Discomfort And Ratings Of Perceived Exertion To Practical Vs. Traditional Blood Flow Restriction Resistance Exercise

Abstract

Elastic knee wraps are used to produce blood flow restriction (BFR) but it is unclear how discomfort and perceived exertion may compare to more traditional ways of producing BFR such as nylon cuffs where the pressure is known. PURPOSE: To investigate how elastic knee wraps (practical) compare in ratings of perceived exertion (RPE) and discomfort after exercising to failure when compared to nylon cuffs (traditional) or low and high loads without BFR. METHODS: Nine participants (male=7, female=2) completed this study. The average age and body mass index were 22 (4) years and 25.4 (1.5) kg/m2. Each participant completed six conditions, in a randomized order, of unilateral knee extension exercise to failure for four sets. Two conditions (30% one-repetition maximum, 1-RM) included elastic knee wraps that were either stretched by two inches from resting length (Practical-Low) or they were stretched to a new length that was 85% of the thigh circumference (Practical-High). Two more conditions (30%-1RM) used nylon cuffs that were inflated to either 80% (BFR-High) or 40% (BFR-Low) of arterial occlusion pressure. The last two conditions had no restriction stimulus and were 30% 1-RM (LL) or 70% 1-RM (HL). Discomfort (0-10) and RPE (6-20) were measured before exercise and at the end of the four sets. The change scores from before exercise to the end of set 4 were used for analysis. Friedman’s test and Conover’s post hoc test were used to determine if there was a difference in discomfort and RPE between conditions. Statistical significance was set at p<0.05. RESULTS: Practical-High had larger changes in discomfort compared to HL (8 vs 6, p=0.007) and LL (8 vs 6, p=0.018). Practical-Low had a smaller change in discomfort compared to BFR-High (7 vs. 9, p=0.028) but it was not different from BFR-Low (7 vs. 7, p=0.450). No differences were found between Practical-High vs. BFR-High (8 vs. 9, p=0.211) or Practical-High vs. BFR-Low (8 vs 7, p=0.316). Practical-Low had smaller changes in RPE compared to BFR-High (12 vs 11, p=0.024) but there was no difference in RPE between Practical-High and the other conditions (p>0.05). CONCLUSIONS: When exercising to failure, both discomfort and RPE are impacted by the pressure used and elastic knee wraps can produce changes in discomfort and RPE levels that are comparable to high pressure BFR.