The Tolerance to Stretch is linked with Endogenous Modulation of Pain

Objectives: The effect of stretching on joint range ofmotion is well documented, and although sensoryperception has significance for changes in the tolerance to stretch following stretching the underlining mechanismsresponsible for these changes is insufficiently understood.The aim of this study was to examine the influence of endogenous pain inhibitory mechanisms on stretch toler-ance and to investigate the relationship between range of motion and changes in pain sensitivity. Methods: Nineteen healthy males participated in thisrandomized, repeated-measures crossover study, con-ducted on 2 separate days. Knee extension range of motion,passive resistive torque, and pressure pain thresholds were recorded before, after, and 10 min after each offour experimental conditions; (i) Exercise-induced hypo-algesia, (ii) two bouts of static stretching, (iii) resting, and(iv) a remote, painful stimulus induced by the cold pressortest. Results: Exercise-induced hypoalgesia and cold pressortest caused an increase in range of motion (p<0.034) and pressure pain thresholds (p<0.027). Moderate correlationsin pressure pain thresholds were found between exercise-induced hypoalgesia and static stretch (Rho>0.507,p=0.01) and exercise-induced hypoalgesia and the coldpressor test (Rho=0.562, p=0.01). A weak correlation in pressure pain thresholds and changes in range of motion were found following the cold pressor test (Rho=0.460,p=0.047). However, a potential carryover hypoalgesiceffect may have affected the results of the static stretch. Conclusions: These results suggest that stretch tolerancemay be linked with endogenous modulation of pain. Present results suggest, that stretch tolerance may merelybe a marker for pain sensitivity which may have clinicalsignificance given that stretching is often prescribed in therehabilitation of different musculoskeletal pain conditions where reduced endogenous pain inhibition is frequently seen.