Likely, dehydration. Dehydration is far more important than the temperature of your sweat since it has a direct effect on performance and health. If you are doing nothing to prevent it then you will need to drink water throughout the day so that there is adequate moisture in the skin cells for optimal hydration.
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How can i cure my shin splints?
By stretching them out prior to running, this stretches out tendons and ligaments which allows them time to recover after each run without causing further problems or slowing down recovery.
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What should i do if im still having leg cramps during long runs?