Question

during a long run, your leg muscles start to feel tired and sore. this sensation is most directly due to the interaction between which two systems?

your brain is signaling for more snacks to boost your energy.

your heart and lungs are sending extra oxygen to keep your leg muscles powered up.

your leg muscles and bones are working overtime to keep you moving fast.

your leg muscles are low on oxygen and switching to a different energy process that causes soreness.

Explanation:

• Analyze each option:
• The first option about the brain signaling for snacks is not related to muscle tiredness/soreness from running.
• The second option describes the heart and lungs sending oxygen, but this is about supplying energy, not directly causing the tired/sore sensation.
• The third option about muscles and bones working overtime does not explain the tired/sore feeling (it's about movement, not the sensation's cause).
• The fourth option: When running, if leg muscles are low on oxygen, they switch to anaerobic respiration, producing lactic acid which causes soreness. This directly relates to the muscle's energy process and the resulting sensation.

Answer:

Your leg muscles are low on oxygen and switching to a different energy process that causes soreness.