A series of carefully coordinated muscle contractions is required to overcome the inherent unsteadiness of upright posture during walking.1 We incorporate compensatory muscle forces and joint torques into the normal gait pattern to minimize the destabilizing forces that occur at certain points in the gait cycle.Coordinated contractions in the muscles of the pelvis and spine help us maintain spinal balance during complex movements.
Efficient human gait and coordinated spinal function are both very dependent on mechanoreceptors in the lower extremities.2 As we move from one location to another, maintaining dynamic equilibrium during walking ensures a steady and safe progression. Two neurological control strategies are used to achieve this state in human walking: proactive balance and reactive balance.3 These two systems normally work together to counteract the various forces that are placed on our bodies during walking. Problems can arise when one or the other of these balance control systems does not function smoothly.
Proximal Muscle Control
The proactive balance strategy for coordination of gait is found primarily in the trunk and hip extensor muscles, the erector spinae, hamstrings, and gluteus maximus, which all start to become active before heel strike, and stay active during the first half or the stance phase of locomotion.4 These proximal and trunk muscles must work together to maintain upper body steadiness and trunk rotation. Recent studies have found that both aging5 and low back pain6 interfere with normal functioning of this system. In fact, both chronic and acute low back pain can result in significantly altered muscle responses during gait.7
The Lower Extremities
The distal balance control of the lower extremities must react rapidly to changes in terrain and ground reaction forces.8 It is the mechanoreceptors in the feet and legs that provide the information necessary for smooth and balanced coordination of the muscles in the lower legs. From heel strike, through foot flat, to toe off, this region adapts to regain balance from moment to moment. With many small joints, lots of connective and articular tissues, and both intrinsic and extrinsic muscles, the feet are very well-supplied with proprioceptive nerve endings.
Mechanoreceptors in the joints, along with the muscle spindles of the foot muscles, are responsible for the positive support reflexes and a variety of automatic reflexive reactions.9 These include the flexor/extensor reflex, which converts the lower limb into a firm, yet compliant pillar. Weight-bearing compresses the joints and muscles, evoking reflexive activity in the extensors and inhibition of the flexor muscles.10 Particularly when there is excessive pronation, these reflexive responses are sluggish, and the reactive control of gait is poor.
Gait and Spinal Posture
As the leg is loaded in gait, trunk side-bending occurs toward the loading leg. The lumbar spine rotates away, and a balancing rotation occurs in the thoracic spine to the same side as the loading leg. The entire relationship of the shoulder, ribcage, and thoracic spine is driven by the cross-crawl neurological reaction to gait.
Even the upper cervical region plays an important role in maintaining and correcting postural alignment, and in determining whole-body balance. The mechanoreceptors in the upper cervical joints and deep neck muscles are very sensitive to changes in postural alignment,11 and are a critical component (along with the vestibular system) in equilibrium and balance.12 In fact, deJong, et al., were able to cause major changes in gait simply by anesthetizing the muscle and joint receptors in the neck.13
Coordination of gait and spinal function are both dependent on multiple factors in the proximal muscles and trunk. The inherent instability of human walking requires a complex interaction to provide both proactive and reactive balance control. Whenever the foot/ankle complex is not functioning correctly, this stress is transmitted to the pelvis and spine with each step. We can improve gait coordination and help ensure stabilized, balanced function throughout the entire musculoskeletal system with custom-made, flexible orthotic support for each phase of the gait cycle. The best orthotics are those that have been individually designed to support the foot through all three parts of the stance phase - from heel strike, through foot flat, to toe off.
- Winter DA, Ruder GK, MacKinnon CD. Control of balance of upper body during gait. In: Winters JM, Woo S-LY, eds. Multiple Muscle Systems: Biomechanical and Movement Organization. Berlin: Springer, 1990:534-541.
- Allum JHJ, Bloem BR, Carpenter MG, et al. Proprioceptive control of posture: a review of new concepts. Gait & Posture 1998;8:214-242.
- Patla AE. A framework for understanding mobility problems in the elderly. In: Craik RL, Oatis CA, eds. Gait Analysis: Theory and Application. St. Louis: Mosby-Year Book, 1995:436-449.
- Shiavi R. Electromyographic patterns in adult locomotion: a comprehensive review. J Rehabil Res Dev 1985;22:85-89.
- McGibbon CA, Krebs DE. Age-related changes in lower trunk coordination and energy transfer during gait. J Neurophysiol 2001;85:1923-1931.
- Selles RW, Wagenaar RC, Smit TH, Wuisman PIJM. Disorders in trunk rotation during walking in patients with low back pain: a dynamical systems approach. Clin Biomech 2001;16:171-181.
- Arendt-Nielsen L, Graven-Nielsen T, Svarrer H, Svensson P. The influence of low back pain on muscle activity and coordination during gait: a clinical and experimental study. Pain 1996;64:231-240.
- Tang P-F, Woolacott MH, Chong RKY. Control of reactive balance adjustments in perturbed human walking: roles of proximal and distal postural muscle activity. Exp Brain Res 1998;119:141-152.
- Freeman MAR, Wyke BD. Articular contributions to limb muscle reflexes. J Physiol 1964;171:20.
- Panzer DM, Gatterman MI, Hyland J. Postural complex. In: Gatterman MI, ed. Chiropractic Management of Spine-Related Disorders (2nd ed.). Baltimore: Lippincott Williams & Wilkins, 2004:297.
- Abrahams VC. The physiology of neck muscles; their role in head movement and maintenance of posture. Can J Physiol Pharmacol 1977;55:332.
- Wyke BD. Neurology of the cervical spinal joints. Physiotherapy 1979;65:72-76.
- deJong PT, deJong VB, Jonkees L. Ataxia and nystagmus induced by the injection of local anesthetics in the neck. Ann Neurol 1977;1:240-246.
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