Fig. 7.

Relative contribution of ATP-producing pathways. The relative contribution of oxidative phosphorylation (ATP_OX; black), the creatine kinase reaction (ATP_CK; gray), and glycolysis (ATP_GLY; open) for the 25 Hz (left) and f₅₀ (right) protocols. There were no age-related differences in the relative contribution of each of the pathways to total ATP production during the 25-Hz contraction, while older muscle generated relatively more ATP by oxidative phosphorylation and the creatine kinase reaction, and relatively less by glycolysis, compared with young during the f₅₀ contraction (P ≤ 0.002).