Data points for determining Delta efficiency using power and VO2


New Member
Feb 27, 2007
Yeah, a little esoteric, but I know there are a few lurking that know what I'm talking about.

I work with power with my clients, and work with a partner who tests VO2 max. I'd like to add mechanical efficiency and delta efficiency to the metrics that are tested and measured. VO2 max, on it's own, is pretty limited in what it can tell me about an endurance athlete. VO2 Max, plus power at VO2, on the other hand, offers some intriguing possibilities for measuring and comparing different athletes and determining strengths and weaknesses relative to efficiency. question....what are the accepted data points (if there are any) for measuring delta efficiency, which require two to measure the difference between the two wattage numbers and then divide the difference between the two O2 numbers?

any takers?


Well-Known Member
Oct 3, 2006
I'm not sure there are established standards for delta efficiency measurements. The only studies I'm familiar with that looked at delta efficiency defined the measurement points based on some particular study parameter like cadence or LT vs. VO2 Max or other points of interest to the study.

There's a lot of good references to studies that looked at delta efficiency here:,%20cycling%20experience,%20and.pdf

I don't know if you'll find what you're after there but it does seem the study linked showed that more highly trained cyclists had higher delta efficiencies at least as a function of cadence than less trained cyclists. Not sure if that gives you the additional metric you're after but it sounds somewhat related.

Seems to me like you'd want GME at VO2 Max and perhaps GME at rest or GME at 1mmol lactate or perhaps the common 4mmol proxy for LT or something like that as anchors for your delta measurement. But I sure don't know of research that ties specific deltas to fitness, lack thereof or yields physiological clues that might help guide future training.

It's definitely an interesting question, I'd be curious what you find out if you start taking a known second GME test and tracking deltas.


Alex Simmons

Mar 12, 2006
can you not just plot VO2 (L/min) v power during a VO2max test, and take the slope? VO2 presumably converted to metabolic energy rate equivalent with 1 L = 20.2kJ


Aug 25, 2009
Isn't efficiency in a ramped VO2max test likely to be different to the efficiency seen on the road at the equivalent wattages in any case? People will reach VO2max at the sort of wattage they can maintain for 5 minutes on the road - how do we know that the efficiency of that VO2max is the same as the efficiency seen on the road given the different preceeding work etc.