Economy of Peformance

This sounds like a good summary, from John Hughes at the UltraCycling.com website.

Economy of performance improves as a result of:

1. a higher percentage of slow-twitch muscle fibers;
2. low body mass;
3. low psychological stress;
4. light, aerodynamic equipment;
5. proper bike fit;
6. low frontal area;
7. eliminating energy-wasting movements;
8. efficiency off the bike.

Edmund Burke at Carmichael Training says cycling economy as important a factor as VO2 max and lactate threshold values "to determine fitness and efficiency of effort." He discusses pedaling mechanics, the value of the interval and tempo training such as we're assigned in our Computrainer sessions, and miscellaneous factors that affect economy:

Fighting the bicycle, holding the handlebars too tightly, using a lot of upper body energy while climbing and riding in an unaerodynamic position during time trials or break-a-ways will affect your economy.