NOS88

First, I believe it is important to recognize that leg cramps can be caused by different things. For example, many cramps are caused by fluid or electrolyte imbalances. Others can be caused by extreme environmental conditions or metabolic problems (e.g. so hot that it is impossible to maintain adequate fluid levels). Yet others can be caused by repetitive motion that triggers a fatigue response (this is an interesting one, because in effect there is neural input telling the muscle to contract, but the neural input telling it to relax is no longer functioning at a similar level. Think about the person who gets hand cramps after typing for long periods of time. He or she is not sweating. Hence there is likely to be no fluid or electrolyte imbalance. Rather, fatigue is causing the cramping). Hence, no single cure will work for everyone.

If you get cramps in muscles that are doing very little work while cycling, a fluid/electrolyte imbalance is likely in play. If, however, you only get cramps in muscles doing most of the work, then you are probably looking at fatigue as at least a partial cause.

Sometimes poor fit can be the cause of cramps, because over time, the muscles are forced to work in an unnatural way and fatigue more quickly.

With all of that said, a reasonable approach might be to keep well hydrated and electrolytes in balance, gradually increase your level of fitness, and make sure you have a proper fit.