Question

During static muscle activity, there is a strong compressive effect from skeletal muscle contraction coupled with an absence of rhythmic muscle activity. Describe how this would change arterial pressure (afterload) and venous return (preload) compared with dynamic activity.

Answer 1

Static Muscle Activity:

When a muscle is contracting and there is no movement in the body, it is termed as static muscle activity. Static muscle activities are involved in maintaining the posture for a period of time. Hence during this activity, there is always a strong compressive effect from skeletal muscle contraction coupled with an absence of rhythmic muscle activity.

Heavy static exercise is characterized by a failure of the local blood flow to adjust to the oxyged demands of the exercising muscles. Respiratory and circulatory responses will be dominated by an incompetence to obtain a steady state condition and hence the worktime is short. After the cessation of heavy static exercise, there will be a sudden increse in cardiac output and oxygen uptake. When the blood pressure increases, even the light static exercises causes more strain in the heart similar to dynamic exercise

By incresing contractility and heart rate, heart responds to the increased afterloadand , therby improving the cardiac output. If a person has a poor cardiac reserve, a rise in the left ventricular end - diastolic pressure is noticed with an immense fall in stroke work index and in response to the increased afterload

These are the outcome of static muscle activity