do you trust spin scan?

[david]

according to spin scan, i'm more efficient with my left leg but more powerful with my right - in a stabbing kinda way. more peaky on the downstroke, if that makes any sense.

efficiency numbers are typically 72/65, left/right.
power % is 48/52-ish left/right.

i'm not way off, but off enough so that if i try to create symmetry according to spin scan then i'm doing things that feel a bit forced - a little more pulling up on the right side and staying with it over the top.

am i creating symmetry or fighting nature?

should i just ignore it?

[toaster]

The makers of Spin Scan may have designed this application back when conventional wisdom said that a cyclist ought to pedal in circles and actively pull up on the upstroke.

Now, current theory seems to insist that the more powerful muscles that power the downstroke actually do the lifting of the opposite crank arm and that any voluntary attempt to engage pulling muscles on the upstroke actually takes away power.

I'm not sure how Spin Scan can account for this, but whatever the scope on Spin Scan shows, the two sides should be equal. The only debate, ATMO, is whether the shape of the Spin Scan profile is round or ovalised.

[Ti Designs]

according to spin scan, i'm more efficient with my left leg but more powerful with my right - in a stabbing kinda way. more peaky on the downstroke, if that makes any sense.


Makes perfect sense to me. The Computrainer only has two inputs, speed of the rear wheel and a crank trigger to establish the interval. It uses changes in rear wheel speed to claculate force on the pedals. It can't tell if power is being supplied from pulling up or pushing down, the only thing it can tell is consistancy or inconsistancy in the rear wheel speed. They make assumptions, which go along with what I tell my own coaching clients. They assume the big muscle groups supply the power, which is true. If your hip flexors are 1/10th the strength of your glutes you're a mutant. But activly firing the hip flexors can change the efficientcy of the pedal stroke. There's this thing called reciprical inhibition, the body's way of keeping you from firing opposing muscle groups at the same time. When you fire the hip flexors your brain shuts down the glutes. Having the glutes relax as the pedal comes up is the basis for efficientcy in that part of the pedal stroke. Now back to the Spin Scan, it reads efficientcy as any slowing down of the wheel. This could be a range of motion problem, it could be firing the glutes while the pedals are on the way up, it could be a leg lenght issue - I'm not in a position to make that call.

[Too Tall]

Yeah, I do trust spinscan it is quite diagnostic. There is alot you can do.
No question I can show people what happens to the plot when they modify their pedal stroke eg. heels down or when they push back in the saddle or pedal knees out/in. Soooooo this is just another arrow in your quiver, it's a tool that graphically displays what happens if "I do this or that" ok?

In the above context it makes a very decent method for validation before and after setup changes. It's a pretty lousy representation of how well you pedal unless your setup is really bad or your pedal stroke is just gawdawful due the the fact folks will correct their pedaling to "make" the output "better" and trust me I do that even if I know I'm trying not to!!! How to prevent that...I dunno maybe turn the monitor away from the rider???

Bottom line I don't like this when used to teach a better pedal stroke.