Holding Power in TT effort outside more difficult than inside

Hey Folks—

Curious if anyone else has this issue.

I keep hearing that a lot of folks are able to produce better power numbers outside when doing intervals, but I’ve mostly had the opposite experience.

For example, if I am doing a 30 min interval inside I can easily average 250 watts, whereas outside the same effort will usually result in a 225 average (235 normalized). I’m using the same power meter inside and out and power match on the trainer.

My self diagnosis is that I just need to practice riding outside more (usually I’m only riding outside 3-4 times per month) and practice that skill, but curious for others’ thoughts since this seems to be the opposite experience of most…

I am also doing most of my outside riding in New England meaning that the streets are generally crappy and it’s never consistently flat — just lumpy — which could be a factor as well I suppose.

I’m similar (I’ve not really done any long inside intervals of late inside but I reckon its scarily in the same ballpark). It might be I can focus on a power number rather than traffic, not falling off etc and get that last little bit out. I’d also be interested if anyone knows how to close that gap.

Lots of possibilities.

Flywheel inertia could be an issue, I usually run the smaller ring and mid-cassette on the trainer in ERG as it provides a smoother experience, but this means less inertia and ‘feels’ more like climbing. If I use the big ring the flywheel really gets going and feels more like riding a flat TT type effort, but I find on my trainer the power fluctuates too much at threshold like this.

You might also find your position changes outside and this impacts how much power you can produce.

I also find riding into a headwind makes intervals ‘feel’ harder, a phenomenon others I know experience too. For example I use a flat length of road between 2 roundabouts for intervals, the headwind direction is harder to produce target power than the tailwind direction… seems odd to me, perhaps the wind is stalling the cranks as they hit the dead spot of the stroke or something…

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I notice people in my groups have trouble keeping power on the decline. Might take a little practice to either ensure you are shifting down or increasing your cadence when the terrain turns down. Undulating terrain is tougher than a pure incline because folks often try to avoid shifting gears when they should.

I do the same on my trainer. I would LOVE to see some studies on how this affects riding outside… if it helps with climbing more than TT efforts and such.

I would say from personal experience that I feel better outside once I switch to small chainring and get into climbing.

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My guess it’s into the realms of marginal gains, my guess is that body position is a bigger factor than flywheel speed. I subconsciously sit up more on the trainer as I don’t need to fight drag and need to consciously make an effort to use the drops/aero hoods positions, I can feel the different muscles being engaged

I am sure you are correct regarding this. I know for a fact that my aero position is weaker than my upright position and that would explain why I feel so much better on the power when seated up and climbing.

I know inertia plays a part, but how much its hard to say.

VO2 and higher intervals I can always do higher outside almost regardless of road as long as it’s not steep enough downhill that I spin out. Steadier threshold intervals I can do higher outside if it’s either pan flat or uphill, but if it’s rolling my NP is ok but AP tends to be about 10W lower. Bad road surface also can impact those steadier efforts - again doesn’t seem to impact the higher intensity where I can throw watts at it.

If it’s actually a TT type effort where you’re focused on speed and not just power then staying aero can also impact power output.