Influence Of The Degree Of Blood Flow Restriction On Muscular Activity During Bench Press Exercise: 259 Board #80 May 31 9

It has been reported that blood flow restriction (BFR) induced increases in muscle activation are correlated with decreased muscle blood flow resulting from external compression (i.e. higher relative pressures) (Sugaya M; 2011). However it has been reported that higher relative pressures may not be necessary with low-intensity exercise with BFR (Loenneke JP et al; 2015). PURPOSE:The purpose of this study was to compare the effects of resistance exercise with different degrees of BFR on muscle activation. METHODS:15 healthy adults performed 3 sets of bench press exercise (30, 15, and 15 reps; load: 30% 1RM) during 4 different BFR conditions: non pressure (N-BFR), low pressure BFR (L-BFR), middle level pressure BFR (M-BFR), and high pressure BFR (H-BFR). Surface EMG was recorded from the pectoralis major muscle (PM), anterior deltoid muscle (AD), and the triceps brachii muscle (TB), EMG amplitude (RMS) normalized as the relative exercise intensity (%) was analyzed (2-way repeated measures analysis of variance, and multiple post hoc test). RESULT:During 3 sets of exercise, gradual increases in RMS were observed in all muscles. The RMS of AD were 44.0±9.4-52.4±12.1-54.7±13.2 (mean±SD, %, 1set-2set-3set, N-BFR), 47.4±11.6-57.4±15.9-61.9±17.4 (L-BFR), 42.1±8.0-58.3±12.2-65.4±15.7 (M-BFR), and 47.0±12.3-68.2±25.9-77.3±33.9 (H-BFR). Interactions between BFR conditions and sets for AD had significant effects (F=2.53, p<0.05). The main effect of BFR conditions was significant for PM, average of 3 sets (mean±SD, %), N-BFR: 46.8±7.6 ; L-BFR: 52.4±14.3 ; M-BFR: 52.2±11.7 < H-BFR: 61.5±21.1, F=3.06, p<0.05, but was not significant for TB (N-BFR: 46.5±14.7; L-BFR: 55.9±20.1; M-BFR: 50.5±10.8; H-BFR: 52.1±17.4, F=0.86, p>0.05). CONCLUSION:These findings indicate that muscle activation was affected by relative differences in applied pressure for non-restricted trunk muscles (i.e. PM and AD), but not affected for restricted limb muscle (i.e. TB). Previous studies have focused on restricted limb muscle following single-joint resistance training. Therefore, it is important that the influence of the degree of blood flow restriction on muscle activation is investigated in multi-joint exercise. :