Symmetrical Tonic Neck Reflex: A New Look at an Old Exercise

Alternating the spine between flexion and extension in four point kneeling has been around for a long time. It is very popular and has found its way into many hospital and clinic based home exercise sheets in different formats.

Biomechanics

McGill 2001 has recommended a variation of this exercise. He feels this exercise facilitates motion for the spine with very low loading, reduces viscous stresses for subsequent exercise, and “flosses” the nerve roots through the foremina at each spine joint. It has been referred to as "milking the spine".

Yoga

These movements are very similar to the popular "Cat - Cow" poses.

Behavioral Rehab

This exercise is used to gradually increase spinal range of motion for people who have fear of large or end range spinal movements.

Specific Movement Pattern Control Exercises

A common specific movement pattern control exercise is to independently perform a lumbo-sacral anterior and posterior pelvic tilt to mid range while maintaining the hips, thoracic (and thoraco-lumbar) and cervical spine in a general neutral (mid-range position). This movement aims to bias the global stability pelvic tilt muscles for anterior pelvic tilt (lumbar multifidus, iliacus, psoas major from above) and posterior pelvic tilt global stability muscles (gluteus maximus, internal and external oblique psoas major from below) over the global mobility muscles (anterior tilt: iliocostalis, longissimus; posterior tilt: rectus abdominis, hamstrings) (Gibbons 2011).

During four point kneeling exercises it is observed that some people cannot perform a specific neutral spine, while others seem to do it very poorly with quite a bit of paraspinal muscle tone. Some even seem to move their cervical spine during this or move their hips into flexion or extension. These people undoubtedly have a Symmetrical Tonic Neck Reflex (STNR) (Figure 1a and 1b). This is one of over seventy confirmed primitive reflexes (PR). The underlying reason for their poor movement pattern will be related to the presence of PR.

PR are brain stem-mediated, complex automatic movement patterns that commence in utero. If PR persist beyond their average lifespan they may begin to interfere with proper CNS development, normal movement and could indicate neurological impairment. They present in conditions such as learning difficulties or movement disorders in children and adults. PR can also reappear due to altered sensory input into the CNS (musculoskeletal injury) or altered processing (i.e. concussion). The presence of PR will influence motor control and can interfere with normal rehabilitation.

Suggested benefits of the rehabilitation of the STNR (in addition to the above)

Spinal mobilization

This extension phase of the exercise will mobilize the thoracic spine into extension particularly when expiration is used. The flexion phase will mobilize the lower lumbar spine into flexion particularly when inspiration is used. These movement patterns are commonly altered in mechanical pain presentations and can aid in improving movement patterns for specific movement pattern control exercises.

Direction Preference

In addition to the above, if a patient has symptoms in one direction, this is a safe movement pattern to move the spine into end range positions to get temporary relief.

Neural Mobilization

The straight leg raise and the slump test frequently improve after the treatment of the STNR. This may be due to the explanations given by McGill and the above as well as non specific reasons.

General Coordination

The STNR is more specific than the popular yoga pose and alternating flexion - extension described above. If opposite or incorrect patterns are practiced, flare ups have been documented. Although they require much less cognitive and sensory motor input than specific movement pattern control exercises, there is a small element of coordination involved. This can be a stepping stone onto more challenging coordination exercises.

Tone

The flexion ad extension patterns alter tone in the relative muscular patterns they are present in. This change is immediate in most people.

Midline Rehab

Despite this exercise being "symmetrical", it is quite relevant for our bodies midline and for body image.

During delivery of an infant, there are six movements of the baby enable it to adapt to the maternal pelvis: descent, flexion, internal rotation, extension, external rotation, and expulsion (Note: some authors refer to seven movements and include "engagement" prior to "descent") (Hacker et al 2009). The STNR is believed to be used by infants to aid in going through the birth canal and also be a bridge reflex for other developmental movements. Hence, there are other movements beyond those depicted in the figures. Note the incorrect pattern of elbow flexion with the extension phase. These subtle movements have the potential to create very abnormal motor patterns. This is one of the reasons why the "cat and cow" in yoga cannot replace the STNR in rehab.

The variations of this exercise have stood the test of time and as noted above, have many benefits. We should put the exercise in its proper place and appreciate it is best used as the STNR.

References

Gibbons SGT 2011 Problem solving in specific motor control exercise rehabilitation. Neuromuscular Rehabilitation Review. 1: 7-12

Gilfoyle EM Grady AP Moore JC 1990 Children Adapt. A Theory of Sensoirmotor-Sensory Development. 2nd Ed. SLACK Incorporated, Thorofare

Hacker NF, Gambone JC, Hobel CJ 2009 Essentials of Obstetrics and Gynecology. 5th Ed. Saunders, Philadelphia

McGill SM 2001 Low back stability: from formal description to issues for performance and rehabilitation. Exerc Sport Sci Rev. 29(1):26-31.