Friends For Life Bike Rally - A Benefit for the Toronto People With AIDS Foundation

During your five days of cycling you will be susceptible to different heat emergencies and knowing their signs and symptoms will help you notice them faster thus helping in your recovery from them.

Prickly heat is also known as a heat rash.  Its cause is the blockage of the sweat glands and results in an acute inflammation of your sweat ducts.  This can be prevented by wearing clean, light and sport-engineered clothing that promote evaporation of sweat.  Using talc powder will not help and might even make it worse.  A light cream like “chlorhexidine” is the treatment of choice.

Heat syncope, simply put, is a fainting spell that happens because of heat.  This fainting spell can manifest itself prior to actually happening by some dizziness (also know as pre-syncope).  It happens when your body tries to thermo regulate by dilating your blood vessels in your arms and legs thus pooling large amounts of blood into your extremities.  This results in a decrease in blood supply to your brain causing you to faint.  The key here is to keep on hydrating during your cycling but also to acclimatize yourself to cycling in the heat.

Heat cramps have been experienced by most of us and we all know how uncomfortable they can be.  They usually affect the calves but can sometimes affect shoulders or thighs.  Proper fluid intake will prevent/limit the possibility of having a heat cramp.  They are usually caused because an individual has only fluid replaced with water.  The key is to use commercially-available electrolyte fluid to help maintain proper cellular levels of potassium, sodium and fluid.  Salt tablets are not recommended as they are a gastric irritant and they do not replace volume.

Heat exhaustion is very difficult to diagnose for anyone.  But signs and symptoms can be a sign of an impeding heat exhaustion and include dizziness, weakness, malaise, light-headedness, fatigue, nausea/vomiting, heat cramps, headache, and myalgias.  All those symptoms can appear by themselves or in any combination but in heat exhaustion your mental alertness remains unaffected. Rest, fluid and electrolyte replacement will help prevent and treat this condition.

We have all heard about a heat stroke but few of us know what it actually is.  It is defined as a triad: core temperature greater then 40.5C (104.9F), CNS dysfunction and anhidrosis.  I know you are now saying: “lack of sweating is what defines heat stroke” and in most cases you would be right.  However, the absence of sweat might be absent for a range of factors.  And some athletes will not have this symptom.  CNS symptoms will manifest as: bizarre behaviour, irritability, combativeness, hallucinations, seizures, and coma.  If you or a friend show any of these symptoms time is key in survival and medical attention is required as your body is now unable to thermo regulate.

As the ride is a few months away, you have time to prepare for the heat and be ready to face these emergencies.  This is known as acclimatization.  Like an alpinist who prepares to summit Everest you have to prepare your bodies for thermoregulation during the heart of summer while doing strenuous exercises.  To acclimatize, one should make repeated bouts of mild to moderate exercise in a hot environment.  This causes physiologic changes: sweating at lower temperature, higher sweat rate, increased peripheral blood flow, and decreased sodium/chloride concentration in sweat and urine.  Ultimately your heart rate, core temperature and your perceived exertion will lower.  Your plasma volume and exercise tolerance time will increase.  For this to happen one usually has to be exposed and exercising in the heat for 14 days and do it for 1 to 4 hours each day.  Acclimatization is lost when exposure to heat stops.

I hope you found some valuable information in this article.  And that during the ride you will remember to re-hydrate before, during and after each day.

 

Martin Johnston is a Paramedic, Level 3.