I can add one thing: It is possible to exercise a muscle beyond it's metabolic capacity and cause serious muscle injury as a result. This happens with non-trivial frequency in sports "boot camp" environments where the participants will be run ragged all day with insufficient food, then subjected to, eg, intense squatting exercises.
Surprisingly, muscles do not expend energy when they contract, but rather the energy is expended when the muscles "reset". If the muscles contract and then it turns out that there is not enough available glucose, et al, to reset them, the muscle cells "depolarize" and die.
In the "boot camp" scenario this results in intense muscle pain in the major muscles of the legs, followed by "rhabdomyolysis" -- the breakdown of muscle -- and "myoblobinuria" -- the excretion of the breakdown products in the urine (seen as a rust-colored sediment -- myoglobin -- in the urine).
In young, healty people there is generally enough "reserve" muscle that, though this injury is effectively permanent, it does not result in any noticeable disability. (However, the myoglobinuria can result in serious kidney damage, and there is a secondary condition where the damaged muscles of the leg swell up and constrict that can also be quite serious.)
In older people, however, especially those on statin drugs and some diabetes meds, the resulting injury itself can be significant and life changing, especially if repeated several times.
The injury is most apt to occur in situations such as a relatively long, intense climb near the end of several hours of cycling, but can occur in shorter episodes of intense energy expenditure. The symptom will be a "muscle pull" type pain that doesn't appear until about 36 hours after the exercise (in fact, long enough removed that the individual may not associate the pain with the prior activity). And, where a regular "muscle pull" usually clears up in 3-6 weeks, the rhabdo injury remains painful for 3-6 months.