Sport-specific exercises to recruit more muscle

'Run tall,' and let the rest hang loose  Credit: Simon Bruty/Allsport
In October, when we get out all of the stuff for Halloween, I start eyeing the cardboard skeleton that hangs on the front door.

Its a pretty simple lever system. If you take a bunch of rubber bands and attach them to a cardboard skeleton (just like your own bag of bones), youve built a muscle.

Each rubber band can be thought of as a muscle fiber only the real ones are microscopic.

If you pull on a rubber band, you act as the nerve that fires a muscle fiber. When you move, its just muscles pulling on bones. The nerves tell which muscles to pull.

When your muscles pull faster and with more force, your bones go faster and you become faster and more powerful.

New recruits
Of course, there is a trick to pulling faster and sustaining that speed. It all gets down to the motor units that you recruit.

A motor unit is a nerve and the muscle fibers that it fires. We all have varying blends of fast-twitch and slow-twitch muscle fibers. Part of your fiber-type distribution is determined genetically, and part of it is altered by training.

A muscle contraction involving predominantly slow-twitch fibers uses oxygen and can use lactic acid as a fuel source. Fast-twitch contractions use carbohydrates and produce lactic acid. They are faster and more powerful, but these contractions tire you out faster.

But there is no difference in the force of contraction between individual muscle fibers. You just recruit more of them to go faster. The power of a fast-twitch contraction lies in the number of fibers activated.

A slow-twitch motor unit will have a ratio of up to 1:300, meaning that the nerve activates 300 fibers. But a fast-twitch nerve can fire up to 2,000 fibers. Because of this, untrained fast-twitch fibers can dump a whole lot of lactic acid into your system, quickly.

Recruitment order works in a system of first recruiting slow-twitch units, and then as you go faster or require more force, recruiting the fast-twitch units.

If you go fast often, those fast-twitch fibers learn to work in an endurance capacity. They begin to take on slow-twitch characteristics and become lactic-acid consumers. Motor units are very adaptable.

Once this has occurred, you establish a whole set of new paces at different effort levels. In other words, you can run faster at a lower effort without succumbing to lactic acid buildup.

In training, we need to recruit these additional units on a regular basis.

Weights increase your recruitment capabilities, but the movements arent specific to your sports. So, a combination of weights and short intervals and sprints adds up to the most motor-unit recruitment.

The first thing is to just simply get them going. The following sport-specific workouts can get you on the right track:

Running: Power is built with short intervals and hills. It is the force at push-off that makes you go faster.

  • Start with 2000-meter repeats at about 20 seconds per mile faster than you can currently run a 10K.

  • Hill repeats of a minute and two minutes develop the force you need. Your recruitment is much higher on a hill, so that when you run on a flat and recruit far fewer units, it feels easy.

    Cycling: Successful bike riders have huge power reserves. That is, they can produce far more power than their normal fast riding requires.

    So, someone who can do 500-watt sprints can sustain 300 watts far more easily than someone who can only do 400-watt sprints, even if their aerobic capacities are the same.

    Sprinting for 20-30 seconds will help to build this reserve, or the ability to call on extra units.

  • First start with 20 second sprints with a minute-and-a-half to two minutes of rest in between each effort.

  • After a few weeks, see if you can hold the same power output for 30 seconds.

  • Hill repeats of two minutes help to build the units for the extra force that you need to sustain higher power outputs later in your training and during a race.

    Swimming: Power in swimming is not quite as simple. You need to learn to recruit both less and more units.

    This is specific timing of motor units. People with efficient strokes have their muscles contract at just the right time during the various parts of the stroke. Less efficient swimmers just make themselves tired by recruiting muscles that dont supply any propulsion.

    There is time for some motor units to rest during recovery, which is why some fast swimmers can look slow until you check the clock.

  • First practice 50-yard swims with a long relaxed stroke. Work on relaxing each arm when it is out of the water and gliding on the outstretched arm under the water.

  • Then do sprint 50s with a minute or so rest between each to enhance the motor unit recruitment. To sprint, think about pulling harder, not turning over faster.

  • A slightly slower pace with 10-15 seconds rest, can teach an efficient endurance pace without losing stroke mechanics.

    But the real power in swimming comes in the finish of the stroke at the point that youre pushing back. You can really start recruiting extra units with a set of progressive or descending 50s in which each one gets a little faster.

    Its all just muscles pulling on bones. You have the muscles. All you have to do is teach them to move your bones faster.

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