Final answer:
During peak exercise, total peripheral resistance decreases due to vasodilation caused by local metabolites and mechanical forces on skeletal muscle arterioles, which allows for increased blood flow to meet the metabolic demand of active muscles.
Step-by-step explanation:
At peak exercise, what happens to total peripheral resistance (TPR)?
Option c, 'decreases due to the local metabolites and mechanical forces on skeletal muscle arterioles,' is the correct answer. During peak exercise, the body diverts blood to areas where it's needed most, such as skeletal muscles that are active. Local metabolites released by these muscles during the high demand for oxygen and nutrients cause vasodilation, which widens the blood vessels. This action reduces the total peripheral resistance, enabling an increased flow of blood to deliver oxygen and remove waste products efficiently. It's worth noting that the sympathetic nervous system does stimulate vasoconstriction in many parts of the body.
However, skeletal muscles respond differently under exercise conditions by increasing blood flow. Therefore, other options like 'increases due to the sympathetic nervous system on splanchnic arterioles' or 'increases due to local metabolites on cerebral arterioles' are incorrect in this context.