African’s vs. Western Runners: Part 4:Muscle recruitment’s role:

Okay, so I lied slightly. Before trying to tie things up nicely and show how some of the previously mentioned findings can apply to your training, I want to mention one other topic. That is muscle recruitment.

We have already looked at the finishing kick in terms of lactate. What seems to happen is that the bigger gap between lactate before the kick, and the amount of lactate that could be reached at the end of the race, the better the kick. That means, we want to work in two directions, one to decrease lactate at race pace and two maintaining or increasing the total lactate which can be produced.

But this is just one part of the picture. What is going on during a kick in terms of muscle fiber recruitment. A recent study by Amann showed that there was an increase in fiber recruitment and power output at the end of a 5k cycling time trial. Despite the fact that the athletes were fatiguing, they were able to increase power at the end, just like a runner being able to increase speed at the end of a race. What they found is that the increase in power output corresponded with an increase in EMG, which is a measure of muscle fiber recruitment.

What does this mean? That the ability to increase speed at the end of a race is also dependent on being able to recruit more muscle fibers. And if we tie this back to the increase in lactate at the end corresponded with an increase in speed, it makes perfect sense. The increase in muscle fibers at the end probably results in this lactate increase. Why? Because, these fibers recruited at the end are probably the higher threshold/harder to recruit Fast Twitch fibers. These fibers work much better anaerobically, but fatigue quickly. So, recruiting these fibers at the end, will result in an increase in lactate, the end product of Glycolysis.

At the end of the race, your body is becoming overwhelmed with fatigue and shutting down fibers that are fatiguing left and right. The ability to recruit additional muscle fibers to maintain or increase pace is of critical importance.
Combining the lactate and EMG data, we can make an assumption that one of the reasons that those Kenyans could increase their lactate and their speed was because of this ability to increase muscle fiber recruitment at the end.

Quick sum up of what we want to do:
1. lower lactate at race pace.
2. maintain/increase max lactate at the end of race.
3. Increase muscle fiber’s an athlete is able to recruit overall.
4. Train the athlete to recruit these fibers during fatigue.

Next, we’ll look into practical applications of all of this infortmation.
Amann M, Eldridge MW, Lovering AT, Stickland MK, Pegelow DF,
Dempsey JA. Arterial oxygenation influences central motor output and
exercise performance via effects on peripheral locomotor muscle fatigue in
humans. J Physiol 575: 937–952, 2006.


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    1. Bill Blancett on March 2, 2009 at 3:04 am

      Good stuff Steve. All you need is a lab and some runners to test your theories. Then you could publish your results.


    2. stevemagness on March 2, 2009 at 3:30 pm

      Thanks Bill. I’m actually trying to do my master’s thesis on my little kick theory. Hook some guys up to EMG to measure muscle recruitment and get some lactate readings before and after the kick. Compare that to the change in speed in the subjects during the kick and I think we’d have some interesting data that is actually usefull.

      I make my pitch to my professor on wednesday so we’ll see.

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