Cardiovascular responses to static exercise.

In light static exercise the heart rate and blood pressure increase much more than during dynamic exercise at the same oxygen uptake level. Heavy static exercise is characterized by a failure of the local blood flow to adjust to the oxygen demands of the exercising muscles. Respiratory and circulatory responses are dominated by an incompetence to obtain steady-state conditions, and thus the worktime is short. After the cessation of heavy static exercise a sudden compensatory increase occurs in cardiac output and oxygen uptake. Due to the higher increase in blood pressure, even light static exercise causes much higher strain on the heart than an equivalent amount of dynamic exercise. The heart responds to the increased afterload by increasing contractility and heart rate and thus improves cardiac output. In persons with a poor cardiac reserve a rise in the left ventricular end-diastolic pressure is seen, along with a fall in the stroke work index in response to the increased afterload caused by static exercise. It is possible that a discrepancy exists between work capacity during tasks demanding also isometric muscle work and a dynamic exercise test performance. The decreased cardiac reserve may first appear after the great increase in afterload, even in relatively light static work.