Assessment Of Intramuscular Blood Flow And Femoral Artery Blood Flow During Submaximal Knee Extensions

It is well known that blood flow through the conduit artery (i.e., femoral artery) linearly increases with exercise intensity to supply oxygen to working muscles. However, the dynamics of blood flow within working muscle (intramuscular blood flow), which would affect exercise performance, remains unclear due to the methodological limitations. Recent studies have shown that power Doppler ultrasonography has potential to assess intramuscular blood flow during exercise. Simultaneous assessment of intramuscular blood flow and femoral artery blood flow is expected to provide the valuable insight into blood flow supply to working muscles. PURPOSE: The purpose of his study was to compare the dynamics of intramuscular blood flow and femoral artery blood flow during intermittent and submaximal knee extensions. METHODS: Ten healthy young men (19.7 ± 1.1 years) performed intermittent (5 s contraction, 5 s relaxation) isometric knee extensions. Five contractions were performed at each force level of 10%, 30%, 50%, and 70% of maximal voluntary contraction (MVC) in random order with a 10-minute rest between sets. Intramuscular blood flow from the vastus lateralis of the right mid-thigh using power Doppler ultrasonography and femoral artery blood flow using pulse-wave Doppler ultrasonography were measured, simultaneously. Intramuscular blood flow was assessed by the area of power Doppler signals which indicate blood flow distribution in the cross-sectional area in the region of interest in the vastus lateralis. Intramuscular blood flow and femoral artery blood flow were normalized by each of the maximum value for comparison. RESULTS: There was no significant difference in the dynamics between intramuscular blood flow and femoral artery blood flow. Compared to one lower intensity, intramuscular blood flow significantly increased 34.7 ± 23.8% at 10% MVC and 37.5 ± 29.8% at 30% MVC, while femoral artery blood flow significantly increased 24.4 ± 8.3% at 10% MVC, 31.6 ± 11.6% at 30% MVC and 21.2 ± 10.2% at 50% MVC. CONCLUSIONS: These results indicate a decrease in the proportion of femoral artery blood flow which was distributed into the vastus lateralis during moderate-to-high intensity exercise. This suggested that blood flow distribution to working muscles was changed. MEXT KAKENHI 22K19728, JST SPRING JPMJSP2125