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Muscular endurance linked to running economy

June 26th, 2011

I blogged a few weeks ago about a study on strength training and cycling efficiency, and a commenter asked why so many of these studies are done on cyclists rather than runners. In response… here’s a interesting running study, just posted online at the Journal of Strength and Conditioning Research, that looks at muscular endurance and running economy.

The question they set out to ask was: does having better muscular endurance allow you to maintain better running economy (i.e. burn less energy while running at a given pace) as you get tired? To test it, they asked 10 well-trained runners to do two 30-minute runs at a moderate pace. In the middle of one of the runs, the runners had to speed up to VO2max pace for four minutes, then slow back down — enough to tire them out a bit without exhausting them. As expected, their running economy got worse after the four-minute surge by 3.0%. This is typical: as runners get tired, their running economy gets worse.

What remains hotly debated is why, exactly, running economy gets worse with fatigue. I’m not going to delve into the details of all the various mechanisms that have been proposed to explain this — it’s almost certainly caused by a mix of many different factors. One possibility relates to your knee flexors (a.k.a. hamstrings and surrounding muscles on the back of your leg above the knee) [UPDATED 6/27: had mistakenly written knee extensors], which contract eccentrically to act as a “brake” during each stride. There’s some evidence that eccentric contractions decline more quickly than concentric contractions during exercise — so as that braking action gets less effective as you fatigue, your stride gets less efficient.

Okay, now we finally get to the point. The researchers also tested the eccentric muscle endurance of the knee and hip flexors and extensors of all their subjects, then looked for correlations with the running economy results. Sure enough, they found that eccentric knee flexor endurance was “strongly related” to how much running economy worsened after the fast section of the run. Bingo!

So what does it mean? Well, there’s a big chasm between saying “hamstring quad endurance and running economy changes are linked” and concluding “therefore, you should do X, Y and Z in training.” However, it’s not crazy to see this as a good argument for some lower-body strength training and plyometrics. Here’s what the authors conclude:

Our results suggest that coaches and athletes could effectively implement conditioning strategies that challenge eccentric muscle actions. These strategies include plyometrics, resistance training with an emphasis on eccentric portion of repetitions, down-hill running and over-speed training.

 

  1. Will
    June 26th, 2011 at 17:38 | #1

    The interesting thing to me is that people only view this type of work as possible via strength training, when more specific options like sprinting or short, intense, hill repeats as examples can work the same way.

  2. June 26th, 2011 at 18:50 | #2

    Thanks for heads up on this study. I’m summarizing as well with a link to your post and just wanted to confirm: Did you mean knee flexors and hip extensors? Thanks, neil

  3. alex
    June 26th, 2011 at 22:29 | #3

    @Will: Agreed — as the last sentence points out, “down-hill running and over-speed training” are both suggestions that the authors make.

    @Neil: Doh! You’re right, of course. Stupid mistake, now corrected above.

  4. June 26th, 2011 at 23:53 | #4

    Very interesting study,

    You said “quad endurance and running economy changes are linked” whereas in the study and the rest of your article you’re talking about knee flexors.

  5. alex
    June 27th, 2011 at 02:02 | #5

    @Thomas Johnson
    Thanks, Thomas. Yes, as indicated in the comment above yours, I had it backwards when I first posted. Hopefully I’ve fixed it everywhere now — but if not, please let me know!

  6. Will
    June 27th, 2011 at 14:05 | #6

    There was a neat study around 1999 to 2001 as I recall, also in the Journal of Strength and Conditioning Research looking at tripple jump performance and a short maximal run, I want to say 200-400 yds (cant remember) and how they related to performance in either 5 or 10K running races. (clearly I should have looked it up prior to noting it here :) ). I think you would like it relative to this line of posts. the tripple jump predicted performance quite well. That was a good paper also.

  1. June 26th, 2011 at 20:43 | #1
  2. June 27th, 2011 at 14:05 | #2