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Heat Injuries

by Coach Seiji

Although pro riders have been spared from the extreme heat they saw back in 2011 and 12, it is still important to know the signs of heat exhaustion and heat stroke.
Well it is August 2013 and in many parts of the country, it’s the hottest month of the year. We were spared the usual heat and humidity bath of Loretta’s but now it’s back to the dog days of summer for lots of riders. Here where I am in Texas, it is 107°F as I write this and a month ago I suffered some heat injury myself on a 104°F day on my bicycle. Everyone pretty much knows to stay hydrated and that acclimatization helps but many do not know what happens in heat injuries or what to do about them before things possibly become much worse. In the interest of safety, read on….

Think of heat exhaustion to exertional heat stroke (EHS) as a continuum of exercise and heat related injury. Heat exhaustion is first on the scale and simply means that you have to stop riding or exercising; your body is just too exhausted and cannot continue to do the work required in the heat. Heat exhaustion can usually be treated with body cooling and fluid replacement. The athlete typically recovers on site without hospitalization and further complications are rare. Think of heat exhaustion as your body’s way of making you stop so you don’t injure yourself any further.

Heat Exhaustion

Heat exhaustion is mainly caused by dehydration. The rising core temperature of your body during exercise in the heat causes profuse sweating as your body attempts to fight rising body temperatures through evaporative cooling. The latest research indicates that this causes central fatigue, which is basically fatigue of your brain and central nervous system. Central fatigue causes the muscles in the blood vessels to relax and lose tone (called vasodilation). Vasodilation increases the total volume of the circulatory system, which is a closed system, so the pressure drops. The resulting cardiac inefficiency leads to a cascade of negative events: less blood flow removing heat from the working muscles, less blood flow bringing oxygen and fuel to the muscles and less blood supply to the brain. All this combined with the increased energy cost of working in the heat (especially in those not acclimatized), causes extreme exhaustion and even collapse.

Symptoms of Heat Exhaustion

Although not too specific, symptoms can include low blood pressure, high heart and breathing rate and the rider appears sweaty, pale and ashen. Other symptoms include: headache, weakness, dizziness, "heat sensations" on the head or neck, chills, goose bumps, nausea, vomiting, diarrhea, irritability and loss of muscle coordination. Muscle cramps may or may not accompany heat exhaustion.

How to Treat Heat Exhaustion

Riders suffering from heat exhaustion should immediately be moved to a shaded or an air conditioned area. All gear and excess clothing should be removed and the athlete should lay down with his or her legs elevated. Heart rate, breathing rate, rectal temperature and nervous system symptoms should be monitored. Cooling therapy can aid in more quickly returning the athlete to a normal state (see treatment for EHS). Hospitalization and medical supervision are necessary for IV fluid intervention if the heat exhaustion is severe or the athlete cannot keep fluids down, has diarrhea, or symptoms do not improve with the treatments listed.

Exertional Heat Stroke

Next on the severity scale is exertional heat stroke. EHS requires immediate treatment and if not reversed quickly, can cause organ damage, organ failure and death. EHS is caused by elevated body core temperature and is clinically defined by a core temperature of 104°F. The massive heat produced by working muscles, outside temperature/humidity and other factors overpowers the body’s cooling mechanisms and core temperature rises faster than it can be reduced. Upon reaching a critical level (around 104°F), a catastrophic chain of events can occur. At this temperature, the cell membranes become damaged and cell energy systems cease to work correctly. This leads to collapse of major cell structures and functions. You can apply simple logic from here: since every organ and tissue in your body is made up of cells - brain, cardiac, renal, gastrointestinal and muscle systems can fail and this cascade of bodily collapse can cause death.

Symptoms of EHS

More specific than heat exhaustion, symptoms include disorientation, confusion, dizziness, irrational or unusual behavior, inappropriate comments, irritability, headache, inability to walk, loss of balance and muscle function resulting in collapse, profound fatigue, hyperventilation, vomiting, diarrhea, delirium, seizures, or coma. Beware: EHS symptoms are often confused with concussion symptoms. Also note that EHS victims almost always have sweat soaked, pale skin at the time of collapse. Classic heat stroke (non-exercise related) victims usually have dry, hot and flushed skin. This is a common misdiagnosis – being sweat soaked DOES NOT rule out EHS. Also note that an athlete can suffer from EHS without passing through heat exhaustion first; it is rare but it can happen. Immediate recognition of EHS symptoms is critical for survival; a rectal temperature should be taken in anyone who collapses or shows signs of EHS and immediate care should be given to anyone above or near 104°F.

How to Treat EHS

Immediate whole body cooling is critical for survival in EHS victims. The mortality rate is directly related to how much time the core temperature remains above 104.9°F and how quickly it can be brought down below this temperature. The cooling needs to be done IMMEDIATELY and ON SITE. Do not wait to transport the victim to a medical facility, begin cooling as soon as you suspect EHS! The absolute quickest way to reduce core temperature is a total body immersion in an ice water or cold-water bath. This treatment has the lowest mortality rates. The next best solution is to rotate towels soaked in ice water as they are applied to the head, trunk and limbs while ice bags are applied to the neck, armpits and groin. The least effective treatment is ice bags only on the neck, armpits and groin. IMMEDIATE BODY COOLING is critical for survival. Again, do it without hesitation and keep doing it until rectal temperatures drop below 104.9°F and nervous system functions return to normal, signaling you are out of the death zone. If you know you will be training or competing in an environment that can lead to EHS, keep ice and a suitable container to be used as an immersion tank nearby! Again, this is a life-threatening situation; know the signs, know how to treat, and BE PREPARED!

These past summers have been especially brutal for both training and racing. Two years ago at Red Bud, the motocross community regrettably lost a member due to suspected EHS and undoubtedly more riders and athletes have suffered heat injuries this summer. Heat exhaustion is very common during the summer months; like I said, I suffered from heat exhaustion myself a few weeks ago. Please arm yourself with the knowledge to recognize both heat exhaustion and EHS, do more research on your own, and be prepared!

That's it for now, until next time, good luck with your training and remember, if you have a question, log on to the Virtual Trainer Expert Forum and have your question answered by a panel of experts. In addition, be sure and check out the Racer X Virtual Trainer archive section. Your complete one-stop information zone for motocross fitness. VT Signature

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