Watt - what meassurement to trust?

leinad.nosnoj

I am quite new to cykling training (although I’m 46 years old). Done a few months of cycling to/from work (20 km/day) and weekend rides (initially about 50 km, lately 100-120 km). I also get on my trainer (elite suito) now and then. Elite claim the Suito measures wattage with something like 1.5 accuracy I think.

A few weeks ago I did an FTP test on my trainer. It indicated an FTP at 198 watt.

Now to what I find really confusing: Due to an unusually mild winter in Sweden I’ve done quite a bit of outdoor training on my gravel bike (Topstone alloy with 38 mm knobbly tyres). I push myself as hard as I am possibly able to sustain over 100 km. During the ride (and afterwards) I feel really exhausted. Still my average speed isn’t any higher than 22-23 km/h (total elevation of ride approx. 1000 m, mostly asfalt). I don’t have a watt meter on my bike, but Strava estimates the average wattage to be in the range of 100. Since I’ve entered my FTP as 198 (the figure Elite Suito told me) Strava tells me that I’ve been riding in zone 1 more than 90% of the time.

Then I do a 50 km ride with similar (perceived) intensity on my trainer. Much higher speed, average wattage 175, and half of the time in zone 4 or higher. Again, completely exhausted, but not any more than during the outdoor ride.

I’m getting completely confused. Am I training in zone 1 or zone 4 (definitely feels more like the latter)? If I am really pushing as hard as it feels, are Strava figures way too low? Or is it the trainer figures that are way too high?

A week ago I tried using a hr monitor on a long outdoor ride. It showed average 164 which (to me) makes zone 1 seem silly.

Thankful for any form of insight!

tonysj

Have you put you stats, weight etc in Strava? You may be free wheeling or coasting on your outdoor rides which will reduce the overall average Watts on the ride. Try going out on the roads for say a 1 hours/18 mile ride and pushing hard, ever on any downhills.
FYI I have a powermeter on my bike and also ride a Turbo and the Watts on the turbo is generally higher as there's no coasting etc.
Also I wouldnt be looking at FTP from a 100k ride its to long a a ride as fueling/hydration plays a big part.

whyamihere

Strava's estimated power will be assuming that you're on slick tyres and making assumptions about aero etc. As you're on knobbly tyres, your rolling resistance will be a lot higher, and your position may be less aero than is used in the estimations. Basically, ignore the Strava estimated power, it doesn't apply well to your bike. If you don't have a power meter on the bike, I would train to power indoors and use HR outdoors.

N0bodyOfTheGoat

What bike type have you classed your gravel bike as in Strava? Closest two options would be "cross bike" or "mountain bike" while using those 38mm tyres.

Also think about the weight you are giving your gravel bike in Strava. Personally, the weight I put for me is just me in my boxer shorts, everything else is assigned to the bike weight...
Water
Cycling kit
Bike tools taken on ride
Mobile phone
Accessories on bike (mudguards, lights, bike computer etc.)
Different "bikes" for different tyres setups (more applicable to my Voodoo fatbike, I can set it up with anything from ~27 to 58mm 700c tyres or 26"x4" tyres... Difference from lightest to heaviest setup is ~3.5Kg IIRC)

The more accurate the weight data, the more accurate Strava's estimate will be of your estimated power.

leinad.nosnoj

Thanks! Apparently I had not setup my bike at all in Strava so it was pre-setup as simply “road bike”. Now I set it up as “cross bike” and added actual weight, with mudguards and water bottles and stuff, which is ca 12 kg. And I added some weight to myself to account for winter clothing. Let’s see if it will make any difference. I wonder if the biggest source of errror isn’t the wind. It’s been quite windy here lately and it’s a huge difference riding into a 5-10 mps headwind. If Strava doesn’t take that into account then the other small adjustments will probably not help much.
As one of you said, it’s probably better for me to set zones based on hr. Or buy a power meter for my bike.

leinad.nosnoj

I meant 5-10 meter per sec wind of course.

fenix

Strava estimates are bobbins. I'd ignore it.

Your trainer should at least be consistent. Use the power readings on that and ignore the Strava figure. Training on a turbo is a lot more controllable.

ugo.santalucia

fenix said:

Strava estimates are bobbins. I'd ignore it.

They are decent for categorised uphill segments. I generally get 250-300 Watt on short 4-8 minute climbs, which is about right.

Flat and downhills segments are generally random numbers... it happens that you work your butt on a flat segment and Strava thinks you averaged 70 Watts

peter101cycle

Couple of things to think about:
- get your age, weight, height exactly the same across all your devices and sites that you use (e.g. Strava, Zwift, etc)
- make sure all the bike measurements are accurate, especially with wheel and tyre size
- consider using HR monitors on both indoor and outdoor training
- one-side power meters aren't that expensive, I use a Stages Power left crank Ultegra. It's worthwhile I find, I may get the right side upgraded as well for both, as I have difference in leg length and want to be sure I'm using both legs similarly

Finally, consider thinking about watts per kilo - it's another way to think of power as it considers your weight as well.

ugo.santalucia

peter101cycle said:

Finally, consider thinking about watts per kilo - it's another way to think of power as it considers your weight as well.

Very much this... unless you are only interested in doing flat time trials, power per mass unit (W/kg) is a much more relevant measurement, as you can compare athletes of very different sizes.
If you are 60 kg, you are unlikely to ever reach an FTP of 300 W, as that would be 5 W/kg, which is pretty big and probably something that belongs in Cat 1 racing (remember the likes of Chris Froome and Egan Bernal are likely to have 6.2 W/kg and anything above 6.4 W/kg is unlikely to be "clean").
Equally, if you are 100 kg, 300 W FTP is only 3 W/kg and even the most average cyclist with no racing ambitions should get there or thereabout with a bit of practice.

thecycleclinic

Or dont worry about all of this and just enjoy riding. The problem with power is one can get obsessed with it and it distracts from the joy of riding.

The actual numbers are not so important. Do you feel good when your out and have you enjoyed it. Job done if that's the case.

I do have 4 power meters but find them utterly useless as all they do is spit out numbers that dont improve the joy of riding. I foolishly thought they would help me in some magical way with training. turned out I was wrong you can do it just as effectively by feel.

leinad.nosnoj

Thanks everyone! I entered the correct bike details, including tyre width, in Strava and I immediately started getting ca 40% higher power figures. Seems to me Strava is over-estimating the importance of equipment. I can’t believe I need to go 40% harder on my gravel bike, compared to my racer, to reach the same speed. However, disregarding that, I think the new figures are probably more accurate.

One of you wrote about hills vs flats. I think you’re right. The power figures on hills seem more consistent. However, the area where I live (Stockholm, Sweden) is quite flat. The highest hill around here is something like 150 m.

Not sure power meters (or speed meeters, or any form of figures really... ) are any good for me to be honest. My challenge in keeping to a training schedule is not to go hard enough. It is that I cannot resist the temptation to turn every ride into a competition. The passed weekend I went for a 120 km ride. I had promised myself to take it easy. But I had a strong headwind on my way out. After 50 km I had averaged 28 km/h and I saw the chance to improve my earlier 23 km/h mark on that distance. Struggling in a strong headwind on my way home I succeeded. But at a high cost, aching legs, cough, increased body temperature... And since I ride my bicycle to work every day, I don’t have any real rest days in between. I think maybe I just need to try to cool down a bit.🙂 It’s just hard for me to find the right motivation unless I turn every ride into a competing challenge (although I’m only competing against myself, at a low level).

amrushton

power meters are only good if you have set them right and can interpret the data. I couldn't be arsed with one and CycleClinic above has the right idea

mrfpb

Power meters on the bike and heart rate monitors measure different things.

HRM meausures input - how much energy your body is consuming to do the work, power meters measure output - how much work is actually done by you and the bike.

You probably want the output on the bike to give performance relevant data - so a power meter is more relevant. People (like me) trying to get or maintain general fitness would need a HRM to get relevant calorie burn / heart rate zone info.

output/input x 100 gives efficiency. This is usually 25% approx. So using both can be useful for training.