Cycling in the Heat: How To Do It Better

Do you love riding in the blazing heat?  Me neither.  If races were only held in cool temperatures, avoiding the heat when training would be simple; only ride in the morning.  But cycling doesn’t work that way.  Inevitably it’s going to be hot, and you’re going to be on your bike.

In simple terms, if you don’t prepare for a hot race, your performance is going to suffer.  Research points toward performance declines of at least 3-6% in hot conditions [1,2].

In other words, if all you do is ride in cooler temperatures, don’t ever expect to ride well when it gets hot.

Stealing Watts

So why does heat steal so many watts?  Even before core temperature reaches the upper threshold for fatigue [3], the body begins to send messages to your legs to work less in an effort to reduce heat production. 

Your body’s anticipatory response to higher ambient temperatures may preserve your life but will likely reduce your power output in the process [4].

Thankfully there’s an effective way to manage this thermal throttling via the process of heat acclimation (HA).  If you live and regularly ride in hot weather you’ll have a leg up, although committing to a HA strategy is still in your best interest [26].

If you generally avoid the heat, or live year-round in cooler temperatures, utilizing some sort of HA strategy is a must.

A quick disclaimer – obviously remaining safe is the most important objective no matter what HA strategy you might try.  If you feel dizzy, light-headed, or in any other way “not normal” during a HA session, pull the plug and cool off.

Heat Acclimation

Like other forms of acclimation, HA takes time.  Research points toward the need for 8-14 consecutive days of heat exposure to realize the full benefits of HA [1].

If you don’t have two full weeks to dedicate to HA don’t despair, even 5 days of consecutive exposure can improve your ability to ride in the heat [5].  Can’t piece together back to back days?  Try nailing a total of 10 sessions spread out over a month (every third day) [6].

Now that we’ve got the timing down, what does HA actually look like?  The table below breaks down the different ways you might engage in heat training utilizing a variety of strategies.

Heat Training Strategies

	Research Highlight	Results
low intensity/longer	Cyclists did 10 consecutive days of 90m rides at 50% VO2max in hot conditions (40°C/104°F) [7].	Increased VO2max by 8%, improved TT performance by 8%, increased power at LT by 5%.
moderate intensity/shorter	Runners did 7 consecutive days of ≈33m runs at 75% VO2max in hot conditions (40°C/104°F) [8].	HR and core temp reduced after acclimation periods demonstrating positive adaptations to heat stress.
hot bath	Runners did 6 consecutive days of 40m treadmill runs (18°C/64°F) at 65% VO2max followed immediately by 40m bath with water maintained at 40°C/104°F [9].	Core and skin temp reduced.  Skin temp at sweating onset lower.  RPE lower.  Improved TT performance.
sauna	Runners did ≈55m runs followed immediately by sitting in a humid sauna (≈90°C/194°F) for ≈33m.  12 sauna sessions spread over 3 weeks.  [10].	Blood volume increased by 5.6%, endurance performance improved by 2%.
hot yoga	Field hockey players did 6 consecutive days of 60m hot yoga (30°C/86°F) sessions with permissive dehydration (no drinking during session) [11].	Small improvements in running speed at submax intensities.
overdressing	Triathletes did  2 weeks of mixed endurance training (rides and runs) around RPE 3-7, in ≈18°C/ 64°F temps while wearing winter clothing  [12,13].	Dressing in additional clothing while riding does increase physiological strain but heat acclimation was not achieved and performance was not improved.

Which strategy should you choose?  Generally the hotter, more consecutive, and more specific to the bike, the better.  Just remember, your HA doesn’t have to be perfect or “by the book” to be effective.  Mix and match strategies and test them on yourself.

The key to an effective HA strategy is to create a thermal impulse strong enough to elicit adaptations [14].   As our table above shows, this can happen through a variety of methods.

The main takeaway is that no matter your training limitations, strategically introducing HA will ensure you give yourself the best chance to ride well when it matters most in hot conditions.

Pre and Mid-Cooling Strategies

So you’ve nailed down your best HA strategy, what about utilizing cooling strategies before and during a race?  Let’s break down some of the most widely studied strategies you might use to cool yourself before or during a race.

Cooling Strategies

	Research Highlight	Results
pre-cooling/cold water immersion	Cyclists were immersed in cool (25°C/77°F) water up to the torso for 30m before executing a ride in hot (32°C/90°F) conditions [15].	Cold water immersion enhanced heat storage and exercise capacity.
pre-cooling/ice ingestion	Cyclists ingested 7g/kg/bodyweight of crushed ice 30m before a ride in hot (35°C/95°F) conditions [16].	Ice ingestion led to lower core temperature, greater heat storage capacity, and improved gross efficiency.
mid-cooling/spraying or pouring water	A fine mist of water was sprayed on stationary cyclists’ heads every 30s during the time to exhaustion ride [17,18].	RPE was reduced, time to fatigue improved by an average of 51%.  Pouring water also effective at increasing evaporative cooling although not studied to date.
mid-cooling ice slushies	Cyclists rode for 60m at RPE 14 followed by 20k TT in hot (30°C/86°F) conditions while ingesting ice slurry ad libitum [19].	Ice slurry ingestion “induced likely and possibly substantial” increase in TT performance and overall mean power output.
mid cooling/cooling collar or ice sock	Participants ran for 90m on a treadmill in hot (30.5°C/87°F) conditions with a cold collar [20].	Performance improved (greater distance was run) while wearing the cold collar even though athletes found it uncomfortable.
mid-cooling/swilling methol solution	Cyclists swilled a menthol solution every 10m while executing a ride to exhaustion in hot  (34°C/93°F) conditions [21].	Endurance capacity (measured by time to exhaustion) was improved.

Cooling Strategies Are Full of Maybes

Are any of the above cooling strategies really worth your time and effort?  Maybe, but a few caveats are in order.

1. Very little pre or mid-cooling research has been conducted on highly trained athletes.  In a practical sense, the more trained you are, the better you’re able to handle riding in the heat, likely reducing the effectiveness of any pre or mid-cooling strategies [22].  Put another way, if you can use HA to “train-away” the potential benefits of pre or mid-cooling, you’re doing something right!
2. While there is evidence to suggest that some pre-cooling and mid-cooling techniques might improve your performance, test, test, test, for yourself.  Some strategies like ice ingestion can lead to significant GI discomfort [23].  I.E., just like with your fueling and hydration approach, utilize the guidelines of science to develop a strategy you can experiment with well in advance of your most important races.
3. Inevitably pre and mid-cooling strategies require greater logistical planning.  Factor in more time/potential stress in your pre-race routine before investing in any “extras”.
4. Pre and mid-cooling strategies should be secondary to nailing your fueling and hydration.  Don’t neglect the basics.

Putting It All Together (TL:DR)

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Edit History

*6/26/19-Originally published post
*6/17/21-Revised HA and cooling strategies tables to be more legible along with other formatting changes

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