Final answer:
The response of muscles experiencing intense exercise-induced fatigue and burning is to relax and rest to recover. This burning sensation indicates lactic acid buildup from lactic acid fermentation used to supply ATP. Pain and fatigue are signs to stop the activity and allow for muscle recovery and repair. The correct option is 4) Relax and rest
Step-by-step explanation:
When a person is performing intense physical exercise and begins to feel fatigue and a burning pain in the muscles, the response of the muscles is not to synthesize more, stop functioning, or shrink in size. Rather, the muscles typically need to relax and rest to recover from the fatigue.
This sensation of burning and fatigue is a sign that muscle cells have been using lactic acid fermentation to provide ATP for energy, which leads to a buildup of lactic acid and a decrease in pH within the muscle cells. Over time, this can affect the muscles' ability to contract and signal the need for a recovery period during which cells can eliminate lactic acid.
Additionally, prolonged physical exercise and intense activity can lead to muscle fatigue, which is when muscles can no longer contract effectively in response to signals from the nervous system.
Factors contributing to muscle fatigue include depletion of ATP reserves, lactic acid buildup impacting pH and enzyme activity, imbalances in electrolytes, and potential structural damage to components such as the sarcoplasmic reticulum (SR) and sarcolemma, affecting calcium regulation.
It is crucial to respect pain and fatigue by stopping the activity and allowing the muscles to rest, preventing injuries like delayed onset muscle soreness (DOMS) and facilitating recovery and muscle mass gain from the repair of any microscopic damage. The correct option is 4) Relax and rest