Blood pooling occurs when the walls and valves of veins in human legs do not work effectively, thereby making it difficult for blood to return to the heart, according to Cleveland Clinic. This condition, known as chronic venous insufficiency, causes blood to pool in veins, a condition called stasis.
Valves within veins in the legs become damaged, causing blood to leak backwards with the force of gravity instead of moving upwards. Valve damage happens due to aging, excessive sitting, extended standing and reduced mobility, notes Cleveland Clinic. Blood pressure in the affected veins remains elevated for long periods, which causes chronic venous insufficiency.
The causes of chronic venous insufficiency include blood clots, vascular deformations and pelvic tumors. Lack of blood flow or sluggish blood movement within leg veins leads to swollen legs. Other symptoms include aching legs, varicose veins, leathery-looking skin on legs, stasis ulcers and flaking skin on legs and feet. Untreated chronic venous insufficiency can lead to burst capillaries in the legs, according to Cleveland Clinic.
Dizziness may be another symptom of blood pooling in the legs. This occurs when someone suddenly stands up after sitting for long periods of time and blood pressure suddenly normalizes, notes Merck Manual. The heart rate increases, and blood vessels constrict rapidly when someone stands quickly after extended sitting.
One way to alleviate chronic venous insufficiency and blood pooling is to walk. The contraction of calf muscles during the walking motion moves blood more efficiently through the legs, according to the Society for Vascular Surgery.