High-Fatigue Dynamic Resistance Exercise Induces Significant Hypoalgesia Effect.

Abstract: Hogge, R, Mascheri, M, Shurik, D, Hanney, WJ, and Anderson, AW. High-fatigue dynamic resistance exercise induces significant hypoalgesia effect. J Strength Cond Res XX(X): 000-000, 2024-Although dynamic resistance exercise is a recommended treatment for patients with musculoskeletal pain, optimal intensity to create hypoalgesia has not been established. Response to exercise may also be affected by biopsychosocial factors that modulate pain response. The first purpose was to compare the immediate effects of a high-fatigue/exertion leg extension, low-fatigue/exertion leg extension, and control condition on pressure pain threshold (PPT) applied to the quadriceps (local effects) and trapezius (systemic effects). The second purpose was to examine if psychological and pain sensitivity factors affected response to exercise. As a within-subject design, subjects completed psychological questionnaires, a control condition, and a 1-repetition maximum (1RM) during the first session. Subjects attended 2 more sessions where they completed 3 sets of a leg extension exercise at 50% of their 1RM until they reached a fatigue level of high fatigue (8/10 on the Borg CR-10) or low fatigue (3/10) with a randomized session order. A within-subject repeated-measures ANOVA was conducted (significance set at p < 0.05). High-fatigue exercise produced significantly higher PPT at the quadriceps than quiet rest after each set (F[6,162] = 3.25, p < 0.01, partial eta2 = 0.11). During low-fatigue exercise, individuals with an efficient endogenous pain inhibitory capacity displayed significantly higher PPT at the trapezius (F[2.14, 55.61] = 3.31, p = 0.03, partial eta2 = 0.11). Lower fear of pain was moderately associated with greater PPT increases at the trapezius (r = -0.38, p = 0.04). Although high-fatigue exercise produces immediate local hypoalgesia, systemic hypoalgesia is affected by variability in pain inhibition and fear of pain.