Running Economy and Age – the other factors, body weight, experience, lactate

In my last post on running economy, Are you too old to have good running economy I shared the results of a recent research article looking at the relationship between age and running economy.

You can find the abstract to that research paper, here

As mentioned, the purpose of that research was to “investigate the relationship that age has on RE and identify factors that influence RE in competitive distance runners.” In which their conclusion was that age was not a factor in running economy, that performance changes in running were more likely due to declines in “maximal and submaximal cardiovascular and hemodynamic variables and changes in muscle power”.

What I would like to do is look at some of the other factors measured within this study. With each variable, I will share a brief thought on it’s possible impact on running economy and performance.

Who was the population studied?

It is always important to review “who” were the subjects. We know the various age groups from the previous article, but what else do we know?

The subjects in this study consisted of 51 runners, 28 male and 23 female. They are described as “competitive distance runners” because they finished 1st, 2nd or 3rd in their age category at a large local 5k or 10k.

Why this is important for running economy? One assumption we can begin to make is that if the runner is placing within their age group at a competitive event, they are likely experienced runners. This is not always the case, but it is a general assumption I feel comfortable making. If the runner has experience running, it is likely that their running economy has developed to the point that they are near their best RE through training.

If the research would also have taken trained versus untrained subjects, I believe we would have saw a difference between those two groups. There would likely be a difference between “competitive” versus “non competitive” groups also. My assumption about the competitive versus non competitive groups is that despite age, the competitive group is doing the training they need to maximize their running economy, while the non competitive group may not be.

What were the measured physiological factors?

The subjects were all tested for heart rate max, velocity at lactate threshold, VO2 at lactate threshold, %VO2 at lactate threshold, heart rate at lactate threshold, % heart rate max at lactate threshold, and V02max.

When you look through these results, we find some things that we would expect in relation to age and performance. For example:

Heart rate max (HRmax) was different between the three groups. Young was 197 +/- 3.6, master was 183 +/- 2.2 and old was 170 +/- 6.2 Not a surprising outcome to see the heart rate maximums decrease as the age group got older. Also, VO2max was different between the old and young, old and master – but there was no significant difference between young and master groups.

Other expected results were that the velocity at lactate threshold was different between all the groups. One reason that this result should be expected is that velocity at lactate threshold is one of the best predictors of endurance performance, other than run performance itself.

As we saw from the last article, while the running economy was not significantly different between the groups, race performances were different. We can see from this data once again that velocity at lactate threshold is a good indicator of race performance.

These cardiovascular and metabolic results remind me of a phrase that used to hang around the slowtwitch forums for some time given by Andrew Coggan, “Fatigue is biochemical, not biomechanical”.

What does my body fat have to do with running economy?

When you look at the subjects, I think that this is one major factor that should not go undisclosed – body weight. Body weight is a big factor when calculating running economy (kg of weight is part of the calculation). This makes sense, it just takes more energy and effort to move 130 pounds than it does 230 pounds.

Here were the findings from the research article,

“No differences among groups were observed for body fat % or body mass in our subjects”

I have discussed the relationship previously in an article titled, Why what you are eating is making you slow. But I’d like the share the Bobby Ross quote here again:

What they found was the Holy Grail to faster running speed. The old equation was still partially correct, but incomplete. It was missing the most important element – the Bodyweight.

There is no question that body weight is a big factor when looking at run performance. I have discussed these issues in my own training as I’ve looked at run performance, body weight/body fat %, running economy and V02 testing. Those articles are here:

- Body Composition Analysis – Why I hate this crap
- VO2max the good results

Relating this all back into our running economy discussion

The body weight of an individual is going to greatly impact a runner’s running economy. The runners in this study were all “competitive” distance runners and had likely maximized or settled into their optimal running form through training.

In the subjects tested, the body weights were not significantly different – neither were their measured running economies. This was true no matter what age group they fell into.

The performance differences among the groups are better accounted for by their differences in velocity at lactate threshold.

There are a couple other factors that remain to be discussed in this research article, they deserve their own discussion. Therefore, I will share my thoughts on them in my next post.