There are numerous reasons for people to suffer from cramps, but the main reason is fatigue after exercising.
Build up of metabolic wastes will influence the normal functioning of muscles which will contract and over shorten.
Electrolytes imbalance can also be a common cause. Here your osteopath will gently manipulate the affected muscle, try to enhance its perfusion, and will look at the against / antagonist imbalance too. Some of you will be suffering from cramps as a result of taking medication, please consult your General Practitioner to explore alternatives.