Author(s): CHUA, M.T., SIM, A., BURNS, S., Institution: NATIONAL INSTITUTE OF EDUCATION, NANYANG TECHNOLOGICAL UNIVERSITY, Country: SINGAPORE, Abstract-ID: 932

INTRODUCTION:
Blood flow restriction (BFR) during high-intensity interval exercise (HIIE) may induce high physiological stress, but this could occur at the cost of training intensity. This study compared the acute physiological and perceptual responses to three BFR methods applied during HIIE.
METHODS:
Twenty-four healthy males (age 25 ± 3.5 years, maximal aerobic power (MAP) 264 ± 61 W) completed four experimental trials in a randomised order. All HIIE consisted of 3 sets of 5 × 30-s on, 30-s off cycling intervals interspersed with 3-min of passive rest. The exercise intensities and BFR applied were: (i) control (CON) – 100% MAP, no BFR; (ii) rest occlusion (RO) – 100% MAP, 80% limb occlusion pressure (LOP) for 2-min during passive rest between sets; (iii) exercise low occlusion (ELO) – 70% MAP, 50% LOP during exercise; and (iv) exercise high occlusion (EHO) – 70% MAP, 80% LOP during exercise. Heart rate (HR), blood lactate (bLa), rating of perceived pain and discomfort (RPD) and rating of perceived exertion (RPE) were measured after warm-up and each exercise set. Surface electromyography was measured on the vastus lateralis (VL) and biceps femoris (BF) on the 1st and 5th repetition of each exercise set, followed by root mean square (RMS) analysis. Repeated measures ANOVA compared measures across conditions and time points, followed by post-hoc t-tests with Bonferroni adjustments where appropriate. Significance was set at p < 0.05.
RESULTS:
Two participants withdrew from EHO due to intolerable pain. The RPE and RPD during exercise were: (mean ± SD) CON = 11.9 ± 2.8 and 1.1 ± 1.4; RO = 12.1 ± 2.8 and 1.7 + 1.7; ELO = 11.7 ± 2.4 and 1.9 ± 1.7; EHO = 13.0 ± 3.1 and 3.4 ± 2.6). Main effects of condition, time and condition × time interactions were observed for RPE and RPD (all p < 0.05) with post-hoc t-tests showing a greater increase in both RPE and RPD across sets in EHO than the other conditions. Similarly, main effects of condition, time and condition × time interactions were observed for both HR and bLa (all p < 0.05) which were significantly lower in ELO than all other conditions (mean HR (bpm) and bLa (mmol∙l-1): CON = 137 ± 27 and 6.8 ± 3.0; RO = 141 ± 26 and 7.1 ± 3.1; ELO = 133 ± 26 and 5.3 ± 1.9; EHO = 139 ± 28 and 6.8 ± 3.0, all p < 0.05). HR was significantly higher in RO vs CON from exercise set 2 onwards (all p < 0.05) whereas bLa was greater in RO than CON 5-min post-exercise. Main effects of condition and time (all p < 0.05) were observed for RMS-VL and RMS-BF, with post-hoc tests indicating significantly higher RMS on CON and RO than ELO and EHO. For RMS-VL, there was a condition × time interaction, with significantly higher RMS observed during the last repetition in RO than CON (142 ± 18.0 vs 132 ± 14.9 mV, p < 0.05).
CONCLUSION:
Applying BFR during rest between HIIE sets (RO) elicits high physiological stresses – perceived pain, heart rate and blood lactate – without compromising muscle activation or exercise intensity.