Brachial and middle cerebral artery blood flow responses during sinusoidal leg cycling exercise

Abstract

To examine the control of peripheral circulation to non‐active muscle and brain during leg cycling exercise, we measured the dynamics of brachial artery (BA) and middle cerebral artery (MCA) blood flow (BF) to sinusoidal (sine) work rate (WR) forcing. Nine healthy subjects performed upright leg cycle exercise with a constant WR for 30 min followed by 16‐min sine WR exercises of 4‐min period fluctuated between 20 W to 60% VO2max. During protocol, we measured pulmonary gas exchange [breath‐by‐breath], heart rate (HR) and mean arterial blood pressure (MAP) [Photoplethysmograph], blood velocity (BV) and cross sectional area of BA [Ultrasound Pulsed‐Doppler], BV of MCA [Transcranial Doppler Ultrasonograph], and forearm and forehead skin BF (SBF) [Laser Doppler] and sweating rate (SR) [Capacitance Hygrometry]. The variable was fitted as y(t)=M+A*sin((2π/T)*t‐θ), where t: time, A/M: relative amplitude, T: period, θ: phase shift. Almost variables traced the sine wave adequately. The phase of variables regarding O2‐transport such as VO2, HR followed sine WR with similar delays (the mean: VO2; 51, HR; 45 °). While the BV in MCA showed the similar phase (73 °), its A/M was small (4.5 %). Contrarily, the response of BA displayed an anti‐phase (175 °) and a large A/M (30 %). The peripheral circulatory responses to nonactive limb and brain is quite different. (Support: JSPS‐KAKENHI, 22370091, 23650390, 24700701, 24247046)