As the running season heads into the hot and humid summer months, two very important issues arise: 1) proper hydration and 2) heat-related illness. The medical consequences of ignoring these issues can be very serious and not to scare anyone, but at times fatal. Of course you are a well trained, fit runner with years of experience, so this couldn't happen to you, right? Well, think again. At the 2002 Boston Marathon, 13% of runners had medical issues related to hydration. One study that looked at fall marathons between 2003-2005 and found that on average 1 in every 10,000 participants experienced heat stroke. More impressive was the rate of heat stroke from the shorter races followed in the month of August: 1-2 per 1000 participants! Many more (20-30 per race) suffered from serious symptoms, just not full blown heat stroke. Surprisingly, it is typically the well trained and experienced runners who have more problems...likely because this personality type is more apt to ignore the early signs of problems in order to get that PR... am I right? So, here is what you need to know to avoid problems so that you can have a safe and enjoyable summer season.

First, the lowdown regarding hydration. This has become a hot topic over the years because overhydration emerged as a bigger problem than underhydration. This condition, known as hyponatremia (low blood levels of sodium) occurs when one drinks too much water and actually dilutes the electrolytes in their blood. However, in the hot summer months, this is not typically as problematic as dehydration. The goal is to understand proper hydration and find a balance. The basic guidelines recommend 8oz of fluid (1 cup) every 20 minutes. Over a one hour period you should aim for 400-800ml and not exceed 800ml/hr. Lean towards the higher amounts if you are a larger, more muscular runner, running hard, or the conditions are very humid. If you run later in the day, try to drink 16oz of fluid 1 hour prior to your run. Try to eat salty foods before your run/race, and if you are out for a long run in very humid weather, bring along a small salt packet and take this in the last half of your run. Despite these recommendations, very hot conditions when you are sweating excessively can make it difficult to know how much to take in. If you are well hydrated, your urine will be clear and light yellow. You can also monitor your weight before and after your runs. Each pound lost requires one pint (16oz) of replacement fluid. Realize that a 1-2% loss of water weight during activity can lead to a 6% decrease in your performance - so drink up!

Dehydration can be a serious problem and hopefully by following the above guidelines, you can avoid any difficulties with it. However, rarely is dehydration by itself a life-threatening medical emergency. Heatstroke and heat-illness are very serious medical emergencies related to an overall rise in core body temperature. Our bodies cool when running by the evaporation of sweat. When it is very humid, the moisture in the air does not allow sweat to evaporate and thus you lose the cooling effect and core body temperatures rise. The intensity of your exercise is the key factor that places you at risk, which is why this is often seen in racing situations. Racing far and hard in extreme conditions, especially if you are not yet acclimatized to the weather should be avoided, as this can place significant stress on your body.

Recognition of heat illness is key. Initially you may feel some nausea and mild disorientation. Muscle cramping may occur, followed my confusion, weakness and dizziness. At times, there may be cessation of sweating, despite the hot conditions. The final stages usually include physical collapse of the runner and a core body/rectal temp of greater than 105&. Of course, avoidance is always the best medicine. One of the most important strategies is to try to acclimate to the humid running conditions. Try to calculate your fluid needs and stay hydrated. When choosing the times you run and race, try to go as early as possible and avoid the peak heat of the day. If you do participate in races, take the weather into account and give yourself a break! Back off your pace and lower the intensity of your run. Remember, with this illness, being young or in great aerobic shape does not protect you. You may actually be at greater risk because of your ability to push harder in extreme conditions.

The bottom line, as always, is to listen to your body. Drink when you are thirsty, stay hydrated, acclimatize to the weather and give yourself permission to back off the intensity on the hottest days. Most importantly, if you don't feel well, STOP - find the shade and get a cool drink. Remember, you can't beat the heat but it can certainly beat you!