Negative Variability Index

Racing ZwiftPower Community
1

Hi - I did the L39ION LA Series Orientation Ride last night. I had a Power output of 216W - but my Normalised Power was set to 192 and the Variability Index was -11%. I was also placed last - which although not that much of an issue - made me wonder of the two facts are linked. I finished pretty well in the middle of the field of 730 riders.

My understanding is that Normalised Power should be greater than actual power -so confused both my that - the negative VI - and how it could have happened. The Source was a FIT file and 216w - fits with what was displayed on the screen when i finished. Anyone able to shed any light on this.

Many thx

2

This should explain it.

1 Like
3

I would say that such a large discrepancy is probably indicative of a bug in the calculation, unless the rider was behaving very unusually. If the timing was out, maybe the integral of squared power was just divided by the wrong number! IIRC, normalised power is basically RMS power (with the 30s smoothing that James referred to).