Final answer:
During exercise, decreased blood pH causes vasodilation near working muscles to optimize blood flow, delivering more oxygen and nutrients.
Step-by-step explanation:
Decreased blood pH near working muscles during exercise causes local vasodilation. This response optimizes blood flow to the muscles that are actively contracting, thus ensuring that they receive more oxygen and nutrients to sustain activity. Increased carbon dioxide (CO2) is a byproduct of muscle metabolism during exercise, which contributes to the decreased pH and signals the blood vessels to dilate. This mechanism does not involve vasoconstriction, which would limit blood flow and is typically associated with reduced demand for blood, such as in areas not requiring immediate oxygen and nutrients.