By J. E. Hinners, MD MPH
The Journal of Applied Physiology addressed this question in a study of 20 cyclists in which 12 cyclists were tested on time-trial performance, lactate threshold, and maximal aerobic power in cold (13 degrees C / 55.4 degrees F) and in hot (38 degrees C / 100.4 F) conditions after a 10-day program for acclimating to the heat. Acclimation training conditions were at a temperature of 40 degrees C / 104 degrees F. Eight matching control cyclists who had not been exposed to the heat acclimation program were also tested in the same conditions.
Although the sample size should ideally be at least 50 subjects for results that are more reliable and powerful, the findings indicated that:
Heat acclimation may indeed improve performance of aerobic exercise.
Significant findings included:
- Heat acclimation increased maximal aerobic power (VO2 max) in cold temperatures by 5% and in hot temperatures by 8%.
- Cyclists were faster after heat acclimation with time-trial performance increasing 6% in cold conditions and 8% in hot conditions.
- Power output and lactate threshold increased by 5% in cold conditions and by 5% in hot conditions.
- Maximum cardiac output and plasma volumes also increased after heat acclimation.
- The control group of cyclists did not show any significant changes in any of the exercise performance measures.
Skin blood flow and endurance
Results from a different small heat acclimation study of 14 subjects showed:
- Significant drops in skin blood flow to both the active and nonactive limbs in heat-acclimated subjects
- Cardiovascular adaptations in heat-acclimated subjects
- Increased endurance ability in hot conditions in heat-acclimated subjects
Older ages versus younger ages
One additional heat acclimation study with 14 subjects suggested that those of older ages still benefited from adaptations in body temperature and sweat loss, but that they did not share the same cardiovascular adaptations that younger subjects experienced after heat acclimation.
Personal heat acclimation training
While there is room for further studies with larger sample sizes to substantiate these findings, perhaps hot temperature training could be explored in the seasoned athlete. It might be advisable to start with a training plan similar to those used in these studies (links attached to each study above).
If you decide to try such training, caution should be taken to avoid dehydration and to follow a training plan that would be acceptable to a healthcare provider who is familiar with your particular health condition.
Do you have personal experience with heat-acclimation training? How did you train and what results did you see? We’d love to hear about your experience in the comments section below.