As summer gets started, it’s that time of year when key events are held at elevation, such as Leadville, Steamboat Gravel, and the Death Ride. Since decreased oxygen at high altitudes reduces physical capacity (1), it’s especially important for cyclists to choose how best to respond to the challenge of riding at elevation.
The most common way to adapt to the demands of elevation is by spending time at elevation (2). However, the logistics and cost of finding a place to stay can be difficult if you don’t already live at elevation.
Recently, a new review article titled “Preserving Athletic Performance at Altitude with Heat Acclimation: A Cross-Adaptive Approach” was published, examining a range of research demonstrating that acclimation to heat can mitigate the negative performance effects of acute hypoxia, a process called “cross-adaptation” (1).
Here in the Sacramento area, there is no shortage of heat, which we can leverage to improve our performance at elevation.
The mechanisms of Heat-hypoxia cross-acclimation
The process of cross-acclimation involves repeated exposure to one stressor to elicit adaptations for a different stressor (1). In this case, heat-hypoxia crossover is the cross-adaption (CA) that uses heat to build resistance against altitude. When the body is exposed to hot environments, physiological responses occur to protect the body internally.
These responses include increased heart rate, vasodilation, sweating, and one of the most important responses, heat shock protein (HSP) expression. HSP72 expression increases after environmental stimuli such as heat, cold, and hypoxia. It’s speculated that HSP72 begins signaling to increase red blood cell production, which is the key for altitude acclimation (1).
Evidence to support Heat-hypoxia CA
This review paper examined multiple studies to support the use of heat acclimation for performance at altitude. Here are a few of the key studies mentioned in the article along with the heat acclimation protocol, stimulated testing altitude, and impact on performance for each study.
| Heat Acclimation Protocol | Simulated Testing Altitude | Impact on Performance |
|---|---|---|
| – 12-day HA regimen – 104 degrees – 120 min of treadmill incline walking – At 35% VO2 max | 7,874ft | – Preserved baseline VO2 max abilities – Delayed onset of blood lactate accumulation (OBLA) |
| – 10 day HA regimen – 104 degrees – 110 min cycling – At 55% VO2 max | 14,271ft | – Average of 2.2% increase in VO2 max at altitude – HR, oxygen saturation, and respiratory exchangeare unchanged |
| – 3 day HA regimen – 104 degrees – 60 min cycling – At 50% VO2 max | 9,842ft | – Enhanced exercise tolerance in hypoxia – Significant physiological and cellular adaptations (including increased HSP72 expression) |
Taking a look at this evidence, these studies suggest that heat acclimation does not necessarily increase maximal output; however, it may preserve or enhance physiological efficiency and submaximal efforts in acute hypoxia (1).
Implementing Heat-Acclimation
As the above studies demonstrate, there are multiple ways to adapt to the heat. For further info on heat acclimation check out our recently updated Cyclists Guide to Training In The Heat.
In general, well-trained cyclists can respond faster to HA protocols, taking as little as 3-8 consecutive heat exercise days to adapt (1). However, the current recommendation is a 10-12+ day program, as the benefits from acclimation are longer-lasting.
If daily heat sessions aren’t available, 1 month of heat exposure every 2-3 days is another way to achieve adaptation. Here’s a table that illustrates each protocol with intensity and session duration.
| Protocol Length | Intensity | Session Duration |
|---|---|---|
| 3-8 consecutive days of heat exercise | 50-70% VO2 max | 30-45 minutes |
| 14 consecutive days of heat exercise | 35-55% VO2 max | 60-120 minutes |
| 30 days with heat exercise every 2-3 days | 50-70% VO2 max or 35-55% VO2 max | 30-45 minutes or 60-120 minutes |
In Summary
- The reduced partial pressure of oxygen at elevation will reduce your performance
- If training at elevation isn’t an option, acclimating to heat can be the next best option
- There are several heat adaptation protocols that are cheaper and more feasible than spending time at altitude
- Heat training will elicit training adaptations to allow you to maintain your submaximal efforts in an acute hypoxic environment
Sources
- Albert, Beverly1; Miller, Michael G.2. Preserving Athletic Performance at Altitude with Heat Acclimation: A Cross-Adaptive Approach. Strength and Conditioning Journal 47(3):p 279-286, June 2025. | DOI: 10.1519/SSC.0000000000000869
- Saunders PU, Pyne DB, Gore CJ. Endurance training at altitude. High Alt Med Biol. 2009 Summer;10(2):135-48. doi: 10.1089/ham.2008.1092. PMID: 19519223.