Posted by: SLS | September 2, 2010


Physicality and motor function is highly driven by “training”, or usage. Unlike machines, a human body improves with use, but high mileage spells ill fate for both man and machine alike.

When you increase your efficiency, in terms of exercise, you are expending less energy for the same amount of work. Over time, this is what training will do, which is why it is important to keep up progression with overload (a physical training term that indicates the stress placed on a system to elicit adaptation). An efficient muscle needs to recruit less fibers and less neuronal signaling to get the job done. While this is beneficial in some ways, certainly for the endurance athlete, it actually lowers or “prunes” away the overall potential of the motor units. If you train so that your body maximizes efficiency, needing less energy, less muscle, and less motor units to perform a given exercise, then you reduce your capacity to progress or adapt to a new or more challenging version of the exercise.

An endurance athlete strives not to be as adaptive as possible, but as efficient as possible. This is all well and good for the sake of the sport, but for the sake of the human subjected to the sport, I beg to differ. As Art De Vany puts it in one of his most memorable, and my personal favorite, quotes, “When the most you can do equals the least you can do, you are dead.” A distance runner is simultaneously doing the most he/she can do (running long distances) and accomplishing it (or attempting to) with the least amount of expended effort. By De Vany’s logic, increasing your room for adaptation essentially distances you from death, so training the slow-twitch metabolically efficient muscle a-priori actually lowers your maximal capacity to perform work. To relate this to the muscle, you want to keep your body guessing, and let it develop the flexibility to be ready for any movement, load, frequency, or intensity. At any given time, you want to be able to activate maximal motor units stimulating maximal muscle contraction, but to also do it in such a way that energy is not wasted. It’s a sort of adaptable, plastic system packaged in efficient wrapping.

So, what happens when muscles and motor pathways aren’t used? They get pruned. Pruning neurons can be good. A large part of motor development from infancy to childhood is the pruning of extraneous nerve pathways in favor of the connections that get the most stimulation. This is why infants, toddlers and children go through a long period of coordination development. They are solidifying the essential motor pathways to give them strength and agility to perform tasks such as walking, running, grasping, throwing, etc. Pruning increases coordination, strength and reaction time. What’s left to us in our developmental maturity is perpetual plasticity, our evolutionary legacy. We depend on this plasticity for further and future adaptation, and you should utilize this plasticity to get the most out of your life, your body, and your sport.

In sum, take off the miles, pump out the intensity and variation. You are not a machine, built to perform repetition, but a human, built to adapt.



  1. Great post, brother. I like the pruning the tree analogy. I think this helps explain the downfalls of over doing long distance cardio in an effort to stay “in shape”. Especially when you are not a serious endurance athlete.

    • Thank you so much for your response. Rereading my post, I would probably amend a few things, but on the whole, I think the pruning description is an accurate portrayal of how neurons enhance or inhibit signaling and growth based on stimulation. I agree that part of the problem with cardio is the steady-state factor and that everything it signals is for the body to catabolize itself and inhibit regeneration in favor of conserving energy. Best, -SLS

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