Influence of Blood Flow Occlusion on Muscle Oxygenation Profiles During Intermittent Maximal-Effort Contractions

• Main Author: Sears, Kylie
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2024
• Subjects: Exercise, kinesiology, and sport sciences; Kinesiology; Medicine; Physiology
• ISBN: 9798383205044

Limb blood flow occlusion has a profound and quickly reversible effect on motor unit excitation and fatigue development during intermittent, maximal-effort contractions but its impact on microvascular oxygenation and intra-contraction oxygenation profiles remains unknown. The purpose of this study was to determine the impact of complete circulatory occlusion and contraction-induced vascular compression on muscle oxygenation characteristics during intermittent, maximal-effort contractions. Sixteen participants (8M/8F; 22±3 yrs.) performed intermittent maximal-effort contractions (forearm flexion) for 5-min under control conditions (CON) and with complete limb blood flow occlusion (OCC) followed by immediate reperfusion. OCC was initiated at the start of the test and persisted until maximal-effort torque was < 15% of initial maximal torque. REP was initiated immediately following OCC and the contractions were performed without interruption until the end of the 5-min test. Oxygenated- and deoxygenated-[heme] of the biceps brachii (oxy-[heme] and deoxy-[heme]) were measured by frequency-domain near-infrared spectroscopy. Total-[heme] and tissue saturation (StO2) were calculated. Data from 3 consecutive contractions were averaged at Start, Min-1, End-OCC (and time-matched data point for CON), and End-Test. Reductions in oxy-[heme] and StO2 were greater, and increases in total-[heme] were less, during OCC compared to CON (all, p<0.05). No differences in deoxy-[heme] were detected between OCC and CON at any timepoint (End-OCC: 101±60 vs. 109±62 µM, p>0.05). During CON, contraction significantly decreased oxy-[heme], total-[heme], and StO2 at all timepoints (all, p<0.05). Contraction significantly increased deoxy-[heme] at Min 1 and the time-matched data point associated with End-OCC (both, p<0.05), but no difference was detected at End-Test (Contraction: 101±58 vs. Relaxation: 95±57 µM, p=0.174). After reperfusion, there were no differences in any oxygenation characteristics between trials at End-Test (all, p>0.05). Complete circulatory occlusion did not increase deoxy-[heme] during intermittent maximal-effort contractions suggesting no significant reserve in oxygen extraction. Muscle contraction increased deoxy-[heme] only during higher intensities above End-Test Torque, suggesting that End-Test Torque represents the highest intensity at which oxygen delivery is matched to oxygen demand.