Feeling Extremely Tired During Races

My 16 year old son is an elite MTB racer, but his performance is super inconsistent. In 3-4 races this year he’s podiumed in very strong fields, and the other 3-4 races he’s basically give up and finished mid pack and even DNF’ed one race. He describes it, always after a very hard start as far as I can tell, as feeling extremely tired after the first hard effort and then can’t recover. He thinks it has to do with not sleeping well, but he does go to bed on the early side for a high school kid and gets 8 hours pretty consistently. He also doesn’t fall asleep in class, in the car, watching TV, or anything like that which would indicate a serious sleeping disorder.

When I race after a bad night or two of sleep, I lose 2-3% performance at most so I’m having a really hard time understanding what he’s dealing with. It honestly sounds more like a bonk or low blood sugar or something like that to me, but he’s pretty adamant that this isn’t the issue.

Has anyone ever dealt with anything like this?

1 Like

If I have too short a warmup I will experience the same issue with hard starts.


I used to have this in CX when when I got my fueling/warm up wrong. I used to do a half assed, easy Z2 warm up, hammer a gel and race. From my understanding, in order for your body to make the best use of that gel, a good hard warmup is needed. Otherwise your body isn’t primed for it and it ends up just spiking your blood sugar and then crashing. Hopefully someone with more science background can chime in and either confirm with sciency terms, or tell me I’m an idiot.


I would think 2 things that others also mentioned. A bad warm up or fueling issues.

Recovery between hard efforts is driven by aerobic mechanisms. These can take a bit to wake up and warm up. So maybe he’s either not warming up enough or he’s taking too much time between the end of the warm up and the start of the race.

For the fueling, it’s possible he’s eating enough but not at the right time. If you eat a gel like 40min before the start of the race you can have ‘reactive hypoglycemia’. Basically you take the gel, your insulin kicks in in response to the raised blood sugar, then it can accidentally drive it too far down below baseline before lower insulin levels. This can cause a tired feeling sorta like a minor bonk.

I like to just sip on some carbs during my warm up to prevent that real high spike and then either on the start line or before I roll over (within 10min of the start) I take a gel. That way it gets into my blood stream but doesn’t have time to then come back down.

Unless he’s only getting like an hour or two of sleep the night before then it’s likely not sleep. That would probably have him feeling tired all morning and not just after the first hard effort.


Does he use power and/or heart rate? I’d compare the starts of the races he did good in to the races he struggled and see if anything stands out. It’s amazing how much harder just a few really good riders can make in a race.


Also agree with this. Without numbers it can be hard to really say. It’s possible the races he hangs on in start with 30s at 500W (for example) but the others he has to do 45s at 650W and that just blows him up.

Tell him to HTFU. It’s normal to go all out fighting for position and end up in the red for too long and blow up. Just don’t quit if you do because you might not win or podium, but you can finish with a respectable place. Lots of racing is convincing yourself not to give up. This is especially hard in cross country and CX, where the rest is all out from the gun.

A sufficient warm up is a 30min ramp up completed about 30min before the gun goes off. I usually spin easy for 10-15 and then do 1-2min steps going up to something like 110%ftp with a 5min cooldown.

Poor sleep the night before doesn’t matter. I raced T&F and coached it at a HS and we are pretty sure it doesn’t matter if you’re up with butterflies the night before. Poor sleep for many nights matters alot.

Can’t win them all, but there’s no good reason to quit if you’re out of the placings. Good luck to your kid

1 Like

How is his training load? Maybe he is just tired?

is he monitoring load with some software and a performance manager chart?

Reactive hypoglycemia sure sounds like what’s going on here, thank you.

Yes, he’s using power and HR and we went through this comparison last night. We looked at peak power, max 30 seconds, and average for the first few minutes of the race. His bad days have definitely been the ones with the harder starts, but when I bring that up he can point to times in the past where he had similar numbers and didn’t blow up.

That’s what I was thinking too honestly, but I want to make sure I’m not missing something else or a possible medical issue.

1 Like

He’s a kid and doesn’t fully know himself as an athlete. Simple. Junior athletes are known to have swings like this, it’s just part of the process.

He may not think he is fatigued because he hasn’t done this long enough to recognize his own markers.

Side note: I genuinely hate the recommendations most people end up giving on boards like these lol.

1 Like

I don’t know your son, but we have a junior in our team and he doesn’t have a clue about nutrition. On a 4/5-hour ride he would usually bring a single 0.5 l bottle and one or two gels. When I am ride leader and know he is joining us, I’m stuffing my pockets. He even refused to eat cake despite me offering him to invite him.

Predictably, he bonked last time it was my turn to lead, and we all had to nurse him back home by sharing what we had. (No problem for me as I brought plenty of extra.)

I would start there: make sure he learns the basics about nutrition, i. e. what he eats before, during and after a ride/race/workout. He should learn that he should not eat a salad the day before a race or something rich in fiber, that focussing on weight alone will bite him in the rear quarters. He should know how much he needs per hour. A common starting point is 80–100 g of carbs per hour. And he should know to replenish right after exercise.

I think most of us, especially those who were active, got away with eating junk all the time. Try to steer him towards better choices.


If you have power & HR numbers compare his races. Is he just redlining too long and blowing up? Are the other races better paced? Is it mental… not in the lead group so gives up?

At this age it could be anything. School stress, friends, girls, social media, etc. are all part of the stress reservoir. Throw in growth spurts, hormones, and who knows what else and performance is all over. As many have mentioned kids who bomb usually didn’t eat lunch “because they are too busy” or are not getting enough sleep. But if you are confident it’s not one of these… it’s probably because of a girl. :crazy_face:

He’s 16, inconsistancy is normal. Watch some of van der Poel’s early CX races, and you can see similar things.

I do get it is frustrating for him (and you) though, so using that as motivation to change something. This might be a good time for him to learn about nutrition, and to work out a good warm up and pre-race food protocol.

If he’s adamant its sleep, maybe see if you can track his sleep with a watch or even just a phone app? Even if its not 100% accurate, it’ll give you some more information, and might convince him that its not sleep and he has to look for something else.

1 Like

Yeah sure but the kid is racing XC for about 1 hr. Even pro cyclocross riders don’t ride with bottles let alone nutrition. It’s not his problem, or at least not why the kid is blowing up in this context

It still matters what he eats the day before and right before the race. Teaching young athletes the basics when it comes to nutrition is super important.

Even for short races, I would still encourage taking on fuel and liquids. It is just a good habit to build. On hot days, maybe he just needs the water even if he can do without carbs.

Unlike CX, XC races have feed zones, and I think you should drink. (AFAIK in CX races if you want a bottle, you’ll get a bike for free.)

Your advice is good advice in general, but it’s out of context. Do you really think this kid is bonking in the first 5-10min of the race? It’s about an hour race


If you don’t eat properly in general, then yes, that might be a reason. Or if it is super hot and humid, you might need to drink even during short races.(*) How many kids do you know who skip breakfast or have an inadequate breakfast. What if they skipped breakfast, drank very little all day, ate junk food from the school cafeteria for lunch or pop tarts and then expected to perform? (I was never one who skipped breakfast, but many classmates in the US did. And we had a toaster for pop tarts at our High School cafeteria. Not sure if this is still a thing.)

Look, I am not claiming “It obviously is nutrition and hydration, and only nutrition and hydration.” In all likelihood, it is the combination of a whole bunch of confounding factors — but I think ticking inadequate nutrition and hydration off the list is the first thing I’d do. The next factor to address is sleep. Hence, my advice is to start teaching him about the value of proper nutrition and hydration. That includes nutrition before, during and after exercise. To reinforce what you ate for dinner the night before may impact your performance.

(*) Two years ago I did a crit race on the hottest day of the year. The longest race was about 45 minutes long, most were under 30 minutes. Despite that, three athletes suffered from heat stroke and had to be taken to a hospital by ambulances. Two of them were in their late teens/early twenties, super fit. Our team captain had to pull the plug during the race, because he was close to having a heat stroke. I remember on the way back (70 km to and from the venue), my heart rate was in the mid-150s just doing easy Z2.

Again, I am not saying this is what happened here, but e. g. hydration can be a factor on even short races, especially if you haven’t recharged your system when you had the chance.


Im just gonna ask if you’ve had him cleared from medical/cardiology standpoint?

1 Like