We all feel the effects of the Hong Kong summer when training, not to mention our race performances. But should we be training outside or in the cool of our local gym?   Some of you may remember the epic battle between Lance Armstrong & Jan Ullrich in the Tour de France last summer.  In the scorching heat, Ullrich opted to warm-up in an air-conditioned bike shop for a key time trial, while Armstrong spent an hour outside on a stationary trainer.  He lost an unprecedented 1minute30 to Ullrich during that stage. Armstrong’s severe dehydration almost cost him his 5th Tour win.  There are times when it makes sense to train indoors and times when it pays to acclimatize to race conditions, but how do we make these decisions?

We need to consider that athletes in the heat can sweat 1-2 Liters an hour and most athletes drink less than they sweat. The result is dehydration. Losing as little as 2% body weight can impair physical performance (Walsh et al, 1994).  This can be a huge factor during the summer when both heat and humidity levels are high and most of us struggle to drink enough fluids.  As a goal, an athlete should drink as much as tolerable and as often as possible during training or a race. Post race/workout, athletes need to drink enough fluids to return their body to its pre-event weight.  You should drink about 1.5 liters (50 oz) of fluid for every kilogram (2.2 lbs) of weight loss.  It is also important to ensure you replace salts & minerals lost in sweat or you won’t hydrate effectively.  I therefore recommend you drink a combination of water and a sports drink, such as Accelerade (www.accelerade.com), as part of your re-hydration strategy.

It would also be easy to assume that, while in the relative safety of your air-conditioned gym, hydration would not be such an important factor.  While this is partly true when we look at the extreme climate in Hong Kong during summer, the truth of the matter is, it’s just as easy to dehydrate in a gym as it is training outside.  It can be useful to weigh yourself before and after exercise, so you are aware of your fluid losses and can hydrate appropriately.
“A study under laboratory conditions showed that endurance time on a bicycle ergometer at an exercise intensity that could be sustained for 94 min at an air temperature of 11°C was reduced to 81 min when the air temperature was increased to 21°C and to 52 min when the temperature was increased to 31°C (Galloway & Maughan, 1995). In the conditions prevailing at the 1996 Atlanta Olympics and at many other sporting events, the reduction in performance would be even greater. It is recommended that hard exercise should not be undertaken when temperature and humidity are high, but major sporting events are seldom canceled even when environmental conditions are extreme.”

When exercising in the heat at the same power output, you will notice a higher heart rate, higher cardiac output, and higher core and skin temperatures (Rowell, 1983). This is usually accompanied by a higher blood lactate concentration, and there is some evidence of a faster rate of depletion of muscle glycogen. These cardiovascular and metabolic alterations are accompanied by a greater subjective sensation of effort and a reduced exercise capacity.  This evidence shows us that recovery from exercise can be much harder if we are training outside where diverse conditions place the body under greater stress.  It may make more sense during the summer to do a couple of your key sessions a week in the cool in order to assist recovery.  It should be noted that world-class marathoners, Ingrid Kristiansen and Christine Clark (both from very cold climates), actually did the majority of their training on a treadmill.  Clark, an Alaska native, was the surprise winner of the 2000 US Olympic marathon trials, which took place in un-seasonably warm conditions.

But if we do many of our key sessions indoors, what happens when we turn up on race morning to 37C plus temperatures and 95% humidity?  Don’t despair, as even a week or two of moderate physical activity in the heat, say jogging 30-45 minutes a day, can jump-start heat acclimation. If you plan to race in Asia, it is important to ensure you have adapted to the hot, humid race conditions.   Regular exposure to these conditions causes a number of physiological adaptations that serve to reduce the adverse effects on exercise performance and lessen the risk of heat injury. Such responses include an increase in blood volume and an enhanced ability to sweat. The increase in blood volume helps assure that the body can meet the demand for blood supply by both muscles and skin. Acclimatization also results in a faster onset of sweating, a greater distribution of sweat over the body, and an increase in the sweat rate. In addition, the sodium content of sweat tends to be reduced with acclimatization as the body attempts to retain sodium to help conserve extra cellular fluid volume.

Some physiological adaptations can occur within the first few days of training in the heat, so that even a few sessions of exercise in the heat can be beneficial (Lind & Bass, 1963). Most physiological adaptations to heat stress occur within about 7-14 days of regular exercise in a hot environment.  There is no doubt that acclimatization is necessary if athletes wish to achieve optimum performance in hot, humid conditions. Though it is not necessary to train every day in the heat, ideally no more than 2-3 days should elapse between exposures. It has been shown that exercising in the heat every third day for 30 days resulted in the same degree of acclimatization as exercising every day for 10 days (Fein et al, 1975). The intention of these training sessions should be to raise body temperature and stimulate sweating without putting yourself at unnecessary risk. There is evidence that acclimatization is most effectively achieved when the duration of exercise is about 100 min; there is no advantage in spending longer periods than this exposed to heat (Lind & Bass, 1963). Intermittent exercise is likely to be just as effective as continuous exercise in stimulating acclimatization.

As with most things in life, a balance is best for us both mentally and physically. Enjoy the summer race season and remember—during a hot road race; stay hydrated, run comfortably, avoid long sprints, "read" your body, and seek help early if you start to feel ill.

Have fun
Claire