Expectancy Reduces Symptoms but not Functional Impairment Following Exercise-induced Musculoskeletal Injury.
OBJECTIVE
To quantify the extent to which the participant-provider interaction influences the response to sham treatment following exercised-induced acute musculoskeletal pain.


METHODS
In total, 40 participants between the ages of 18 and 35 volunteered for the study. Participants came to the laboratory for 3 test sessions 48-hour apart (day 1, 3, and 5). During the initial session, baseline measures were assessed and participants underwent a fatigue protocol for the biceps brachii. Participants were then assigned to a positive expectation or a no-expectation condition before receiving a sham laser therapy treatment. The positive expectation group received symptom improvement priming before their sham treatment. Participants allocated to the no-expectation condition received no feedback before the sham treatment. Maximum voluntary isometric contraction; relaxed elbow angle; visual analog scale; and the QuickDash questionnaire were used as outcome measures.


RESULTS
The positive expectation group had a significant reduction in perceived pain compared with the no-expectation group at day 3 follow-up, with the mean scores being 34.65 mm (SE=4.44) compared with 49.4 mm (SE=5.79), respectively. There were no between-group differences with respect to maximum voluntary isometric contraction, QuickDash, or relaxed elbow angle outcomes. In addition, there were no significant between-group differences observed with expected pain on follow-up visits, the effect sizes were d=0.26 on day 1 for day 3 and d=0.51 on day for day 5.


CONCLUSIONS
Positive expectations before a sham treatment enhanced reduction in pain intensity but did not improve functional impairments following exercise-induced acute musculoskeletal injury.
Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL.
William C
WC
Hedderson
Department of Exercise Science, Concordia University, Montreal, QC, Canada.
Geoffrey C
GC
Dover
Department of Orthopaedic Surgery and Duke Clinical Research Institute, Duke University, Durham, NC.
Steven Z
SZ
George
Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL.
Joshua A
JA
Crow
Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL.
Paul A
PA
Borsa
D000293:Adolescent; D000328:Adult; D004185:Disability Evaluation; D004311:Double-Blind Method; D004551:Elbow Joint / Q000294:innervation; D015444:Exercise / Q000502:physiology; D005500:Follow-Up Studies; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D053685:Laser Therapy / Q000379:methods*; D053580:Muscle Strength; D059352:Musculoskeletal Pain / Q000209:etiology / Q000523:psychology / Q000628:therapy; D010147:Pain Measurement; D015990:Placebo Effect; D016059:Range of Motion, Articular; D055070:Resistance Training / Q000009:adverse effects*; D057566:Self Report; D055815:Young Adult