Running Physiology – The State of the Art
Part 4 – Running Economy
By Richard
Gibbens
We have made some significant progress in our study
of the concept of VO2max, the most prominent theory of endurance
performance. Today we will be discussing running economy. As always our
focus will be on practical matters; what is running economy, what it
means, and can it be used to improve running performance? This series has
proposed some significant challenges to the theory of VO2max and lactate
threshold. Let’s see if it’s any different for running economy.
Running Economy
Running economy is a measure of the amount of oxygen an athlete uses at
any running speed. It was first suggested in the 1930s that athletes might
use markedly different amounts of oxygen while running at the same speeds.
It was thought that this difference in oxygen consumption, or “running
economy”, could be a major factor in explaining differences in running
performance even though VO2max was essentially the same amongst the
competitors.1
For example, let’s say you and I are together on a training run, we are
running along at 7:00 minutes per mile, and we have the same VO2max of 65
ml/kg/min. Based on just that information it would be expected that we
would both be putting out the same level of effort, would be running at
the same percentage of VO2max, and would have the same running pace at
VO2max.
However, during a 5k race you can maintain a 5:00 minutes per mile pace,
while the best I can do is a 5:30 pace. If we have the same VO2max, why
are you able to run so much faster than I? The answer provided by
physiologists is running economy.
In my example above, physiologists would say you are more economical than
I. At any running pace, your muscles use less oxygen than mine. That means
that it takes less effort and energy for you to run along at our 7:00
minutes per mile pace than it does for me. And since you use less oxygen
for any running pace, you are also able to achieve a higher pace at
VO2max. Running economy is similar to fuel economy in your car. If you get
more miles to the gallon than I, then at any speed you are using less
gasoline than I.
Running economy answers two major VO2max challenges. It answers how you
can run farther at a given pace (answer: that pace is an easier effort –
the easier the pace, the further you can run at that pace) and it answers
why you have a faster pace at VO2max (answer: greater economy equals a
faster pace before reaching VO2max).
That naturally leads us to the next question. What makes you more
economical than I? Unfortunately, physiologists aren’t sure. There have
been various suggestions put forth, but none have been proven. Some
indirect evidence suggests it may be related to the distribution of muscle
fiber types an athlete may posses.2 Additionally, physiologists can’t tell
you exactly how to improve your running economy either. We do know that
running economy seems to improve slightly with training, but the specific
kinds of training which improve it are anyone’s guess.3
In any case, some factor other than oxygen consumption is at work here.
These unidentified factor or factors are playing a pretty big role in
performance. I think it was ingenious for physiologists to tie these
unknowns back to VO2max. They needed a way to account for runners with
lower VO2maxs outrunning those with higher VO2maxs and the concept of
“running economy” fit the bill. Since the cause of different running
economies is not known, physiologists could employ this concept and still
propose that oxygen consumption was the true limit to endurance
performance.
Now we come to the big question. Is the concept of running economy valid
and is it related to VO2max? First, there is no doubt that there is
considerable variation in oxygen consumption in any group of runners. That
fact is not disputed. Is running economy related to VO2max? It is only in
that it is simply a measure of how much oxygen you are using at any
particular pace. However, just because you use more or less oxygen than I
to run at some pace doesn’t mean that oxygen consumption is limiting your
performance.
Running economy is currently controlled by an unknown factor or set of
factors. It is these unknowns that determine the pace at which you run at
any level of oxygen consumption.
Physiologists say that if you can improve your running economy you will
run faster and you will do so without any improvement to your VO2max. You
could improve performance by improving running economy and never improve
your VO2max. If you stop and think about it for a minute, it’s as if
VO2max isn’t important, only running economy.
Doesn’t that suggest to you that whatever factor(s) control running
economy are what limit you in races of 5k and beyond, instead of VO2max or
lactate threshold limiting you? I submit that linking running economy to
VO2max has enabled physiologists to continue focusing on VO2max and
lactate threshold and has kept them from adequately exploring other ideas
on performance limitations.
The main counter argument that can be made is to say that if you increase
your VO2max or lactate threshold you will be a faster runner, and then you
wouldn’t have to worry about running economy. My response to that argument
is to ask this question; Does increasing my VO2max or lactate threshold
make me a faster runner or does becoming a faster runner increase my
VO2max and/or lactate threshold? That is a crucial question which we will
address next.
Till then keep on running.
References:
1. Noakes, T (1991). The Lore of Running, 25-27.
2. McArdle, Katch, Katch (1996). Exercise Physiology, 168.
3. Pfitzinger, P; Douglas, S (1999). Road Racing for Serious Runners, 38.