This week I want to address the issue of a common strength deficit that leads to the dismantling of proper movement and impacts performance. I will tell you the mechanics as well as show you the exercises to correct this common strength imbalance.


Let's get into it. It's called: Sling Theory.

Foundation of a Strong Core

Not only do you need a good range of motion (mobility) but the ability to resist movement (stability) and to move correctly under external resistance (dynamic stability). The core is made up of the abdominals, gluteals, and lower back muscles. Since all other body appendages are connected to the core, it is necessary to have a solid core in order to achieve proper movement of the appendages without breaking down in form and becoming prone to faulty movements which leads to injury. One of the first assessments that I like to perform on an individual who is looking to strengthen core is the static sling stability assessment.


Sling Theory

There are many muscles that work together to creat fluid movements. These muscles cross joints, are held together by fascia, connect by ligaments and are anchored by tendons to the skeletal system. The nervous system is in charge of recruiting these muscles in the right order, and at the right time to provide us with the ability to switch from static resistance to fluid movement under under different resistances. In order to conceptualize sling theory we have to divide the body into four quadrants and visualize slings that work like straps that can be pulled on to stabilize, anchor, and create movement. There are four slings or straps that span diagonally across the shoulders to the hips on both the front and back of the body.

Tip From the Trainer

"Finding imbalance between these slings and balancing the strength and coordination of these slings will improve performance and is a primary concern for any strength and conditioning specialist." - Cory Schidler

Strengthen Your Core:

Anterior Oblique System

Basically this system tells us that the obliques help provide stability and mobility in gait. They are both important in providing that initial stability during the stance phase of gait and then contribute to pulling the leg through during the swing phase. This system is important in helping the body create more stability as speed increases in activities like sprinting, but also important as the body brakes and decelerates during change of direction. Exercises to enhance this system:
     -Staggered Kettlebell One-Arm Swings
     -Rear Leg Loaded Sandbag Shoulder Forward Lunge
     -Split Stance Around the Worlds

Posterior Oblique System

This system is also seen most commonly in gait. Where the glute max of one hip works with the lat of the opposing side to create tension in the thorocolumbar fascia. The action of these muscles along with the fascial system is thought to both fight the rotation of the pelvis that would occur during gait as well as store energy to create more efficient movement. Exercises to enhance this system:
     -Drop Step Bent-Over Row with Load in Opposing Hand
     -Cable Rows from Split Stance
     -Half-Kneeling Press with Load in Opposing Hand

Deep Longitudinal System

The DLS uses both the thoracolumbar fascia and paraspinal system to create kinetic energy above the pelvis, while the biceps femoris acts as a relay between the pelvis and leg. What is also important to note is the relationship between the biceps femoris and antior tibialis. This relationship is both to create stability and help build as well as release kinetic energy to help more efficient movement. Exercises to enhance this system:
     -Deceleration Step Deadlift
     -Walking Lunge with Balance Step
     -Walking Sled Pulls

Lateral System

Very simply, as the name implies the lateral system provides lateral stability. Not to be confused with lateral motion, the lateral system is often used to create stability in the pelvis during walking, stepping, etc. Often we overlook this system and it may be very unwise, as it may lead to issues such as Trendelenburg gait which can lead to many other issues such as hip pain, proper knee tracking, and possibly ankle sprains and ACL incidents. Exercises to enhance this system:
     -Split Stance Med Ball Chest Pass
     -Kettlebell Off-set Rack Loaded Step-Ups
     -Sandbad Rotational Lunges

Understanding the body is how we ultimately create more specific programs for our clients as they progress from the foundational movement patterns. Where most programs go wrong is they train the body for the weight room, and not for life.

Let's Get Practical

Once the deficits have been identified the proper exercise makes it easy to correct. The bread and butter exercises to correct and strengthen the slings are these two easy exercises and you should try to incorporate them into your core workouts.


1. Push-Pull Anti-Rotation Cable Cross


2. Half-Kneeling Chops and Lifts