Aging and gait – Life and longevity, part 7

 We all take gait for granted, but it is a complex activity which essentially affects our health, our functional abilities and our sense of who or what we are. Can you imagine your life without gait? We need to first become aware of this gift – called gait – understand and nurture it, so that it serves us even when we are 100 years old.

What causes our gait to change, when does it begin, what areas of our body are most affected and how do we prevent decline which we have come to accept as part of the aging process? As we understand more factors regarding what it is and how gait is controlled, we’ll gain insight on how to nurture and keep our gait at optimal levels, so we can enjoy life as we age. An in depth assessment with equipment is necessary by a Chiropractor or Physical Therapist.

To begin, here is a review of some of the basic components of gait. A human walking cycle has two main phases: Stance phase and Swing phase. During stance time the foot is on the ground and represents about 60% of the gait cycle. The swing period constitutes approximately 40% of the gait cycle and describes the period when the foot is not in contact with the ground.(1) Parameters such as foot placement, step length, step width, velocity and limb angles, must be considered along with muscle involvement for everything mentioned above. Once you include muscles, the Nervous System comes into play for muscle contraction, strength, sequencing, co-ordination, balance and posture. No wonder gait is so complex!

Physiological changes in the Nervous System and body are altered with aging and these changes affect the gait pattern. Reduced walking speed is the most consistent age-related change, but there are other contributors to an altered gait including impaired balance and stability, lower extremity strength, and the fear of falling.(2) According to the WHO, limited physical activity (gait), is the fourth most common premature death risk factor in the world. Physical activity and gait has a positive effect on the quality of life and cognitive functions of the elderly.(3)

Lower Limb
It would be helpful if there was an identified age of major gait decline, because this would allow for timely preventable interventions to occur, as lower gait velocities are associated with falls, decreased mobility, frailty and death. A study looked at a large sample of women and found that gait decline began at 65 and peaked with major declines at 71 years.(4). This article will review factors that affect the entire body, beginning from the feet and moving up to the brain.

With advancing age, there is a general tendency for the body and especially the feet to exhibit increased soft tissue stiffness, decreased range of motion, decreased strength and in the feet a more pronated posture. Pronated feet will reduce joint mobility and function, making them less efficient for propulsion when walking.(5), and a  study showed that foot disorders currently affect between 71 and 87% of older patients.(6) As well, aging and leg strength are related, and both contribute to the age-related changes in mechanical output during gait.(7) Age-related changes in neuromuscular activity contribute to stiffening of the lower limb and to reduced push off power at fast walking speeds.(8)

The neuro-muscular junction may also be compromised, which will affect the ability of a muscle to produce force. The muscle force interaction hinges on structural changes in the muscle, ie., decrease Type II fibers and nerve muscle synergy (9), in aging skeletal muscles. (10) Age affects the hamstring muscles, lowering both contractile function and motor unit discharge rates. The discharge rates can be specific to a part or a compartment of the muscle.(11) This can lead to increased (25%), co-contractions around the knee joint in the aging compared to young adults and this will affect the swing phase of walking and stair use.(12) Aging also affects the proprioceptive signal which enters the body via the feet, causing dysfunction in the neural pathways, decreasing sensitivity, acuity, and integration of the proprioceptive signal. These signal alterations will causes major changes in postural control, decreasing their effectiveness, which will have deleterious consequences for the functional independence of the aging individual.(13)

Aging changes the neuro-muscular environment, which affects how the muscles in the lower limbs contract, or co-contract. These muscle changes will affect the coordination between the foot and the lower leg, changing ankle motion and ankle power. This loss of ankle strength and power has to be compensated by other parts of the lower limbs in order for the normal gait cycle to occur. Knee power increases in order to maintain gait efficiency.(14) But this changes the dynamic foot-shank coordination (15), which further changes gait mechanics, speed, postural balance and can lead to abnormal wear of the joints. The speed and postural chaanges will also selectively affect the motor neuronal pools in the lumbar and sacral areas, which will further affect center of body mass, power production and may alter the performance of specific locomotor tasks.(16) Assessing and strengthening foot and lower limb muscles will help and correcting the ankle joint mechanics can help to improve the hip abductor muscle strength.(17)

Pelvis and Trunk
If there are muscles in the lower limb that can affect gait, are there pelvic and trunk muscles which can also impact gait? A percentage of people, especially women, develop thoracic kyphosis which affects the mass of the erector spinae and psoas major muscles.(18) The kyphosis weakens the erector spinae and decreases stability, changes the center of mass of the body and contributes to pelvic flexion and psoas major atrophy. The psoas major is important for the initial swing phase of gait and pelvic stability, so an atrophied psoas muscle will affect stride length and pelvic stability. Because of the instability in the spine and pelvic areas, these persons use these areas less (19), compensating more in the lower limb structures, so walking speed and stride length are decreased, causing a more cautious gait.(20) Because the spine and pelvis are not swaying in a rhythmic pattern with walking, step width increases to improve balance.(21,22).With all these adaptations occurring in the spine, pelvic and lower limb, some studies are showing there may be a link to the increased energy demands and slowing gait pattern  in the aging person.(23,24)

Nervous System
Are there brain areas that have an effect on the gait cycle? There is a basic locomotor program which controls adjustments of posture, muscle tone and rhythmic limb movements. It consists of proprioceptive signals coming in from the feet, entering the spinal cord, projecting to the cerebellum and all the receiving areas. Information goes out from the cerebral cortex, basal ganglia and brain stem to the descending corticospinal tracts for muscle tone of posture and rhythmic limb movements.(25) If we were capable of consciously controlling these activities, it would consume our entire day and all our energy. Proprioceptive, visual and vestibular sensations, act on certain parts of the brain for posture-gait control and descending tracts control balance and precise stepping.(26,27) Think of taking a step. It is a complex activity involving cognitive and cortical(motor), ie. sensorimotor control. If you add more demanding tasks such as changing speeds or dual tasks, other cortical areas must be involved(28,29), and aging affects corticospinal control and precise stepping mechanics.(30)

Are there specific brain areas that contribute to changes in the gait cycle and pattern? Persons with vestibulopathy causes changes in slowing of gait and step width variability, especially at increasing speeds (31), and may result in difficulty performing functional tasks and increase falls risk.(32)

Recent studies of the gait pattern of cerebellar patients highlights a few key symptoms of increased step width, reduced ankle joint range of motion and increased co-activation of the antagonist muscles. These changes cause a chaotic coordinative behavior between trunk and hip that affect gait performance and stability transforming the upper body into a generator of perturbations.(33) The corticospinal system is also affected (34), more so in challenging walking conditions (35), as are the frontal cortex and basal ganglia regions.(36) The entire nervous system is involved in gait, so we should all walk regularly for our physical and cognitive health.

References

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DR. jimmy buffet is fuga. As aut facieturc to patient-centred ideas for every chiropractor. He can be reached at angelosantin@gmail.com or 807-344-4606.et omnihic to patient-centred ideas patient-centred ideas for every chiropractosantin@gmail.com or 807-344-4606.