"Economy" vs. "Efficiency" - which is it?

Terms "economy" and "efficiency" are often used interchangeably in the field of sport and exercise. Are they really the same?

The need for elucidating the exact meaning of the terms is needed for better understanding and communication between sport, exercise and other related experts.

Economy - refers to the energy cost of an exercise condition.

Efficiency - the mechanical energy produced relative to the metabolic energy expenditure

For example;

The VO2 during running is often termed “running economy” or “submaximal VO2”.

A person with a lower running VO2 for a given pace has better economy. Conversely, if a person requires a smaller increase in VO2 during a change in running pace, then that person has better efficiency. Economy and efficiency can be related, but the terms should not be used interchangeably.

Another term that is strongly connected to measurement of efficiency is "kinetics"

- (for ex. VO2 kinetics)

Let's say you are a runner who wants to know how efficient his running pattern is.

What you can do is a spiroergometry testing on treadmill in which you will be calculating the difference between VO2 consumption on two different speeds. If you ran 10km/h and suddendly accelerate at 15km/h then the difference in VO2 consumption between those two levels will be what you want to calculate.

- you can find out more at: http://www.unm.edu/~rrobergs/426L11IndCalorim.pdf