Why does a shortage of potassium lead to muscle cramping?
There could be 2 different effects of low K+ that could lead to cramps. First, K+ is involved in the repolarization of the muscle membrane during an action potential. If the K+ concentration is low within the cell, the driving force on K+ is lower, and the repolarization is slower. This will have no effect on the absolute refractory period of the action potential (the time when it is impossible to initiate another action potential), but the muscle cell will be more depolarized than usual following the absolute refractory period and thus closer to the AP threshold.
