Thursday, July 14, 2011

Training/Racing in the Summer Heat

With the summer already here and the temps skyrocketing, making it feel like you are running from Satan, I thought it would be appropriate to discuss training in the heat.  Today, I went for a run at 10:00am, with the temperature at 82 degrees.  The warm-up was easy, but by the time I got home, the Heat Index said 94.  That's a pretty big difference in only an hour (granted, I’m not sure what the Heat Index was when I started).  I snapped a photo after the run:

I am Terminator. I'm from da Futcha....
Training in excessive temperatures can be dangerous.  While some athletes early in the year may train at the warmest part of the day, especially in the spring to get accustomed to the increasing temperatures, doing so in the summer should be done with caution.  Training in the heat brings about 3 problems:  Dehydration, hyponatremia, and overheating (not overeating). 

Dehydration:  As your core body temperature begins to rise, our natural physiological response is to perspire to reduce the temperature.  If fluid is not replaced, your body has less volume to circulate throughout your body.  Less water volume leads to increasing core temperatures, increased usage of glycogen for activity from stores in the liver and muscles, and decreased performance.  The amount of fluid people lose when they sweat varies drastically, ranging from .5 liters to 4 liters per hour (Sindballe, 2011). The maximum amount of fluid an athlete can absorb in an hour is 30 ounces.  So, math problem:  If an athlete sweats an average of 2 liters per hour (67.6 ounces) and can only absorb 30 ounces, how many ounces does the athlete lose overall?

That is correct! 37.6 ounces! And that’s just one hour.  If someone was racing in an Ironman event, like in Kona, there would be some serious issues of the body shutting down.  Basically the only way to solve this is slow down and try to keep your core temperature lower.

Hyponatremia:  When you sweat, you lose electrolytes.  This is why Gatorade is so popular.  This is also why the Dannon water commercial is kinda crap. YOU LOSE MORE THAN WATER! DUH!  Hyponatremia is the medical term for imbalances in your sodium, potassium, magnesium levels in your body.  It is very serious, can lead to a hospitalization, and is why athletes exercising over 45 minutes should consider replacing electrolytes with a sports drink.  At the very least you will be replacing some energy stores in your body.

Overheating:  During exercise, 25% of our energy stores is used to keep us moving.  The remaining 75% of the energy we have is turned into body heat (Sindballe, 2011).  When your body is unable to release the body heat you have, your core temperature rises and sets off a chain of events (increasing sweat rate, decreasing electrolytes, decreasing performance).  Eventually, if someone was pushing to the limits, your brain will go into a “shutdown” mode, activating less gross motor muscles and saving the available energy to keep your organs or brain “cool”.  It is similar to neurological reflexes (pulling your hand off a hot stove before you feel it.) 

Tips for a safe summer

GET ACCLIMATED!  In late spring, try to work out during the hottest parts of the day.  This will eventually get you acclimated to the warmer temperatures coming soon.  This is something that I regrettably did not do this spring, as most of my workouts were indoors.  Try to get outside, or work out in more clothing than normal to get your core temp up! The human body can get acclimated to different climates in as little as 9 days, with maximal improvements seen at 30 days (Sindballe, 2011). Getting outside and hot earlier in the year may lead to better race performance and training in the summer months.

HYDRATE LIKE CRAZY!  Get in at least 16 ounces of fluid at least 1 hour prior to exercising.  It is also recommended to consume 6-10 ounces of fluid during every 20 minutes of training or racing (Ley, 2006). And remember: Sports drinks beat water because they contain glucose and sodium (sugar and salt), which increase your water-absorption rate, replace the electrolytes you lose in sweat, and taste good, encouraging you to drink

KNOW YOUR SWEAT RATE!  This is something that I have not done yet, but definitely plan on doing soon.  Knowing your fluid loss during specific temperatures will give you a better idea of how much hydrating you should be intaking while training or racing.  To find out your sweat rate (unscientifically…) is to weigh yourself before a run (Naked.  Weigh yourself naked.  Don’t run naked. Trust me…), go for an hour run, then weigh yourself immediately after (again, in the nude).  The difference in weight will be how many pounds you lost during the run.  Multiply that number by 0.472, and that’s your sweat rate in liters per hour (Ricci, 2008).  One rule of thumb to follow is replacing every pound lost with at least 16 ounces of sports drinks following a workout. 

BE SMART!  You know yourself better than anyone, so listen!  If you are pushing yourself to the point of overheating, don’t be afraid to slow your pace.  In the big scheme of things, training to the point of exhaustion is counterintuitive.  It sets you back further than where you were starting from.  Being able to back off a bit will allow you to conserve your energy stores, decrease your core temperature, and allow the sweat to evaporate (you don’t cool until it evaporates from your skin).  Also make sure to rehydrate immediately after the workout, consuming 16-24 ounces of a sports drink for every pound you lost.  This will decrease the amount of time you will need to recover from the workout.

I hope these help.  Many are common sense, but still very important.  One thing that I personally am about to start trying are electrolyte tablets and salt licks.  I am a heavy, heavy sweater, and tend to cramp like you wouldn’t believe.  This isn’t necessarily due to the loss of fluid, but more along the lines of electrolytes.  I am hypothesizing that when I lose the fluid, which is VERY concentrated with electrolytes, I cannot consume and absorb enough Gatorade to balance out the levels (aka leads to cramping 45 minutes in).  Someday, I plan on having my sweat rate and electrolyte loss scientifically evaluated, so I know exactly what I need to do.  Until then, I will continue experimenting until I find something that works!


Ley, A. (2006). Tips for training and racing in the heat and humidity. USA Triathlon, Retrieved July 14, 2011, from

Ricci, M. (2008). Racing a Triathlon in the heat. D3Multisport. Retrieved July 14, 2011, from

Sindballe, T. (2011). Heat Training. Inside Triathlon: Archives. Retrieved July 14, 2011, from 


Mark said...

Excellent post. I'm really struggling with my hydration the past few weeks. Consequently, I'm having serious issues controlling my HR, particularly during the second half of my runs. It's been getting higher than I've ever seen it before. I'm actually swinging by Gribble's this afternoon to get some S-caps or something. It's shocking how many pounds you can lose (easily 4+ for me...with hydrating during the run).

Jr said...

Yeah, I never thought it would be that high. And I've been noticing HR changes too. And I can't say its from overtraining...