The Effect Of Blood Flow Restricted Isometric Forearm Exercise On Discomfort And Force Production

Abstract

Blood flow restricted exercise results in greater discomfort compared to the same exercise without blood flow restriction. However, this has only been investigated post exercise and it is possible that intra-set discomfort may differ compared with resting discomfort. No study has investigated discomfort during blood flow restricted exercise. Additionally, discomfort with isometric blood flow restricted exercise has not been investigated. PURPOSE: To investigate discomfort and changes in force to isometric exercise with and without blood flow restriction. METHODS: 60 participants (21 males, 39 female; 18-35 years old), completed 2 experimental visits. For both conditions, the participants performed four sets of two minute isometric handgrip contractions, with one minute of rest intervals, at 30% of their maximal voluntary contraction. Discomfort ratings (0-100) were given one minute into the exercise set. For the blood flow restriction condition a 12 cm nylon cuff was placed at the most proximal position on the individuals’ dominant arm and inflated to 50% of the pressure needed to occlude blood flow. Average force was recorded for each set. To assess differences in discomfort and force we conducted a Bayesian repeated measures ANOVA (condition by time) (prior = .5). RESULTS: There was no evidence for or against an interaction (BF10 = .435) for discomfort. There was evidence for an effect of condition (BF10 = 215.29) and time (BF10 = 8.006e+13). Blood flow restriction induced greater feelings of discomfort compared to isometric exercise alone (40.5 vs. 35.7 AU respectively). Discomfort increased with subsequent sets. There was evidence against an interaction for differences in force (BF10 = .025). There was a main effect of time with force declining across sets, but no main effect of condition. Average force for both conditions was 12.1, 11.3, 10, and 9.6 kg for sets 1, 2, 3, and 4 respectively. CONCLUSIONS: Our results suggest that isometric exercise with blood flow restriction causes greater discomfort during exercise. This difference appears independent to changes in force. Further restriction of venous return by blood flow restriction may increase metabolite build up more than unrestricted exercise, causing greater discomfort.