I just read an article by Joe English, professional marathon and triathlon coach, where he mentions the “4 H’s of Hurt” – Heat, Humidity, Head wind, and Hills. Welcome to South Florida; you may only have to deal with 3 of them, but you have to deal with them constantly (no hills in South Florida). As summer bears down on the US “normal” people in South Florida (and the rest of the country) begin cowering indoors to the comfort of their AC units, but runners are still hitting the streets, braving temperatures in the 90’s and high humidity.
Heat can make even easy runs feel hard, and if you’re not ready for it, can be devastating to your race results. Heat forces your circulatory system to work harder to regulate muscle and core temperatures (more blood flowing to outer extremities for cooling reduces volume of blood available to be pumped per heart stroke), reducing it’s ability to efficiently supply nutrients to key muscles, it induces dehydration, and reduces your ability to push yourself (survival theory – your brain limits your body from pushing to injury) In worst case scenarios, if you’re not careful, heat and humidity can even be deadly. However, this doesn’t mean you can’t excel with the mercury starts rising, it just means you have to do more to be ready to combat they heat.
- Find Shade – Find shade both before and during the race. Radiant heating zaps energy like crazy, even when you’re just sitting around. Avoiding the sun as much as possible will give you that much more energy towards your run / race.
- Stay Hydrated – A 2% loss in body weight due to dehydration can cause a decline in performance up to 10-20%. If you start or get dehydrated, you’ll never catch up during activity, and if you start feeling thirsty during a run, it’s already too late. Stay well hydrated before your runs, you should be peeing “clear and copious.” Drink early and drink often during runs in warm weather and you should be able to stay ahead of dehydration.
It’s also helpful to record your daily weight before and after runs – this allows you to see how much water you’re losing on runs, and thus how much you need to replenish as well as allowing you to watch for sharp decreases in your weight trend which may point to general dehydration or other issues.
- Stay “Electrolyted” – When running in warm weather you can expect to lose a fair amount of electrolytes through sweat. Electrolytes are crucial in maintaining your body's ability to transmit nerve impulses and contract muscles, as well as maintaining water balance and distribution to working cells and acid-base balance. The symptoms of electrolyte imbalance are often the same as those of dehydration, and may include; muscle and/or abdominal cramping, light-headedness, nausea, confusion and muscle spasms.
During and after workouts where you sweat a lot it may seem natural (or at least common sense) to rehydrate, but you should also be sure to restore lost electrolytes. Energy drinks are decent sources of electrolytes, coconut water is an even better source and bananas are also a great source of potassium, one of the important electrolytes. (Sodium, chloride, potassium, magnesium and calcium.) During long runs or races where electrolyte depletion might be a concern salt or electrolyte tablets can also be an option.
- Ease Off the Warm Up – The purpose of warming up is the increase the heart rate, increase the body’s core temperature and to loosen up muscles. However during hot days there is little to no need to raise core temperatures and muscles will naturally be looser in warmer weather. This means in warm weather your body needs less time to warm up, moreover, the longer the race the less time you’ll need to warm up before the race as there will be plenty of time to warm up during the beginning of the race. If you’re running a short fast race, you may want to do a short warm up to get everything ready for the faster paces at the beginning of the race, but for longer races you’ll want to take the warm up very easy or scrap it altogether. There is also evidence that prerace cooling might be beneficial for hot weather racing – see the next tip.
- Ice Packs – Using ice packs before and during races and runs can help decrease core temperatures basically aiding your circulatory system in the heat battle. Holding a bag of ice in your hand, or placing it on your wrist or on the back of your neck are great ways to help cool down your whole body, allowing it to run more efficiently in the heat.
Studies have shown that pre-cooling can be beneficial to your warm weather performances. One study showed that pre-cooling by air exposure at 5°C increased performance in 24°C at 51% humidity by 16%. http://www.pponline.co.uk/encyc/exercise-heat.html#ref
- Acclimatize - Heat acclimatization is one way to improve your ability to run well in hot environments by conditioning the body to maintain a higher blood plasma and volume level (which help combat increased heart rate), increased sweat rate, decreased salt amounts in the sweat produced, and quicker onset of sweating. Improvements in heart rate can be seen in as little as 4-5 days of heat acclimatization, and improvements in sweat rate and core and skin temps in 1 week. Increases in sweating and comfort in the hot environment can take up to 1 month.
- Adjust Expectations and Training Zones – When you’re running in the heat your heart rate skyrockets as your circulatory system works to cool your body while still delivering needed nutrients. As such, to keep within your typical training HR / effort zones, you need to slow your pace.
Additionally heat will have an effect on your race times. If you’re trained for a 17 min 5km in cool weather, you won’t be able to run it in hotter weather. (Joe English’s article has some good examples: http://coachjoeenglish.wordpress.com/2007/05/16/training-racing-in-heat-and-hot-weather/)
There’s no perfect formula for predicting paces (or heart rates) in heat – some use dew point indexes some use temperature, and of course everyone will be affected slightly differently.
Galloway's Book on Running (1984 – back when he was a serious runner) has a chart called "Adjusting race pace for heat".
Estimated temperature at finish...Slower than goal pace
55-60 degrees.....1%
60-65 degrees.....3%
65-70 degrees.....5%
70-75 degrees.....7%
75-80 degrees.....12%
80-85 degrees.....20%
above 85.....forget it, run for fun
He attaches a note: "This chart is based upon my own experience in the heat and talking to other runners. It has no scientific verification, but I think you get the general idea."
This table seems a bit extreme to me and geared more towards longer races when heat becomes even more of an issue. My 17:20 5k in 80 degree weather recently would not equate to a 15:28 in perfect weather as this table would suggest. In any case, the hotter the temperature and the longer the race, the more your race time will be affected.
Ultimately safety and success in hot weather running comes from understanding what’s happening to your body, and taking the proper actions to protect yourself. Staying hydrated and not pushing yourself into the danger zone are extremely important. At the end of the day you will probably not run your best possible times when the heat is on, but by following the tips above you can still safely and successfully train, run and race in the heat.
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