During exercise, what percentage of cardiac output (Q) is directed to the muscles?

During exercise, the body experiences significant physiological changes to meet the demands of increased physical activity. One of the most critical adaptations is the redistribution of cardiac output (Q) to the working muscles. During intense exercise, the percentage of cardiac output directed towards the muscles can increase dramatically compared to rest.

At rest, a smaller proportion of cardiac output is supplied to the muscles, as other systems, such as the digestive system, also require blood flow. However, as exercise intensity increases, mechanisms such as vasodilation occur within the skeletal muscles, allowing for more blood to flow to those areas. This adaptation ensures that muscles receive adequate oxygen and nutrients to sustain activity and also helps clear metabolic wastes.

Research indicates that during vigorous exercise, around 80% of cardiac output can be directed to the skeletal muscles. This high percentage allows the body to maximize performance while efficiently meeting metabolic demands. Consequently, the answer indicating that 80% of cardiac output is directed to the muscles during exercise accurately reflects the body's response to vigorous physical activity.