In exercise physiology we refer to the acute changes that occur in a sytem, organ, or cell during exercise as responses . An example is the increase in heart rate that occurs when we jump up from our chair and start jogging. Those long term changes that occur as a result of repeated bouts of exercise are called adaptations . Cellular adaptations generally involve an increase or decrease in the rate of synthesis of a specific cellular component.
All muscle cells are in a constant state of synthesis and degradation.
If synthesis rate exceeds degradation rate, an increase in the cellular component occurs. A change in protein synthesis requires a cellular signal. Biologists and physiologists continue to explore the communiction process by which different forms of muscular work induce cellular changes. At the cellular level, there are some theories, but no complete understanding. However, we do know quite a bit about what adaptations do occur, even if we aren't sure how just yet.