Guide to Training and Performance in Hot Weather

Heat is the enemy of endurance performance and an underlying cause for diminished performance, dehydration, heat stress, gastrointestinal distress, and impaired recovery

Guide to Training and Performance in Hot Weather

This guide will provide you with the tools and information you need to PREPARE for training and events, PERFORM at your best, and RECOVER optimally in hot weather.

Part 1: Heat Acclimation & Preparing for Exercise in Hot Weather

No one is immune to the detrimental effects of exercising in hot weather. Some athletes respond better than others, but high ambient temperatures and high core temperatures diminish endurance performance for everyone. The good news is that everyone competes in the same conditions, and your response to high temperatures is trainable. The first step to improving your performance in the heat is to PREPARE with the following hydration and thermoregulation strategies.

Quick Facts:

- Assess day-to-day hydration with WUT protocol (Weight, Urine, Thirst) upon waking. If two or more indices point to dehydration, take corrective action.
- Increase intake of fluids and high water content foods
- Acclimatization takes up to 14 days.
- Acclimation activities like passive heat exposure and low-intensity training in the heat can be effective preparations when done prior to traveling to hot environments.
- Pre-cooling with ice slurry drinks, an ice vest, and/or cold towels can improve performance by enabling you to start with lower skin and core temperatures. Ice slurry drink is the most practical method.
- Hyper-hydration or preload hydration products should be reserved for extreme conditions and/or very long and strenuous workouts and events.
- Interval workouts should be scheduled at cooler times of day. It can be advantageous to conduct some moderate-intensity endurance workouts during the heat of the day to aid in heat acclimation.
- Day-to-Day Hydration
- Monitoring day-to-day hydration is important year-round, but never more important than during hot weather or during the transition from cooler weather to hot weather. When you wake in the morning, there are three indices you need to look at: Weight, Urine, and Thirst.

The WUT concept, devised by researchers Cheuvront and Sawka for hydration status assessment, states that when only one of three indices is positive your hydration status is likely good. When two of the three indices are positive, you are likely dehydrated. And when all three indices are positive you are very likely to be dehydrated. The method is easy. When you wake up, assess your level of thirst. Then observe the color of your urine. After you have urinated, weigh yourself without clothing.

Your morning urine should be light in color or relatively clear. The tipping point for the WUT assessment is if your urine is approximately the color of apple juice or darker. Be aware, however, that clear urine does not necessarily mean you’re in the clear (bad pun intended). If you guzzled a full bottle of water before bed, your morning urine may be light in color because you consumed so much water in a short period of time.  Ideally, you also need to evaluate the color of your urine stream, not the diluted urine in the toilet.

Your weight should remain relatively constant from day to day, varying about 1%. Even if you are gradually losing weight as part of a weight management goal, the changes from one day to the next won’t vary more than 1%.

Why WUT Matters

The WUT assessment is important because it can indicate whether your overall daily fluid intake is adequate to replenish all water losses. You are constantly losing fluid, from respiration to keeping yourself cool in a warm office environment. Exercise fluid losses simply add to this daily water loss. In many cases, athletes start workouts already 2% down in bodyweight due to mild dehydration, meaning that a further 2% loss during exercise actually puts you at a 4% deficit during the latter part of your workout or race. Starting your day with a better hydration status means you are optimally prepared for a better and more productive training session or competition.

What to do if the WUT Assessment Indicates Dehydration

When athletes perform the WUT Assessment and it indicates dehydration is likely or very likely, the common response is to guzzle a relatively large volume of water. The problem with this is that it doesn’t address the underlying cause of the problem. The WUT Assessment essentially tells you how well you met your hydration needs over the preceding 24 hours; guzzling fluids overloads your gut and much of the fluid you consume passes right through you and results in a higher urine volume.

A more comprehensive approach to fixing the problem is to increase your fluid consumption across the whole day. The following tips accomplish this goal in a gradual and balanced manner:

- Consume 16-20 ounces of water immediately upon waking.
- Consume 8-20 ounces of water with each meal during the day.
- Carry a water bottle. Out of sight is out of mind, so carrying a water bottle reinforces the imperative to continue consuming fluids throughout the day. It also helps distribute your water intake across the entire day, rather than only focusing it on consuming relatively high volumes of water a few times per day.
- Increase consumption of fruits and vegetables. While there is some variation in the water content of various fruits and vegetables, nearly all of them are at least 80% water by weight. Food typically makes up about 20% of the fluid you consume during the day, and including more fresh fruits and vegetables can help to both boost your water intake and displace low-water content foods. Some of the highest water-content choices include watermelon, strawberries, Romaine lettuce, cantaloupe, tomatoes, pineapple, and bell peppers. Consider cold soups and smoothies.

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