Summer is here, and it’s a hot one across the country. Don’t let the heat beat you up, keep you from having fun or having success. When we first experience summer’s furry, our bodies are not prepared to run the internal swamp cooler. As we overheat in those first hot days, our heart rate spikes, efforts are difficult to maintain, we feel wiped out after a minimal workout, and our muscles are more tender than expected afterwards. However, with a thoughtful training block targeted to stimulate adaptation to heat, we can perform in the summer with minimal ill effects.
Why We Suffer in the Heat; a Little Physiology Lesson
- To sweat and cool, blood, which carries heat generated by working muscles, needs to flow to the skin. Blood caries heat generated by working muscles. With blood being diverted from our muscles and heart, power and endurance are diminished.
- Sweat is comprised of plasma and electrolytes. Increased sweating depletes these resources from the blood, making it thick. Thick blood (low blood volume) is taxing for the heart to pump, so heart rate increases to sustain the workload. An endurance pace may feel like a sprint.
- With less oxygen-carrying blood making it to our muscles, aerobic capacity, the oxygen fueled energy system relied upon for long duration efforts, is decreased and we must rely on carbohydrate-greedy anaerobic metabolism, which is sustainable for only a short duration and is the primary culprit for delayed-onset muscle soreness.
- With reduced blood volume, VO2 Max is reduced, meaning our bodies are not able to take in as much oxygen. This means that we are less efficient and are putting more stress on our bodies for any exertion.
Fortunately, we are incredible at adapting to heat. Once adapted, if we continue to train in these conditions a few times a week, we will return to our previous fitness profile. If we actively work on acclimating to hot conditions, it can be accomplished in 10 – 14 days.
Hiding in the Cool Will Not Help You Acclimate
- Stay out of air conditioned spaces to adjust to the heat, but do not get hot. Keep cool with a fan, cold showers, dips in a lake, etc.
- If you can, sleep with the windows open. However, if it is too hot to sleep, use the AC sparingly (set it to the warmest temperature you are comfortable in).
- Drink as much water as you can, alternating pure water with electrolytes. Avoid/ reduce caffeine and alcohol intake while acclimating as they dehydrate you.
- Stay out of the sun when not training, and do not get sunburnt! A burn will reduce your ability to sweat.
- If you are traveling to an environment that is more warm or humid than your home turf, arrive as many days before the event as possible.
Guidelines for Heat Adaptation Training Block
After training for an hour a day for two weeks in peak heat with two rest days in the mix, the body should be adapted. If we train to exhaustion, overheat, neglect our nutrition, or don’t recover from training sessions, the process will take longer- often much longer and to the detriment of our fitness.
- Pre-cool your body with a cool shower or spending time in an air-conditioned area before you work out.
- Wear clothes that wick moisture away from your skin. Avoid cotton, tight filling garments, and dark colors.
- Train through the peak of the heat each day for a short period of time. Heat stress sessions for one hour a day will trigger a physiological response. Increase the time or intensity each day, but do not stay out if you start to feel excessively hot or fatigued. You want to stimulate your body to adapt to the heat, but if you stress your body too much you will spend your rest time recovering instead of adapting.
- Ease up. Slow your pace, reduce the time, and decrease the weight/reps if power training.
Maintain Heat Adaptation
- After this adaptation period, slowly increase duration or intensity of your workouts in the heat.
- Train for at least one hour, twice a week in the heat to maintain physiological adaptation.
- Unfortunately, it only takes 5-7 days to lose heat adaptation.
Train to Refuel and Rehydrate in the Heat
When it’s hot, our appetites are suppressed, and drinking feels like a chore. However, we will not be able to do endurance or intense workouts in the heat if we don’t refuel and rehydrate while exercising. Fortunately, we can train our bodies to digest food and absorb liquids. When our digestive tracks are not heat adapted, a sour stomach, bloating or the feeling of liquid sloshing around in our bellies is common. These usually lead to stomach cramps and we stop refueling and rehydrating. This leads to disaster! Eat a good meal three hours or more before a heat stress workout. It will take three hours to digest this meal.
- Eat a good meal three hours or more before a heat stress workout. It will take three hours to digest this meal.
- Drink while exercising, and make sure you are hydrated before you start.
- We need to drink more water than usual when training in the heat. In arid climates, it is easy to think we don’t need to replace lost fluid because our sweat is evaporating so rapidly our skin and clothes are dry. Aim to drink .5 – 1L of fluids per hour. Drink even more when in conditions like Death Valley or the Amazon.
- Freeze half of liquids in a bottle/ hydration bladder, or fill bottles 2/3 with ice cubes. Hot liquids are unpleasant to drink and are generally still untouched when we finish training, leaving us completely wiped out. Cool liquids will help cool your core temperature too.
- Replace lost electrolytes. Alternate pure water and electrolyte mix during training sessions or follow hourly training dose guidelines for specific electrolyte tablets like MetaSalt or Endurolytes.
- It is hard to digesting food in the heat. Err on the side of moist carbohydrates such as sports drinks, gels, blocks, rice balls, etc. instead of dry bars, sandwiches, trail mix, and the like. Fats and proteins are especially hard to digest in hot conditions. Avoid them during workouts or add them in carefully.
- You will burn calories keeping cool. Consume more calories than you usually do.
What Physiologically Changed During the Heat Acclimatization Training Block?
- Our blood volume increases. Blood no longer becomes thick and taxing for the hearts to pump. Heart rate and V02 max return to normal zones. Efforts feel as they should: endurance pace no longer feels like a fast pace, and sprints are fast again.
- Our cardiac output increases. We can now get oxygen-carrying blood to our organs, working muscles and skin at the same time. This returns our endurance, recovery between intervals and power to normal, and it diminishes Delayed Onset Muscle Soreness (DOMS).
- We sweat more profusely at lower temperatures but with less electrolytes lost. This lets us dump heat efficiently and reduces cramps.
- We also improve fluid and nutrient absorption. We can now fuel our long sessions and intense efforts.
Traveling to a Hot Location to Race or Adventure In?
- Arrive in the climate as many days prior to the event as possible.
- Spend the two weeks before departing adapting to heat by training in the warmest location available. Be creative! Crank the heat in a small room for a trainer session, go to Bikram yoga, train in excessive layers, etc.
- If the destination will be humid and you live in arid conditions, you will want to adapt to this as well. In humidity, sweat does not evaporate well off our bodies. Find a steam room to use daily and increase the time in it each day in addition to heat stress training. Our bodies will adapt to this too if asked nicely.
- Continue the adaptation routine on arrival, but do not get exhausted before the big day! Training days should be short, at an easy effort, and ended before the heat is impacting performance. Cool down as soon as the training session is complete.
Summer heat? Bring it on!