Are endogenous opioid mechanisms involved in the effects of aerobic exercise training on chronic low back pain? A randomized controlled trial

Abstract

Aerobic exercise is believed to be an effective chronic low back pain (CLBP) intervention, although its mechanisms remain largely untested. This study evaluated whether endogenous opioid (EO) mechanisms contributed to the analgesic effects of an aerobic exercise intervention for CLBP. Individuals with CLBP were randomized to a 6-week, 18-session aerobic exercise intervention (n = 38) or usual activity control (n = 44). Before and after the intervention, participants underwent separate laboratory sessions to assess responses to evoked heat pain after receiving saline placebo or intravenous naloxone (opioid antagonist) in a double-blinded, crossover fashion. Chronic pain intensity and interference were assessed before and after the intervention. Endogenous opioid analgesia was indexed by naloxone–placebo condition differences in evoked pain responses (blockade effects). Relative to controls, exercise participants reported significantly greater pre–post intervention decreases in chronic pain intensity and interference (Ps < 0.04) and larger reductions in placebo condition evoked pain responsiveness (McGill Pain Questionnaire—Short Form [MPQ]-Total). At the group level, EO analgesia (MPQ-Total blockade effects) increased significantly pre–post intervention only among female exercisers (P = 0.03). Dose–response effects were suggested by a significant positive association in the exercise group between exercise intensity (based on meeting heart rate targets) and EO increases (MPQ-Present Pain Intensity; P = 0.04). Enhanced EO analgesia (MPQ-Total) was associated with a significantly greater improvement in average chronic pain intensity (P = 0.009). Aerobic exercise training in the absence of other interventions appears effective for CLBP management. Aerobic exercise–related enhancements in endogenous pain inhibition, in part EO-related, likely contribute to these benefits.

Does aerobic exercise effect pain sensitisation in individuals with musculoskeletal pain? A systematic review

“…The characteristics of the included studies are reported in Table 2 . Of the 11 included studies, seven studies had an experimental, repeated measures design [ 33 , 37 , 41 , 45 – 48 ] and four were randomised controlled trials [ 49 – 52 ]. Five studies recruited individuals with chronic low back pain [ 33 , 37 , 47 , 48 , 52 ], three studies examined those with chronic musculoskeletal pain [ 33 , 37 , 45 , 46 , 51 ], two investigated individuals with neck pain [ 49 , 50 ], and one included individuals with knee pain due to OA [ 41 ].…”

“…Of the 11 included studies, seven studies had an experimental, repeated measures design [ 33 , 37 , 41 , 45 – 48 ] and four were randomised controlled trials [ 49 – 52 ]. Five studies recruited individuals with chronic low back pain [ 33 , 37 , 47 , 48 , 52 ], three studies examined those with chronic musculoskeletal pain [ 33 , 37 , 45 , 46 , 51 ], two investigated individuals with neck pain [ 49 , 50 ], and one included individuals with knee pain due to OA [ 41 ]. Four studies were conducted in Denmark [ 45 – 47 , 50 ], two studies were undertaken in the United States of America [ 37 , 52 ], and the remaining studies were conducted in Belgium [ 33 ], Ireland [ 41 ], Turkey [ 51 ], Spain [ 48 ] and Poland [ 49 ].…”

“…Five studies recruited individuals with chronic low back pain [ 33 , 37 , 47 , 48 , 52 ], three studies examined those with chronic musculoskeletal pain [ 33 , 37 , 45 , 46 , 51 ], two investigated individuals with neck pain [ 49 , 50 ], and one included individuals with knee pain due to OA [ 41 ]. Four studies were conducted in Denmark [ 45 – 47 , 50 ], two studies were undertaken in the United States of America [ 37 , 52 ], and the remaining studies were conducted in Belgium [ 33 ], Ireland [ 41 ], Turkey [ 51 ], Spain [ 48 ] and Poland [ 49 ]. Three studies were published before 2010 (in 2005 [ 37 ], 2009 [ 50 ] and 2010 [ 33 ]), 5 studies were published between 2016-2018 [ 41 , 45 , 46 , 49 , 51 ], and the remaining 3 studies were published in 2020 and 2021 [ 47 , 48 , 52 ].…”

Slowly repeated evoked pain (SREP) as a central sensitization marker in episodic migraine patients

“…Thus, SREP sensitization might be useful in the discrimination of bottom-up versus top-down CS processes, and this could be useful clinically in the context of individualized treatment. Thus, if SREP primarily reflects top-down CS mechanisms, patients with greater SREP sensitization may obtain greater benefit from therapies that may enhance descending inhibition, such as physical exercise, psychological interventions, and medications enhancing neurotransmitters involved in pain inhibition (e.g., selective norepinephrine reuptake inhibitors (SNRIs) 6,79,80 .…”

Clinical guidelines and care pathway for management of low back pain with or without radicular pain

“…Based on a systematic review of the exercises that can be performed after rehabilitation, no exercises have been contraindicated, and multiple practical modalities can be proposed to the patients [40]. The effectiveness of physical activity is probably linked not only to a change in muscular strength but also to other mechanisms such as endogenous opioid mechanisms [41], mood improvement, reduction of kinesophobia, and cortical reorganisation [42].…”