Unraveling the pain trajectory in chronic low back pain patients during a physical exercise training program

Physical exercise can transiently decrease pain intensity within a single session and improve physical capacities while reducing pain over a training program. However, the pain trajectory throughout a concurrent physical training program remains unknown. This study aimed to model the pain trajectory during a training program including both aerobic and resistance exercises, considering both acute (within-session) and chronic (across-program) effects of physical exercise.

Prospective observational study.

Participants completed a 14-week training program (42 sessions; n = 28) or were assigned to a waiting list (n = 29). In the exercise group, low back pain intensity was measured before and after each training session. Pain intensity in the past week was measured before and after the 14-week period in both groups. The pain trajectory was modeled using linear mixed-effects with a quadratic term to capture potential non-linear pain reduction.

Past week pain decreased only in the exercise group (exercise: 4.9 ± 0.3 vs 2.5 ± 0.3; control: 5.6 ± 0.3 vs 5.3 ± 0.3). The pain trajectory was characterized by a linear and a quadratic term (p's < 0.001), suggesting pain reduction is greater early in the training program. Pain intensity decreased after each training session (p < 0.001) with this effect remaining constant throughout the program (non-significant interactions, p's > 0.585).

Pain decreases more markedly during the initial weeks of the program. Acute exercise-induced hypoalgesia persisted throughout the program, suggesting patients may use physical exercise to manage pain flare-ups even after several weeks of training.