Way more watts but way slower - how's that possible?

I was doing Intervals outdoors on a specific segment on gravel a couple of weeks ago with quite some bad form. I averaged 160 watts with an initial quite hard sprint of 350 watt for 20 seconds and the resulting other nutmbers for the rest of the segment.
I today had a way better form and had the very same conditions: No wind, standing start, dry ground, no drafting, same bike, same weight, straight road and I did a constant average 185 watt for the segment.
So I expected to also improve within the used time but I indeed needed 20 seconds more. So while I had 3:00 minutes with 160 watt average, I had 3:20 with 185 watt average today and I measured it with trainingpeaks analysis, not strava - so no GPS malfunction.
I am very lightweight with just 40 kilograms, so 25 watts more is quite a thing for me and I expected to be way quicker now but obviously not.
Anybody got an idea what the issue could be? Is there any analysis tool I could use to lay both GPX/fit-files above each others to do something similar to a strava flyby?

I don’t have an answer for you, but to rule out the abnormal result, I’d repeat it a third time and see which result is in line with your third attempt.


Was the temperature the same? Did you calibrate your power meter before each ride? Has the ground dried out any more? Tire pressure? Do you weigh the same?


Calivrated pedals multiple times before both events. 8 degrees less and tire pressure wasn’t also the very same (but pretty similar) but though: That may lead up to some 3% difference - if at all - but I had 15% more power and the result is more then 11% more time needed?

Yeah weird. Maybe try a couple other informal “tests” to see if you get data all over the place or that was just an outlier?

Gravel vs road?

Brake rub, frame rub?

Did more tests in both workouts and they all have the same tendency: Way more power leads to way longer segment times…

Both times the very same segment (else I wouldn’t wonder) with the very same conditions at 99.9%. Brake rub is the only thing I could think of too but such a heavy effect? Those brakes must be nealry melting

I’m not sure I’m understanding the exact tests you did, but it sounds like you started the first test with a “sprint” and just rolled into the 2nd starting at 185 watts? If that’s the case, it could be the difference on such a short test. On a ~3 minute effort on flat-ish ground, putting out extra watts to get up to speed and then soft pedaling is going to be faster that holding a steady power the entire time. A lower power can absolutely be faster on a given segment if you were “smarter” about how the power was applied. Also, a 3 minute segment from a stop is a tough thing to use as a comparison. Might be somewhat repeatable if it’s a pure uphill with no wind, but for a flatter segment you really want a longer test if you are trying to compare efforts.


Agreed, for something this short, the sprint to get up to speed can probably be on the order of 10+ seconds. The standing start might not have been as smooth the second time for another second or two. Gravel makes it hard cause if you hit twice as many bumps or slow spots then that another 5 seconds or so.

Also, was this with the same kit and position on the bike? Not sure how fast you’re going for this but aero can play a decent role and account for a large handful of seconds.

  • pressure in tires can make pretty big difference
  • choosing slightly different path can make a big difference
  • look after NP watts instead of average
  • if you sprinted at the beginning and there is somewhere an incline - the harder effort there could make a big difference
  • different kit can make a difference

It can be multiple factors all together making a big difference