thanks for sharing your experience, since am doing the 20k pacesetter next year january, i will take your suggestion into consideration
personally i have not experienced any notable muscle cramp during my race & training but muscle fatigue + side stitches is quite common in my case.
my opinion six months ago was:
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i think once you get use to the 21km distance, fatique will not be an issue. Goodluck on your recovery.
and now i would like to add a few addition to that. although there is no solid scientific evidence that can exactly pin point the root cause, personally i feel that this can be closely relate to the following factors:
1) Build up of lactic acid, either through an extended mileage or excessive pace.
- Mileage: when running a long distance race, the continual increment of lactic acid in the muscle will potentially cause muscle spasm when the volume of lactic acid is beyond the threshold. hence, there are many article on the net that suggest using Tempo run to increase one's lactic threshold in order to maintain a constant speed without the traumatic cramp.
- Overspeeding: During intense exercise, aerobic metabolism cannot produce ATP quickly enough to supply the demands of the muscle. As a result, anaerobic metabolism becomes the dominant energy producing pathway as it can form ATP at high rates. Due to the large amounts of ATP being produced and hydrolysed in a short period of time, the buffering systems of the tissues are overcome, causing pH to fall and creating a state of acidosis, a natural process which facilitates the easier dissociation of Oxyhaemoglobin and allows easier transfer of oxygen from the blood[2]. This may be one factor, among many, that contributes to the acute muscular discomfort experienced shortly after intense exercise. (quoting from wiki)
In short, when a runner is running above beyond his existing optimal speed, there is possibility that the o2 supply is not sufficient to support aerobic metabolism in the muscle. Lactic acid is a by product when the cell is in anaerobic metabolism stage.
2) Dehydration, losing vital electrolyte.
- From my own experience, when the blood becoming thicker due to dehydration, it travels slower within the blood vessel and as a result our muscle cell is not getting the supply of O2 + nutrients on time which in turn cause muscle fatigue.
more reading on muscle cramp>>
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generally i think you will get different suggestion from different peoples, while getting the right one that works for you matter the most. I am glad that you found something that fix your cramp