Pain responses following resistance exercise with and without blood flow restriction in individuals with multiple...

Pain is a common symptom among individuals living with multiple sclerosis (MS). Exercise-induced hypoalgesia (EIH), a reduction in pain sensitivity following resistance exercise, typically requires high loads. Blood flow restriction (BFR) training may offer a lower-load alternative to elicit EIH. This investigation aimed to assess EIH responses following resistance exercise with and without BFR in individuals with MS.

15 participants diagnosed with MS completed three exercise sessions consisting of isotonic, unilateral leg extensions with the current exercise recommendation (high-load, 70% of 1RM), low-load BFR (LL + BFR, 30% of 1RM with BFR), or low-loads (30% of 1RM without BFR). Pain pressure threshold ("uncomfortable") and tolerance ("painful") of the rectus femoris were assessed before and after each exercise session. After each exercise set, participants rated their pain (0-10) which was used for mediation analyses.

Participants completed similar exercise volume (high-load = 3056.0 ± 728.2 kg; low-load = 3208.3 ±  1041.5 kg) but pain pressure threshold was greater (p = 0.012-0.025) following LL + BFR (1.04 ± 0.97 Δkgf) compared to high-load (0.37 ± 0.70 Δkgf) and low-load exercise (0.28 ± 0.69 Δkgf). Pain pressure tolerance was greater (p = 0.015) following LL + BFR (1.41 ± 1.01 Δkgf) compared to low-load exercise (0.23 ± 1.69 Δkgf). Peak pain was greater (p = 0.004-0.030) during LL + BFR (4.3 ± 2.9 au) compared to high-load (1.6 ± 1.7 au) and low-load (2.3 ± 2.4 au) exercise but was not a significant mediator of the EIH response.

LL + BFR elicited a local EIH response compared to the current exercise recommendation (high-load) and low-load resistance exercise. These findings suggest that LL + BFR may be an potent exercise intervention to acutely alter pain sensitivity in patients with MS.