The Giro is upon us, and this Grand Tour always seems to feature chaotic weather. How does being cold affect our cycling performance, and is there a difference between just having cold skin and muscle versus actual hypothermia?
The 2024 Spring Classics were marked by pretty horrendous weather, with near freezing temperatures and heavy rain throughout both Fleche Wallone and Liege-Bastogne-Liege. Fleche was especially bad with those conditions coming all day long, such that only 44 riders finished the day. Unfortunately, others ended up shivering and shaking so uncontrollably that they had to stop riding and be carried off.
Throw your memories back to the 2023 Giro, and nearly every single day featured wet and/or cold weather. And of course there was the epic 2013 Milan-San Remo, featuring snow and a mid-race rider transfer over the Turchino Pass.
Milan-Sanremo 2013
At the same time, while the calendar may say May, here in southern Ontario it remains shoulder season, with temperatures cool but yet temptingly close to the range where we can ditch the longsleeves and leg/kneewarmers. The question is, should we?
Cold Cases
What’s the effect of having our skin and muscle cold on whole-body exercise capacity? The intuitive response is likely that our muscles don’t work as well when they’re cold. After all, one of the whole premises of a warmup is to actually warm up our muscles. Surprisingly though, short of long cold-weather expedition research, there’s been little directly done in this area. Most existing lab research bring participants into a cold environment and immediately have them start exercising, such that there’s minimal skin, muscle, or core cooling actually occurring.
My own lab started this research in 2018, where we elicited 0.5°C core temperature through passive exposure in 0°C air (Ferguson et al. 2018). Then we had these trained cyclists ride a 15 km time trial at that same temperature. Not surprisingly, there was a lot of shivering going on by the time they hopped on the bike, and mean power output dropped from 260 W at room temperature to 246 W with this mild core cooling.
Wallace et al. 2024
Never leaving well enough alone, my PhD student Phil Wallace led a followup study that was just published this January in Journal of Applied Physiology (Wallace et al. 2024). Here our focus was the dose-dependent response of cold. Specifically, how much does just cooling the outer shell of our body (skin and some muscle) affect our exercise capacity? And how does this compare to actual core cooling? Secondly, since we already demonstrated that 0.5°C core cooling impaired performance, what about greater core cooling to 1.0°C?
We had 10 trained and fit participants perform a hard ride to exhaustion at 70% of their peak power output in 4 conditions:
- Room temperature (22°C, 50% relative humidity)
- Cold Shell. From room temperature, the chamber was gradually decreased to 0°C over ~15 min. They then stayed seated for another 15 min before cycling.
- 5°C Core Cooling. After the chamber cooled, they stayed seated until their core temperature cooled by 0.5°C from resting.
- 0°C Core Cooling. After the chamber cooled, they stayed seated until their core temperature cooled by 1.0°C from resting.
The Cold Facts
First off, we were successful in creating the distinct thermal conditions of: 1) neutral, 2) Cold skin without core cooling, and 3) Cold skin with core cooling. Due to strong shivering, we weren’t able to create a really distinct separation between the -0.5°C and -1.0°C conditions, but their core and skin temperatures were much cooler than the Cold Shell condition.
What was clear from our data is that there was already a distinct impairment in endurance capacity from just having a cold shell. Without any significant change in core temperature from the thermoneutral condition, just having skin cooling decreased time to exhaustion by 31%, dropping from 23.75 min to 16.2 min.
What happened with actual core cooling? There was a further large decrease in time to exhaustion, down to 8.46 min (-61% from neutral) and 6.46 min (-72% from neutral) for -0.5°C and -1.0°C core cooling, respectively.
Cracking the Cold Case
What are the big takeaways from this study?
It’s obvious and intuitive that, if we’re so cold that our body temperature is dropping and we’re uncontrollably shivering, we’re not really able to ride as hard. There’s also the simple matter of our shaking so much that we’re barely able to hold the handlebars still or brake.
So if it’s really cold and wet out, you absolutely want to dress appropriately. In such conditions, it’s always better to be a bit too warm than a bit too cold, so I would always err on the side of more clothes. For myself, my hands and feet are especially sensitive and sites of extra care.
But the biggest takeaway from this study is to take care in those “cool but not crazy cold” conditions. Yes, you will generate a lot of heat from exercising, but if you start already a bit cool, your performance is going to suffer.
- So if you’re at the start line of a big event or CX race, where you might be in the start corral on a cool morning for a long time, ideally keep bundled up until the last minutes and have someone there to take your extra clothing.
- The classic advice of layering and starting a ride with more clothing (or packing clothing with you) still applies. After all, you can’t put on what you didn’t bring! Cycling gear is so much better now that arm/knee/legwarmers take up little space. Same with a thin vest or wind/rainshell. Living in the age of gravel cycling, there’s also so many great handlebar bags as additional storage options too.
Stay warm, ride fast, and have fun!
References
Ferguson SAH, Eves ND, Roy BD, et al (2018) Effects of mild whole body hypothermia on self-paced exercise performance. Journal of Applied Physiology 125:479–485. https://doi.org/10.1152/japplphysiol.01134.2017
Wallace PJ, Hartley GL, Nowlan JG, et al (2024) Endurance capacity impairment in cold air ranging from skin cooling to mild hypothermia. Journal of Applied Physiology 136:58–69. https://doi.org/10.1152/japplphysiol.00663.2023
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