I am just wondering what sort of power loss you usually expect to see when it’s really hot?
I’ve been trying to build up my heat tolerance this year by not actively avoiding riding in hot weather, but I would say that my comfort zone for cycling in a jersey and shorts is 7-17c. Beyond 20c, I start to suffer. Beyond about 23-25c, I notice a power drop.
I rode yesterday morning after the hottest night of the year (I’m in SE Sweden, for context - we do have hot summers here). 0730, it was 28c but crucially, close to 80% RH. That’s a humidex score of almost 40c.
I did a couple of 6 minute hill efforts (I am trying to build my heat tolerance) and I was a good 10% down on where I would normally be. I don’t think I have ever sweated so hard - I poured water over my head after both efforts and it didn’t noticeably increase the drip rate from my brow!
If I was to properly dedicate myself to heat training, how much of an improvement could I expect to see? I’ve always been someone who is happiest in the cold, and I’m perfectly comfortable training in mid-winter here when it’s below -10c, or even -20c.
You can get heat acclimated to a point but there is a ceiling where risk/reward tips in favor of heat stroke or heat fatigue. you’ll also lose watts in those conditions (like performing at altitude), you can only adapt so much and that takes a couple weeks usually.
You don’t have to do workouts, just go ride easy in the hot conditions. Even after you’ve adapted you will want to be choosy about trying to do an actual workout in the heat. There are studies indicating you can sensitize yourself to heat (the opposite of what you want) if you experience heat stroke. Summer is indoor season for us because of oppressive heat/humidity. I don’t bother with anything outdoors when humidex is 40c or higher - which happens by mid morning around here May-September. Also, you may find yourself more tired or need a bit more recovery after really hot sessions so might need to space those sessions out more than usual.
i had a 4 hour ride yesterday, and was really struggling the last hour. i couldnt figure out why- I was fueling/drinking. the scale verified this as i only lost 2 lbs over the ride. However when i looked at my garmin information later it corelated with the heat- once garmin registered over 100(37C) i decoupled, with the worst of it when it registered 110(43c full sun no shade & pavement).
I only do endurance or group rides outside this time of year. anything vo2 or challenging happens inside with fans.
Thanks for the replies guys. It’s good to hear that I’m not alone in struggling horribly.
It’s cooled significantly and the humidity has gone now, so back to normal training. Humidex temperature is down from about 41c on Sunday to 25c now. It’s a huge difference.
I was out every day in the European heatwave last week. Garmin reckons I am 5% heat acclimated. It would take weeks and weeks for that to say 100%, assuming it grows linearly. I do no think us northern europeans are going to acclimate to heatwaves until they become the new normal. In other words no longer a heatwave, just the normal summer temp being 35-45C in northern Europe. Estimated to be about 20 years away from that at current emission levels.
It’s a depressing prospect. That sort of heat is going to change the way that everyone lives.
I had a cracking ride today - 2.5hrs at 365w on the Aeroad, at exactly 40kph on a not flat course. I actually let the demons get in a little this last week that I was somehow losing strength, but it was just the sodding heat.
I don’t understand why would they start so late in day, exactly when the temps are highest. Asphalt has been burning all day. It’s understandable at the working days, but for weekends can be done. Heat is part of the challenge, but it’s challenge for the spectators too. Many old fellas prefer to stay home instead watching them in scorching heat. I get that there is a lot of preparation. Some places people wait for hours and can’t leave immediate after the peloton.
Last year I had two consecutive weeks in which the daily high was 35-40°C, and it was difficult for me to generate much power after 90-120min riding. Here are a few portions of rides in which I had continuous stretches in Z2-power. They are all within a two week period (one during the heat, a couple during the transition, and one when it was gloriously cool). Obviously day-to-day variations will play a factor, but there’s a pretty huge difference between the hot and the not-hot. My normal Z2 HR is 133-140bpm, and normal max is ~178. Probably too many numbers below, but scanning/comparing will give some ideas.
Heat Example 1:
Average temp 35° for (1:21, 232W, 139bpm) with peak of 166bpm.
The last part was (30min, 254W, 153bpm); at the end of this I realized I was fully cooked and limped home for (48min, 196W, 142bpm). This included a 60sec, 300W mini-hill which spiked my HR to 163!
Heat Example 2:
Average temp 35° for (1:00, 219W, 127bpm) with peak of 151bpm riding out to catch a tailwind return.
After turning around, I then did…
Average temp 35° for (0:40, 255W, 150bpm) with peak of 172bpm (right near end).
Reasonable temperature examples:
Average temp 21° for (1:53, 264W, 133bpm) with peak of 152bpm.
Average temp 21° for (1:30, 247W, 137bpm) with peak of 151bpm. This started 2 hours into my ride which until then, had averaged 27°.
Average temp 15° for (1:13, 255W, 127bpm) with peak of 137bpm.
That is absolutely a thing. Last weekend we had 38–40 degrees plus humidity. (We have a lake across the street.) I was doing 40–55 % FTP and yet my heart rate went to 135~140 bpm. These are not conditions where you want to ride hard. Ditto when I lived in Japan.
Relatively speaking, the temps you quote are lower, but it still is true that your body likely isn’t used to operate in them.
What you can do to mitigate the temperatures is head out very early in the morning, 4–5 am, and keep your rides short enough that you are not riding in the heat. The latter is a bad idea, and not really a test of fitness.
I remember one crit race in Japan which was on the hottest day of the year. We had three guys in their 20s who suffered from a heat stroke, at least two of them were eventually hauled away by an ambulance. Our team captain almost suffered from a heat stroke, he had to pull the plug on the race. The ride back (about 70 km) for me was hard even though I wasn’t putting out any power.
Trying to hit my sweet spot and threshold workouts with a window AC on its last legs Room/ambient temp would be an interesting data point to feed into TR, or at least a “heat” post ride survey option. I can’t imagine riding the tour in these temps!
I’ve been contemplating my performance in the heat for a while now. Last week I was doing sweet spot intervals in the garage at my dad’s house. It was ~77°F in the garage, and after 2 of 4 intervals I was coming apart. I hopped off and started up the air conditioning which got the room down to ~74°F in short order and I was able to cruise through the remainder of the intervals. This was with a fan throughout.
It got me thinking though; when is too much cooling too much? Is our performance artificially boosted by perfectly controlled conditions? Can I set personal bests if I run the a/c down to 60°F? Will TR think I’ve made some miraculous improvement?
Heat has been shown to reduce power output by about 15% in a number of studies. The level of heat and humidity is obvious a factor in how much reduction. Cooling is a short term answer. But is could also be argued that training hotter helps you acclimate to the heat and ultimately deliver the better performance. But it requires patience and belief.
There are a fair few studies on this. Tim Pogacar is a good open book on this. There are psychological and physiological aspects to the increased RPE. Research cited by Dr pogacar suggests that despite core temperature remaining nearly stable in hot conditions (human body doing its thermoregulatory thing), Sense of overheating is proportional to skin temperature which is elevated, Psychological protection kicks in a reduces muscular recruitment etc. Conversely, if you force internal body temp to rise, but keep the skin cool, the athlete continues with almost unaffected RPE. Wild that. From a carb point of view, demand for CHO increases during hotter conditions, but CHO uptake is reduced - the results are as you would expect. I would assume that physiological law of habituation would result if you were to spend greatly increased time in conditions you current find difficult. I presume CHO uptake would increase to more ‘normal’ levels, CHO usage would reduce to more ‘normal’ levels and psychological sense of overheating would dampen.
Room/ambient temp would be an interesting data point to feed into TR, or at least a “heat” post ride survey option. I can’t imagine riding the tour in these temps!