Teenage son and FTP - mystery

My 13 year old is a keen cyclist, and will beat me by over two minutes on a 10 mile TT. However, on TR, our FTPs are similar (mine is actually a bit higher), and yet he is unable to complete the workouts based on his FTP. We’ve set his FTP at about 20% lower, and he still finds it very hard (and sometimes impossible) to complete a workout. It’s not lack of effort, as he is a very good trainer, and knows how to push himself. Any theories as to what is going on would be welcome, as he is understandably a bit discouraged.

I’m guessing that he beats you outside because he has a way better power to weight ratio.

He is doing the ramp test on TR? He could be over testing. Maybe try the 20 minute test?

That said, I’d be hesitant with a 13 year and hard structured training. Just riding regularly and enjoying the bike might help more than trying to find genetic limits at age 13. On TR, maybe look at Traditional Base or an easier aerobic building plan. You don’t want him to be one of those athletes that is burned out at 23 after 10 years in the sport.

BTW, it is really cool that he is so into it. My son is 9 and sadly, he doesn’t love cycling. When I was 9 I was a maniac on my BMX bike and I wish my son was more similar. I might have to give him more time.


With regard to the TT, size and weight certainly factor in, so if he is smaller and/or lighter than you with a similar FTP it would make sense that he could be faster over that distance. Do you have power files for TT efforts by chance?

With regard to the workouts - are there specific types of workouts that he struggles with? My gut reaction would be that he possibly has a stronger short power profile relative to his FTP and sustained power profile. This would mean that comparatively he would perform well in a Ramp Test but a long effort workout 3x15, 2x20, 3x20, etc. would be very difficult for him at his ramp tested FTP. A 20 minute FTP test might yield a result that would be more manageable for his training. This wouldn’t be surprising for a younger rider either, in my mind (to have a better short power profile than sustained).

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Thanks both for your replies. I don’t have the power profiles for the TT unfortunately. He’s done both the ramp test and the 20 minute test - his 20 minute test did give him a lower FTP, so I guess his VO2Max is disproportionately high compared to his FTP. However, he still can’t complete the workouts on the lower FTP. Mainly he tries sweet spot workouts, although today he tried a new one (three times 8 minutes above FTP) and couldn’t get past the first 8 minute segment. I think you’re both right, that (i) in a young, and growing, rider, it’s probably natural to be better at short workouts, and (ii) TR may not be right for him at this age. I think I’ll take him off it for now, and go on the road more together - trouble is I’m going to need an electric bike to even stay close to him before long… Thanks again for your responses, and good luck with your son AJS - definitely best to let them come to it on their own - with me, my son was the one who got me into cycling, rather than the other way round.

id imagine its pretty normal in younger riders to have disproportionate VO2 component, especially on a ramp test

It seems a bit weird that he cannot complete sweetspot workouts with the 20 minute test result.

I mean his 20 minute average test power multiplied by 0.95 is his FTP. Sweetspot ranges from 0.83 to 0.97 of that value. So basically his 20 minute power by 0.95 by 0.83-0.97.
So for instance, if he would hold 250 watts for 20 minutes that would place the lower end of sweetspot slightly below 200 watts. That should be doable.

Could it be a mental thing? Like he is able to push himself for races/tests but not so much for training?

Also, can you rule out any technical eventualities? Same trainer for tests and workouts? Same bike? Does he zero the power meter? Does he use a ventilator?

Need to make sure you’re doing the 5 min blow out before the test. That takes a lot of zap out of the legs.

And it could be mental/not wanting to deal with the pain. When I did Xc in middle school and one year of HS I never wanted to make it hurt because it HURT! But when doing track like the 400 there was nothing I loved more than turning myself inside out for a time between 50-55 seconds.

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Your son is adept at absorbing the Zenergy of the great outdoors, but still needs to figure out how to do it indoors.

Poor Feng Shui in the pain cave, mayhaps.


Your son is stronger than you. Get used to getting your arse kicked. :stuck_out_tongue:

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when doing track like the 400 there was nothing I loved more than turning myself inside out for a time between 50-55 seconds.

I would call you names and try to run away, but you’d catch me pretty quickly. But yeah, turning oneself inside out in pursuit of a time can be pretty fun {I’m more of a 10 mile guy}.

@AdamA are you both using the same trainer?

I’d be curious to see how his performance compares to higher intensity workouts- might establish whether it’s the FTP that’s the issue, or those specific kinds of workouts. Both SS and longer suprathreshold repeats have a pretty large aerobic component, so that might point to a weakness there. (especially in the case of a very young athlete- in many cases they simply haven’t had as much time to build up the aerobic base that older athletes generally have prior to starting structured training.)
Good luck to your son though! Sounds like he’s killing it already :sunglasses:

Definitely a topic that needs to be covered on the podcast,


Do you have zwift? I think if my kid was that young, into cycling and wanted to try indoor training, zwift would be the go to solution. Imho to keep him interested, he has to have fun. For a 13 year old, racing your dad up a hill is fun, but hitting a number in a screen for 12 minutes is perhaps not.


Is he using ERG mode and the cadence dropping so sapping the legs trying to get back on top of the gear? Might be worth checking cadence data out.

Thanks again for replies. Yes, we use ERG mode, and the cadence drops off until he can’t turn the pedals any more. I’m pretty sure I can rule out technical issues. Suspect it is a combination of poor feng shui, a bit of psychology, and young growing legs not yet having the strength endurance to power a body that is getting heavier week by week. Anyway, just signed him up for Zwift.


Have him try a workout in resistance mode with Zwift in the background!

I wasn’t cycling at 13 but I was a competitive swimmer. And I can say that I never would have been able to do the workouts in my own house like I could in a pool with 20 of my friends. But now I have no problem doing 2 hour trainer workouts in my garage. I’ve seen kids literally pass out in the pool because they were racing their friends in 50s underwater and they refuse to come up for air and lose the race.

I’m sure your son is able to dig much deeper when he is racing his dad outside than he is by staring at a computer screen. Kids just aren’t motivated by the same things that adults are and thus need to train differently to bring out their true capabilites.

Also, he is probably considerably more aero than you are outside simply because he is likely shorter, more flexible, and has narrower shoulders. So that on top of that he is probably much lighter which would give him a considerable advantage on the ups.

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It’s not really a mystery.

My son and I have similar profiles in the middle. My short power is higher, by a few hundred watts, and my long power extends out farther, but relative to weight he’s a good bit above me in all categories. At my power, I’m a bit above 3W/kg, about 3.2W/kg. He’s above 4W/kg. At 12% grades and a 3+ mile climb, he’s faster than me by a good 5-10 minutes. Even though I have more absolute short power by about 200-300W, I can’t really out sprint him, as he accelerates faster, especially on a slight incline.

I used to be able to drag him on long rides, but now he waits for me. A 3hr sweet spot ride for me, hard pace, is about 2.5hr for him, at endurance/tempo pace.

My son has been beating me uphills since he was 10yo. He was always in “reach” then, but not any more. I get dropped on the climbs, hard. 16yo, pretty much cat 1/2 in MTB now.

e-bikes, some parents on his race team have that. I haven’t yet, as I still want my own power, but I can no longer ride with them.

For the training, that’s expected. My son hates it, and can barely do some work. He’s constantly getting upset when he has to do a workout indoors. A good portion of it is mental. With that attitude, yeah, a long tempo interval is going to be met with lots of stops, lots of fidgeting, getting off to do other things.

That’s to be expected, IMO. It’s pretty typical of that age.

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This may help but there’s really no way to tell. Sometimes a blowout effort will leave you too wrecked for the 20 minutes, or still you can overcook the 20. It’s rather individual.