Be warned - this is a deep dive and quite long!
Hot-weather training and racing can be humbling.
A pace that normally feels comfortable suddenly feels like threshold effort. Power begins to drop even though heart rate keeps rising. Your legs may still feel capable, but your body seems unwilling to cooperate.
That is not a lack of fitness or toughness.
When we exercise in the heat, our cardiovascular system has two demanding jobs: delivering oxygen to our working muscles and sending blood toward the skin to release heat. As we sweat and lose fluid, blood volume can decrease. The heart compensates by beating faster, producing the familiar heart-rate drift that occurs during longer hot sessions.
The result is simple: your normal pace or power costs more in the heat.
We cannot eliminate that physiological cost, but we can prepare for it, reduce it and make better decisions once the temperature rises.
This week, we will look at two parts of hot-weather performance:
- How to prepare in the days and weeks before a hot training session or race.
- How to pace, cool and fuel yourself once you are actually out there.
PART 1: PREPARING FOR HOT TRAINING AND RACING
1. Acclimate to the heat
The most effective preparation is repeated exposure to exercise in warm conditions.
Heat acclimation teaches your body to manage heat more effectively. Common adaptations include:
- An earlier and more effective sweating response
- Increased plasma volume
- Lower heart rate at a given workload
- Lower core and skin temperatures
- Improved skin blood flow
- Reduced perceived effort in the heat
Most athletes can develop meaningful adaptations through approximately 7–14 days of repeated heat exposure, although some improvements may begin within the first several sessions.
A practical approach might include 45–75 minutes of easy or moderate exercise in warm conditions on most days during the final two weeks before an important hot race.
This does not mean every session should become a sufferfest. The goal is controlled exposure, not heat exhaustion.
Keep hard interval sessions focused on training quality. Heat exposure can be added during easier runs, endurance rides or short brick sessions.
2. Begin gradually
Do not jump directly from air-conditioned indoor training into your hardest session of the summer.
During the first few hot days:
- Reduce intensity
- Shorten the session
- Take additional recovery between intervals
- Choose a loop that allows easy access to fluids
- Increase exposure progressively
Your body needs time to adapt. Treat the first week of hot weather as a new training stimulus rather than expecting normal summer performance immediately.
3. Use passive heat carefully
Athletes who cannot regularly train outdoors in the heat sometimes use passive heat exposure, such as a hot bath or sauna after an easy workout.
This may provide some heat-adaptation signals without requiring every workout to be performed in hot conditions. However, research on the performance benefits of passive methods is less consistent than research on exercising in the heat.
If you experiment with this approach, begin conservatively, avoid it when dehydrated or ill and do not let it interfere with recovery from important training sessions.
4. Learn your personal sweat rate
Sweat losses vary tremendously between athletes. They also change with temperature, humidity, intensity, clothing and acclimation status.
One simple field test is:
Pre-exercise weight – post-exercise weight + fluid consumed – urine produced
Each kilogram, or approximately 2.2 pounds, of weight lost represents roughly one liter of fluid.
For example, if you lose two pounds during a one-hour run while drinking 16 ounces, your total sweat loss was approximately 48 ounces for that hour.
You do not necessarily need to replace every drop while exercising, but knowing your approximate sweat rate helps you avoid relying on a generic hydration number that may be completely wrong for you.
Repeat the test under conditions similar to those expected on race day.
5. Build a hydration plan - but do not force fluids
Begin important sessions and races normally hydrated. Pale-yellow urine and normal thirst are generally more useful practical signs than trying to consume excessive water before the start.
During longer events, the goal is to limit excessive dehydration without drinking so much that you gain weight.
Overdrinking plain water can contribute to exercise-associated hyponatremia, a dangerous dilution of blood sodium. More is not always better.
Your plan should consider:
- Personal sweat rate
- Expected temperature and humidity
- Exercise duration
- Fluid availability
- Gastrointestinal tolerance
- Sweat sodium losses
Drink regularly according to a practiced plan and thirst rather than forcing down large quantities simply because a chart told you to.
6. Do not forget sodium
Sweat contains both water and sodium. Heavy or salty sweaters may lose substantial amounts during long, hot sessions.
Possible clues that you lose a lot of sodium include white salt marks on clothing, frequent stinging sweat in the eyes or unusually salty skin after training. These signs are not a precise test, but they may indicate that your hydration plan should include additional sodium.
The correct amount differs widely between athletes. Use the same sports drink, electrolyte mix, capsules or salty foods in training that you plan to use during the race.
Do not introduce an aggressive sodium strategy for the first time on race morning.
7. Practice your complete cooling and fueling plan
A race-day strategy should be rehearsed.
Practice:
- Carrying additional bottles
- Drinking while running or riding
- Picking up fluids at aid stations
- Using ice in a hat, jersey or clothing
- Taking carbohydrates with cold fluids
- Handling higher fluid volumes without stomach problems
- Opening electrolyte capsules or food with sweaty hands
- Running after a hot bike leg
Triathletes should pay particular attention to the transition from cycling to running. Airflow on the bike can make the heat feel manageable, but core temperature may already be rising before the run begins.
8. Consider pre-cooling
Pre-cooling increases the amount of heat your body can store before reaching a limiting temperature.
Practical options include:
- Resting in air conditioning before the start
- Wearing an ice vest or placing cold towels around the neck and shoulders
- Drinking cold fluids
- Consuming an ice slurry or slushy
- Using a brief cool shower or cold-water immersion
- Staying in the shade for as long as possible
Pre-cooling appears most useful before longer endurance efforts in genuinely hot conditions. It should make you cooler at the start—not cold, shivering or unable to warm up properly.
9. Adjust your warm-up
A long warm-up that works perfectly in cool weather can unnecessarily raise core temperature before a hot race.
In the heat:
- Shorten the warm-up
- Reduce unnecessary jogging or spinning
- Perform key efforts close to the start
- Stay shaded when possible
- Use cold fluids or cooling towels
- Avoid standing in the sun after warming up
You still want the muscles prepared, but you do not need to arrive at the starting line already overheated.
10. Review medications, illness and recovery
Exercise in the heat becomes more dangerous when we are sick, sleep-deprived, significantly dehydrated or recovering poorly.
Some medications can also affect sweating, circulation or fluid balance. Athletes with medical conditions or concerns about medication should speak with a qualified healthcare professional before training aggressively in the heat.
Missing one hot workout is much better than creating a medical emergency.
PART 2: DURING HOT TRAINING OR ON RACE DAY
1. Accept that pace and power may need to change
The most important race-day decision may be accepting that your original pace or power target is no longer appropriate.
Research examining prolonged cycling in temperatures of 86°F or higher has found substantial reductions in average power compared with cooler conditions. Running pace is also commonly reduced as temperature, humidity and sun exposure increase.
Trying to force cool-weather numbers can create a huge physiological cost early in the race.
A slower pace is not giving up. It is adjusting your strategy to the conditions in front of you.
2. Start more conservatively than you think you need to
The opening miles of a hot race can feel deceptively manageable. You are fresh, core temperature has not peaked and cardiac drift has not fully developed.
That is precisely when athletes make expensive mistakes.
Begin slightly below the effort you believe you can sustain. Allow heart rate and perceived exertion to stabilize before increasing the pace.
In hot races, a conservative first half often produces a faster overall result than banking time early and losing far more later.
3. Let effort guide pace and power
On a hot day, pace and power tell you what you are producing. Heart rate and perceived exertion tell you more about what that output is costing.
Use all four pieces of information:
- Power: Is your bike output appropriate for the conditions?
- Pace: Are you slowing despite working harder?
- Heart rate: Is cardiovascular strain rising unusually early?
- RPE: Does the effort feel sustainable?
Heart rate will often drift upward during prolonged hot exercise even if pace or power remains unchanged. That does not mean heart rate is useless. It means you should interpret it alongside RPE, duration and conditions.
When heart rate and RPE are much higher than expected for a given output, believe the message your body is sending.
4. Cool early - not only after you overheat
Do not wait until you feel terrible to begin cooling.
At aid stations or during training stops:
- Put ice in your hat or cap
- Place ice around the neck or upper back
- Use cold towels
- Pour water over your head and clothing
- Drink cold fluids
- Carry ice in your hands briefly
- Use sponges on exposed skin
Cooling the head, neck and torso can improve thermal comfort. Wetting the skin may also assist cooling, especially when airflow is available and humidity is not extremely high.
Cyclists should take advantage of airflow by wetting clothing or exposed skin when practical. Runners and triathletes may benefit from using every aid station as a brief cooling opportunity.
5. Separate drinking from pouring
At aid stations, athletes sometimes pour most of the available water over themselves and forget to drink - or drink everything and use nothing for cooling.
When possible, take separate fluids:
- One cup or bottle for drinking
- One for cooling
Sports drink can provide carbohydrates, fluid and sodium. Plain water is generally a better choice for pouring over your head unless you enjoy finishing the race covered in sticky sports drink.
6. Keep fueling even when your appetite drops
Heat can make eating feel more difficult, especially during running.
However, reducing pace does not eliminate carbohydrate needs. Long events still require fuel.
Use foods and drinks that are easy to tolerate:
- Cold sports drink
- Gels taken with water
- Chews in small portions
- Diluted carbohydrate drinks
- Small, frequent doses rather than large servings
Cooling and pacing properly may also improve your ability to continue fueling. An overheated athlete is far more likely to develop nausea and stop eating.
7. Be cautious with concentrated nutrition
As fluid needs rise, athletes sometimes combine highly concentrated carbohydrate drinks, gels and electrolyte products in ways they have never practiced.
That can lead to gastrointestinal distress.
Keep track of the total amount of carbohydrate, fluid and sodium coming from all sources. A bottle containing concentrated fuel may require additional plain water to digest comfortably.
Nothing new on race day applies to heat strategies too.
8. Use planned walk breaks
Walking is not failure. It can be an effective pacing and cooling tool.
For runners and triathletes, short walk breaks can:
- Lower metabolic heat production
- Make drinking easier
- Allow more effective cooling
- Reduce heart-rate drift
- Improve fuel intake
- Prevent a complete late-race collapse
Walking 20–40 seconds through aid stations from the beginning may cost very little time. Waiting until you are forced to walk continuously can cost much more.
Trail and ultra runners can also power-hike steep climbs earlier than usual, particularly when the terrain offers little airflow.
9. Shorten intervals during hot training
A hot training day does not always require canceling the entire workout.
Modify it intelligently:
- Reduce interval duration
- Increase recovery
- Lower target pace or power
- Complete fewer repetitions
- Move the most intense work indoors
- Choose a shaded route
- Start earlier
- Replace a long continuous tempo with shorter blocks
Preserve the purpose of the workout rather than becoming obsessed with the exact numbers originally written on the schedule.
10. Change the route when necessary
For hot training sessions, choose routes that give you options.
A short loop near home or a parked car allows you to refill bottles, pick up ice or stop safely. A shaded trail may be better than exposed pavement. An indoor trainer or treadmill can be a smarter choice than a remote route during an extreme heat warning.
Being tough does not require being reckless.
11. Reassess expectations throughout the day
Heat stress accumulates.
A target that seemed reasonable at the start may no longer be appropriate two hours later. Conditions can also become more difficult as the sun rises, cloud cover disappears or wind decreases.
Regularly ask:
- Is this effort still sustainable?
- Am I able to drink and fuel?
- Is my heart rate continuing to rise?
- Am I thinking clearly?
- Am I becoming chilled or developing goosebumps despite the heat?
- Do I need to slow down, walk or stop?
The best athletes are not simply good at suffering. They are good at recognizing which discomfort is manageable and which signals require action.
12. Know the warning signs
Stop exercising and seek assistance for symptoms such as:
- Confusion or unusual behavior
- Loss of coordination
- Collapse
- Severe headache
- Repeated vomiting
- Inability to continue safely
- Fainting
- Altered mental status
Confusion or central nervous system changes during exercise in the heat should be treated as a medical emergency. Rapid whole-body cooling and emergency medical care may be required.
Do not assume that an athlete who is struggling simply needs motivation to keep moving.
THE BOTTOM LINE
We cannot race hot conditions exactly as we would race a cool day.
The athletes who perform best are usually not those who ignore the heat. They are the ones who respect it early.
They acclimate when possible. They begin hydrated. They practice their cooling, fueling and drinking plans. They reduce unnecessary heat before the start. Most importantly, they adjust pace and expectations before the conditions force them to.
When the heat arrives unexpectedly, the same principles apply:
Slow down early. Use effort rather than ego. Cool yourself before you feel desperate. Keep drinking and fueling without overdoing either. Walk when it helps you regain control.
The goal is not to produce your cool-weather numbers at any cost.
The goal is to make the best possible decisions for the conditions—and get the most out of the fitness you brought to the start.
Train smart. Stay cool. Keep moving.
All the best,
Nate Thomas
UNIQ Endurance
