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Tom as his alter ego 'Anaconda Man' taking local surfers back in Aus through one of his rigorous stretching routines.
Science
Water – It's Liquid Gold
Any type of endurance activity in hot climate brings into question the supply of liquid gold…water. The sun is overhead, the humidity could be high, no breeze to speak of and someone says…. what about paddling down the Nile, or lets go for a walk with a few camels, or some other form of exercise that will take many hours?
Now there is absolutely nothing wrong with being active at any time, in any place. If you have to be active in a hot environment, then the key to enjoying the whole activity bout – outside of clothing to wear (another story), acclimatisation (another story) or changing the time of the activity - is a regular supply of water. Water….cool, clear, water (sounds like a song coming on).
The water we are taking about is the one you drink. That’s right; the body is at its best with plenty of water on board. The body itself is approximately 70-75% water. So when the fluid levels of the body are altered then the body commences a complex series of processes to protest itself from cooking. In the main, these processes will begin automatically and the body will start to respond according to the situation or fluid level it is confronted with. The big factor in determining these responses can be the sweat rate. Sweating pushes water to the skin and as the water is lifted from the skin the body begins to cool. This is how you cool off or manage your body temperature. The process of sweating itself is not cooling anything – it just drains the water from the body. So this vital substance (water) must be constantly replaced. Eventually if your body has to stop sweating to help preserve the remaining fluid…you are in big trouble!
Think about how much water you lose if you are active where there is little to no ventilation - game of squash, exercising in plastic top for example. Sweating after you get out of the pool or off the push bike after exercising is further evidence of how the body is trying to cool down. Fluid loss is a major factor in your comfort level whilst active and it helps you maintain your general health and well-being when you are recovering from activity in the heat. Think water, and think electrolyte replacement if you are active in the heat. In very extreme conditions you may even want to think salt replacement.
The message is very clear. If you choose to be active in an environment that is hot and/or humid, you must consume fluid before, during and after the event. If you happen to be regularly active or in training for an event - a 2% reduction in your body weight takes you outside the safe limits in which to exercise. That means, if you are a 100kg person and your body weight is below 98kg as you go to start the next activity bout or training regime - you are putting yourself at risk...do not do it. You will be lacking water as well as vital electrolytes. Remember that 2kg is 2 litres.
As a general guide if you are thirsty during or following your activity then you are well short of the fluid balance that is required to perform at your optimum. Further to this – there is a 5% drop in physical performance for every 1% drop in body weight. Dehydration is the scourge of those who are active in the heat but it can be managed quite well if you consume water and electrolyte drinks on a regular basis. Maximum sweat rates are around one litre per hour, so just to maintain the balance the consumption of replacement fluid should be one litre per hour.
Wear loose cotton clothing, covering up with a hat and some form of sun protection all help the comfort factor when being active in the heat. The pace of the activity will also influence how the body copes with exercise in this type of environment. Taking it easy…slow and steady…will help the body cope with the extra strain of exercising in the hot environment. Simply being active in the heat is an extra workload on the body as it needs to get rid of the heat being generating both during and after the workout.
The body also has to manage the balance of water in the blood. The body has to maintain a temperature gradient between the body’s core temperature and skin temperature to help the cooling process. If there is no ventilation or movement of air across the skin then the increase in heat of the body is obviously much greater then if there was movement of air across the skin. This evaporation process is essential in keeping the body cool. There are other cooling methods but evaporation is the most significant.
So, when exercising in the heat the body needs plenty of water. It also spends a great deal of time working at keeping the core body temperature constant by shifting fluid around the body and ultimately to its extremities so cooling can occur. Activity can be maintained in hot climates but think about the safest time (coolest part) of the day to be active. The hot/humid environments automatically increase the workload on your body - without you doing anything else. So if it s humid take extra care and plan your fluid and fuel intake – it could save your life.
Enjoy the paddle, walk or whatever you choose... wherever you may be!
Graeme Wright
Clinical Exercise Physiologist
www.optimumhms.com.au
24th August 2011