Problem: Johanna returned from jogging and was breathing heavily and sweating profusely. They complained that their legs ached and felt weak. Their partner poured them a sports drink and urged them to take it easy until they could "catch their breath." Based on what you have learned about muscle energy metabolism, respond to the following questions:
a. Why is Johanna breathing heavily?
b. What ATP-harvesting pathway have their working muscles been using that leads to such a breathing pattern?
c. What metabolic product(s) might account for their sore muscles and their feeling of muscle weakness?
d. How has Johanna recovery from COVID-19 five months ago impacted this process?