CSSD Practice Exam 2025 – Complete Study Resource

During exercise, especially vigorous activities, muscles experience a significant increase in blood flow to meet the heightened demand for oxygen and nutrients, as well as to facilitate the removal of metabolic wastes. The correct range for additional blood flow required by muscles during high-intensity exercise can indeed go as high as 15-80% of the resting blood flow.

This substantial increase occurs due to several physiological adaptations: as the intensity of exercise rises, blood vessels leading to the muscles dilate (a process known as vasodilation), allowing more blood to flow to the active tissues. Additionally, the body prioritizes blood flow to vital organs and to the muscles being engaged in the activity. This adaptive response underscores the muscles' need for more oxygen and substrates during exercise, thus validating the choice reflecting a substantial percentage increase in blood supply during physical activity.