Acute Muscular Responses to Practical vs. Traditional Blood Flow Restriction Resistance Exercise

Abstract

PURPOSE: To compare the impact of blood flow restriction (BFR) resistance exercise on changes in muscular force output (MVC), muscle thickness (MTH) and total exercise volume (TEV) when using elastic knee wraps (practical) or nylon cuffs (traditional) inflated to 40 and 80% of arterial occlusion pressure (AOP). METHODS: Participants (male=7, female=2) were 22 (4) years and had a body mass index of 25.4 (1.5) kg/m2. A randomized cross-over study design used unilateral knee extension exercise (4 sets to failure) with six different conditions at three separate visits. Low-load (LL, 30% 1-RM) exercise was performed with four conditions: elastic knee wraps (Valeo ®) stretched two inches from resting length (K2) and to a value that was 85% of thigh circumference (K85), and nylon cuffs inflated to 40% (BFR40) and 80% (BFR80) of AOP. LL (30% of 1-RM) and high-load (HL, 70% of 1-RM) exercise without restriction were also performed. MVC and MTH were measured pre and post exercise. TEV was also calculated for each condition. Two-way [Condition x Time] repeated measures ANOVA and one-way repeated measures ANOVA were used to analyze the data. Data reported as mean (standard deviation). Statistical significance was set at p<0.05. RESULTS: MVC decreased from pre to post-exercise for all conditions [∆HL: -90 (81) N, ∆LL: -126 (57) N, ∆BFR40: -168 (89) N, ∆BFR80: -240 (134) N, ∆K2: -178 (91) N, ∆K85: -197 (57) N, p<0.05]. The changes in MVC were significantly different in K85 vs. HL (p<0.001) and K85 vs. LL (p=0.013). HL and BFR80 MVC at 15 minutes post-exercise were not different from pre-values (∆HL: -53 (68) N, p=0.095; ∆BFR80: -67 (77) N, p=0.138) but LL, BFR40, K2 and K85 were still significantly below pre-values (p<0.05). MTH changes were similar from pre to post-exercise [∆HL: 0.22 (0.22) cm, ∆LL: 0.26 (0.1) cm, ∆BFR40: 0.26 (0.14) cm, ∆BFR80: 0.28 (0.19) cm, ∆K2: 0.26 (0.21) cm, ∆K85: 0.25 (0.13) cm, p=0.892]. HL TEV was higher [889.6 (227.7) kg] compared to all the other conditions (p<0.05) while the LL [686.1 (173.1) kg] was higher than the BFR40 [576.8 (160.7) p=0.026], BFR80 [434.9 (142.3) kg, p<0.001] and K85 [520.2 (139.2) kg, p=0.023] conditions. CONCLUSIONS: Exercising to fatigue with elastic knee wraps could be used to produce similar acute changes in MVC, MTH and TEV compared to known BFR pressures.