To investigate the joint effects of body posture and calf muscle pump, the calf blood flow of eight healthy volunteers was measured with pulsed Doppler equipment during and after 3 min of rhythmic exercise on a calf ergometer in the supine, sitting, and standing postures. Muscle contractions seriously impeded calf blood flow. Consequently, blood flow occurred mainly between contractions and reached a plateau that lasted at least the final 100 s of each exercise series. After exercise the blood flow decreased much faster in the sitting and standing postures than in the supine posture. There was no difference in blood flow between various postures during the same submaximal exercise. However, subjects in the standing posture were able to perform exercise with a higher load than in the supine posture, and blood flow in the standing posture could become twice as high as in the supine posture. We conclude that calf blood flow is regulated according to needs; available perfusion pressure determined maximal blood flow and exercise; and compared with the supine posture, the standing posture and calf muscle pump increase the perfusion pressure.
With strain gauge plethysmography various procedures to assess the competence of the venous system in the lower leg were compared in 10 normal subjects. The reproducibility and ease of use were established, and normal values were obtained. It is concluded, that measurements in the sitting position are preferable to those in the standing position. To measure the venous capacity, the dependency test is the method of choice. Rhythmic exercise to assess the effectiveness of the calf muscle pump can be restricted to five successive contractions. The refill time after exercise is not a suitable parameter to assess the competence of the venous valves.
A transcutaneous Doppler velocimeter has been used for monitoring changes in blood flow in the popliteal artery during and after exercise of the calf muscles on a calf-ergometer. The instrument and the positioning of the probe are described. The validity of the Doppler measurements has been assessed by comparing results after exercise and after 5 min arterial occlusion with venous occlusion plethysmography. For 10 healthy volunteers calibration lines were found which are curved. This can be ascribed partly to alinearity of the Doppler instrument and partly to changes of the diameter of the popliteal artery. Displacement of the probe with respect to the artery, which influences the measured velocity signal, can be detected and to a certain extent corrected by taking into account the intensity of the Doppler signal. The largest deviation of a data point from the corresponding calibration line varies for the ten subjects between 90 and 170 Hz in the high flow range (mean Doppler frequency around 1000 Hz) and between 20 and 60 Hz in the low flow range (mean Doppler frequency below 200 Hz).
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