Keep yourself safe while exercising in the heat

With memorial day just around the corner, warmer temps are soon to follow. As the summer begins, heat-related issues during exercise become more common. Before I discuss the tips to help you safely exercise in the heat, it's important to understand how heat and humidity affect your body during exercise.

As you exercise, your muscles create heat. To keep your body safe as you begin to build up internal heat, your body increases your sweat rate to remove heat from the inside of your body – this happens through evaporative cooling. Overtime, as you become dehydrated (from fluid loss), blood volume decreases. As a result, blood gets thicker. And the more blood going to the skin means less blood going to your heart which means less blood to your working muscles. To maintain cardiac output (the amount of blood pumped by the heart per minute), heart rate increases in order to supply the working muscles with blood. But due to a decline in blood availability (because of cooling), less blood is available to go to the working muscles. When the body can no longer take care of all of its responsibilities (remember - all of this is happening so you don't die in the heat), your body will start to slow down by shutting down to keep you safe. If you ignore the signs of overheating, heat builds up in your body, your core temp increases and you are at risk for overheating and may experience heat stroke.

Here are a few helpful tips for exercising in the heat:

Acclimatization
Complete heat acclimatization requires up to 14 days but body systems of the body adapt at varying rates. Be mindful that every time you exercise in the heat, you gain more tolerance but it could take at least 2 weeks for you to feel more comfortable exercising in the heat. But there's no point suffering in the heat if you are unable to complete a quality workout, which means sometimes you just need to exercise indoors.

Change in physiology
It is very important to lower the intensity during the first 2 weeks of exercising 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 in the first few weeks of acclimating. You will likely notice an increase in cardio strain and your perceived exertion will increase. You may also feel more tired, fatigued and exhausted than normal. Positive cardio adaptations occur in the first 5-10 days whereas changes in sweating mechanisms can take 10-14+ days.

Training modifications
Consider splitting up your workout (half outside, half indoors). Find shady areas to exercise. Opt to exercise indoors when the humidity is very high. 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 safely adjust to the heat. 

Hydration
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. If you are exercising in the heat for more than an hour or you are sweating perfusely in the heat, opt for a well formulated sport drink (at least 30g carbohydrates, 240mg of sodium and at least 16 ounce water per hour).
Although your daily diet helps to keep you nourished and fueled, the diverse nature of hot and humid weather validates the importance of consuming well-formulated sport nutrition drinks during specific outdoor workouts.

Females
Females who menstruate regularly each month may notice an increase in thermal strain during exercise 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 females to feel bloated from fluid retention. Additionally, whereas females are more likely to feel cold during the estrogen-dominant follicular phase, progesterone acts on the hypothalamus (temp control center) which increases body temperature. Females may feel warmer than normal, which makes it more difficult to dissipate heat (although a helpful physiological response for racing in cooler weather events). Females 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 exercise 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. Bring a sport drink with you and sip consistently (every 10-15 minutes). 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.

Nutrition tips to help you excel in a warm weather race

As you go from winter to spring to summer, it takes much more effort and energy to maintain a "normal" pace as the temperature rises. As a way to keep your exercising body safe in the heat, your body increases your sweat rate to remove heat from your body through evaporative cooling. As you become dehydrated (from fluid loss), blood volume decreases. In turn, more blood going to the skin means less going to your heart. To maintain cardiac output (the amount of blood pumped by the heart minute), heart rate increases in order to supply the working muscles with blood. But due to a decline in blood availability (for cooling), less blood is available to go to the working muscles. When the body can no longer take care of all of its responsibilities (remember - all of this is happening so you don't die in the heat), your body begins to shut down to keep you safe. If you ignore the signs of overheating, heat builds up in your body, your core temp increases and you are at risk for overheating and may experience heat stroke.
If you've ever struggled running in the heat, you are not alone. There are a few primary reasons why performance declines in warmer temps.

1) An increase in overall body temperature. Similar to a fever, the higher your core temperature, the greater the perceived effort (everything feels harder).

2) In the warmer temps, a significant amount of blood flow is redirected from the working muscles to the skin in order to cool the body. Cooling (which is very important to the health of your body - your organs don't want to overheat!) happens from sweating and evaporation. Therefore, less blood is available to transport oxygen to the working muscles. Less oxygen in the heat is similar to training at altitude. But in humid conditions, the air is full of water vapor and it can't hold any more so sweat has a difficult time evaporating (which means it can't cool you like it would be able to do in low humidity).

3) Dehydration increases in hot conditions. When you are dehydrated, you lose blood volume which causes your blood to get thicker. This makes it harder for your heart to supply blood to your muscles. As a result, your heart has to work even harder to pump that blood. Additionally, when fluid levels drop, you have a harder time controlling body temperature which causes the core temperature to rise even faster.

4) You DO NOT lose sodium without fluids. Dehydration comes from fluid loss - not from sodium loss. If you are simply focusing on sodium and carbs (salt tabs, gels and chews) but not drinking enough water each hour, the sodium and carbs will not do anything to help you avoid dehydration. You must drink enough of a well-formulated sport drink to properly keep yourself hydrated.

The bottom line is that the harder you work in the heat, the more heat is generated from the working muscles. Blood in your body competes for the working muscles (energy), the skin (to cool you) and the gut (aid in absorption and digestion of calories). The greater the metabolic heat production, the more energy is needed to cool the body (top priority to prevent you from overheating) - which means more stress on the cardiovascular system. Heat stress also causes an increase in fluid, electrolyte and glycogen loss (which is why pacing is critical) but the heat impacts the ability to effectively digest and absorb calories and fluids. Thus the greater risk of GI issues in higher heat environments.

As you prepare yourself mentally for your upcoming long distance event, keep in mind that working at a higher effort than your body can dissipate heat is going to produce a build-up of internal heat.

• Create a race strategy that will allow you to use your fitness in a smart way.
• Your fastest performance is the one where you minimize a massive slow down.
• Navigate the conditions you are given on the day, don't chase a PR or metrics. Listen to your body.
• Focus on what you can control. Make sure to "check-in" with yourself and respond accordingly.
• Take walk breaks (reset breaks) when you run. The longer you let the heat build up, the greater the slow down (and greater risk of GI issues).
• Back off the effort. Start out conservatively to minimize the risk of irreversible heat stress. Save your heart beats.
• Go in with no expectations. Race your own race.
• Go into the event well-hydrated and fueled so you are in the best state of health possible to perform in the race conditions. Have a plan - don't just figure things out as you go along.
• Fuel and hydrate consistently and frequently. Moderate amounts of fluids consumed frequently will digest and absorb easier than large or tiny amounts consumed periodically. 
• Prioritize liquids over solids for easier digestion. As a general rule, the higher the carbohydrate content (and fat/protein) and lower the fluid intake, the slower the absorption rate.
• Focus on the process. Think of the race as a project, checking off to-do's and overcoming obstacles as you go through each mile.
• Keep yourself cool on the bike so you can start the run with a slightly lower (or normal) core body temperature. Use water from aid stations to douse the body.
• Your mour muscles demand more fuel (glycogen) in hot conditions. Muscles are more taxed which can affect efficiency and can also cause greater tissue damage.
• On the run, your stomach can only empty about 5-7 ounces of fluid every 15 minutes. If you drink more than you can empty from your stomach, you will risk a sloshy stomach. Also, if you only drink water, you risk diluting sodium in the blood. Make sure to rely on a sport drink throughout the race (that’s why I also suggest to wear a hydration belt on the run) and use water only for sipping and cooling.
• Use ice in your hands, on your head, around your neck and near your groin to help with cooling. Also use a cooling towel.
• Minimize the risk of a sunburn by using sunscreen.
• Wear a hydration belt with your sport drinks on hand so you can keep to your own drinking schedule.
• The harder the effort, the more your body temp will increase as more heat is being generated. The harder you push, the greater the increase in heat production. You will know when your body temp is increasing because you will feel yourself getting warmer. Control your effort to better manage your body temp throughout the entire race.
• Look for shaded areas on the course to avoid running in the direct sunlight.
• If you feel overly hot, dizzy or chills. Stop immediately, sit down and get yourself cooled.

If you found this information helpful and you'd like to learn more about sport nutrition (like should you concentrate your bottles during a race, how do I fuel before a long distance triathlon and more?) check out our team membership. 

Hot Weather Training - Health and Safety Tips

 

Heat. 🔥

The summer presents a vulnerable time for endurance athletes who are training outside in an effort to gain fitness for an upcoming event.

High heat and humidity challenges the limits of the cardio system, central nervous system and skeletal muscle system. Maintaining core body temperature and keeping body fluids in balance are key priorities for your body. Training in a hot environment can put your body under a significant amount of physiological strain, which can negatively impact your health.

By understanding how the heat can impact your health and performance, you can do a better job of keeping yourself healthy this summer.