Final answer:
Supplementary energy sources after exertion provide additional energy to support recovery and replenish energy stores in the body.
Step-by-step explanation:
The purpose of supplementary energy sources after exertion is to provide the body with additional energy to replenish energy stores and support recovery.
One example is the use of supplements like erythropoietin (EPO) and human growth hormone (hGH) by endurance athletes to enhance oxygen availability in muscles and promote muscle healing and recovery.
Another example is the utilization of creatine phosphate and glycogen to produce ATP, the energy currency of cells, during intense muscle activity.