Biomechanics
By Amanda Brunner

Dealing with the Summer Heat

For much of the country the weather is really beginning to heat up as summer is upon us. The singletrack everywhere is finally perfect but don’t forget to protect yourself from the heat and sun. The heat can do a number to the body if proper precautions aren’t taken. The first rule of thumb is to avoid extensive workouts in the middle of the day when the heat is at its worst. Ignoring the heat and pushing your body brings about damage in three phases: Heat cramps followed by heat exhaustions and finally (often life threatening) heat stroke.

Heat exhaustion and the more serious heat stroke (hyperpyrexia) are caused by a breakdown of the body’s heat regulation system. This can occur for many reasons: Extended heat stress (which can occur day or night), insufficient physical fitness, being overweight, alcohol intake, too much physical stress, overly warm clothing, medications (e.g. water pills), infections, and most commonly, insufficient fluid intake. Stroke takes place when sweat production diminishes and the body temperature rises to temperatures of around 39-41°C. The skin becomes dry and red; severe headaches occur.  

Because the body must maintain a relatively constant body temperature (around 37°C) it needs to be able to eliminate excess heat to survive. Most of the heat is conducted in the blood stream to the skin and then the heat is released in three ways:

1. Evaporation: in which excess heat is transferred to sweat which is then evaporated. Evaporation aides in releasing heat but in high humidity it can not occur as easily. Therefore, on a hot, humid day, you can be dripping with sweat, but because the sweat is not evaporating it is not doing you any good.
2. Radiation: in which excess heat is carried by means of electromagnetic radiation to cooler objects around the body. Blood vessels near to the skin dilate to provide a greater surface area. However, if the temperature of the surrounding air is at body temperature or above is will not have that much of an effect.
3. Convection: in which excess heat it transferred to air passing over the skin, particularly if it is windy.

Heat illnesses from least to most severe include:
Heat Cramps: caused by an insufficient amount of salt in the body. When this occurs, the best way to treat is to replace the salt and fluid loss and to stretch and massage the affected muscles. Cramping usually occurs but us not limited to the abdomen and legs.
Heat Syncope (fainting): in an effort to increase heat loss, skin blood vessels dilate to such an extent that blood flow to the brain is reduced resulting in faintness, dizziness, headache, increased pulse rate, nausea and vomiting. Dehydration is a main contributor to this. Treatment includes cooling the person slowly, cooling to fast can cause greater damage. If the person is conscious re-hydrate slowly, approximately a half a cup of water or Gatorade every fifteen minutes.
Heat Exhaustion: this occurs when fluid losses from sweating and respiration are greater than fluid reserves. The lack of fluid causes the body to constrict blood vessels especially in the arms and legs causing the skin to become pale and clammy, have decreased urine output and make the affected person feel weak, dizzy and thirsty with possible nausea and vomiting. Treatment includes re-hydration and cooling the affected person by placing them in the shade and covering them with damp cool (not cold) towels. Elevate the feet above the heart. Putting half a teaspoon of salt and half a teaspoon of baking soda in each liter of water helps to replace lost electrolytes if Gatorade or other electrolyte drinks are unavailable.
Heat Stroke: The most dangerous of them all, this is a life-threatening condition where the core body temperature rises to above 41°C. This can occur if heat exhaustion is not cared for. This occurs when the body no longer produces sweat. The affected person will be pale and dry. If the should occur call 911 immediately, keep the person calm, bring them into the shade, cool slowly with damp towels, if conscious re-hydrate the person slowly until help arrives.

Helpful tips include: Stay hydrated and cool before exercising in hot weather (best avoided entirely though, if possible). Drink half a liter of water upon waking and add some salt to your breakfast to make sure you do not start the day dehydrated or low on sodium levels. During exercise, wear light clothing to allow sweating and breathing. Take on plenty of water and use cold, wet cloths to stay cool if humidity is high enough to counteract the evaporation process. Be sure to drink and rest regularly. Sweat consists of sodium, chloride, potassium, protein and fatty acids; in order to replace what you are losing consider beverages high in sodium and potassium (bananas are very high in potassium). After exercise continue drinking regularly for the rest of the day to replace lost fluids.