mequon, WI.
authors.forename: Kathy J
authors.initials: KJ
authors.lastname: Lemley
authors.forename: Sandra K
authors.initials: SK
authors.lastname: Hunter
authors.forename: Marie K Hoeger
authors.initials: MK
authors.lastname: Bement
mesh_terms: D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001132:Arm; D003080:Cold Temperature; D015444:Exercise / Q000502:physiology*; D005260:Female; D005528:Foot; D064368:Healthy Volunteers; D006801:Humans; D007101:Immersion / Q000503:physiopathology; D007537:Isometric Contraction; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D010147:Pain Measurement; D058748:Pain Perception / Q000502:physiology*; D017288:Pain Threshold / Q000502:physiology* / Q000523:psychology; D011312:Pressure / Q000009:adverse effects; D014867:Water; D055815:Young Adult
chemical_list: D014867:Water