What is one substance necessary for muscle activity that is delivered to muscles more effectively as a result of increased in heart rate?

One substance necessary for muscle activity that is delivered more effectively to muscles with increased heart rate is oxygen. As heart rate rises, blood flow to the muscles increases, enhancing the delivery of oxygen through the bloodstream. This improved oxygen supply is crucial for aerobic metabolism, which supports sustained muscle contractions during physical activity. Additionally, increased heart rate also facilitates the removal of metabolic waste products, further benefiting muscle function.