Standing

The human center of mass is in front of the ankle, and unlike in quadrupeds, the base of support is narrow, consisting of only two feet.

Traditionally, such correction was explained by the spring action of the muscles, a local mechanism taking place without the intervention of the central nervous system.

Before each tilt reaches the tipover point, the nervous system counters with a signal to reverse direction.

Electromyography has detected slight activity in the muscles of the calves, hips and lower back.

Orthostatic hypotension is characterized by unusually low blood pressure when the patient is standing up.

It can cause dizziness, lightheadedness, headache, blurred or dimmed vision and fainting, because the brain does not get sufficient blood supply.

Normally, the body compensates, but in the presence of other factors, e.g. hypovolemia, diseases and medications, this response may not be sufficient.

Prolonged still standing significantly activates the coagulation cascade, called orthostatic hypercoagulability.

[17] Characterized by fast (12–18 Hz) rhythmic muscle contractions that occur in the legs and trunk immediately after standing.

No other clinical signs or symptoms are present and the shaking ceases when the patient sits or is lifted off the ground.

The high frequency of the tremor often creates a rippling effect on the leg muscles while standing.