Increased temperatures and humidity cause increased heart rates. Consequently, it takes much less effort to elevate the heart rate into the training zone, but the training effect is the same. These facts underscore the need to use combat-development running and to monitor heart rates when running, especially in hot, humid conditions. Some important changes occur as a result of acclimatization to a hot climate. Sweat production is increased.
Blood volume is increased.
Heart rate is less at any given work rate. Exercising in Cold Environments Contrary to popular belief, there are few real dangers in exercising at temperatures well below freezing. Since the body produces large amounts of heat during exercise, it has little trouble maintaining a normal temperature. There is no danger of freezing the lungs. However, without proper precautions, hypothermia, frostbite, and dehydration can occur.