Training in the Heat: The Essentials
This time of year, when the air starts to feel heavy with humidity, running outside begins to feel different. I’ve always kind of liked the aftermath of a summer run — the sweat layered thick on my arms and legs, my (Sarah here) ponytail soaked through and tangled with humidity. Maybe catching a bit of a tan en route. I look like I’ve done something hard, and I have! On days when the weather is textbook-perfect, I miss that feeling.
Still, I won’t lie: running in the heat is hard. It can feel like you are losing fitness. It can feel like your goal race pace is impossible to reach, even for just 25% of the time/distance you want to run it for. It can feel like you are going backwards and that confidence can take a real hit. These feelings are normal and felt by pretty much everyone during this time. But let’s be clear, it’s not you, it’s the heat. A new form of stress has been added to your training and it’s going to make things harder, and for quite a while too.
But it’s also an opportunity. When done with care, training in the heat unlocks adaptations that cold-weather sessions never ask from us. It teaches the body, yes — but also the mind.
So, I want to talk about that. About what happens to us when we choose to keep running even when the sun tells us not to. I hope to break it down simply — clear enough that you, and your middle schooler, will understand and hopefully take something helpful away to aid your summer running journey.
Why is running in the heat hard?
- Training in the heat increases your core body temperature, forcing the body to work harder on cooling itself down, instead of working harder on helping you run faster.
- Blood is redirected from working muscles to the skin for cooling and sweat. This reduces blood available for muscles and heart, and the heart must work harder for oxygen delivery and output.
- Since blood is mostly directed to the skin, this also means that less blood is going to the intestines and this can cause an increase in GI issues. The stomach may be extra sensitive during those summer runs and it may take some gut training to reduce the likelihood of GI issues.
- All of these factors and more cause a higher perceived exertion, making running in the heat pretty dang hard. Ever noticed that feeling when you run on the treadmill indoors and it feels harder than your normal run? It’s a similar feeling here. This feeling is enhanced when that dew point is high as it feels like we are running against an external force.
- Greater electrolyte loss: sweat is more concentrated (saltier) and can dehydrate you quicker on those first hot, humid runs. If you haven’t been carrying your hydration flask with you and mixing in electrolytes then we recommend doing so now for any runs >45min.
How long does it take for the body to acclimatize to the heat?
- 7-14 days of gradual heat exposure are recommended, progressively increasing the intensity and duration of the physical activity. Even when you are acclimatized, it’s not as if running is going to start feeling easy again. It’s still going to feel hard, but your body is better prepared for it to help you perform better than when you were not acclimatized!
- If not maintained, the physiological benefits will decay within 3 weeks (NATA). We’ll share more about how you can maintain the physiological benefits of heat training even when the weather cools down in a future post.
What benefits do we get from training with heat exposure?
- More efficient thermoregulation – You will start sweating (cooling) earlier, with more dilute sweat that will not dehydrate you as quickly. (Swaka)
- Improved cardiovascular efficiency, such as increased blood plasma volume, meaning lower heart rate at same effort. (Garrett)
- Capillary Growth – Repeated heat stress and associated muscle activity can stimulate new capillary growth, particularly in skin and muscle. Why it’s helpful: More capillaries mean better oxygen delivery and waste removal, enhancing endurance and recovery. Result: Muscles become more aerobically efficient (Hoier)
- Grit – Training in the heat builds character. If you can train through these tough conditions, you are ready to tackle other difficult challenges ahead
Strategies to help us adjust to the heat in the initial stages
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SLOW DOWN – Your typical easy pace is not your current easy pace. Your spring marathon pace is not your summer marathon pace. That baseline time trial you did in 50 degrees weather. That doesn’t sync with your summer training. The heat is a new stress and you need to adjust. Focus on effort and making sure the easy days stay conversational and relaxed throughout.
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Be Flexible with Workout Paces – The pace recommendations included in your workouts are guides and are generally based around ‘best case scenario’. They are not targets to beat!! If there’s a pace range, consider starting off the workout at the slower end of that range. With or without a pace range, take a moment before a workout to assess the environmental conditions and the condition of your body and adjust. Remember faster is not always better, it’s about trying to provide the right amount of stress to your body in a manageable way. Sometimes that means being slower than a previous attempt, or even slightly slower than the pace suggested AND THAT’S OKAY! We need a hero/heroine for a training block, not for a week!
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Walking Recoveries – If you are struggling during a workout, don’t hesitate to take a walking recovery instead of a jog. I frequently do this in the summer, especially if I feel my body tipping over the edge. If I sleep in and choose to punish myself with an afternoon workout, I may even take a standing rest in the shade. There’s no shame in this and it does not take away from your workout if it allows you to run your harder reps. Do what you need to do to get through the workout!
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Hydration: Ensure you are hydrating before, during, and after activity. Not only can you drink your electrolytes, but eating our intake of sodium from our meals is often forgotten, and arguably more enjoyable (NATA). Also, during this time we should be carrying hydration with electrolytes for runs >45min!
- Clothing: Opt for lightweight, sweat-wicking materials, bonus points for UPF clothing that protects from the sun’s rays. Or, lose the shirt if that’s your vibe.
- Time: Run early in the morning or when the suns goes down
- Pay attention to your body’s signals, like headaches, nausea, or chills, and adjust accordingly.
- Run in shaded areas
- Break workouts into smaller chunks with recovery breaks between (i.e. instead of a 30min tempo, try 3*10min with 2min walking recoveries)
- Access to ice cloths, water sponges, or applying cool water to regulate body temperature
- Ignore Heart Rate – This is a rare period where we’ll tell those that wear a reliable external heart rate monitor (i.e. chest or armband – we know that wrist based watch monitors are not reliable) to ignore their heart rate for several weeks as the body acclimatizes. Your heart rate is going to be higher on most types of runs. Using the interventions mentioned above will help to control the heart rate, but it will still likely be higher than normal. It’s a great time to truly listen to your body.
- Grace: Be patient with yourself and know that some days will be tougher than others.
With patience, adjustments, and working with your body rather than against it, your summer miles will certainly bring you some fall smiles!
Written by Sarah Watts. and Mike McMillen
References
Sawka, M. N., Leon, L. R., Montain, S. J., & Sonna, L. A. (2011). Integrated physiological mechanisms of exercise performance, adaptation, and maladaptation to heat stress. Comprehensive Physiology, 1(4), 1883–1928.https://doi.org/10.1002/cphy.c100082
Garrett, A. T., Goosens, N. G., Rehrer, N. J., Patterson, M. J., & Cotter, J. D. (2009). Short-term heat acclimation is effective and may be enhanced rather than impaired by dehydration. American Journal of Human Biology, 21(6), 764–769.https://doi.org/10.1002/ajhb.20900
Douglas J. Casa, Julie K. DeMartini, Michael F. Bergeron, Dave Csillan, E. Randy Eichner, Rebecca M. Lopez, Michael S. Ferrara, Kevin C. Miller, Francis O’Connor, Michael N. Sawka, Susan W. Yeargin; National Athletic Trainers’ Association Position Statement: Exertional Heat Illnesses. J Athl Train 1 September 2015; 50 (9): 986–1000. doi: https://doi.org/10.4085/1062-6050-50.9.07
Hoier B, Hellsten Y. Exercise-induced capillary growth in human skeletal muscle and the dynamics of VEGF. Microcirculation 21: 301–314, 2014.