This study investigates whether walking or running prevents the formation of edema in the lower leg. In 18 volunteers changes in calf volume were measured using strain gauge plethysmography during slow (3 km/h) and fast (6 km/h) walking or running (10 km/h) on a treadmill for 20 min each. Venous pressure was measured in a superficial vein near the ankle. Low-pass filtering removed motion artifacts from the signals. Slow walking reduced the calf volume in a biphasic manner: a rapid decrease was followed by a slow decline, lasting from about minute 2 to minute 20, its mean rate being -0.073%/min. Besides a rapid initial decrease, no significant change was observed during fast walking. During running, the calf volume first increased within 7 min to a maximum of 2.5% and subsequently decreased with a mean rate of -0.096%/min. The medians of venous pressure were 84.0, 23.5, 30.4, and 29.5 mmHg during quiet standing, slow and fast walking, and running, respectively. The experimental results prove the hypothesis that walking prevents dependent edema formation. This effect, however, cannot be fully explained by the lowered venous pressures.

During motionless standing an increased hydrostatic pressure leads to increased transcapillary fluid filtration into the interstitial space of the tissues of the lower extremities. The resulting changes in calf volume were measured using a mercury-in-silastic strain gauge. Following a change in body posture from lying to standing or sitting a two-stage change in calf volume was observed. A fast initial filling of the capacitance vessels was followed by a slow but continuous increase in calf volume during motionless standing and sitting with the legs dependent passively. The mean rates of this slow increase were about 0.17%.min-1 during standing and 0.12%.min-1 during sitting, respectively. During cycle ergometer exercise the plethysmographic recordings were highly influenced by movement artifacts. These artifacts, however, were removed from the recordings by low-pass filtering. As a result the slow volume changes, i.e. changes of the extravascular fluid were selected from the recorded signal. Contrary to the increases during standing and sitting the calf volumes of all 30 subjects decreased during cycle ergometer exercise. The mean decrease during 18 min of cycling (2-20 min) was -1.6% at 50 W work load and -1.9% at 100 W, respectively. This difference was statistically significant (p less than or equal to 0.01). The factors which may counteract the development of an interstitial edema, even during quiet standing and sitting, are discussed in detail. During cycling, however, three factors are most likely to contribute to the observed reduction in calf volume: (1) The decrease in venous pressure, which in turn reduces the effective filtration pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

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To examine whether the so-called musculovenous pump counteracts the development of interstitial edema in the lower extremities of man in the upright position, the volume changes in the calf which occurred during twenty minutes of rhythmic muscular exercise were measured in twenty-three subjects by impedance-plethysmography. The results were compared with the volume increase found during quiet relaxed standing for the same length of time. Contrary to the hypothesis, and edema-protective effect of the musculovenous pump could only be shown in about half the number of the subjects. In the others, muscular exercise led to increases in calf volume which were higher than those measured in the normal upright position. These results show that the calf muscle pump does not generally have a edema-protective effect but rather that muscle contractions also activate mechanisms which stimulate the extravasation of fluid. In a second test-series with twenty subjects, changes in calf volume were measured during the course of the day. In nearly all cases, the calf volume was greater in the evening than in the morning. It could be shown that the volume increases in the evening are caused by an increase in extravascular fluid. Compared to the increase in extravascular volume occurring during twenty minutes, in a normal upright position, the accumulation of extravascular fluid during the day is, however, remarkably low. Although it is still unknown how interstitial edema in man's lower extremities is prevented during the day, these findings lead to the hypothesis that the edema-preventing mechanisms, for instance the muscle-lymphpump, do not become maximally effective until a certain volume has accumulated in the interstitial space.

The venous pressure in the saphenous vein at the ankle was measured in ten healthy subjects (5 men, 5 women) aged 19-33 years during supine posture, orthostasis and cycle ergometer exercise (50 W, 50 rpm). Measurements were made at 20, 28 and 36 degrees C at 50% relative humidity. A custom-built setup consisting of two pressure transducers and a differential amplifier was used to compensate for the hydrostatic effects, temperature influences and movement artefacts that disturbed the pressure measurements. Pressure was lowest in the supine position and varied only slightly with the ambient temperature. The mean pressures were 7 (SEM 1) mmHg [0.9 (SEM 0.13) kPa], 7 (SEM 1) mmHg [0.9 (SEM 0.13) kPa], 4 (SEM 1) mmHg [0.5 (SEM 0.13) kPa] at 20, 28 and 36 degrees C. The venous pressure increased when the subjects were passively tilted from a supine to an upright posture. The rate of the increase was smaller at 20 degrees C than at 28 degrees and 36 degrees C. The final level the pressure reached during motionless standing differed slightly. The mean pressures were 76 (SEM 2) mmHg [10.1 (SEM 0.27) kPa], 79 (SEM 7) mmHg [10.5 (SEM 0.93) kPa] and 75 (SEM 3) mmHg [10.0 (SEM 0.40)] at the three temperatures. When starting exercising, venous pressure decreased within the 1st min to a level which remained virtually constant until the end of exercise. However, this level was found to be temperature dependent. It was lowest at 20 degrees C (26 (SEM 3) mmHg [3.5 (SEM 0.40) kPa]) and increased with temperature.(ABSTRACT TRUNCATED AT 250 WORDS)