In article <
[email protected]>, "Andy Coggan"
<
[email protected]> wrote:
> "Tim McNamara" <
[email protected]> wrote in message
>
news:[email protected]...
> > In article <
[email protected]>,
> > "Kraig Willett" <
[email protected]> wrote:
> >
> > > For those interested in doing your own analysis on the power meter data that I collected for
> > > the following review (the big three power systems on the same bike for several weeks),
> >
> > Interesting. I didn't have time to scour your report, but I found myself wondering:
> >
> > 1. Did the SRM pick up "spikes" that were in fact not significant in terms of speed (e.g., one
> > really hard pedal stroke as you stood up on the right pedal on a steep hill). I guess I'm
> > asking if the device is overly sensitive to this type of input.
>
> Well, one way to look at it that all such "spikes" in power are significant in terms of your speed
> - after all, it's not like the extra energy is wasted. However, it is true that the SRM, PowerTap,
> and (to a lesser extent) Polar S710 can measure power on a much shorter time scale than may be
> necessary for routine use on the road. For other purposes, though, you need as much - or even more
> - temporal resolution as these devices offer.
>
> Personally, I find the default value of displaying a 3 second rolling average to be about right -
> anything significantly longer than that I find annoying, since it creates a discrepancy/time shift
> between what my legs tell me and what the display reports.
Which would be similar to the lag problem with heart rate monitors Kraig mentions early in his
article. OTOH, the power measurement could still be useful for something in training (I'm not really
sure what, to be honest- after all the winner is who gets there first, not who produces the most
power. Cipo has has more power than Lance, but Cipo ain't ever gonna win the Tour).
> > 3. Does chain tension reliably measure power?
>
> Yes - but the question really is, how reliably can you measure chain tension? The answer seems to
> be "well enough, but not in every circumstance".
Good point.