Testing and setting FTP in cold conditions

As its winter here in Northerner Europe I’m now training in colder conditions.
I still prefer training outdoor but my indoor trainer is also in a unheated shed, this means that I’m training in around 5 to 10°C ( 41 to 50 °F) indoors as well as outdoor.
I feel like I have less power in colder conditions, and the data backs up this feeling.

Today I did an FTP test in 8°C (46.4°F) and lost 8 watts compared to the latest test 1 month ago when the temperatures were higher.

I’m now wondering:
Should I stay at the old FTP to get the same training stress and adaptations, or use the new (-8W) FTP as it fits the current cold training conditions ?

In other words, should I train a bit harder than the FTP advice in winter to compensate for the extra effort of keeping warm, or should I just consider this training stress as well and expect the power zones to be lower ?

My main concern is not training in the correct power zones and not getting the right adaptations.
I’m now starting a Low vol. Sweetspot Base phase with one added long zone2 ride and a little (max 30min) VO2Max mountainbike fun in the weekend.

The goal is just to have fun, with the fitness gains being part of that.

I actually find the opposite. Cold in the NE of the US here so I’m training indoors and outdoors in similar conditions.

I believe it’s been discussed on the podcast a number of times that much of our energy goes to thermoregulation.

So given that you’re ok with training in cold weather, I would suggest a longer warm up before testing. That way you get the benefits of a colder room, which will be a lower load on your body trying to keep cool, and your body is properly warmed up for hard efforts.

For example, instead of a 10 minute warm up, you stretch it to 15 or 20 minutes.

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Thank you for the reply.
I’m always trying to do the FTP test in de same condition as I would do my workday training.
After a day of work (machine mechanic) I have a 15 min easy (zone1 - 2) bike ride home and then jump straight on the trainer for the workout.
After that recovery shake followed by dinner.

Could I perhaps have a more realistic FTP test and more productive workout if I make the ride home a bit harder (higher zone) ?


Today I did my first structured workout of this year (Monitor) with the new (-8w) FTP.
It felt like a proper workout with the heartrate and RPE where I expect it to be for Sweetspot efforts.
Was warm enough that I even needed the fan to be on.

Looking back at December, it was a “structured by feel” month.
No obligations, just having fun and try to keep somewhat of a structure.
But looking at it now it was either zone 2 easy rides, or short hard MTB/CX rides.
That (bad structure) together with unhealthy food and more than usual work stress might be the cause of the FTP drop, and not the cold.

So I’m going to keep training at my lower FTP for now and retest in a couple of weeks.

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