mschwett 

i noticed a bit of a drop in my power late last year, at similar exertion levels and on similar courses. recovered early this year, without being totally sure what the cause was, if any. have been getting just a tiny bit faster on my favorite routes, with more focused efforts on rides in the 1.5 to 2 hour range three times a week and steady 200w ish efforts on 3-5 hour rides once a week.

what i noticed while looking at ride data was that my power imbalance has also shifted a bit over time. for most of last year, it was around 46/54, with the right leg doing 17% more work. ((54-46) / 46). that declined rapidly at the same time as the steepest drops in power to an average of 44 over several weeks, which is 27% more output from the right leg. pretty signficant! it hasn't recovered much, hovering around 45.

one disclaimer, the metric i track most closely is the average power (not normalized) for the strongest one hour of the ride, because most of my rides have an hour or more with few or no obstacles to going as hard as i want. maybe one or two stop lights, maybe one descent that requires letting off briefly. however, i can't figure out how to extract the power balance data for just that hour, so i'm relying on the balance for the entire ride.

anything interesting or suggestive here, or is this just noise?

PeteHski

My first thought is that the power trend line is maybe not very significant given the relatively wide spread of data points. Your power actually looks pretty consistent within that range. It's just that you didn't have any upper range points in that period at the end of the year.

The shift in right/left power balance does look more significant. I would be tempted to experiment with saddle height to see if it affects your power balance. for example you may be compensating for a lack of reach/mobility on one side.

GhostRider62

I second saddle position. Up/down and fore/aft. At least I see that for me. (the muscle that connects to the left ass bone is too short and gets sore, I need slightly lower and slightly more forward saddle than preferred....3-5 mm is enough to make a difference in both)

You did not happen to have COVID a year ago or thereabouts? I had it in early December and my power levels are way, way off still. Hoping to see a trend line like yours.

Hermes

In my case, I put the L/R 3 sec balance on my Garmin. And for endurance rides, I put more focus on the power balance and if I do, it is always around 50/50. At high power, the balance is always around 50/50. If I am just rolling around, my right leg does most of the work.

mschwett 

interesting. i will try that for sure. i’m not very flexible, hadn’t thought of it as a mobility issue, as opposed to a strength issue. the power data is a little hard to make heads or tails of, but that same pattern (the drop and recovery) is actually seen in a couple other places, like segment times and strava’s fitness estimate. so i do think it’s a decrease in performance of some kind, maybe just fewer good rides and more weak ones.

i actually did have covid, january 1, 2022. but it was so mild that other than skipping two or three days i just rode through it. it is possible that there was some effect in the longer term, but at the time i actually felt pretty good due to the elevated heart rate, which was extremely obviously on every ride that week or two.

i find it very hard to stay focused on my left side, but i definitely can concentrate it into 50/50 or higher for brief periods. i should move L/R onto the data screen i typically use.

thanks for the replies guys, food for thought.

RChung

You can often spot puzzles by looking at retrospective data but it's hard to solve them retrospectively.

1. What power meter are you using, and did anything change in installation or bike or shoes/cleats, or anything else around that time?
2. Can you extract the gearing you used during those one-hour periods?

mschwett 

meter is a 4iii precision pro, dual sided. it has been good but not perfect - the first few weeks of data with it are excluded here because quite a few of them were accidentally only one side or the other, producing huge swings.

i made some minor changes through the beginning of last year, went tubeless, had a bike fit which moved a few things a few mm. interestingly, just before the increase in power in november ish i went 10mm longer and 5mm lower on the stem. felt great immediately, so maybe it gave me an enthusiasm boost. otherwise the data series is basically from when i felt like i had the bike dialed in, with few equipment changes. same shoes and cleat position since the fit.

gearing, hmmmmm. not directly, i don’t have anything connected to the di2 that would record it. i think i’d have to do it manually in golden cheetah from speed and cadence. both my big and small cogs get a workout though, climbing and then descending. what would i look for there?

RChung

I was actually wondering more about cadence and crank torque (but gearing is related to that) to see whether your putative L/R balance was related to a change in them.

Basically, I was wondering whether this was a change in how the PM was measuring power and L/R balance, or if this was a change in you. It's always good to try to eliminate measurement error before you start thinking that there's something different about you.

mschwett 

i’ll look at the cadence data. i’m guessing any longer term averages will be thrown off by descents, but it would be interesting to compare cadence, speed, and power on the climbs that i know i always do in the big cog, since the relationship should be very consistent.

the meter doesn’t exactly instill confidence, but i’m not sure i can see it gradually reporting lower values and then gradually higher. i have excluded a ride or two where the data was very spiky, resolved by replacing batteries and cleaning contacts. fussy device.

RChung

I feel your pain. We buy expensive power meters so they can help us answer hard questions, not raise new ones.

PeteHski

When riding at endurance power with a normal cadence, leg strength will not be your limiting factor. So if one leg is working significantly harder than the other at that power level, then it will be due to some kind of mobility/fit issue that is preventing you from pedalling more symmetrically. I would start with saddle height and take a guess that you might be too high. I would suggest putting power balance in real time on your head unit and see how it varies with power (for example, most riders tend to subconsciously favour one of their legs at very low power when soft pedalling and then become more balanced at threshold power) and then experiment with saddle height changes. Ideally you want to get a 50/50 balance at your steady endurance power level. Or at least a bit closer than you are.

Edit: I'm presuming this imbalance is real and not a measurement error.

mschwett 

that makes a lot of sense - and it explains why as average power dropped, the imbalance became larger.

will lower my seat 2mm today. very exciting, haven’t moved it in a year 😂

mschwett 

so, i have to say i'm a LITTLE bit skeptical of my PM readings now.

the total always seems very believable compared to the range of reasonable values from bikecalculator (given that wind and grade can't be absolutely perfectly known), but today i made a conscious effort to watch the power balance and the left reading seems way low. even if i do a hard effort on the left leg, with the right leg essentially just being spun around by the crank (clipped in), the balance only goes to around 55/45, maybe 58/42. the opposite is not true, if i just let the left leg go along for the ride, it goes over 40/60, and then some. on top of this, i'm still struggling to find the sort of a once-per-revolution "tick" sound from the BB/crank area that is often stronger when pedaling primarily on the left side. shop is stumped, the most likely suspects have been eliminated, but i'm starting to wonder if something in the crank, attachment of crank to spindle, etc, is both ticking and throwing the PM reading on that side off by 10%, accounting for some of the pedal imbalance.

any all out, out of the saddle, 750+ watt effort shows 50/50, 49/51, 51/49 pretty consistently though, so *maybe* this is just a physiological thing? i've moved my seat down 2mm, have to say i can't tell yet.