Cycling during the warmer summer months can be complicated. From how to hydrate to dealing with elevated heart rates, most of the advice available seems to suggest taking it easier as the temperatures rise to avoid risky scenarios like heat exhaustion or even heat stroke.
But while going for a midday ride in 90ºF temperatures should be done with caution, in recent years, much of the scientific literature surrounding exercising in the heat has taken a slightly different stance. Acclimating, and even spending time cycling in the heat, has shown to have the potential to improve perspiration rates needed to control core body temperature more efficiently, reduce blood lactate, and also have positive training benefits such as increasing blood plasma volume and VO2 max. In fact, in some instances, studies have shown it to be more beneficial than training at altitude.
The question that remains is whether the potential risks involved with cycling in the heat outweigh any potential benefits, and whether the everyday recreational cyclist should consider including heat training to improve their overall fitness.
To get a better understanding of what we should and shouldn’t be doing in the heat, Dr. Dana Kotler, of the Spaulding Cycling Medicine Program, offers her advice on the subject.
Q: There have been a few studies indicating that training in the heat might have positive benefits such as increasing blood plasma. Is training in the heat something cyclists should try to gain fitness?
Kotler: This is a challenging question, because there have been a lot of studies on this topic but most cohorts have been small. Some studies evaluated highly trained cyclists, but others involve other types of athletes but use cycling as a test (which may be less relevant).
One of the more recent studies (Reeve et al, 2019) looked at a cohort of 23 highly trained, non-heat acclimated, male cyclists — and this seems to be one of the larger sample sizes. There are questions about the type of training that should be done while in the hot environment. The study showed no significant benefit from high-intensity interval training (HIIT) during a five-day heat acclimation training program.
Many of the studies mention potential plasma volume increases, but this can be subject to the athlete’s previous chronic hydration level. Longer courses (≥10 days) of heat acclimation at lower intensities have shown some improvement under cool ambient conditions. This same study suggests an increase in plasma volume when shorter courses of heat acclimation with restricted fluid intake have been performed.
Despite the measured increase in plasma volume the overall benefits of the high intensity, shorter duration training were minimal. There was some benefit in the perception of heat tolerance and thermoregulation, but this was often offset by the potential for over-reaching during training and the reduced exercise capacity following this type of training.
Overall, most of these athletes are highly trained cyclists who are training under very closely guided protocols and there was still minimal benefit. So, it’s important to understand the very real risks of overtraining or potential heat-related issues (heat exhaustion, dehydration) versus the benefits for the average athlete.
Q: How would you recommend gradually introducing yourself to training in the heat?
Kotler: Unless you were training while in the sauna, there would be little benefit. Building tolerance to heat while cycling requires training in the heat, starting at a lower intensity and volume and steadily increasing to test tolerance seems to be the safest bet. The average athlete should understand their needs with regard to hydration and electrolyte balance as well as considering workload while training in the heat. Consulting with a cycling coach would likely prove very helpful to plan workouts and avoid overreaching.
Q: What are some of the precautions cyclists should take when riding during the warmer summer months?
Kotler: First, make sure to wear sunscreen. Cyclists often spend hours on the bike exposed to the sun’s rays, which can lead to sunburns, skin damage and skin cancer. Don’t forget about the top of your head, where the sun can get through the vents in the helmet.
Cyclists must also make sure to hydrate while on the bike as well as maintain good hydration habits off the bike (both before and after riding). Keep at least two water bottles with you, and for longer routes, make sure you know where on the route there are drinking fountains or other facilities to get a drink. If you forget to drink during rides, many cycling computers can be programmed to give alerts to remind you.
With that said, overhydration could also pose a problem. Overhydration can affect the body’s electrolyte balance, and lead to a dangerous condition called exercise associated hyponatremia (EAH), often seen in distance runners, which is characterized by altered mental state, headache or nausea.
You can also weigh yourself before and immediately after a ride to get a basic understanding of the amount of fluid loss your body has during a ride in the heat. If you are seeing weight gain, you may be heading down the road of overhydration. Other considerations may be the type of clothing and helmet you’re wearing. For summer riding, consider helmets with increased ventilation and clothes that promote wicking, particularly for recreational riders or commuters.
Q: Should cyclists train at lower intensities in the heat?
Kotler: The additional variable of increased heat can affect both the perceived and actual physiological load — and it’s prudent to start at lower intensities and test your personal tolerance. While nearly all athletes can increase tolerance to hot weather training, some are more physiologically adept at dealing with the heat than others.
While you might see marginal gains by training in the heat, the potential pitfalls seem to negate the possible benefit for the average athlete. While it sounds appealing that there could be a quick way to get a bump in fitness, you’re going to be much better off with a consistent training plan that has been thoughtfully compiled by a coach or knowledgeable cycling professional. Hydrate responsibly, get enough rest and recovery and have some fun training during the dog days of summer.