School of Kinesiology and Rehabilitation Sciences, College of Health Professions and Sciences, University of Central Florida, Orlando, Florida, United States of America.
Musculoskeletal Research Lab, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, Florida, United States of America.
PLoS One. 2024 Apr 16;19(4):e0299481. doi: 10.1371/journal.pone.0299481. eCollection 2024.
Exercise produces an immediate lessening of pain sensitivity (Exercise-Induced Hypoalgesia (EIH)) in healthy individuals at local and distant sites, possibly through a shared mechanism with conditioned pain modulation (CPM). Dynamic resistance exercise is a recommended type of exercise to reduce pain, yet limited research has examined the effects of intensity on EIH during this type of exercise. Therefore, the primary purpose of this study is to compare changes in PPT at a local and distant site during a leg extension exercise at a high intensity, a low intensity, or a quiet rest condition. A secondary purpose is to examine if CPM changes after each intervention. The final purpose is to examine if baseline pain sensitivity measures are correlated with response to each intervention.
In a randomized controlled trial of 60 healthy participants, participants completed baseline pain sensitivity testing (heat pain threshold, temporal summation, a cold pressor test as measure of CPM) and were randomly assigned to complete a knee extension exercise at: 1) high intensity (75% of a 1 Repetition Maximum (RM), 2) low intensity (30% 1RM), or 3) Quiet Rest. PPT was measured between each set at a local (quadriceps) and distant (trapezius) site during the intervention. CPM was then repeated after the intervention. To test the first purpose of the study, a three-way ANOVA examined for time x site x intervention interaction effects. To examine for changes in CPM by group, a mixed-model ANOVA was performed. Finally, a Pearson Correlation examined the association between baseline pain sensitivity and response to each intervention.
Time x site x intervention interaction effects were not significant (F(5.3, 150.97) = 0.87, p = 0.51, partial eta2 = 0.03). CPM did not significantly change after the interventions (time x intervention F(1,38) = 0.81, p = 0.37, partial eta2 = 0.02. EIH effects at the quadriceps displayed a significant, positive moderate association with baseline HPT applied over the trapezius (r = 0.61, p<0.01) and TS (r = 0.46, p = 0.04).
In healthy participants, PPT and CPM did not significantly differ after a leg extension exercise performed at a high intensity, low intensity, or quiet rest condition. It is possible pre-intervention CPM testing with a noxious stimuli may have impaired inhibitory effects frequently observed during exercise but future research would need to examine this hypothesis.
在健康个体中，运动产生即时的疼痛敏感性降低（运动诱导的痛觉减退（EIH）），在局部和远处部位均如此，其可能通过与条件性疼痛调制（CPM）共享机制产生。动力抗阻运动是一种推荐的减轻疼痛的运动类型，但关于这种运动类型中强度对 EIH 的影响的研究有限。因此，本研究的主要目的是比较在高强度、低强度或安静休息条件下进行腿部伸展运动时，局部和远处部位的 PPT 变化。次要目的是检查每次干预后 CPM 是否发生变化。最终目的是检查基线疼痛敏感性测量值是否与对每个干预的反应相关。
在一项 60 名健康参与者的随机对照试验中，参与者完成基线疼痛敏感性测试（热痛阈值、时间总和、冷加压测试作为 CPM 的测量），并随机分配至以下三种干预之一：1）高强度（75%的 1 重复最大值（RM），2）低强度（30%的 1RM），或 3）安静休息。在干预过程中，在局部（股四头肌）和远处（斜方肌）部位测量每次组间的 PPT。然后在干预后重复 CPM。为了检验研究的第一个目的，采用三因素方差分析检验时间 x 部位 x 干预的交互效应。为了检查各组 CPM 的变化，采用混合模型方差分析进行。最后，皮尔逊相关检验了基线疼痛敏感性与对每个干预的反应之间的关联。
时间 x 部位 x 干预的交互效应不显著（F(5.3, 150.97) = 0.87，p = 0.51，部分 eta2 = 0.03）。CPM 在干预后没有显著变化（时间 x 干预 F(1,38) = 0.81，p = 0.37，部分 eta2 = 0.02）。股四头肌的 EIH 效应与斜方肌上施加的基线 HPT（r = 0.61，p<0.01）和 TS（r = 0.46，p = 0.04）呈显著正中等关联。
在健康参与者中，高强度、低强度或安静休息条件下进行腿部伸展运动后，PPT 和 CPM 没有显著差异。可能是由于预干预时使用的疼痛刺激物可能会损害运动时经常观察到的抑制作用，但需要进一步研究来检验这一假设。
