In my experience, cramping is caused by at least 5 factors that i’ve encountered. these are:
1. Strength – lack of strength in your muscles means they are faster to tire and cramp up due to lack of ability to keep up with your demands of the muscles.
2. Fitness – poor or lowered fitness in that activity or overall can cause cramping as muscles unaccustomed to an action are forced to do that action repeatedly.
3. Overworked muscles – muscles that are pushed beyond their ability to keep up will inevitably cramp. This can be either a function of 1 or 2 above or something more non-obvious like your nervous system not working right to make all your muscles in a kinetic chain fire off in the right way or at all. This will put more stress on the muscles that are doing the work versus ones that are shut down. The glutes are a typical muscle group that has shut down due to inactivity of sitting, which overworks the back erectors and hamstrings when running and squating.
4. Not enough blood/nutrients getting to your muscles – this can happen in situations like windsurfing in cool seas where hypothermia starts to set in and your muscles simply stop getting enough blood flow to function properly. I encountered this during the LA Marathon 2010 when my right quad cramped up under rainy, cold weather. I thought it was lack of strength which may have contributed in general, but an examination of my heart rate trace showed a slow drop in heart rate, which meant that not enough blood was getting to my muscles while I was demanding so much from them during a race.
5. Electrolytes – you may not have enough electrolytes in your system to support that level of activity, or through sweating and hot weather racing/training you lose it through the skin and it is not replenished. electrolytes are important for proper functioning of muscles and the nervous system. Without proper levels, you will undoubtedly cramp. I sweat a lot, more than other people, and I take 3 Saltstick pills per hour during Ironman races in moderate warm to hot weather. This has become more of a preventative measure now as my strength and fitness has increased.
Science has not been able to pinpoint the exact causes of cramping but suffice to say that training over the years and trying many things, these are things that I’ve worked on the most and have nearly removed cramping situations, except for the extra cold, wet conditions experienced during the LA Marathon 2010.
My latest experiments have been in the area of increasing strength (but not bulk or weight) via Russian strength training techniques in benchpressing and deadlifting. Another has been in the area of recovery between intervals, relative to my fitness level. I have found some great results in training intervals with full recovery in between them, versus trying to use set minimal recovery intervals in order to build endurance. The last has been in the area of removing “gluteal amnesia”, which is getting my glutes to reactivate in the kinetic chain involving running. This has all but removed issues with hamstring cramping and I have also improved my running speed as well.