Human lower leg muscle pump acts like a stream diversion pump during locomotion

Abstract

BackgroundCalf muscle pump (CMP) failure is associated with the development and progression of chronic venous insufficiency as characterized by ambulatory venous hypertension (AVH). However, the explicit interconnection between AVH with CMP failure remains uncertain because the concept of CMP function is controversial. The study aimed to measure pressure in different segments of the great saphenous vein (GSV) and intramuscular vein of the gastrocnemius (GCM) during exercise.MethodsTwelve legs of nine healthy volunteers were enrolled in the study. Continuous pressure (IVCALF, GSV at ankle, proximal calf, and mid-distal thigh) and electromyography data (GCM and anterior tibial muscle [ATM]) were recorded during treadmill walking, running, and plantar flexion exercises. The pressure gradient (PG, mmHg) between adjacent points of measurement was calculated. Minute unit power of muscle pump ejection and suction (, and, MPa/min) were calculated and compared with the arterial blood supply of the lower extremity (LBF, L/min).ResultsPG demonstrated a consistent pattern of changes during walking and running. An absence of PG directed from the calf to the thigh (centripetal) in the GSV was observed. Instead, a retrograde PG was verified throughout the entire stride cycle. Its value decreased with the increase in stride cycle frequency. The dynamics of PG between the IV and GSV were the following: It was directed from the IV to GSV during GCM contraction and was reversed during ATM contraction and GCM relaxation (swing phase). LBF,, anddemonstrated similar exponential growth with the increase in stride frequency during walking and running.ConclusionsThe pressure gradient in the GSV prevents centripetal flow during locomotion. Instead, PG directs blood flow from the GSV toward intramuscular veins. The increase in CMP unit power was tightly coupled with lower extremity arterial blood supply growth that prevented ambulatory venous pressure rise during exercise.Novelty and Significance What Is Known?The existence of a pressure gradient in superficial veins directed centripetally (from calf to thigh level) has been confirmed for the state of rest only (lying and standing).The existence of a pressure gradient directed from intramuscular to superficial veins or vice versa has been confirmed for the artificial exercise tests only (tiptoe movements, walking in place etc.).The main calf muscle pump function was considered as its ability to eject blood centripetally by posterior calf muscle group contraction.What New Information Does This Article Contribute?An absence of pressure gradient directed from the calf to the thigh (centripetal) in the great the saphenous vein during locomotion.During locomotion, at the lower leg level, the primary route of blood outflow from the superficial veinous network toward intramuscular veins is a horizontal route (through perforating veins).New parameters are introduced to assess calf muscle pump effectiveness as its ability to maintain accordance between the muscle pump output and arterial blood supply during locomotion.The calf muscle pump (CMP) is known as a significant contributor to venous blood outflow from the lower extremity due to its ability to effectively eject blood in a centripetal direction. Therefore, CMP failure refers to an impaired ejecting ability associated with chronic venous insufficiency (CVI) occurrence and progression. It is expressed in the increase in ambulatory venous pressure referred to as ambulatory venous hypertension (AVH). However, multiple studies demonstrated a lack of agreement between defined CMP failure and AVH, the severity of CVI, and quality of life.Here we show that during locomotion, the CMP acts as a stream diversion pump redirecting blood flow from superficial veins (SVs) to intramuscular veins (IVs) through perforating veins. This is because the observed pressure gradient prevents centripetal blood flow from the calf to thigh level in the SVs and favors blood flow from SVs to IVs during the swing phase of the stride cycle. This function is provided by the synergetic work of antagonist calf muscles (anterior tibial muscle and gastrocnemius). Thereby, the CMP prevents pressure growth in the superficial veins of the lower leg (AVH) during exercise when the arterial blood supply increases according to exercise intensity.

Live to Move and Move to Live: The Health of the Lymphatic System Relies on Mobility and the Foot and Calf Pump Connection

“…On the contrary, during the swing phase, the anterior tibial muscle contracts while the gastrocnemius relaxes, essentially generating negative pressure in the intramuscular veins. The pump redirects blood flow from superficial to intramuscular veins during natural locomotion, acting like a "stream diversion pump" [15].…”

“…Finally, ground reaction forces on the foot during stance and gait create a foot pump, highlighting the importance of mobility and ambulation to help move blood and New evidence suggests the muscle pump functions differently during the natural gait cycle compared to activities such as ankle pump exercises. According to Tauraginskii et al, the muscle pump involves the synergistic work of antagonist muscles, the ankle joint, and the posterior calf muscle group [15]. This is further explained by looking at the gait cycle: during the stance phase, the gastrocnemius contracts while the anterior tibial muscle relaxes, creating high pressure in intramuscular veins.…”

“…This allows blood to flow by aspiration into the deep veins [23]. Within the deep veins of the calf lie intramuscular venous sinuses that act as conduits, transferring blood from the intramuscular veins to the axial deep veins for the muscular pump of the calf [15]. Muscular pumps compress stiff vein walls running through the muscles and their fascial compartments, supporting flow out of the lower extremities [22][23][24].…”

“…Venous reflux is due to valve incompetence resulting from congenital, primary, or secondary thrombotic diseases. The main cause of venous reflux in the case of valve incompetence is a poorly functioning muscle pump [15,28]. Most venous reflux affects superficial and perforating veins, but sometimes, only deep veins or all three vein types are affected [29].…”