Development of a strong core can be a common goal for numerous reasons, such as: improving physical physique, preventing/relieving back pain, improving performance in recreational or competitive activities and building a stable base for our arms and legs to perform normal activities of daily living. This article will correct any myths about proper core activation. It will explain how development of a strong core will improve overall function for not only the lower back, but our bodies in general.
The first key to a strong core is developing a stable inner core. The inner core works as a unit to create dynamic stability around the spine and pelvis.
The inner core is made of up of four muscle groups:
- transversus abdominis
- pelvic floor muscles
Transversus Abdominis (TA):
Transversus abdominis is a muscle that lies deep within the abdomen, attaching to fascia at the spine and wrapping forward towards the belly button, creating an internal corset. The function of the TA muscle is to stabilize your low back and pelvis prior to moving your arms or your legs. This muscle should be engaging subconsciously with any arm/leg/back movement throughout the day; however for many of us this is not the case. Reasons for inhibition of this muscle include: low back pain, surgery to the low back or abdomen, or pregnancy. To re-educate this muscle you must learn to tighten your lower abdomen without tilting your pelvis or puffing out your chest. Engagement is achieved by gently drawing your belly button in towards your spine feeling tension develop on the sides of your pelvic bones. Make sure you remember to breathe naturally from your abdomen as you hold this contraction. Once the muscle is activated, movements of the arms and legs can be added to increase the difficulty and by integrating TA contractions into activities of
The second wall of the inner core is composed of the pelvic floor musculature. This creates the floor or base of the inner core unit. Contraction of these muscles can be achieved by envisioning that you are stopping your urine flow midstream. This exercise is very similar to the traditional Kegel exercise, and adds a second component of stability to our inner core. Please note that if you are experiencing any incontinence or retention issues you should visit a pelvic health physiotherapist before starting pelvic floor exercises.
The third component of our inner core is the multifidus muscle. Multifidus is located on either side of the spine. This muscle is a segmental spinal stabilizer, and atrophy can be seen at one or multiple levels. To retrain this muscle you will likely need the help of a physiotherapist. Your physiotherapist will palpate (touch) the sides of your spine and you will be asked to swell the muscle under their fingers. This is difficult for many of us to do without the help of additional muscles. Common ways we cheat to mimic this muscle function is by tipping the pelvis forward, flexing the hips or tightening the muscles of the buttock. A good way to feel multifidus activate would be to take a step forward while palpating the gutters beside the spine; you will feel a small bulge of muscle under your fingers as multifidus contracts.
The fourth component or roof of the inner core is the diaphragm muscle. To ensure correct stability/function through this muscle, make sure you breathe from your stomach (abdominal breathing) rather than from your chest during the inner core contraction. Breathing from the chest is less than ideal for proper core function and limits the use of the diaphragm muscle.
Why Core Engagement Helps Prevent Muscle Injury:
Dysfunction of the inner core results in increased pressure placed on passive structures (ligaments, bone/joints, discs, capsules) of the lumbar spine due to lack of support and stabilization when moving. If the passive structures are not supported with the core, repeatedly or over a prolonged period of time, injury or dysfunctions such as stiffness or poor movement patterns may occur, creating pain.
Lack of Proper Inner Core Strength Can Lead to Injury:
Often exercises that are meant to strengthen the core can lead to injury. A common mistake individuals make is performing exercises that challenge outer core muscles without proper endurance of the inner core. Performing exercises such as sit-ups and planks without a stable foundation can lead to injury of the lower back/pelvis due to the lack of dynamic stabilization around these joints. Without a strong core, maintaining the correct exercise position is also difficult and can lead to injury. Similarly, if an individual performs a lift without anticipatory engagement of the inner core, increased load is placed on the passive system of the back and pelvis, possibly leading to an injury.
Functional Retraining of Proper Core Engagement:
The core acts as a foundation or stable base on which all body movements are generated to maintain back and pelvic stability. Strength of core musculature enables effective load transfer throughout the body with functional movement and activity.
The exercise strategies listed above can be utilized to re-educate use of the inner core muscles. Once inner core activation is successfully achieved, activation should be performed in differing functional positions and levels of difficulty. Following successful re-training of the inner core, your physiotherapist will begin to introduce outer core exercises (to challenge your rectus abdominus, external obliques, internal obliques). Isometric outer core engagement will be integrated while performing arm and leg movements, ensuring that the spine remains stabilized in neutral throughout.
The outer core can be categorized into four sling systems, which exist in the body to help with stability around the trunk and pelvis. Your physiotherapist can create a graduated outer core retraining program using these slings once correct inner core engagement is achieved.
Outer Core Sling Systems:
Four sling systems (specific groupings of muscle) exist in the outer core. These sling systems are designed to help with Force Closure to the joints of the low back and pelvis (SI joint). Force closure describes use of the muscular and fascial system to assist with stability around joints.
Posterior Oblique Sling:
The posterior oblique system assists with force closure by use of the following muscles/fascia:
- Gluteus maximus
- Opposite latissimus dorsi (lats)
- Thoracodorsal fascia (band connecting trunk to lower extremity)
An example of an exercise that incorporates use of the posterior oblique sling is bird dog.
Functionally the posterior oblique system is used during walking and rotational activities (ie. swinging a golf club).
Anterior Oblique Sling:
The anterior oblique system assists with force closure by use of the following muscles/fascia:
- External obliques
- Opposite internal obliques
- Transversus abdominis
An example of an exercise that encourages use of the anterior oblique sling is dead bug.
Functional use of the anterior oblique system is used during the acceleration phase of throwing.
The longitudinal sling system assists with pelvic stability. The muscles/fascia making up the longitudinal sling include:
- Erector spinae (low back extensors)
- Thoracodorsal fascia
- Sacrotuberous ligament (ligament at the SI joint)
- Biceps femoris (outer hamstring muscle)
An example of an exercise that would engage the longitudinal sling is the reverse boat pose in yoga or a superman exercise.
The longitudinal sling is functionally utilized during walking and running activities.
The lateral sling is important for force closure across the pelvis, and also ensures positional control of the pelvis during single leg stance and walking. Muscles/fascia included in the lateral sling system are:
- Gluteus medius and minimus
- Opposite hip adductors (inner thigh muscles)
Exercises designed to promote activation of the lateral sling are often performed in a single leg stance position, ensuring correct core and pelvic control. Specific exercises for the lateral system include: step ups, step downs and side step ups.
The lateral sling is used functionally during walking and any single leg activity.
The final step to successful core retraining is to obtain full function. Performing functional movements while maintaining controlled trunk and limb movements in changing environments is the first step in functional retraining. Once you are comfortable with this activity, speed of activation and increased load can be added to challenge the core further. Further information and a staged exercise program can be discussed with your physiotherapist.
Diane Lee & Associates: training for the deep muscles of the core (Internet). South Surrey: D G Lee Physical Therapist Corp; (cited 2016 Jan 12). Available from: http://www.dianelee.ca/article-training-deep-core-muscles.php