On the edema-preventing effect of the calf muscle pump

Abstract

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)

Effect of Lower Body Positive Pressure on Fluid Turnover in Human Legs

“…Thus, if an application of LBPP raises the interstitial pressure, lymphatic flow will increase markedly. Accordingly the decrease in the tissue fluid during LBPP is probably attributable to an increase in lymphatic outflow and/or to a decrease of the capillary filtration, the mechanism of which is different from muscle pump activity during walking 6) . These results suggest that applying LBPP and walking respectively prevent gravity-induced leg swelling in upright human.…”

“…The equation (1) indicates that a rise in the capillary hydrostatic pressure due to gravitational force increases the capillary filtration 6) . A part of the fluid that is filtered out of the capillary is reabsorbed into the venous end of the capillary.…”

“…For the reasons mentioned above, when the net filtration increases and/or lymphatic outflow decreases in the lower extremities, the interstitial fluid increases. In addition, muscle pump activity elicited by walking or cycling affects fluid turnover in the legs of upright human 6) . Muscle contraction during leg movement propels the blood in the vein toward the heart, which lowers the venous pressure 4) .…”

Effect of Running on Volume of the Foot and Ankle

“…There were larger increases as the work load increased. In a study by Stick et a1 where 15 males and 15 females progressed from a recumbent position to standing or sitting to exercising for 20 minutes on a cycle ergometer, all subjects demonstrated decreases in calf volume after the exercise contrary to the increases during standing and sitting (19). If the different durations and intensities of cycling or the proportion of males and females did not account for the varied findings in the previous two studies, differences may have been attributed to the ways of measuring the subjects.…”

“…If the different durations and intensities of cycling or the proportion of males and females did not account for the varied findings in the previous two studies, differences may have been attributed to the ways of measuring the subjects. Stick et a1 (19) related the following factors as potentially having contributed to the decreases in extravascular volume: a decrease in venous pressure that reduced filtration pressure, an increase in lymph flow that removed fluid and osmotically active colloid proteins from the interstitial spaces, and an increase in muscle tissue pressure during the muscle contraction.…”