Complete heat acclimatization requires up to 14 days but the systems of the body adapt at varying rates. Be mindful that every time you train in the heat, you gain more tolerance to the heat. In other words, you do not need to make an effort to train in the hottest time of the day acclimate to the heat. Continue to build fitness in a temperature controlled environment, alongside training in the heat (you don't need to be outside in the heat for every workout). There's no point suffering in the heat if you are unable to complete a workout and stay consistent with your training. Sometimes you just need to stay indoors.
Change in physiology
It is very important to lower the intensity during the first 1-2 weeks of training in the heat (ex. early summer) as your body is trying to improve control of cardio functioning. Be mindful that acclimatization will require you to reduce your effort/intensity so be OK with seeing slower paces/watts in the first few weeks of acclimating. This is for your health and safety - which trumps trying to gain fitness in the first few weeks of training in the heat. During the early adaptations of heat acclimatization (ex. early summer or first warm days of the year), you will likely notice an increase in cardio strain due to the added stress of exercising in the heat. Your perceived exertion will increase (especially at higher intensities and prolonged durations) and you will feel more tired, fatigued and exhausted than normal. Cardio changes occur in the first 5-10 days whereas changes in sweating mechanisms can take 10-14+ days. Because of this, you may need to make some modifications to your training.
It is very important to lower the intensity during the first 1-2 weeks of training in the heat (ex. early summer) as your body is trying to improve control of cardio functioning. Be mindful that acclimatization will require you to reduce your effort/intensity so be OK with seeing slower paces/watts in the first few weeks of acclimating. This is for your health and safety - which trumps trying to gain fitness in the first few weeks of training in the heat. During the early adaptations of heat acclimatization (ex. early summer or first warm days of the year), you will likely notice an increase in cardio strain due to the added stress of exercising in the heat. Your perceived exertion will increase (especially at higher intensities and prolonged durations) and you will feel more tired, fatigued and exhausted than normal. Cardio changes occur in the first 5-10 days whereas changes in sweating mechanisms can take 10-14+ days. Because of this, you may need to make some modifications to your training.
Training modifications
Consider splitting up your workout (half outside, half indoors). Find shady areas to train. Opt to train indoors when it's just too hot outside. Or try to workout when it's not as hot (early morning or early evening). If you try to push your normal efforts in the heat, your body cannot adjust to the heat. Do not try to chase paces/efforts that you could easily hold in cooler conditions. You'll only push back the time that your body could be acclimating (plus, this is a sure fire way for a good workout to quickly go bad).
Sport Nutrition
Proper fueling and hydration during workouts helps maximize training adaptions. Falling short on fluid, carbohydrate and electrolyte needs may increase the risk for immunosuppression or injury. Plus, the symptoms of underfueling and dehydration are not pleasant.
A sport drink provides a practical and easy way to obtain fluids, electrolytes and carbohydrates - in the precise formulation - to optimize digestion and absorption.
Gels, bars and chews are portable, convenient sources of carbohydrates to consume during a workout but they lack the fluid and sodium found in a sport drink, and without this precise formulation they are more difficult to digest and absorb - increasing the risk for GI issues.
Although your daily diet helps to keep you nourished and fueled, the diverse nature of hot and humid weather, long distance workouts, intervals, brick workouts, two-a-day sessions and strength training validates the importance of consuming well-formulated sport nutrition drinks during specific workouts.
Fueling and hydration
When it comes to fueling/hydrating, do not view two back-to-back workouts as two separate workouts. If you are “only” running 20 minutes off a 3 hour bike, you need to see this as a 3:20 hr workout NOT a 3 hour bike + 20 minute run. Same goes for bike or run after a swim workout. And when you are running, you are using much more full-body muscle than when you are cycling - which requires more fluids for thermal control. Plus there is less breeze when running vs. cycling. Do not compromise your ability to have one long quality workout and recover quickly by not bringing adequate sport nutrition/hydration for both workouts.
Although pouring cold water on the body can help you feel cooler in hot temperatures, you still need to ingest fluids. To help prevent a sloshy stomach and to assit with optimal rehydration during your workout, you need to consume a sport drink regularly during your workout. Make sure you always have a sport drink with you when you train (not just water) and be mindful of the negative health issues that you may experience by overdrinking water in the heat OR under-consuming sport nutrition without adequate calories and electrolytes. Plan stops to refill your sport drink bottles before you run out of fluids. Overconsuming salt/electrolytes and fluids before and during workouts will not help you acclimate to the heat but staying adequately hydrated and well fueled will help you better perform and respond to the heat.
Female athletes
Female athletes who menstruate regularly each month may notice an increase in thermal strain during the luteal phase (high hormone phase) before and during menstruation. The increase in progesterone causes body temperature to increase in preparation for the fertilization of an egg. When fertilization does not occur, estrogen and progesterone decrease before the follicular phase. The high concentration of progesterone during the luteal phase affects fluid balance, causing female athletes to feel bloated from fluid retention. Additionally, whereas female athletes are more likely to feel cold during the estrogen-dominant follicular phase, progesterone acts on the hypothalamus (temp control center) which increases body temperature. Female athletes may feel warmer than normal, which makes it more difficult to dissipate heat (although a helpful physiological response for racing in cooler weather events). Female athletes should be mindful of how the body responds to training in the heat, specifically in the 7-10 days before menstruation and adjust efforts accordingly.
Minimize heat stress
There are several ways to minimize heat stress. Your training gear should be breathable, light, wicking and should help you stay cool and minimize exposure to the sun. Your clothing should protect the areas of your body that are most exposed to the sun (ex. back, neck, shoulder, face). Always wear broad spectrum sunscreen when you train outdoors and reapply. Wear a cooling towel around your neck and regularly re-wet throughout your run. Use water to cool your body on the bike and run. Search for shaddy sections to run and select "cooler" times in the day to workout.
Know the warning signs
Identify the warning signs of heat cramps (muscle cramps), heat exhaustion (thirst, profuse sweating, fatigue, pale and cool skin, weakness, headache, nausea, chills/goose bumps, cessation of sweating, faintness, dizziness) and heat stroke (strong and rapid pulse, hot and dry skin, confusion). If you suddenly feel like you are experiencing a heat related illness, stop exercising, get into a cool environment and drink electrolyte-based liquids. An extreme loss of appetite, excessive sleepiness, headache, chills or abnormal fatigue during or post workout can all be signs that you are not properly hydrating (or fueling) during your workout.
Sport Nutrition
Proper fueling and hydration during workouts helps maximize training adaptions. Falling short on fluid, carbohydrate and electrolyte needs may increase the risk for immunosuppression or injury. Plus, the symptoms of underfueling and dehydration are not pleasant.
A sport drink provides a practical and easy way to obtain fluids, electrolytes and carbohydrates - in the precise formulation - to optimize digestion and absorption.
Gels, bars and chews are portable, convenient sources of carbohydrates to consume during a workout but they lack the fluid and sodium found in a sport drink, and without this precise formulation they are more difficult to digest and absorb - increasing the risk for GI issues.
Although your daily diet helps to keep you nourished and fueled, the diverse nature of hot and humid weather, long distance workouts, intervals, brick workouts, two-a-day sessions and strength training validates the importance of consuming well-formulated sport nutrition drinks during specific workouts.
Fueling and hydration
When it comes to fueling/hydrating, do not view two back-to-back workouts as two separate workouts. If you are “only” running 20 minutes off a 3 hour bike, you need to see this as a 3:20 hr workout NOT a 3 hour bike + 20 minute run. Same goes for bike or run after a swim workout. And when you are running, you are using much more full-body muscle than when you are cycling - which requires more fluids for thermal control. Plus there is less breeze when running vs. cycling. Do not compromise your ability to have one long quality workout and recover quickly by not bringing adequate sport nutrition/hydration for both workouts.
Although pouring cold water on the body can help you feel cooler in hot temperatures, you still need to ingest fluids. To help prevent a sloshy stomach and to assit with optimal rehydration during your workout, you need to consume a sport drink regularly during your workout. Make sure you always have a sport drink with you when you train (not just water) and be mindful of the negative health issues that you may experience by overdrinking water in the heat OR under-consuming sport nutrition without adequate calories and electrolytes. Plan stops to refill your sport drink bottles before you run out of fluids. Overconsuming salt/electrolytes and fluids before and during workouts will not help you acclimate to the heat but staying adequately hydrated and well fueled will help you better perform and respond to the heat.
Female athletes
Female athletes who menstruate regularly each month may notice an increase in thermal strain during the luteal phase (high hormone phase) before and during menstruation. The increase in progesterone causes body temperature to increase in preparation for the fertilization of an egg. When fertilization does not occur, estrogen and progesterone decrease before the follicular phase. The high concentration of progesterone during the luteal phase affects fluid balance, causing female athletes to feel bloated from fluid retention. Additionally, whereas female athletes are more likely to feel cold during the estrogen-dominant follicular phase, progesterone acts on the hypothalamus (temp control center) which increases body temperature. Female athletes may feel warmer than normal, which makes it more difficult to dissipate heat (although a helpful physiological response for racing in cooler weather events). Female athletes should be mindful of how the body responds to training in the heat, specifically in the 7-10 days before menstruation and adjust efforts accordingly.
Minimize heat stress
There are several ways to minimize heat stress. Your training gear should be breathable, light, wicking and should help you stay cool and minimize exposure to the sun. Your clothing should protect the areas of your body that are most exposed to the sun (ex. back, neck, shoulder, face). Always wear broad spectrum sunscreen when you train outdoors and reapply. Wear a cooling towel around your neck and regularly re-wet throughout your run. Use water to cool your body on the bike and run. Search for shaddy sections to run and select "cooler" times in the day to workout.
Know the warning signs
Identify the warning signs of heat cramps (muscle cramps), heat exhaustion (thirst, profuse sweating, fatigue, pale and cool skin, weakness, headache, nausea, chills/goose bumps, cessation of sweating, faintness, dizziness) and heat stroke (strong and rapid pulse, hot and dry skin, confusion). If you suddenly feel like you are experiencing a heat related illness, stop exercising, get into a cool environment and drink electrolyte-based liquids. An extreme loss of appetite, excessive sleepiness, headache, chills or abnormal fatigue during or post workout can all be signs that you are not properly hydrating (or fueling) during your workout.
Here's a video helping you understand how to best fuel and hydrate during warm weather training: