Most probably it won't. Keep in mind that while sweating the body is losing valuable minerals as well. An imbalance of the mineral salts in your body might result in fatigue, cramps and other physical discomfort. You can replenish this shortage with isotonic drinks which will be provided during the race at the Drink Station (DS). Your sachet of hydration salt might be handy whether you are not close to a drink station when you need isotonic fluids.