Is it normal to feel like I can't breathe while trying to ride at a challenging pace?

This is really hard to assess just from the description and we cannot really give a health advise. It is common to get out of breath when going full gas but one should also get the muscles tired. What comes in which degree depends on many factors but they usually go hand in hand.

BTW, it often happens to me that my nose is quite closed and I can mostly only breathe with my mouth. Nose obstruction should not be a big problem on its own, you should still be able to perform reasonably well. Asthma could be a factor here, even a exercise-induced one. Only a doctor can tell and even they may only be able to tell after a spirometer measurement without and with exercise on a stationary bike. I sometimes get such short-time asthma after cross-country skiing. (edit: mine is probably the cold-induced one referenced by @Cyclist, that is indeed also another possibility for you).

It is good to monitor your hearth rate and medical assessment is advisable when doing any kind of sport. There are even specialized sport medicine doctors and specialized sport fitness checks.

It's hard to say whether you specifically are encountering something abnormal and/or dangerous, but what you describe sounds pretty normal.

I just glanced at the results of a quick search on chronic sinusitis, but it sounds like it mainly affects just your nose. So maybe it makes breathing through your nose harder, but not being able to breath mostly through your nose is normal in any endurance sport when you push yourself. You can breath just through your mouth, or combine both nose and mouth especially for breathing in.

High pulse and being out of breath without a lot of muscle burn can happen when your muscles are in better shape than your cardiac system and lungs. That is fairly often the case with young people who do some game sports in school but seldom do endurance training. It can also happen with people of any age who previously didn't do endurance sports, but maybe went to the gym regularly and might even be very strong.

• Regarding the pulse: You can (and should) do short intervals of a few minutes where you push it as high as you can (if you are healthy), but you should keep it at a 'normal' level otherwise. Either you can do that based just on how you feel (not a bad method!), or get a sports watch to help you.
• Regarding the feeling of lack of air and burning sensation in your lungs: At first be careful, but you can pretty much ignore that. Your body will increase your lung capacity only if it's currently not enough, and the way it tells you that it noticed that the capacity is currently not enough is by this burning sensation.

I think you should always check with a doctor if you have concerns about your health. While you probably can get advice on your health from this forum, this is not the best place to seek specific medical advice that is going to be right for you.

With that said provided you have no issues that can stop you from training here is what worked for me and others to improve:

• Try to use a heart rate monitor to train and/or cadence sensor
• What you want to do is ride for 30-60 minutes at a constant heart rate and a cadence of 75-90 RPM (Note if you are trying to do strength work going as low as 65 RPM is ok, but note it does put more stress on your knees so listen to your body).
• What you want to do is use the gears on your bike to allow you to maintain that cadence and maintain a heart rate that essentially stays flat for the duration of the ride. If you ride in spurts, like you pedal hard and then recover, that will not help as quickly to build your aerobic base up. Your aerobic base will let you ride longer without going above your anaerobic threshold.
• Interval or training in Zone 4/5 is something that usually is done less often to help increase speed or functional threshold power (FTP). For example, once you build up a base, can ride around for a while, and know the gear that works best for you to do that you can go to the next harder gear in your rear cassette and try to ride for 30-60 min at 65 - 90 RPM. That will make your heart work slightly harder and force your cardiovascular and skeletal muscles to adapt to the harder work load. Your heart rate will probably slowly keep climbing when you do this and you will probably ride at a slower speed until you fully adapt.

The approach above worked well for me to go from being able to ride only 13 MPH to being able to go 17-20+ MPH while staying under my anaerobic threshold within a year or so.

Here is a boring stretch from one of my rides with metrics where I am doing some of the things outlined above.

• Pedaling the whole time.
• Managing the gear I am in so that I am able to keep pedaling between 75-90 RPM and my heart rate in Zone 3/4 for me. Yes in a few small inclines I dip below that cadence, but I usually do strength work between 65 and 75 RPM so it is something I have adjusted to. On a separate note, for some of my personal goals some of my rides focus on Zone 2/3 and Zone 5 depending on what I am trying to work on.
• Note your target heart rate will probably be different than mine - Heart Rate Calculator.

Doing some rides like this where you are not trying to push max speed or go up super tough climbs I found has helped and often takes some self discipline to do cause let's face it...going fast and/or climbing hills is fun ; ). You can also take this same approach to a mountain bike on a gravel or off-road trail as well.

Also note there is no way I could do this ride at this effort level 3 months into riding. I still remember having to stop in the middle of a 13 mile ride when I picked up my new bike. However, with doing the things outlined above I eventually got there and you can too.

Hope that helps.

Addition: One this I struggle with in the cold is breathing through my nose and often due to the cold breathe better through my mouth. Also as others have mentioned, in sports to get more oxygen into your body you should breathe through your mouth.

It's impossible for us to give an answer to you here, since shortness of breath can be due to simple lack of fitness, undiagnosed obstructive airway disease or even undiagnosed cardiovascular disease.

It is common that people are recommended to check with their doctor before beginning an exercise program, although this advice is usually for (older) adults rather than people in their teens.

Since you have a pre-existing airway-related health condition, and since you are concerned, I would suggest talking to your family doctor just to be sure.

Do note that 3 months is a short time when it comes to aerobic fitness, and if you're training ad-hoc rather than following a specific training program, it can take a lot longer to improve.

For any somewhat fit rider, the limiting factor will not be their muscles. The limiting factor for biking is oxygen transport to the muscles. Your heart plays a role, your blood plays a role, and your lungs play a role. The more efficient your cardiovascular system is able to get the oxygen to your muscles, the faster the speed that you can maintain.

That said, I have experienced myself after a long, forced break from biking, that my lungs needed to learn efficient oxygen uptake again. And it took years for getting better. During that time, I always needed to breathe rather quickly to maintain a high enough oxygen level in my blood for the effort I was putting on my bike.

Also note that, however well your lungs/heart/blood are working, biking is a sport that requires getting very high volumes of air into and out of your lungs. So, breathing through your nose is totally out of the question if you want to ride at your physical limits. Noone's nose is able to channel as much air through it as that same person's mouth. And, as the limiting factor is oxygen supply, a person breathing through their mouth can sustain a much higher speed than that same person trying to use their nose.

Of course, I don't know your exact health issues, and I am not a doctor. So, if your doctor says you must breath through your nose, stick to it. However, if breathing through your mouth is possible, that is the way to go:

Forget about your nose, open your mouth, and enjoy your biking.

Don't know what the weather is currently like for you, but where I live, it is currently about freezing temp when I go out cycling and running. All the answers above are good points and I had the same question you had a few months ago when it started getting cold. "Why can't I breath?" I then checked out Cold-induced asthma, an irritation of your respiratory tract from icy temperatures. When airway muscles spasm, it makes asthma symptoms harder to control. Turns out, when you do a hard activity that puts you body under stress, you breath harder! I know right! And when that "cold-air" or "dry-air" is constantly going up and down your throat and esophagus, it drys them out leading to your airways constricting due to the inflammation in your airways. This is a common problem that effects people all around the world. Not saying this is the case here, but it is worth checking it out!

If you think this may be the case, here are some things you can try to prevent cold-induced asthma: Taken from: https://www.singlecare.com/blog/cold-induced-asthma/

How to treat cold-induced asthma

1. Focus on breathing through your nose.

Note: This can be a bit of a challenge doing a hard activity such as cycling for example. I understand and I personally breath through my mouth when cycling hard. Something that will help instead when you can't only breath through your nose is to use some sort of face covering like a gaiter. This will trap some of the heat and moisture in your breath and should reduce the irritation.

That way your airways will be filled with warm air, not cold air that’s breathed through your mouth. If you find you can’t resist mouth-breathing, or will be exerting yourself (by shoveling snow), bundle up by wearing a scarf or face or ski mask over your mouth. This will help ward off potential pollens and warm the air you are breathing in.

2. Consider moving your workout indoors.

If you normally exercise outdoors, consider switching your routine. And if you can’t resist that jog around the park, head out during the warmest part of the day.

What’s more, “If you have exercise-induced asthma, your doctor may prescribe an inhaled bronchodilator that contains albuterol, that you will use about 30 minutes before exercising outside,” Dr. Berger says. Those symptoms can be even worse when you work out in cold air.

3. Move away from the fireplace.

It’s tempting to stay warm next to a blazing hearth. Smoke, even when it appears to be escaping up the chimney, can irritate your lungs and trigger asthma symptoms.

4. Bring your inhaler with you.

This goes without saying, but many folks forget theirs, especially when it starts to get nicer in early spring.

“Carrying your rescue inhaler is recommended, and for those that are on maintenance inhalers, taking them as prescribed and practicing proper inhaler technique is necessary to get the most out of your inhaler,” says Dr. Lan. “If you feel your inhaler is not working and you have not been taught how to properly use your inhaler, ask your medical provider or pharmacist to show you how to use it.”

If you think its not anything mentioned above, then don't worry about it. When I started doing some hard workouts on the bike I breathed hard and still do. It is something you will become accustomed to if your thinking about racing or doing any moderate ride with your friends.

Hope this helps!