intense exercise of short duration
via Human Anatomy and Physiology Marieb Hoehn 8th Edition, Chapter 9
intense exercise of short duration
It can be strained, but not fatigued. It must constantly beat, and so can not afford to give up.
It's probably just fatigued
Scientifically speaking our eye lids flicker or flutter or twitch because the muscle surrounding the eye is becoming fatigued. The muscle becomes fatigued after it has been constricting for long periods of time.
The fatigued muscles would need more glucose and oxygen.
Muscle cramps
if you are spinning on your toes or with your toes pointed, the calf muscle is hurting because it is being used and is probably cramping or becoming fatigued
It allows your muscles to work there for allowing more blood and oxygen to help them get less fatigued
Massage, if done correctly, relaxes the muscles. Quickening the recovery.
interruption in the muscle's blood supply or lack of acetylcholine in motor neuron axons
Cardiac muscle has the ability to rapidly adapt the strength of contraction based on how much stretch there is in the muscle.
myocardium myocardium
How well a muscle group can preform over a given time without becoming overly fatigued.