Near-infrared Spectroscopy Measures Of Sternocleidomastoid Blood Flow During Exercise And Hyperpnea: 1503 Board #97 May 28 10:30 AM - 12:00 PM

Respiratory muscle work exerts an influence on the distribution of blood flow during exercise. Most studies have focused on blood flow to the locomotor musculature rather than respiratory muscle owing to their complex anatomical arrangement. PURPOSE: To examine changes to accessory respiratory muscle blood flow in response to increasing ventilation (V̇E) during whole-body exercise. METHODS: Blood-flow index (BFI) of the vastus lateralis (VL), sternocleidomastoid (SCM), and 7th intercostal space (7IC) was measured during five-minute bouts of cycle exercise at 30, 60 and 90% peak-power output (EX). Participants then mimicked the hyperpnea of exercise (HYP) achieved during each exercise bout. BFI was measured using near-infrared spectroscopy optodes and indocyanine green. RESULTS: Six healthy males completed this study (age: 26 ± 3 years, V̇O2max: 56 ± 9 mL· kg-1· min-1). V̇E was matched well between EX and HYP (EX-30%: 53 ± 10 vs. HYP-30%: 56 ± 14; EX-60%: 86 ± 14 vs. HYP-60%: 87 ± 18; EX-90%: 159 ± 31 vs. HYP-90%: 142 ± 40 L· min -1, all p > 0.05). BFI-VL increased from 0.15 ± 0.09 μM·second-1 at rest to 2.57 ± 1.10 μM·second-1 during the EX-30% trial and 0.44 ± 0.23 μM·second-1 during the HYP-30% trial and did not significantly increase thereafter in either condition. No interaction effect was observed between condition and intensity, however, BFI-VL was significantly greater in the EX trials compared to the HYP trials (p < 0.05). BFI-SCM increased slightly from 0.87 ± 0.48 μM·second-1 to 1.01 ± 0.54 and 1.67 ± 1.54 μM·second-1 in the EX-30% and HYP-30% trials respectively. We observed no effects of condition or intensity when measuring BFI-SCM (p > 0.05). At rest BFI-7IC was 0.84±0.59 μM·second-1 and in the EX-30% and HYP-30% trials increased to 1.20 ± 0.75 and 1.26 ± 0.60 μM·second-1, respectively. No differences in BFI-7IC were observed between condition or intensity (p > 0.05). CONCLUSION: Previous studies have shown that during heavy whole-body exercise there exists a competition for blood flow between the locomotor and respiratory muscles during heavy, whole-body exercise. In this study, BFI-SCM was similar between exercise and hyperpnea mimicking trials across a range of ventilations, suggesting blood flow to accessory respiratory muscles is preserved during exercise. Funding: NSERC