VI

Variability index. A ratio of NP to Pavg for your ride.

pdr said:

Sorry for the remedial question here. I'm using WKO+ and seem to understand most of the charts. A few of the numbers are not explained and I was wondering if someone could help.
"VI" in the summary box. I am clueless as to what this is.
"Pw:HR" "Pa:HR" I know what the letters stand for but what are their relevance?
TSS and IF I understand and there is a lot of reference out there for them.
Thank you,
Paul

As jollyrogers said, VI is variability index or how bursty vs. isopower your ride was. Steady power rides or steadily ramped rides tend to have AP very close to NP which yields a VI near 1.0 where more random bursty rides like criteriums or sporty group rides typically have NP >AP and VI >1.0.

Pw:HR and Pa:Hr are relationships between Average Power and Average Running Pace and Heart Rate and were added to WKO+ a while back to support the notion of 'Heart Rate Decoupling'. I dug out my old HR strap when they introduced that feature and paid attention to that metric for a while. Even under the fairly controlled circumstances where it's supposed to tell you something (iso power L2 ride segments) mine was all over the map, often highly negative and didn't track fitness, peaking, establishment of sufficient base or any of the other stuff it's supposed to predict. AFAIC it's a dubious metric and certainly not applicable to a run of the mill ride and at best something that might make sense to display in conjunction with a specific test segment, not displayed for all rides and all captured 'ranges' on the main page. I don't run, nor capture pace data so I never used the Pa:HR metric but I'd be equally suspicious of its value.

-Dave

pdr said:

"VI" in the summary box. I am clueless as to what this is.

You know how they use "Pw:HR" or "Pa:HR"? VI is simply "NP:AP".

Thanks everyone.
Paul