Eduardo D. S. Freitas1, Ryan M. Miller1, Aaron D. Heishman1, Japneet Kaur1, Brady Brown1, Michael Bemben1 FACSM.

1University of Oklahoma, Department of Health and Exercise Science, Neuromuscular Laboratory

PURPOSE: We investigated the acute physiological responses to continuous and intermittent blood flow restriction (BFR) resistance exercise (RE) (at 50% of BFR) and compared these responses to low and high-load RE without BFR. METHODS: Ten untrained males were randomly assigned to 4 RE conditions: 1) low-load with continuous BFR (cBFR); 2) low-load with intermittent BFR (iBFR); 3) low-load without BFR (LI); and 4) high-load without BFR (HI). For all low-load conditions, participants performed 4 sets (30-15-15-15 reps) of bilateral leg press and knee extension at 20% of 1RM whereas the HI condition performed 4 sets (10-10-10-10 reps) at 70% of 1RM of the same exercises. Whole-blood lactate (WBL) was assessed using a portable lactate analyzer at rest, immediately post (IP), and 5 min post-exercise (5P). Muscle thickness (MT), assessed through ultrasound, estimated muscle swelling at rest, IP, 5P, and 15 min post-exercise (15P). Two-way repeated measures ANOVA with Bonferroni correction followed by separate one-way repeated measures ANOVAs were used in the case of significant (p≤0.05) interactions. RESULTS: WBL was significantly (p<0.05) greater for HI compared to all conditions at IP and 5P, while no significant (p>0.05) differences existed across cBFR, iBFR, and LI at any time point. All conditions elicited significant (p<0.05) increases from rest at IP and 5P, with IP being significantly (p<0.05) greater than 5P for iBFR and LI only. For MT, there were no significant (p>0.05) differences across conditions at rest, IP, or 5P. At 15P, HI was significantly (p<0.05) greater than LI, but there was no significant (p>0.05) difference between cBFR and iBFR. Across time, cBFR and iBFR displayed similar responses in which all post exercise values were significantly (p<0.05) greater than rest. IP was significantly (p<0.05) greater than 15P, but not 5P (p<0.05). HI also elicited significantly (p<0.05) greater increases at all time points compared to baseline, however, no significant (p>0.05) differences existed across any of the post exercise measures. For LI, only IP measures were significantly (p<0.05) greater than both rest and 15P values. CONCLUSION: cBFR and iBFR induced similar acute physiological responses and that these responses were similar to those observed with HI and LI for WBL and to LI but not to HI for muscle swelling.

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