I did some research into Exercise Induced Muscle Cramps (EIMC) for an MSc paper, here is a brief summary of what I found...I hope it helps. It is not meant to be definitive by any means!

Serum electrolyte and dehydration related theories postulate that systemic disturbances of fluid and electrolyte imbalances would lead to gramps. Fact is that chronic disorders, causing sodium and calcium depletion are not commonly associated with cramps. Systemic abnormalities would lead to generalised muscle cramping (Maughan, 1986; Schwellnus et al., 1997), before these cramps occur the athlete would be likely to suffer muscle fasiculation, dizziness, disorientation and stomach cramps.

Muscle fatigue, due to glycogen depletion within the muscles and liver, cause a relative deficit of ATP and thus a resultant inability of crossbridges to detach, causing contractures (McArdle et al., 2001). However as the body has the ability to produce ATP from a number of reserves athletes are likely to be unable to continue competing well before contractions occur and these contractions (or cramps) are likely to affect more than 1 muscle group.


EIMC are of sudden onset, often with no warning. What is more likely to cause them is an abnormality in the alpha motor neurone activity. This may be centred around fatigue, leading to a reduced control of the excitatory effects on muscle spindle afferent activity and inhibition of the golgi tendon (GT) afferent activity. Contractions occurring in muscles held in a shortened position causes a reduced tension in the tendons, thus the golgi tendon activity is reduced and cramping is likely to occur (eg. contraction of the calf whilst foot held in plantarflexed position - as in kicking a ball). When the ground is rough, muddy, up or down hill muscle activity is increased further and the risk of cramping increases.

Passive stretching results in immediate relief as the stretching increases the GT activity and thus reciprocal inhibition, causing the muscle to relax.


What this all means to you....
If you are not suffering from shortness of breath, dizziness, muscle weakness (at rest) and any other general systemic problems then it is most likely that it is a localised muscular problem.
Seeing a physiotherapist for a neuromusculoskeletal assessment would be a good start...to assess peripheral control, assess muscle imbalances, biomechanics etc.
Often trigger points maybe a factor, these can be treated with accupressure, accupuncture, soft tissue massage, stretching.
A specific program of exercises addressing muscle imbalances, muscle conditioning, flexibility, posture / body awareness (pilates, Alexander Technique, yoga, swiss ball...may be helpful) and task specific activities would all be of use...as well as looking at your training patterns and nutrition (to aid recovery post exercise).

Personnally having played rugby for over 12 years I found that I started to suffer from calf cramping at the beginning of the season. What was causing it for me was poor cool down, lack of good stretching habits and my boots. I ran with antipronation trainers but never thought to look at my boots...no insole support. Also studs too long when the ground was hard etc... Changing my boots, adding support for my feet, and better training habits...as well as some soft tissue work resolved the problems I was having.

Good luck...don't forget to give yourself time to recover in your training program.