Increase cadence?

Cadence is my gut reaction also.

Shut Up Legs!!!

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"What's your claim?" - Ben Gravy
"Your best work is the work you're excited about" - Rick Rubin

Common experience for runners who get into cycling… cardio engine can rev much harder than the puny cycling muscles can handle. Definitely also consider upping cadence, as per other suggestions.

What power and cadence are you doing for those intervals? Type of trainer? Erg mode or no? Getting out of the saddle at all?

 

This is normal for me and I’ve been cycling for 10+ yrs. For most bike intervals and efforts my hr is never the limiter it’s always the legs. And I have big quads and glutes so I’m also surprised as I thought the big leg guys wouldn’t be more cardio limited but it’s def not that way for me on the bike.

Interesting, hadn't thought about that. Looking back at my workout yesterday - for 4 minute intervals my cadence started around 95-100 and gradually decreased as I got more tired and finished most intervals around 80. Thoughts?

Thanks for the reply. Yesterday's workout was 1hr Z2 followed by 4x4 at 120% FTP, 4x1 at 125% FTP, 4x30sec at 130% FTP. The shorter intervals I have no problems with. FTP is currently 282 so 120% target is 353 watts. Cadence starts 95-100 and gradually decreases to 80 at the end of the interval as I get tired. Saris Hammer H3 on erg mode, and no I stay seated the whole time usually.

You need to work on your math 😉

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https://acprestation.se/

Very normal i think
I cycling legs give up first
In running lungs give up first

So you did an incredibly hard workout and are wondering why your legs are tired before you start breathing hard?

The intervals are too short for you to start breathing hard.

Normal. Some athletes are limited by their cardiorespiratory system and some are limited by their muscular system. If I had to guess you have a history of training other sports longer than you've been cycling.

Sounds like you're not recovered or possibly overtrained.

4 min is plenty of time for CO2 to build up and drive a significant respiratory response.

Turn off erg mode. Constant watts with a 20% drop in cadence is a 20% increase in torque demand as you are tiring.

Retest your ftp. My guess is it's too high, if you can't hold 120% ftp for 4 minutes. What method do you use for testing your ftp?

Same as lightheir and lassekk - Cycling was the first sport I did and then grew into triathlon, still, legs always give out before the cardio. I think pretty normal.

You say you are "back riding seriously". Did your legs used to not give up first?

Just to be clear in responding so this point doesn't get lost: 353 is 125% of 282; 120% of 282 would be 339. OP either miswrote 120%x282=353, or misrode 4x4'@125%.

Classic cycling vo2max intervals should be limited to 120% ftp. 125% is unlikely to be sustainable for the typical 3-6m duration, by most people.

Again that assumes an accurate ftp (sustainable for about an hour). Soooo many people use some short ramp test or a 20m test without the blow-out, or whatever that overestimates what they can truly hold for an hour. That's only made worse when escalating to things like vo2max.

I have the same problem as OP. I use 20min test as FTP basis. I can't even do workouts with 3min intervals at 120% without my legs failing on the last couple reps. However, I am able to do 90min rides with an IF in the range of 0.90-0.93 on threshold workouts which always made me think my FTP was pretty accurate. Do I have spaghetti legs or just a poor understanding of how FTP should translate into achievable workouts?

I can't really tell. You ought to be able to do 2+ hours at 0.9IF, so if your out of gas at 90min...that's probably an indicator also.

But, my number 1 rule for intervals is that if you can't do the workout, it's too hard. So, back off to the point that you can. And increase from there.

If you take one of these classic workouts like a 4x4 or a 5x5... You should do them at an intensity that just allows you to complete the whole thing with an even pacing. The exact %ftp isn't totally critical. And you should aim to increase the time or the power week over week (good reasons for either). Even pacing is better than over-shooting and fading to the end.

As for the ftp test. If you don't do the 5min blowout before the 20min test then your ftp is probably too high. Even with the blow out, it's still pretty easy to overshoot a single 20min. So, if I'm going to do a test, I do a longer test. But, I don't bother much, except in specific circumstances. I follow the "do what you can do, and doa little more next time" method I posted above.

I’m a competitive cat 1 cyclist that does 10000+ miles / year and that would be a hard workout for me.

Maybe it’s normal your legs get tired?!? Or maybe more likely, your FTP is just too high. How did you get your FTP?

1. Like mvenneta said, it's an incredibly hard workout for most (save maybe for the few people who have A LOT of room between their FTP and their VO2max power).
2. If muscular endurance is the limiter, try low cadence intervals at tempo intensity (about 80-85% of threshold), starting at like 3x10' at your preferred cadence minus 20 to 25 and then lengthening the repeats or adding more of them, or 4x8', or whatever.

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"FTP is a bit 2015, don't you think?" - Gustav Iden

It sure is, but not at the level of fatigue the OP is likely carrying.