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I have primarily 3 questions:

  1. Is wearing a ski helmet a bad idea for winter weather bike riding?
  2. Is it possible or likely that while I feel warm primarily due to my head being warm, that my core temperature could be dropping? What are some signs to be aware of?
  3. How can I stay hydrated and fueled in the cold when I don't want to uncover my hands or stop for a drink or restroom break?

In the winter, when temperatures are below 50°F (10°C), I wear a ski helmet and goggles mainly for the benefit of keeping my eyes from tearing up. However, I'm thinking that is probably a bad idea because at 50°F and moderate exertion, I notice my head sweating quite a bit. After about an hour, that sweat saturates the foam pad on the goggles which then starts to run down my nose or drip on the inside of my goggles.

Perhaps I should revert to a balaclava, ski goggles, and regular bike helmet as the balaclava serves as a wind screen, insulating layer, while it is also breathable. Ski helmets have few ventilation holes and are probably meant for a lower activity level.

Even when temperatures dip to 30°F (-1°C), I feel my head sweating quite a bit whereas the rest of my body could be cold or comfortable.

Lastly, I went out when it was about 40°F (4.5°C), wearing my ski helmet, goggles, cycling shorts (no tights over top), base layer, insulating layer, (I removed my wind break layer after feeling warm), and an outer visibility layer. All of those layers were breathable. It dropped to about 30°F after about 2 hours and I was out for a total of 4 hours. My head was certainly warm as my helmet was damp with sweat, but upon returning, having something to eat, and getting a shower, I was shaking for about 10 minutes because I was still cold. Prior to heading out, I had breakfast which would have been around 800 calories (3300 kJ) and had a similar snack the night before, but at about 300 - 400 calories (1300 - 1700 kJ).

Even though I understand that my head could be warm while my core body temperature could be dropping, wouldn't I 'feel' cold? I understand too that not drinking or eating for such a long time also factored into being cold by shutting down my body in order to conserve energy.

I generally don't wear tights until the temperature is 30°F or below, perhaps I'm losing a lot more heat than I realize as a result.

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    Experiment with different under-helmet caps, the variety of materials and quality is astounding these days. I have a couple very similar-looking winter caps from different manufacturers, both very thin, but I sweat and freeze like crazy in one and can ride for hours comfortably in the other one. The same goes for other clothing items. Dec 23, 2023 at 12:02
  • I never wear a ski helmet even when skiing. A bike helmet is much more flexible and can easily be made warmer by adding a wool cap under it and possibly a hood / windbreaker on top. Dec 24, 2023 at 12:06
  • True, I guess you can say peer pressure, I already look silly enough wearing a ski helmet with goggles, but a bike helmet with ski goggles might be a bit much :).
    – John Doe
    Dec 25, 2023 at 18:35

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It wouldn't occur to me to wear a ski helmet for cycling. It looks like they undergo the same sort of impact testing, so from a safety perspective, it's a reasonable option, but I've never ridden in weather cold enough that I said to myself "I wish I was wearing a helmet with more coverage." When it's cold, I wear a thin cap under my helmet—and it needs to be around freezing before I think of doing that.

Clearly different people have different ideas about what's comfortable to ride in. For instance, if it's below ~50°F/10°C, I definitely want my knees covered. In addition to your head, you also lose a lot of heat through your hands and feet, so keeping them warm is important. I have both cool-weather gloves (good down to ~40°F/5°C) and cold-weather gloves. The cool-weather gloves are extremely snug and I can do pretty much anything with them on that I can do bare-handed (removing them when they're wet takes a minute). My cold-weather gloves are obviously bulkier and more awkward.

I have had uncontrollable shivering when exhausted after (or during) a cold bike ride—my hypothesis is that my body loses the ability to regulate its temperature when exhausted; the more exhausted I am, the colder I feel in even moderately cold weather. How tired would you have been after 4 hours riding in mild weather?

This point relates to another: cold-weather cycling gear is designed for a certain level of exertion. There are some winter jackets, for example, that are designed in the expectation you're keeping your furnace hot by riding fast. But if you are exhausted, you're not riding fast, your furnace is cooler, and you're not trapping as much heat as you need. So calibrating your insulation to the weather and your exertion level is a bit of a trick, and I think that's a trick we only learn by experience.

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  • I have a ski helmet and goggles and gave it a try one day and was happy from the perspective of my eyes no longer tearing up. I'm starting to reconsider. Yes, I would say I was exhausted mainly from the standpoint that I was not hydrating or fueling. Yes, I agree on that point too, as soon as I stop moving, I need to layer up (unless I go inside). When I first start out, I wear more layers than I would after I'm warm and need to stop in about 10 minutes to remove a few layers.
    – John Doe
    Dec 22, 2023 at 17:44
  • I'm sure temperature regulation suffers a lot from fatigue. Especially late in a long ride, or after it, is pretty much the only time I feel cold, but I'm also prone to overheating for a few hours afterwards, at the slightest exertion
    – Chris H
    Dec 23, 2023 at 8:44
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    Some rides, you simply can't match your clothing to the conditions. Rolling hills would have you changing layers every few minutes (unzipping at the throat can help), and stop-start urban riding leaves you at the mercy of the traffic, shivering at the lights and/or overheating on a clear stretch
    – Chris H
    Dec 23, 2023 at 8:47
  • Thanks, I wanted some feedback on what others wear and what is most likely going on. I would tend to agree that my head was overheating whereas the rest of my body was chilled. I should instead try to keep it pretty balanced. In terms of hydration and fuel, gloves or mittens are a big hurdle. While a camelbak is one potential option for hydration, I still need something for fuel. The simplest option is anything that is well-packaged.
    – John Doe
    Dec 25, 2023 at 18:38
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There is a lot of blood flow between head and the rest of the body, so the temperature of the inside of your head and the core of your body (i.e. chest) is pretty much always the same. You can’t overheat in your head while the rest of your body is in hypothermia.

Having a lot of insulation on your head simply means you lose less heat on your head.

I think a ski helmet is sub-optimal for cycling because it will often be too warm and too heavy and usually doesn’t allow much airflow. I’d also doubt it’s 100% suitable from a protection point of view.

Your body restricts blood flow to your extremities to preserve heat in cold conditions. When you get back inside and step into a hot shower the blood flow increases and you can suddenly feel colder than before, especially since you are no longer generating a ton of heat through exercise.

As for clothing: What works well for me down to -5°C: Winter cycling jacket with insulating base layer, winter windstopper bib tights, overshoes, winter gloves, baclava. My sister swears on heated gloves and overshoes.

As for drinking: I use a normal bike bottle. Works okay-ish as long as it doesn’t freeze. I fill it up with hot tap water at home so it stays warm-ish for the first half hour or so and doesn’t freeze as early. I’ve considered getting an insulated bike bottle.

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  • Yes, I agree that once I stop exercising, I'm no longer producing heat and that results in feeling cold, but I was inside, under the bed covers shivering trying to get warm after having eaten, replacing some lost fluids, and getting a nice shower. My head could be much warmer than my legs. Hypothermia is any part of the body < 95F, en.wikipedia.org/wiki/Hypothermia. I still think it is certainly possible that my head could be sweating while the rest of my body may be cold and my core < 95F.
    – John Doe
    Dec 22, 2023 at 17:32
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    There is a big artery running directly from your heart to your head. As for feeling very cold after being back and having a hot shower: This is really because your extremities are still cold but now blood is flowing through them and getting cooled down, making your core temperature drop (or at least not get back to normal). I dimly recall a first aid course where it was not recommended to put patients with hypothermia in a hot bath or shower precisely because of this effect and instead just use lots of blankets and warm beverages.
    – Michael
    Dec 22, 2023 at 18:20
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I use a downhill bicycle helmet that covers much more of the head, also stopping wind and visor shields from snow as well. The ventilation works well for me, all head is equally cool - big progress from the cap under ordinary helmet when it was hot on the top still too cold around.

Maybe because it is E bike, under around zero temperatures an even little above the helmet is not too hot. Enhanced protection will not do harm on winter roads as well.

I also use heated gloves and good quality breacheable waterproof pants that stop also wind very well. All this costs money of course but where I live all gear was still cheaper than yearly ticket for bus and train.

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Is wearing a ski helmet a bad idea for winter weather bike riding?

I'm not aware of how well-protecting ski helmets are, but bicycle helmets are notoriously bad in real accidents. So entirely possible you don't make any tradeoffs in protection by using a ski helmet. Another possibility would be to buy a second bike helmet with somewhat larger size and tape over its ventilation holes with duct tape. Then you can use some cold-weather hat between the helmet and your head too since you chose a somewhat larger size.

Is it possible or likely that while I feel warm primarily due to my head being warm, that my core temperature could be dropping? What are some signs to be aware of?

Your body is doing everything to keep your core temperature high enough. If you're at the danger of losing too much heat, your body sacrifices your arms and legs first. This means that if your arms and legs are not well-insulated, you are at the danger of frostbite there. So no, if you feel warm your core temperature isn't dropping. Your core temperature could be at the danger of dropping if your hands or feet feel frozen -- or it could be that by sacrificing your hands and feet, the core temperature stayed acceptable.

So if your hands or feet feel frozen, there are two major causes: either they don't have enough insulation, or your core doesn't have enough insulation and for this reason no matter how much insulation you would have at hands or feet, they would freeze anyway.

How can I stay hydrated and fueled in the cold when I don't want to uncover my hands or stop for a drink or restroom break?

You don't need to do anything else than to ensure you are well-hydrated and well-fed before the ride. In summer, rides over 50km might require hydration since you lose so much water as sweat, but in winter this generally doesn't happen since it's cold. Well I guess theoretically you could be using so much clothes that you sweat a lot, but this would mean the clothes would be soaked in sweat which you don't want.

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    The 50 km ride I went through a week ago definitely did require hydration. Yes, I did not go through the whole 0.7 l bidon, but I definitely was thristy. Also, when cross-country skiing, I definitely do require frequent hydration, at least every hour, even when it is -10˚C. One bidon of 1L will not be enough for a long day. Dec 23, 2023 at 9:42
  • The low water content of cold air means you lose more water through your breath. For a four hour ride like OP did nutrition is definitely important. I’ve also found that being hungry/under-fueled and cold is much worse than just one of the two, maybe it’s just psychological.
    – Michael
    Dec 23, 2023 at 11:51
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Around freezing, whatever obscure value that has in degrees of Rankine, Reamuer or Fahrenheite, I would definitely not consider any closed (alpine) skiing helmet. If you feel too much cold wind through the cycling helmet and a skull cap is not enough, there are windproof helmet covers available.

Regarding the clothing, normal winter cycling jacket with some long underwear and long winter cycling bibs (with optional underwear) should suffice for the body. Without winter shoes it is inportant to wear good overshoes, e.g., from neoprene. It migh be a good idea to waterproof the soles around the cleats as well. Warm gloves are also important.

I do not think it is very likely to get a body core hypothermia with a hot head. I would not be surprised by hypothermic extremities, though. In extreme situations, which would however rather happen to a person sitting somewhere and not cycling, it may even be dangerous to move someone as cold blood can suddenly flow to the heart and cause shock.

Everyone is different. I'v been known to cross-country ski even at -5 to -10 in very thin gloves (single layer of leather), because my movement gives enough warm blood to my hands. However, the other day my hands almost froze when I was hit by several hours of freezing rain.

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  • Does hypothermia relate strictly to the core body temperature only?
    – John Doe
    Dec 22, 2023 at 20:19
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    @JohnDoe Hypothermia proper yes, it is low body temperature. If you only have low temperature in your extremities, it is still very dangerous (either risk of frostbite or of shock from cold blood flowing into the body core), but it should be described by other words. Dec 22, 2023 at 20:24

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