Isometric Back Exercise Has Different Effect on Pressure Pain Thresholds in Healthy Men and Women

Objective. Isometric exercises produce an acute decrease in the pain sensitivity, known as exercise-induced hypoalgesia (EIH). Existing EIH paradigms use exercises at the extremities with more pronounced EIH at local compared to remote body sites, indicating local inhibition in addition to central inhibitory mechanisms. So far the results on EIH in patients with low back pain (LBP) are equivocal and no studies have investigated an EIH paradigm targeting the lower back in order to assess EIH in patients with LBP. Thus, the aim of this pilot study was to assess pressure pain sensitivity at local and remote assessment sites, before and after an isometric back exercise in healthy women and men. Methods. In a pre-posttest design, pressure pain thresholds (PPT) were assessed at the lower back, biceps femoris muscle, and hand in 29 healthy subjects (17 women) before and after 120 seconds of the isometric Biering-Soerensen back extension test. Results. After exercise, PPT increased significantly at the hand in women, but not in men ( P  = 0.027). Moreover, PPT at the leg increased independently of sex ( P  < 0.004). The increase in PPT at the lower back after exercise approached significance ( P  = 0.07). Conclusions. The results of this pilot study indicate that isometric back exercise produces local and remote hypoalgesia. Remote EIH was only demonstrated in women, supporting the influence of sex in the hypoalgesic response after exercise. The effect of isometric back exercise on pain sensitivity in patients with low back pain should be investigated in future studies.