University of Missouri - Columbia.
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Posted 11.07.05

'Muscle Pump' Important for Cardiovascular Health, Researcher Says

COLUMBIA, MO -- It's not something that most individuals think about daily, or even once a year, but the discussion of whether or not a "muscle pump" exists in the human body has been a large controversy in the scientific world for several years. One University of Missouri-Columbia researcher is convinced that the pump does exist and that it is vital for good cardiovascular health.

The muscle pump refers to the ability of contracting muscles to help the cardiovascular system keep blood and lymph fluid moving up through the body from the lower extremities. Some research has demonstrated that when muscles contract around a vein, they generate anywhere from 30 to 100 times as much pressure in the cardiovascular system than when the muscles are at rest. This could have a implications for future research on the effects of exercise on the cardiovascular system.

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Medicine and Science in Sports and Exercise

"Skeletal muscle tone while standing, in the absence of any movement, has critical bearing on the quantity of blood displaced into the legs," said Harold Laughlin, professor and chair of the Department of Veterinary Biomedical Sciences. "Due to gravity, blood pools in our lower extremities, our legs and feet. This can make it very difficult for blood to get back to the heart. While the valves in our veins do help control venous blood pressure and fluid weight, the pressure is confined to the blood between each valve. As muscles contract, they increase the pressure and help the blood return to the heart and continue circulating around the body."

This research explains why some people faint when standing for long periods of time with their knees locked. When knees are locked, the muscles don't contract and there is less pressure forcing blood back to the heart, Laughlin said. The Mizzou researcher also believes this could have positive implications for problems such as varicose veins.

"Our research has indicated that exercise might fine tune the muscle pump," Laughlin said. "We know that blood vessels are remodeled daily to perform their job, so it makes sense that physical activity might influence that. Controversy exists concerning whether or not this pump exists because current technology is limiting the research. Right now, it's difficult to test many of the hypotheses that are present in this field because the equipment and technology needed to confirm the hypotheses doesn't exist."

Laughlin said the principle of the muscle pump is similar to that of cardiopulmonary resuscitation (CPR). In CPR, the rhythmic compressions help maintain some flow of circulation. Laughlin's research and comments on this topic have been published in several scientific journals including the Journal of Applied Physiology and Medicine and Science in Sports and Exercise.



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