the accumulation of acid lactic (propanoloic acid)
When muscles work too much they generally breakdown and start to deteriorate without the much needed stretching and rest in-between workouts.
This condtition is called hypertrophy.
lactic acid
Strain.
it can overwork the muscles and so its important to let the body return to normal once the "event" has passed.
The muscles will atrophy (shrink) if not used.
you excersise
They contract
The overuse of a muscle is when you overwork or tire out your muscle, and it can be very dangerous. If you carry too much weight for too long or if you exercise for way too long, your muscles will become cramped, and not only will they ache but you could end up pulling a muscle or a hamstring. It's important to stretch before exercising and to not overwork yourself. Know your limits!
you will die
you exhale (:
contrast
Im not expert, but isn't it the diaphragm and rib muscles, the muscles between the ribs, internal and external intercostals.
What happens when a muscle shortens is that it is contracting. This is when the fibers of the muscles generate tension.
muscles relaxes
Atrophy