During intense (heavy) exercise, the ability of oxidative phosphorylation to provide enough atp for force generation by the skeletal muscle is thereby causing the muscle fiber to derive energy from

a) enhanced : substrate-level phosphorylation
b) diminished : substrate-level phosphorylation
c) enhanced : fatty acids
d) enhanced : glucose
e) diminished : fatty acids

B) diminished : substrate-level phosphorylation

Explanation:

During an intense workout, muscles cannot derive energy from aerobic cellular respiration since the oxygen supply is not enough to support the process. Under these conditions, muscles switch to lactose fermentation in which the reduction of pyruvate into lactate regenerates NAD+ to continue the process of glycolysis.

Glycolysis yields 2 ATP molecules per glucose by substrate-level phosphorylation. The process of ATP synthesis wherein the substrates such as 1,3-bisphosphoglycerate or phosphoenolpyruvate serve as a donor of the phosphoryl group is referred to as substrate-level phosphorylation.