Muscle blood flow at onset of dynamic exercise in humans

被引:222
作者
Rådegran, G [1 ]
Saltin, B [1 ]
机构
[1] Rigshosp, Copenhagen Muscle Res Ctr, Sect 7652, DK-2200 Copenhagen N, Denmark
来源
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY | 1998年 / 274卷 / 01期
关键词
blood pressure; muscle pump; intramuscular pressure; vasodilatation;
D O I
10.1152/ajpheart.1998.274.1.H314
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
To evaluate the temporal relationship between blood flow, blood pressure, and muscle contractions, we continuously measured femoral arterial inflow with ultrasound Doppler at onset of passive exercise and voluntary, one-legged, dynamic knee-extensor exercise in humans. Blood velocity and inflow increased (P < 0.006) with the first relaxation of passive and voluntary exercise, whereas the arterial-venous pressure difference was unaltered [P = not significant (NS)]. During steady-state exercise, and with arterial pressure as a superimposed influence, blood velocity was affected by the muscle pump, peaking (P < 0.001) at similar to 2.5 +/- 0.3 m/s as the relaxation coincided with peak systolic arterial blood pressure; blood velocity decreased (P < 0.001) to 44.2 +/- 8.6 and 28.5 +/- 5.5% of peak velocity at the second dicrotic and diastolic blood pressure notches, respectively. Mechanical hindrance occurred (P < 0.001) during the contraction phase at blood pressures less than or equal to that at the second dicrotic notch. The increase in blood flow ((Q)) over dot was characterized by a one-component (similar to 15% of peak power output), two-component (similar to 40-70% of peak power output), or three-component exponential model (greater than or equal to 75% of peak power output), where (Q) over dot (t) = (Q) over dot(passive) + Delta(Q) over dot(1).[1 - e(-(t - TD1/tau 1))] + Delta(Q) over dot(2). [1 - e(-(t - TD2/T2))] + Delta(Q) over dot(3). [1 -e(-(t-TD3/tau 3))]; (Q) over dot(passive,) the blood flow during passive leg movement, equals 1.17 +/- 0.11 1/min; TD is the onset latency; tau is the time constant; Delta(Q) over dot is the magnitude of blood flow rise; and subscripts 1-3 refer to the first, second, and third components of the exponential model, respectively. The time to reach 50% of the difference between passive and voluntary asymptotic blood flow was similar to 2.2-8.9 s. The blood flow leveled off after similar to 10-150 s, related to the power outputs. It is concluded that the elevation in blood flow with the first duty cycle(s) is due to muscle mechanical factors, but vasodilators initiate a more potent amplification within the second to fourth contraction.
引用
收藏
页码:H314 / H322
页数:9
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