Grayson Sossamon, Timothy R. Rotarius, Jakob D. Lauver, Justin P. Guilkey. Coastal Carolina University, Conway, SC.

BACKGROUND: Aerobic exercise with blood flow restriction (BFR) has been shown to elicit positive physiological adaptions. A mechanism of adaptation with BFR is increased local metabolic stress, however, BFR can also increase cardiac work. Metabolic stress and cardiac work could be affected by the work interval duration during BFR but the acute physiological effects of interval duration with BFR are unexplored. This study will examine the effect of work interval duration on the local metabolic stress and cardiac work during low-intensity aerobic exercise with BFR. METHODS: Healthy males (18-25 yrs) will complete a graded exercise test to determine WR for experimental conditions. On separate days, participants will complete three experimental interval (INT) exercise protocols with intermittent BFR, in a random order. All protocols will consist of a 4-min warm-up ([20 W] WU), work INTs (35% peak power), and 1-min recovery INTs (20 W) between work INTs. The work INTs in the three protocols will be: 1) six 2-min INTs (2-min INT), 2) twelve 1-min INTs (1-min INT), and 3) three 4-min INTs (4-min INT). During work INTs, BFR cuffs will rapidly inflate to 60% of limb occlusion pressure (LOP) and deflate during recovery INTs. LOP will be the pressure at which the posterior tibial artery pulse ceases by Doppler auscultation. In each protocol, the duration of work INTs and BFR will be 12 mins. Gas exchange, heart rate (HR), and tissue oxygen saturation (StO2) of the vastus lateralis, via near-infrared spectroscopy, will be collected throughout exercise. To quantify local metabolic stress, StO2 will be averaged over the last 30 sec of the WU and expressed as change from WU. Blood pressure (BP) will be taken manually and rate pressure product (RPP) will be calculated to assess cardiac work. Due to the different protocol durations, data will be compared at 0% (end of WU), 33%, 67%, and 100% of each protocol duration. Differences between protocols will be determined by a 2-way (trial x time) repeated measures ANOVA. Significance will be established if p ≤0.05. ANTICIPATED RESULTS: It is hypothesized StO2 will have a greater decrease from WU and RPP will be greater, suggesting greater local metabolic stress and cardiac work in 4-min INT compared to 1-min INT and 2-min INT. If the hypothesis is confirmed, training with longer intervals could elicit greater local adaptations, but cardiac work will be increased during training.

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