I used to be able to ride 50 miles a day 3 to 4 days a week.

I had lung cancer and had a lobectomy in August 2020. By April of 2021 while living in Washington DC I rode 40 miles without a problem just before moving to Las Cruces New Mexico, and after having been off the bike for a while I got back on. Initially I was only riding 26 miles but had to stop three or four times during the ride.

On two occasions I was so fatigued after 17 miles, I had to stop 12-15 times. On another day I rode 40 miles without stopping. Lately again I’ve become fatigued after 15 to 17 miles trying to do 30 miles.

Today I quit after 18 miles.

Why am I experiencing fatigue some days and not others?

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    I’m voting to close this question because it is seeking medical advice that we are not qualified to answer.
    – mattnz
    Apr 2, 2022 at 20:08
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    This is similar to what I've experienced. Turns out I had polio at age 2 and "recovered", but am now suffering from "post-polio syndrome". I wouldn't be surprised if there are a dozen other maladies that can produce similar symptoms. Apr 2, 2022 at 23:18
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    What is the question? Apr 3, 2022 at 4:50
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    Please consult your physician. All advice you will find here is guesswork and might lead you to ignore health issues that have to be checked by a health professional.
    – gschenk
    Apr 3, 2022 at 9:47
  • Hi Thomas, as you can see we are (rightly) quite cautious here about things that may well be medical issues and require assessment by a medical professional. But IF you have taken that path and want to update your question to outline that advice then we can possibly help.
    – Andy P
    Apr 4, 2022 at 8:01

5 Answers 5


Altitude. Las Cruces is at approximately 1191m (a little less than 4000 feet) above sea level, while Washington, DC is right at sea level. Combined with the loss of a lobe and time away from the bike is probably enough to really decrease endurance, even if it's not enough altitude to feel just walking around.

  • Great spotting! Some checking shows that 1 atmosphere at sea level will result in 0.87 atmospheres at 20 degrees C. And that at sea level we get an effective oxygen percentage of 20.9%, 1000 metres is 20.1% and 2000 metres is 19.4% oxygen, leaving about 20.0% at 1200 metres (interpolation) Not enough to perceive, but definitely enough to effect, specially with decreased lung surface area.
    – Criggie
    Apr 3, 2022 at 8:19

This could be normal.

I’ve recently had 2 hip surgeries and getting back into bicycling was really tough (and still is). My first ride (four weeks after the second surgery) was just 12km at 120W of power and afterwards my legs were burning and I was tired and exhausted for 2 days. A year ago I could do 100km at 150W without problems and wouldn’t even record a 12km ride. I’m an otherwise healthy male and 29 years old.

This is just to illustrate what a few days and weeks of inactivity can do. I went for short (2km) walks right until surgery, I only spent 10 days on crutches, I did a lot of upper body workouts (and as much as I still could for my legs), my resting heart rate was still around 40 … and yet I lost a ton of strength and endurance.

I guess if you want to make sure you should go and see a doctor to rule out an underlying health issue (e.g. heart disease).

But once that is ruled out there is really no way around normal training. Don’t ride until total exhaustion, make sure you get enough rest and protein, make sure you get enough water and carbs during and immediately after the rides (probably not that important for <1h rides), try to keep the effort steady-ish (unless you want to do interval training). It helps to record your training so you can observe trends. The good news is that starting at a low level you should see improvements quickly.

If you struggle with training sessions you had no problem with a few days ago, try to find out why. Was the intensity really the same? What about the weather? Did you change something about the bike? How did you feel before the training? (rested? hydrated? hungry?)

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    What question are you answering? Apr 3, 2022 at 4:51
  • Please don't suggest "normal training" to someone recovering from such severe illness. Training ought only happen after being cleared with sport specific examination and under supervision by the patients physician.
    – gschenk
    Apr 3, 2022 at 10:00
  • @gschenk: Of course, and I presume that has been done. I don’t think the principles of training are inherently different for someone with reduced lung function.
    – Michael
    Apr 3, 2022 at 13:26
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    at the most basic level the principles of training should be the same. ride slowly and recover well -> builds an aerobic base. With reduced lung capacity slowly might be slower than before and recovery might be longer but the principles are the same. Question could perhaps be revived if more details are added, it's entirely possible the medical side has already been addressed and this question is seeking to remedy a lack of training knowledge
    – Andy P
    Apr 4, 2022 at 7:56

You have to see your physician immediately.

No advice given here can rule out any of the countless possible medical causes for such a sudden fatigue. Do not ignore signs that could indicate serious health concerns.


Please for your own sake don't try to find the answer here, on the forum, but consult your doctor.

I would try to ask for spiroergometry, which is a great way to find out how your body tolerates physical activity (and with a bit of luck you can also find out your VO2max with a decent accuracy).


To hazard a guess, you're suffering from the same malady that will get us all in the end, increasing age.

That you've had lung cancer and lost lung capacity in surgery suggests you're an older rider, and we all have our good and bad days.

You might be a prime candidate for an ebike, where the assist is to help you complete the route on the bad days. Don't give up riding completely, it will help exercise the remaining lung area, and keep you as fit as possible.

  • What question are you answering? Apr 3, 2022 at 4:51
  • Age doesn’t affect endurance sports that much. A 41 year old ran a marathon in 2h8m, a 73 year old in 2h54m (of course those are world records, not saying that OP could necessarily achieve those times). The important thing is to keep training consistently. What gets much harder with age is building muscle and maximum strength. Same for flexibility.
    – Michael
    Apr 3, 2022 at 5:41
  • @Michael yes, but that's the inverse, showing that some people can still perform really well at age. My point is that OP is comparing earlier efforts with current efforts. Time catches us all. Though looking at Livius' answer, that's probably the most significant factor.
    – Criggie
    Apr 3, 2022 at 8:13

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