Muscle Action vs. Muscle Function

At the start of the year I attended the Muscle Camps Seminar with Dr. Jordan Shallow and Ben Pakulski. It was an incredible day with a lot of key take homes. After listening to Ben discuss the benefits of meditation and focus I downloaded the Sam Harris ‘Waking Up’ App and haven’t looked back since. Jordan’s presentation on ‘Mobility, Stability and Strength’ added depth to many of the key concepts we teach at Strength Culture to the lifters and coaches we come in contact with. This blog is to discuss one of the points raised by Jordan regarding Muscle Action and Muscle Function, how they differ and how it can alter the way in which you train for certain outcomes.

Out angled on all fronts.

Out angled on all fronts.

Muscle Action - The muscle origin pulling on the muscle insertion. When training for strength and hypertrophy, muscle action is of highest importance.

Muscle Function -  How the muscle integrates into the global stability demand of the system. When aiming to improve stability outcomes, muscle function is of highest importance.

In our educational streams we taught this same concept, however, Jordan’s way of categorising the 2 different musculature demands was new to me and we have since altered how we define these outcomes of ‘strength’ and ‘stability’.

The easiest way to understand this is when talking about the core musculature. Most people are aware that the best way to integrate core training into your strength and conditioning programs is through ‘anti’ movements - anti extension, anti rotation, anti lateral flexion etc.

The Pallof Press trains the core musculature’s function of ‘anti rotation’.

The Pallof Press trains the core musculature’s function of ‘anti rotation’.

This ‘anti movement’ is categorised as the core’s FUNCTION, which is to control these ranges through isometric and eccentric muscle contractions. Whereas, a sit up would be classified as training the muscle ACTION of the rectus abdominis, bringing the xiphoid process down towards the pubic synthesis. A plank or ab wheel roll out would be classified as training the muscle’s FUNCTION, controlling the desire to extend the spine/ thorax, or ‘anti extension’. In terms of transferability to sporting performance we are better off chasing muscle function outcomes of stability and controlled ranges rather than hitting the muscle action of trunk flexion with 100’s of crunch variations.

The plank trains anterior core FUNCTION by controlling extension moments.

The plank trains anterior core FUNCTION by controlling extension moments.

Another example would be the gluteus medius, a muscle that is often identified as ‘weak’ within the kinetic chain. The glute med has a muscle ACTION of hip abduction, hip external rotation (posterior fibres) and hip internal rotation (anterior fibres). Glute med muscle FUNCTION is to control the hip adduction moment when the centre of mass shifts laterally causing an adduction moment in the hip. This is best seen in the stance phase of gait cycle, where the centre of mass shifts laterally over the base of support as you stand on one leg. In this moment, the glute med must not only control the hip adduction moment but also control the internal rotation moment of the leg as the foot pronates towards toe off which drives internal rotation up the tibia and femur. The function of glute med is to control the opposite moments of which its action create - control hip adduction and internal rotation by creating hip abduction and external rotation force, the exact same as our core example above.

When the right leg is in contact with the ground the centre of mass shifts towards the right. This movement is controlled by the right side hip abductors and external rotators (glute complex).

When the right leg is in contact with the ground the centre of mass shifts towards the right. This movement is controlled by the right side hip abductors and external rotators (glute complex).

Training the glute med with banded crab walks and a myriad of hip abduction moments may be great to improve the ‘mind muscle’ connection or simply drive a hypertrophy outcome. However, if you desire to have hips that can withstand squatting and deadlift intensity without dumping into knee valgus you will at some point have to ditch the mini band and actually learn to control the relative positions of your femur and pelvis in standing postures against heavy external loads (gravity and barbells). The same way you wouldn’t program crunches to improve core stability and bracing for squats and deadlifts.

I am yet to come across a competent squatter who’s ‘knee valgus’ moment had been rectified with the use of a mini band. The real improvements to frontal plane hip stability during squats come from understanding to use the connection of your feet on the ground and your ability to brace effectively. The same way the lateral hip musculature was designed to function - anatomical structure dictates function.

At Strength Culture we use ipsilateral and contralateral loaded variations of split squat, lunge and 1 leg RDL/ deadlift variations to incorporate the frontal plane function (global stability demand) of the core and hip as discussed in this article. The offset loads manipulate the systems centre of mass and shifts it laterally, in the same way it does during the gait cycle, increasing the demand of the lateral hip musculature, adductor complex and core to stabilise and keep the relative hip and femur positions ‘optimal’, or at least whatever you deem to be optimal.

Contralateral and Ipsilateral loaded Bulgarian split squats - both challenge the ability keep the centre of mass over the front foot.

Contralateral and Ipsilateral loaded Bulgarian split squats - both challenge the ability keep the centre of mass over the front foot.

For anyone that doesn’t already I would recommend following Dr. Jordan Shallow (@the_muscle_doc) on his socials, YouTube and podcast (Movement Prescribed - Rxd Radio).

About the Author
Jamie Smith, Owner and Director of Coaching at Melbourne Strength Culture
IG: @j.smith.culture
YouTube: Melbourne Strength Culture

Email: jsmith@melbournestrengthculture.com