I was reminded on a past vacation to one of those hot and sunny areas, how much heat can affect your ability to be active. For those of you who are contemplating a late winter or early spring vacation in a sunny climate, you should consider that your body is used to being in the rainy, cool environs of the Fraser Valley and that if you plan to be active, you should prepare for the transition to a warm environment.
During the transition from rest to heavy exercise (such as jogging or hiking), the heat generated from energy metabolism can easily increase 10-fold in active healthy persons, and up to 20-fold in well-trained athletes. About 80 per cent of this energy is released as heat; only a small proportion is converted to muscular work. To counter heat storage and rising core temperature, metabolic heat is transferred from the core to the skin, then dissipated to the environment.
During exercise in a hot environment, the cardiovascular system adjusts by increasing blood flow to the skin allowing evaporation. Shunting blood to the skin improves heat loss but diminishes the blood supply that provides oxygen to working muscles. Consequently, in hot weather the cardiovascular system must meet the competing demands of thermoregulation and muscle metabolism. This is why in athletics, record-breaking endurance performances are almost always set under cool conditions.
There are a few things you can do to avoid running into problems with heat stress. First thing you can do is exercise before you travel because getting fit increases your body’s capacity to perform at a higher level for a given heat load, and it increases heat elimination from the body. However, be aware that it takes weeks to see measurable improvements in fitness level, so if you’re not currently exercising, plan well ahead.
Attention to clothing is also important. Fabrics that minimize heat storage and enhance sweat evaporation should be selected. White or light colors, cotton, dry-fit or other breathable fabrics, and designs that maximize skin exposure are beneficial. Remember your sun-screen though!
Hydration is important because chronic dehydration retards acclimatization. Effective hydration involves drinking plenty of fluid two hours before exercise, 150 to 300 ml of fluid every 15 minutes during exercise, and fluids with increased sodium content after exercise. Take a water bottle with you.
On transition to a warmer climate, exercising persons must allow time to become acclimatized. Keep in mind that full acclimatization typically requires 10 to 14 days to get used to the warmer environment, but 75 per cent of the adaptation is believed to occur within the first five days. Intense and prolonged exercise when competing in a sports event before acclimatization occurs may be detrimental to the child’s physical performance and well-being and may lead to heat-related illness, including heat exhaustion or fatal heat stroke. The rate of acclimatization for children is slower than that of adults. A child will need as many as eight to 10 exposures (30 to 45 minutes each) to the new climate to acclimatize sufficiently. Such exposures can be taken at a rate of one per day or one every other day. So as a practical suggestion for athletes who may be travelling to a warmer climate to compete, it is recommended to be as fit as possible and/or arrive to your destination as early as possible before your event and allow time to acclimatize.
Kerry Senchyna holds a bachelor of science degree in kinesiology and is owner of West Coast Kinesiology in Maple Ridge (westcoastkinesiology.com).
