Ischemic Pain Threshold And Tolerance Are Not Altered Following Submaximal Blood Flow Restriction Exercise

Reductions in pain sensitivity (e.g., increased pressure pain threshold) have been shown when low-load resistance exercise is paired alongside blood flow restriction (BFR), but other indirect markers like ischemic pain threshold and tolerance have yet to be investigated. PURPOSE: To determine the effects of BFR combined with submaximal resistance exercise on ischemic pain threshold (IPT) and tolerance (IPTOL). METHODS: Forty-four participants completed four experimental visits in a randomized order. Conditions included: (1) submaximal knee extension exercise paired with BFR (70% of the most repetitions they could do under 80% arterial occlusion pressure (AOP)) [LL + BFR], (2) without BFR [LL], (3) 70% maximal free flow repetitions [LL + EFFORT], and (4) time-matched control [CON]. IPT and IPTOL were assessed using a post-test design (after each experimental condition). Participants had a cuff wrapped around their upper arm and this arm was held up in the air for 30 seconds. The cuff was inflated to 150% AOP and then the arm was lowered down to their side. Upon lowering the arm, the ischemic handgrip protocol began (≤20 reps of 30% maximum handgrip strength). Participants were told to call out “pain” for when they first perceived pain (threshold) and “stop” for when they could not tolerate the feeling (tolerance). If they were still tolerating pain following the 20 repetitions, the participants sat in silence until they either said “stop” or for a maximum of 15 minutes. These values were analyzed with Bayesian repeated measures ANOVA. Data are presented as mean (SD). RESULTS: No differences were found between conditions for IPT (BFinclusion: 0.125) or IPTOL (BFinclusion: 0.053). The times (in seconds) for IPT were 149.7 (101.8), 169.1 (133.8), 164.5 (133.8), and 158.6 (111.7) for the LL + BFR, LL, LL + EFFORT, and CON conditions, respectively. The times for IPTOL were 340.7 (181.4), 354.5 (198.7), 335.5 (183.3), and 330.9 (190.8) for LL + BFR, LL, LL + EFFORT, and CON conditions, respectively. CONCLUSIONS: The hypoalgesia effects of BFR as measured by IPT and IPTOL were absent. Since previous work routinely finds alterations to pressure pain threshold, this may suggest that distinct mechanisms may underlie endogenous pain modulation for different types of noxious stimuli.