Trunk and Core Strengthening

It seemed like for a while the biggest fitness craze was core stability training with every fitness and rehab guru flooding the internet and social media with exercises using every combination of positions, movements, and equipment possible. I’m sure I saw someone doing quadruped bird dogs with ankle/wrist weights with a resistance band pulling them one way while maintaining balance on a BOSU ball that a buddy was unpredictably tapping to create perturbations on an unstable service. Yeah, exercises like that can be effective and meet the intent, but it doesn’t need to be that complicated. Additionally, oftentimes such exercises can be too challenging and complex for the “Average Joe”. In this article, we’ll dive into a simple way to progress trunk and core stability exercises. But first, let us quickly dive into a quick anatomy review and the why behind the importance of maintaining a strong trunk.

The trunk musculature can be divided into two categories based on their primary function: movers and stabilizers (note: each trunk muscle can have both a mover and stabilizer function but has a primary role of one over the other). The movers are the bigger muscles located more externally and primarily work to move the body in different directions. This includes the abdominals (flex the spine), paraspinals (extend the spine), and the obliques (side bend and rotate the spine). Stabilizers are deeper and function to maintain a spinal trunk position at rest and during movement. These include the transverse abdominis (TrA), quadratus lumborum (QL), and the lumbar multifidi (LM) muscles.

When looking at the trunk and reviewing its function, it helps to view the entire system as a three-dimensional cylinder around the spine and guts. The abs and anterior portion of the TrA comprise the front of the cylinder, the obliques with the lateral TrA fibers make up the outer walls, and the LM and paraspinals solidify the backside. Like a soda can, this cylinder also has a top (diaphragm) and a bottom (pelvic floor musculature). A healthy and properly functioning cylinder will be able to generate pressure against all walls within it, locking down and stabilizing the trunk during exertion (like the stiffness of a full unopened soda can). A poorly pressured cylinder will not be as strong and stiff (like the walls of an empty opened can). Now, the cylinder does not need to be fully pressurized all day, everyday but only when needed to complete the task. And the amount of pressure generated can and should be based on the demand. For example, generating 100% pressure and stiffness is needed for a max deadlift effort but not for picking up an empty laundry basket. Having an appropriately pressurized cylinder will reduce injury risk by maintaining proper mechanics and evenly distributing the force to the right load-bearing structures.

Now, how do we initiate a trunk strengthening program correctly with a good progression? There are certainly different strategies and approaches out there. For the most part, there isn’t a necessarily “right” or “wrong” way as long as the exercise and dosing is appropriate for the person. For example, it may not be a good idea to perform heavy deadlifts right away for a deconditioned individual with acute low back pain. I personally view trunk strengthening progression as a three phase process:

Phase 1: Isometric holds maintaining a static position for a designated period of time, starting with a shorter time then increasing duration to build endurance and confidence. Examples include front planks, side planks, and back bridges.

Phase 2: Build off the isometric holds from Phase 1 by incorporating an unweighted or minimally resisted dynamic limb movement. The purpose is to train the trunk to remain stable and strong while moving the arms and legs. Examples include bird dogs, dead bugs, and rolling planks.

Phase 3: This phase is where I introduce more dynamic movements and heavier loads to challenge the trunk strength and endurance. These are oftentimes referred to as more “functional” exercises as they replicate natural movements and carry over to tasks we commonly perform during the day. With these exercises, the trunk is usually not the primary focus or working muscle group but serves more of  a supporting role (but extremely important, nonetheless!). Examples include kettlebell swings, deadlifts, and weighted carries.

Check out the videos below for examples of this outlined progression for the lateral and posterior trunk musculature.

As you can see, phasing a trunk strengthening program like above helps progressively build up the trunk strength and endurance appropriately. It doesn’t seem smart to overload a patient or client with heavy deadlifts if they aren’t able to hold a basic unweighted back bridge for more than ten seconds, right? Overloading a patient or client too soon without the proper baseline strength and endurance will increase injury risk, aggravate an existing injury, create frustration, and/or compromise trust with the provider/trainer. Let’s train and rehab smarter!

This isn’t rocket science but hopefully seeing a phased trunk strengthening progression is beneficial for you. The goal is to start small and progressively build strength and confidence while keeping it simple!