Training Tip Tuesday #7- A Look at Running Economy: Part 1

Ahhh running economy. That elusive, mystic enigmatic variable we have heard reference to but aren't quite sure exactly what it means. We shall attempt to delve into the intricacies of this nebulous term and hopefully come out better informed and wiser on the other side. In this post I will do my best to explain the definition of running economy, what it measures and the implications thereof.

Much of the information on running economy I will present today comes from a review article titled, "Factors Affecting Running Economy in Trained Distance Runners (Saunders, Pyne, Telford & Hawley 2004)." In their article, Saunders et al., summarizes the information on running economy gathered from over 100 pieces of literature. For the purposes of this post I will be mainly referring to the Saunders, piece. If you have questions about the other sources and references please feel free to contact me and I will be happy to provide the references for you.

What the deuce is running economy, you ask? Well, allow me- "Running economy (RE) is typically defined as the energy demand for a given velocity of sub maximal running." Say whaaa???? To put it more simply, running economy is essentially how much oxygen we use to run at a given speed. RE is measured at a much lower speed than maximal intensity because it's not very applicable to see how efficient we are with oxygen while sprinting. The reasons for this are 1) because sprinting 100m has little to do with the aerobic energy system and 2) because we don't sprint a 5k, 10k or marathon off the bike. It is much more applicable to find out how efficient we are with oxygen while running 10k pace or half marathon pace than running 4:00 minute pace for 200 meters.

An example protocol for testing RE would be to have all subjects perform a 10min run at 8 mph (7:30 pace). During this run the subjects VO2 and respiratory exchange ratio (RER) would be measured. (RER shows what percentage of fat versus carbohydrate our body is using for fuel. An RER of 1.00 reflects 100% carbohydrate utilization to fuel the working muscles). Having better running economy basically means that we need less oxygen to run at a given intensity. I don't know about you but I'm all for conserving every spare O2 molecule I have when I'm racing hard trying to beat the fellow next to me.

This helpful little graph from the Saunders paper shows how two elite level runners can have nearly identical values for their VO2max but have drastically different running economy (and different 10k times).

With RE it isn't about how fast or how far you can go, or how high your VO2max is, It's about how efficiently you can use the resources (oxygen) you have while running at a given intensity.

This is important because racing is all about efficiency. The goal of a race is to get to the finish line as fast as we can. Now, if we can conserve energy by being more… dare I say economical? This will allow us to go faster at the same level of effort.

To put it another way- lets say my "threshold" intensity is 50 mL of oxygen per kilogram of body weight per minute (mL/kg/min) and I can run 7:30 pace at this intensity. If I can improve my running economy so that I only have to use 45 mL/kg/min of oxygen to go 7:30 pace, that means that I can now bump my intensity back up to 50 mL/kg/min (my threshold) but I'm now running 7:15 pace instead of 7:30 pace. I'm running at the same intensity but my pace is faster at that intensity because I'm more economical That means I'm going faster and more likely to beat you!!

Hopefully this exiguous attempt at analyzing running economy was somewhat enlightening and didn't confuse the issue more. Next week I'll discuss ways we can improve running economy. In the meantime feel free to chime in with comments, questions, complaints or disagreements you may have.

Until next time!

Saunders, P. U., Pyne, D. B., Telford, R. D., & Hawley, J. A. (2004). Factors affecting running economy in trained distance runners. Sports Medicine, 34(7), 465-485.