Muscle Of The Month – The Deep Longitudinal Subsystem

The deep longitudinal subsystem is one of four common muscle synergies used by the body during exercise and other movements.

Stretching down the back and legs, it’s a combination of muscle groups, membranes and ligaments, including the erector spinae, thoracolumbar fascia, sacrotuberous ligaments, and biceps femoris.

The origination and insertion of the Deep Longitudinal Subsystem

As a major muscle synergy, the deep longitudinal subsystem has several points of origination and insertion.

The uppermost part is the erector spinae, which comprises three muscles: the iliocostalis, the longissimus and the spinalis. These originate and insert at various points between the base of the skull and the cervical transverse processes.

Other muscles in the system originate and insert at various points in the back, hips and legs.  

The action and basic functional movement of the Deep Longitudinal Subsystem

The Deep Longitudinal Subsystem works alongside three other muscle synergies:

• The Lateral Subsystem
• The Posterior Oblique Subsystem
• The Anterior Oblique Subsystem

Personal trainers and other fitness professionals should understand how these four systems work together as a unified system during exercise, each having its distinct role to play.

The muscles and ligaments in the Deep Longitudinal Subsystem group transfer kinetic energy up the legs and above the pelvis, allowing you to walk, jog and run. They also help you bend forward, squat, and lunge, as well as carry out other contralateral movements in the sagittal plane, which divides the left and right sides of the body from back to front.

The Deep Longitudinal Subsystem helps stabilise the sacroiliac joint (SIJ), which is located between the sacrum and the pelvis. Support in this area is vital for avoiding back pain. It also acts to stabilise the whole body – the back, core, and hips.

Problems associated with the Deep Longitudinal Subsystem

Because it covers such a large area of the body, numerous issues can arise from problems with the deep longitudinal subsystem. These range from joint pain and restricted movement in the neck, back, hips, and legs to a lack of core stability.

As so many people suffer from back pain, it’s worth remembering the importance of this system in supporting and allowing movement in the back. In particular, individuals who spend a significant amount of time seated at a desk may find it challenging to engage in physical activities, especially those that require the use of their legs, such as squatting or deadlifting. This process can be eased by using a foam roller after being seated and before a workout.

Exercises to strengthen the Deep Longitudinal Subsystem

Exercise that activates the whole group of muscles in the deep longitudinal subsystem can help strengthen its component parts. These include:

• Squats
• Bent leg deadlifts
• Alternating forward lunges
• Anterior lunges with reach at knee height
• Alternating power step-ups
• Hip hinges with overhead lift
• Bridge and curl

Static stretches for the back, hip flexors, and hamstrings are also helpful.