Which of the following is a way that muscle fibers get energy needed for contraction? 1) When a muscle is contracting during peak activity, it quickly uses up stored creatine phosphate which was produced during moderate exercise. 2) During moderate exercise, such as jogging on the treadmill, pyruvate and hydrogen ions accumulate causing muscle fatigue. 3) During peak activity levels, glycolysis is the only pathway by which ATP can be produced to supply energy to the muscle. 4) Because energy demands are low in a resting muscle, a resting muscle is able to meet its ATP requirement through glycolysis. 5) Aerobic exercise is beneficial to a muscle because it increases muscle's ability to acquire greater amounts of glucose from

ATP serves as the main energy molecule in our bodies. Although our body can store ATP but the requirement of energy at the time of high activity or exercise is more as compared to the stored amount of ATP. Hence, our bodies tend to produce ATP by the cycle of glycolysis. In glycolysis, glucose is broken down to yield pyruvate molecules with the release of ATP ( energy ) molecules.