Heat Adjusted Running Pace
Running in Hot and Humid Weather As most runners are well aware, when temperature and humidity rise, it becomes much more difficult to run at
As Arizona-based marathon runners, it’s safe to say we know a thing or two about running in the heat. The Run Lab CBD team regularly races fall marathons which means we have to put in a lot of hot summer miles to be race ready by fall. Summer temps in Arizona regularly reach highs of over 110° F with lows in the 90s. Over the years, we have found several techniques that have allowed us to run high mileage training weeks at these extreme temperatures. We do whatever it takes to get the miles in, even if it means running 88 laps around a 1/4 mile track in 110° weather (read on to see why we would do such a thing!)
Most people lose an average of one liter of fluids per hour of exercise. Extreme heat can cause this number to increase to as much as three liters per hour. That’s 6lbs of fluids lost per hour! The big problem with losing fluids at this rate is that you can’t replenish the fluids as fast as you are losing them. While your body is capable of losing three liters per hour, it can only absorb up to one liter per hour. This means it’s very easy to become dehydrated while running in the heat.
Increase your fluid and electrolyte intake the day prior to running to ensure you start your run properly hydrated. It’s also important to hydrate during your run. There are several options for runners wanting to carry fluids with them including handheld bottles, running belts, and running vests. If you prefer to run without the added weight of carrying everything with you, we suggest setting up your own aid station to run short loops past (more on this later.) Hydration should remain a priority until you are feeling fully recovered, this could be hours or even days after your run.
It’s important to start small and increase your training volume slowly until you learn how your body reacts to training in the heat. Mild dehydration causes a decrease in performance but isn’t dangerous, while severe dehydration can cause death. It is very important to listen to your body and not push it too far. You can determine what stage you’re in by paying close attention to the symptoms of dehydration and by weighing yourself before and after running.
PERCENT WATER LOST — SYMPTOMS
0% — none, optimal performance, normal heat regulation
1% — thirst stimulated, heat regulation during exercise altered, performance declines
2% — further decrease in heat regulation, hinders performance, increased thirst
3% — more of the same (worsening performance)
4% — exercise performance cut by 20 – 30%
5% — headache, irritability, “spaced-out” feeling, fatigue
6% — weakness, severe loss of thermoregulation
7% — collapse likely unless exercise stops
10% — comatose
11% — death likely
[Nutrition for Cyclists, Grandjean & Ruud, Clinics in Sports Med. Vol 13(1);235-246. Jan 1994]
Don’t wear a cotton t-shirt! We are lucky to be living in a time where sportswear companies are releasing lighter and cooler materials every year. These high-performance fabrics are lightweight, breathable, and moisture-wicking, unlike traditional cotton fabrics. A hat and sunglasses can also help keep you cool by shading your face from the sun. Invest in some proper summer running gear, it makes all the difference!
If you are an evening runner, changing your schedule to mornings could dramatically improve your summer training. Running at 5 am when the weather is slightly cooler has helped us achieve much better training cycles. We don’t love waking up at 4 am either, but we always thank ourselves later when we check our weather app and see triple-digit temps!
We’ve gone as far as running 22 miles around a 1/4 mile track. This might sound crazy to some, but this is the best way we’ve found to survive a summer long-run in Phoenix (110°+.) We set up an aid station on the track with gels, water, electrolytes, and a cooler full of ice water. Running at the track ensures we’re never far from water or anything else we might need, allows us to run long distances without having to carry anything, and allows us to stop at any time if things go wrong (you do not want to be 10 miles from the car when heat exhaustion kicks in.) We have also found that dipping a cooling towel in ice water and throwing it over our shoulders every mile or so helps keep us cool and keep our heart rate lower. Depending on how extreme the temperatures are and how far your run is, you can scale this strategy up from 1/4 mile laps at the track to several mile loops past your house. Come up with an option that works for you and go run some laps!
Exercising in the heat causes blood to be redirected from working muscles to your skin to help keep you cool. This extra work inside your body causes increased heart rate and lactate production. Dehydration will also set in much faster as your body uses perspiration as another method of cooling itself down. With all of this happening, we cannot expect our body to perform as it does in cooler temperatures. We recommend forgetting about pace when it heats up and instead using perceived effort or heart rate to measure your training intensity. For more on this, check out our Heat Pace Calculator and our Heart Rate Training Calculator.
Training in the summer often requires more preparation and more caution than training during the cooler months, however, we shouldn’t use that as an excuse to stay inside. The tips we listed above can significantly improve your summer training and lead to a surprise speed boost come fall race season. In fact, some coaches and researchers even believe training in the heat is more effective for increasing VO2 Max than training at altitude. Just remember to stay hydrated and know your limits!
Marathoner and Co-Founder of Run Lab CBD
Running in Hot and Humid Weather As most runners are well aware, when temperature and humidity rise, it becomes much more difficult to run at
Heart Rate Training Zones Heart rate zones are an accurate way to measure training intensity. There are many other methods of measuring your training effort,
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