Outer Unit Sling Systems and Performance

I’ve mentioned many times that effective posterior chain training is not as simple as throwing in a few glute and hamstring exercises and hoping for the best- A well educated program needs to not only understand the importance of ‘angle of pull’  and fiber ratios but also how ‘sling systems’ effect movement patterns.

The human body is a complex machine made up of multiple layers of muscle, tendon, ligament and fascia. These structures allow us to walk, run, lift, and generally produce sufficient mechanical force to complete tasks. Effective utilization of these structures ensures good functional ability- and of course dysfunction impairs ability.

Think of the body as a double-layered system- the inner system comprises muscles that stabilize the spine and typically attach to the axial skeleton. The outer system serves to facilitate more phasic functions related to movement. Such movements must occur through a series of 3D movement planes and therefore require mechanical control to enhance movement timing, control and effort. This is where slings systems come in to play:

1. Anterior Oblique System: External and internal oblique with the opposing adductors and intervening anterior abdominal fascia.
2. Posterior Oblique System: The latissimus dorsi and opposing glute maximus.
3. Deep Longitudinal System: Erectors, the innervating fascia and biceps femoris
4. Lateral System: Glute medius and minimus and the opposing adductors of the thigh

Due to the context of this article and its links to glute training in speed in power (relative to forward propulsion) we will be analyzing The Posterior Oblique System (POS) as seen in Image 1.

Image 1

The POS is particularly important in controlling gait- the glute maximus on one side of the body works in concert with the contralateral latissimus dorsi via a common attachment called the thoracolumbar fascia (A). The combined contraction of both muscles counters unnecessary rotation around the spine by evenly producing tension at opposite ends of the TLF and therefore distributing workload. This allows the whole system to work as a mechanical spring or ‘sling’ as it transfers stored elastic energy into kinetic energy, whilst simultaneously stabilizing the sacroiliac joint of the leg in contact with the floor (stance leg). Effective relationships between these structures helps to facilitate speed and power by maximizing motor control, but also helps to reduce any unnecessary metabolic cost (energy leakage). However, dysfunction in any of these structures will impair power production.

Signs of POS Dysfunction

• Sacroiliac or general lower back pain
• Knee pain
• Excessive internal rotation of the hips
• Flexion posture
• Poor acceleration (including timing and reaction)

Exercises to Improve the Posterior Oblique Sling Timing and Co-ordination

In a practical context, it is important not only to include more ‘isolative’ glute exercises in your program but also to include exercises that innervate the contralateral latissimus dorsi simultaneously if your goal is to maximize speed and power. Here are a few examples of effective exercise patterns:

• TRX Squat Row
• Static Lunge to cable row
• Dynamic lunge to cable row (variety of cable heights to accommodate lat pennation angles)
• Single leg deadlift to row
• Bridge Lat Pull
• Step Ups

Note: All exercises to be performed contralateral but where technique is not sufficient consider regression to a bilateral stance until competent

The fundamentals of POS resistance training are important to fully restore or enhance POS function, especially after an injury. Whilst isolated glute exercises are great as a supplementation, in order to maximize transfer to speed, power and improve timing, a more full body approach should be considered.