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External stability; the case for machines

Updated: Dec 30, 2022

What is External Stability?

External stability refers to the stability that is provided by something other than you body itself. This can come in a variety of forms and may be as simple as holding on to a squat rack when performing a lunge or may be as complex as a fixed path machine (such as a leg press or pec deck). These supports reduce the internal stability that your body must generate to keep you from falling over or deviating from your desired movement pattern.

Why Does Stability Matter?

The external stability that is provided my machines is often criticized in fitness as it, “isn’t functional” and “doesn’t apply well to actual life”. These criticisms come from a grain of truth but often overemphasize the value of “functional” movements, especially when an individual’s goal is to just get stronger and look better. While doing exercises that require more stability may be more similar to real world movement requirements, they also limit our ability to exert force and therefore grow muscle. Training for hypertrophy (muscle growth) mainly comes down to our ability to exert significant force through target muscles. This can be difficult to do when we are unstable because our bodies limit our force output when we lack stability. Our body views stability as a fundamental prerequisite for maximal muscle contraction. A great example of this output limit is a bosu ball squat. If you try to do a simple bodyweight squat on a bosu ball, you will likely be surprised by how hard it is. Furthermore, if you try a max squat on the flat ground and then try a max squat on a bosu ball (don’t actually do this. It’s a really quick and stupid way to get injured), your bosu ball max will be far lower. When our output is significantly limited by stability, it is unlikely that we are inducing much, if any, hypertrophy.

Implementation into a Hypertrophy Training Program

So now that we know that stability is important, we need to address its proper implementation into a hypertrophy program. While it would be an easy leap to simply use all machine exercises, there is more nuance to this problem. Machines provide stability but they don’t always fit an individual’s body and may become stale overtime. Free-weights, cables or bodyweight exercises allow for far more flexibility in both execution and general programming. Modifying the angle of a dumbbell to fit your body is often far easier than modifying a machine. Additionally, only using machines may not provide you with much variety in your movement patterns and could potentially lead to overuse injuries. For these reasons, we recommend that you use a combination of both externally and internally stabilized exercises.

When performing internally stabilized exercises, it is important to practice the movement over multiple weeks before pushing intensity too high. When intensity is increased on these exercises, keeping at least one rep in reserve (ie from failure) is likely a good idea so you don’t risk injury due to form breakdown. Externally stabilized exercises are safer to push to higher intensities and are often useful when you are not focused enough to perform an internally stabilized movement (periods of sleep deprivation or significant weight loss for example).

When performing internally stabilized exercises, there are also ways to add a component of external stability. Use one arm to support yourself during your lunges. Make sure your feet are firm on the ground during your bench press. Opt for a back supported overhead press as opposed to standing overhead press.

In a single session, internally stabilized exercises should be performed before externally stabilized exercises because they require focus and may suffer if the target muscle and nervous system are already fatigued.

In summary, external stabilization should not be seen as a crutch, but rather a tool that can be used strategically to increase muscular output. Used in the proper context, external stabilization can allow us to increase the force we can put through a muscle, and therefore increase muscle growth.

Connor Crouse, PN1, PTS

Head Nutrition Coach

KPCC Coaching

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