Monday, February 17, 2014

First experiment in L-R balance w/ Garmin Vector

After putting a box of kitty litter on my pedal wrench to precision-torque a pair of Garmin Vectors, then replacing one of the batteries (which was dead), I was ready to roll.

torque wrench

The goal was to ride over to Sports Basement in the Presidio, from where I was going to do the gorgeous run to Sutro Baths and back. It turned out to be a bit more of an adventure than I'd anticipated, including scaling this staircase out of Baker Beach. I don't recommend it, since it ends at private property, presently under construction.

The Sutro Baths were spectacular, however:

Here's the full thing, with an 800 meter distance shortfall due to my GPS crapping out on me and Strava interpolating a straight line through a very nonstraight trajectory. I love the instant upload from the Strava iPhone app, but the Garmin Forerunner 610 is likely more reliable.

This capped off a 103 km running week for me. That's a personal record. That risks being excessive. Less than one week to my 30 km race. So mini-taper into that, do a good run there I hope, then a full week of recovery before building back toward my 50 km goal.

But the ride to and from the run was the focus of this blog post. It was my first measurement of L-R power. The result was interesting:


In the exponential fit I weighted the points by the cube of the power, due to a relative shortage of high power points. There's also a running average where I binned the points into 10-watt bins and took the average of each bin, plotting versus the bin center-point. Also note I did a bit of one-legged pedaling, left and right, which showed up as 0% and 100% points. These points were excluded from the fit and the running average.

At low powers, it indicates right-leg dominance, but then at the higher powers, I converge to essentially 50-50 (51-49 in favor of the left foot). That's interesting. But it makes sense, perhaps. At low powers, when I've got no issues producing enough force, I choose one leg over the other. But at higher powers I need to use more of my available capacity, so I no longer have as much luxury of one leg slacking off.

Of course, I need to do more, including comparison to PowerTap to make sure the Garmin is set up properly, and examining data where my legs aren't trashed from running up and down staircases, of which the run today had many (most in better condition than the one in that photo).

1 comment:

Rainmaker said...

You officially take the cake on the best torque-wrench twist out there.