The Study
Title: "Exercises for Spine Stabilization: Motion/Motor Patterns, Stability Progressions, and Clinical Technique."
Authors' Affiliations: University of Waterloo - Spine Biomechanics Laboratory, Waterloo, Ontario, Canada.
Publication: Archives of Physical Medicine & Rehabilitation, 2009;90:118-126.
Background
Spinal stabilization exercises have become very popular, and for good reason. They are commonly prescribed for a wide range of lower back and other musculoskeletal conditions. These exercises are aimed at improving motor control, endurance and coordination of key trunk muscles that contribute to spine stiffness, stability and coordinated motion. Recent research has indicated that results of these exercises are improved when "neutral spine position" is maintained,1 something to keep in mind as you read this review.
Prudent clinicians are very adept at making "on the fly" adjustments and modifications to patient performance of spinal stability exercises. Encouraging postures to spare painful joints, knowing when to engage in corrective exercise, and knowing when to adjust coactivation patterns to make an exercise more tolerable for a patient are all crucial skills, yet little literature exists to guide us.
Sufficient spinal stability requires adequate activation of numerous trunk muscles. It has been well-established that when these muscles contract, they create both stiffness and force. Muscle force may not be stabilizing, butmuscle stiffness is always stabilizing.2
Many clinical populations of LBP patients have compromised load-bearing capacity; therefore, exercises are preferred that impose minimal spinal load. In this small basic science study (eight healthy male subjects of university age), three such exercises well-known by most evidence-based manual therapists - the curl-up, side bridge and bird dog (the "Big 3") - were investigated for muscle activation, 3-D spinal mechanics and the influence of clinician correction. Clinical progressions for these exercises were also outlined and evaluated.
Study Methods
Eight university-age, healthy male volunteers participated in this study, which included measuring EMG and orthogonal 3-D spine position measurements during the three exercises. Five of the subjects repeated the exercises with the guidance of an experienced clinician. This data was collected and analyzed according to the methods previously used in this laboratory (Dr. McGill's at the University of Waterloo, the leading authority on this topic).
Pertinent Results
Let's take a look at results for each individual exercise and focus on technique recommendations for implementation and progression. Spinal bracing was applied in the same manner with all exercises. Patients were instructed to contract and stiffen the abdominal wall as if they were about to be "hit in the belly" while not pushing out or sucking in. Facilitation was achieved withfascial raking - the clinician rakes the obliques while not encroaching on the rectus abdominus with the ends of the fingers; firm but not painful pressure should be used.
Curl-Up (Including the "Dead Bug")
Patient instructions:
- Patient is supine with one leg flat on the ground and one foot flat on the floor (with knee at 90 degrees).
- Both hands are placed under the lumbar spine to support the neutral curve and the elbows are on the ground
- Patient is instructed to pivot about the sternum and lift the shoulder blades off the mat while maintaining neutral neck position for 5 seconds.
- Progressions: can include elevating the elbows, pre-bracing (stiffening) the abdominal wall, and deep breathing during the exercise.
- Dead bug: patient is supine with one hand under the lumbar spine - starting with the hips, knees and shoulders at 90 degrees, patient then extends the other arm/opposite leg to a horizontal position (but still elevated slightly from the ground) and holds for 5 seconds.
- Dead bug progression: a plyometric, short-range movement; the patient pre-braces the midsection and then contracts ballistically to create motion only at the shoulder and hip, but not the torso.
- Raising the elbows caused a trend of increasing rectus abdominus (RA) activity while reducing upper erector spinae (ES) activity, indicating more of a flexor torque challenge.
- While using the abdominal brace - both internal obliques (IO) and external obliques (EO) increased their activation. (IO reached roughly 30 percent of maximum voluntary contraction level.)
- The addition of heavy breathing did not increase abdominal muscle activity (in some cases it actually reduced activity).
- Although not likely significant, the authors noted that gluteus medius activity increased from 3 percent to 6 percent MVC with bracing.
- During performance of the dead bug, increased muscle activity was noted in all muscles.
Side Bridge
Patient instructions:
- The easiest variation has the patient resting on their elbow (directly under the glenohumeral joint) with their hips back in a squat position and knees on the floor (legs bent backward).
- Support is then shifted from the hip to the knee as the pelvis is raised (up and forward) in alignment with the sternum and knees.
The opposite hand is placed over the supporting shoulder to stabilize the weight-bearing shoulder. - Progressions: Patient removes their opposite hand from the weight-bearing shoulder and places the hand on their waist, extending to a full side bridge with support on the feet (top foot over lower foot), rotating slowly from a side bridge to a front plank position (attempting to lock the rib cage to the pelvis during the transition - see below).
Results from the study:
A clear progression emerged - the lowest muscle challenge was noted when the exercise was performed from the knees, increasing with foot support, and being the highest when rotating from a side bridge to a front plank. (Muscle activity approached 50 percent MVC in the RS and IO/EO, and 30 percent in the latissimus dorsi.)
Bird Dog
Patient instructions: The starting position is on all fours with hips and shoulders at 90 degrees.
Progression: just arm elevation, just leg elevation, both arm and opposite leg elevation (full bird dog), then the addition of abdominal bracing and/or deliberate slight abduction of the shoulder with further elevation, finally drawing squares with the hand and foot while they are extended (with motion occurring only at the hip and shoulder).
Results from the study: The progression of muscle activation followed the progression mentioned above.
Effect of Expert/Clinician Correction
Corrections were aimed at correcting asymmetries in spinal twist axis posture toward neutral spine posture; fascial raking was employed as described above. Clinician correction resulted in subtle but important changes:
- Fascial raking increased MVC in the obliques and reduced RA activity during the curl-up, while also reducing spinal flexion to maintain neutral spine position.
- Correcting the locking of rib cage to pelvis while rotating from a side bridge to front plank increased activity in IO/EO and reduced torso twisting.
Conclusions and Practical Application
The "Big 3" exercises used in this study have been well-researched. The data presented in this study can be used to assist clinical decisions regarding where to begin exercise progressions, how to implement corrective techniques, and which exercises to select. Most of the exercise progressions corresponded with predictable increases in difficulty and muscle activation.
One finding that may contradict common thought and practice is that the addition of heavy breathing did not affect muscle activation to a significant degree versus abdominal bracing. Further, subjects showed varying muscle activity linked to inspiration and expiration, indicating that some patients can entrain their respiratory muscles to function independently of their spine-stabilizing role.
Prudent clinicians should take time with their patients to teach correct form on spinal stability exercises to ensure proper motor skill attainment and minimization of unnecessary spinal loads. This study demonstrated that simple clinician corrections using hands-on methods can have positive influences on exercise performance.
Study Critique
This study, despite having a small number of subjects, utilized well-described and previously published methods of data collection and exercise implementation. It should be noted, however, that these subjects were healthy males with no history of LBP. Further research is necessary to clarify best practice for implementing these exercises effectively with LBP patients.
Additional References
- Suni J et al. Control of the lumbar neutral zone decreases low back pain and improves self-evaluated work ability: a 12-month randomized controlled study. Spine, 2006;31:E611-620.
- Brown SH, McGill SM. Muscle force-stiffness characteristics influence joint stability. Clinical Biomechanics, 2005;20:917-922.
Dr. Shawn Thistle is founder and president of the Research Review Service (www.researchreviewservice.com), from which all content for this and other articles by Dr. Thistle is derived. Research Review Service posts approximately 60 reviews like this each year and currently has a database of more than 250 reviews. Dr. Thistle graduated from the Canadian Memorial Chiropractic College, where he has been a faculty member since 2004. He holds an honours degree in kinesiology (McMaster) and a certificate in contemporary medical acupuncture. He is also fully ART-certified and is a certified strength and conditioning specialist. Dr. Thistle practices full time at Shape Health and Wellness Centre in Toronto.