You should also eat from 250 to 400 calories during that hour. Your water bottle in your pack does not help you reach this goal. Carry a water bottle with you where it is easily accessible or even better invest in a hydration pack that allows you to sip water at will. Non-carbonated sports drinks like Gatorade seem to help, although there is debate in medical society on how much benefit there is. Waiting to drink until you are thirsty is a bad approach, once you are thirsty, you are already getting dehydrated , and you are one step closer to getting cramps.
Fatigue seems to also contribute to cramps.
Dr. Martin P. Schwellnus MSc from the University of Cape Town in South Africa established the theory that fatigue, not dehydration causes cramps, and his theory is gaining many supports in sports medicine circles. Sports medicine doctors have observed that athletes in the beginning of the season tend to have a lot more cramps then towards the end of the season. The conclusion is that they are less conditioned at the beginning of the season and more prone to fatigue. Most hikers who live in cold climates and get holed up in the winter seem to experience this same phenomenon. Staying in shape and not over extending yourself is also sage advice when on the trail.