Core stability is a hot topic amongst rehab and fitness professionals. What does core stability really mean? Do sit ups, crunches, and planks count as core stability? Is it possible to have strong abdominals and still have a weak core? What type of core stability is best for people recovering from an injury and transitioning back to the gym?

Movement is medicine for the body and core stability is a vital part to any injury recovery or prevention program. Breathing, stretching and strengthening exercises can improve your posture, relax tense muscles and provide an overall sense of well-being.

The History of Core Stability

Core stability was initially described by academics “as the ability to withstand buckling from compressive forces” (Crisco, Panjabi 1995) and over time refined into “the ability to prevent shear and spin at each level of the vertebrae and pelvis”. (Bogduk et al 1995) The working definition of core stability has since evolved to include an integration of the body’s control, passive and active systems. These 3 systems contribute equally to spinal stability. The goal of exercises prescribed to “improve core stability” should be to train these three systems to produce effective movement.

The Active System

This system includes identifying, isolating muscles and integrating them into functional movements. This is one of the most important parts of the systems from a rehabilitation point of view and has 2 components which are the Local Active system and the Global Active system.

Coordinating the local and global muscles of the trunk is like coordinating musical instruments in an orchestra. Each instrument contributes to the final sound, but individual contribution is needed for optimal function. Local stability muscles need to be isolated to bring awareness without global system compensation. Once this is learned with awareness then it can begin to be recruited unconsciously while we move.

The Local Active System

The local system is a group of small muscles that contribute to developing control of local segments or “blocks” of the spine. These muscles control stiffness and position of spinal segments in relation to one another. Effectively, our spine is a complex stack of blocks. Each block or spinal segment balances on top of one another. These muscles will engage prior to movement and can be recruited unconsciously to keep them balanced. These muscles only need to be recruited for 25% MVC (maximum voluntary contraction) to be effective.

Dysfunction occurs when these muscles are inhibited and cause decreased strength, endurance and increased movement of spinal segments.

These local muscles work together to form the inner core unit of the body or the CORE 4. They need to work in balance to one another.

1. Diaphragm – The diaphragm is the primary muscle for inspiration. It descends into the abdominal cavity when it contracts to help open the rib cage.
2. Pelvic Floor – The pelvic floor is a group of muscles at the base of the pelvis that serve to help control bladder and bowel function, stabilize the sacrum and support the pelvic organs. The pelvic floor work together with the diaphragm.
3. Transverse Abdominis – This “corset” muscle is the deepest abdominal layer. It runs horizontally to flatten and create tension from the pelvis to ribcage.
4. Multifidus – These multiple muscles extend, stack and rotate individual spinal joints.  They prevent the shear and rotation in the spinal joints. These muscles act like “pulleys” in the spine decreasing the work need to move.

The Global Active System

These are muscles that generate torque, create movement and transfer load from ribs to the pelvis. They control movement and support posture. Dysfunction of the local system may present as imbalanced over-activity and tightness within the global system. This may result in excessive compression, increased intra-disc pressure and loading through the spine resulting in risk of degeneration and pain. (Nachemson and Morris 1964).

The Passive System

The passive system includes the skeletal structure, ligaments, and intervertebral discs that passively limit movement of the spine. Neutral alignment is where we start training the core muscles. Finding and working in neutral alignment is optimal because the local muscles are easier to isolate and it offers the least impact to the passive system. If the passive system is injured or is unstable it becomes important to enhance the other components of stability. The passive system can also become compressed when there is an exaggerated active response.

The Control System

The Control system includes our nervous system. The nervous system is challenged to control and move the spine. The control system must continually interpret the status of stability and plan appropriate responses. Control errors come as forces that are ‘too small, too large, too early or too late or not at all’. (Gardner-Morse et al 1995)

For example, imagine being bumped while standing. Your body naturally adapts to reverse the force to stay upright prevent tipping over. This reaction has to be perceived, the right intensity, the right timing and the right direction to be effective. The same can be said about core stability. Knowing which muscles to use, in the right timing and at the right intensity is essential to create an efficient system.

Pain turns off and “lowers the volume” on your ability to contract the local muscle system. This often presents as delayed muscle response, loss of awareness of abnormal passive movement (shear and spin). This loss of local stability causes pain and the cycle continues. Pain results in muscle bracing, stiffness, fatigue and overall sense of discomfort. Over recruitment or a “too large” response leads to chronic over-activation of the global system. Often, core stability training is relearning how to quiet the large global muscles in order to identify the deeper local system. This requires mental focus and concentration. Developing this awareness is essential to developing a balanced and efficient core. Imagining and connecting images to these body parts and exercises helps reinforce this awareness and control.

Why is core stability important after back injury?

Research suggests that exercise, in general, is important for recovery of nonspecific mechanical back pain. Some evidence suggests impaired firing, decreased endurance and strength were found in the local system did not necessarily return on its own. Even further, some evidence suggests that those with impaired function of deep back stabilizers had a higher incidence of repeated occurrences of low back pain. It is recommended to improve your awareness of the local system prior to engaging in higher level core stability and strengthening.

Do crunches and planks count as core stability?

No, crunches and planks are abdominal strengthening exercises but not necessarily core stability exercises. These exercises are not appropriate for everyone. Postpartum mothers who suspect or have been diagnosed with pelvic floor dysfunction or a Diastasis recti are cautioned when returning to these as improper technique and underlying imbalance and weakness within the core can worsen both conditions.

Planking is a very high-level whole body core stability. It is very difficult to do without firing effectively through the local system first. Remember the global system will take over and compensate. If done incorrectly, you may be strengthening your trunk but not necessarily strengthening and balancing your core. There is a difference.

You can have strong abdominals and have a weak core.

What can you do to improve your core stability?

1. Breathe – Breathe in through your nose and expand your ribcage like an upside down umbrella. Exhale slow through pursed lips (imagine blowing out through a straw). Breathe often, breathe deep and breathe slowly. This helps your body relax and helps increase mindfulness.
2. Lift pelvic floor – Think of your pelvic floor as a trampoline under your pelvis. As you inhale it relaxes down to ground, and as your exhale it lifts up. Connect your breath and your mind to your pelvic floor. Keep the contraction at a low intensity (20%).
3. Engage Corset – Think of your Transverse abdominis as an internal corset running from your ribs to your pelvis. Exhale a little more by imagining blowing out birthday candles. Feel some muscle energy between your ribs and pelvis. If it is too strong, turn the volume down to 25% so you can still breathe deep into lower ribs. Try isolating with pelvic floor lift for a deeper connection.
4. Stack your spine – Sit with optimal posture. Sit balanced evenly on your sitting bones, stack your ribs directly on top of your pelvis and lift neck to sit over top of shoulders. Exhale and peel and flex your spine forward by resting your hands on your knees. Inhale and stack your spine, segment by segment back on your chair. Think of lifting and growing taller as you extend up. Connect your breath to your movement.