ReviewThe energy expenditure of normal and pathologic gait
Section snippets
Energy conservation
Human locomotion involves smooth advancement of the body through space with the least mechanical and physiological energy expenditure. While the goal of walking is progression in the forward direction, limb motion is based on the need to maintain a symmetrical, low amplitude displacement of the center of gravity of the head, arms, and trunk (HAT) in the vertical and lateral directions. This conserves both kinetic and potential energy and is the principle of biological ‘conservation of energy’
Energy sources and transfer
After several minutes of exercise at a constant submaximal workload, the rate of oxygen consumption reaches a level sufficient to meet the energy demands of the tissues. The cardiac output, heart rate, respiratory rate, and other parameters of physiologic workload also plateau and a ‘steady state’ condition is achieved. Measurement of the rate of oxygen consumption at this time reflects the energy expended during the activity.
Resting and standing metabolism
The basal metabolic rate (BMR) is the minimum level of energy required to sustain the body’s vital functions in the waking state [9]. The BMR is proportional to the body surface area, as well as the percent lean body mass, and this in part accounts for a 5–10% difference between females and males. As a function of age, the BMR decreases approx. 2% every decade through adulthood [9]. This reduction in BMR with age coincides with the progressive change in body composition that results in a lower
Range of customary walking speeds
Most adults prefer to walk at speeds from 1.0 to 1.67 m/s, (60–100 m/min) [26], [27], [28]. In a study of adult pedestrians 20–60 years of age who were unaware they were observed, the mean walking speed for males, 1.37 m/s (82 m/min) was significantly higher than for the females, 1.23 m/s (74 m/min) [26]. Similar values were obtained during energy expenditure studies performed around an outdoor, circular track when subjects were instructed to select their natural customary walking speed (CWS)
Energy expenditure following hip and ankle arthrodesis
Measurement of energy expenditure following joint fusion provides a method of assessing the relative importance of specific joint movements to the gait cycle.
Energy expenditure of flexed-knee gait
Orthopedic diseases can result in joint contractures and spasticity of upper motor neuron disorders can result in a crouched or flexed knee gait. The significance of knee flexion deformity was illustrated by a study in which the energy cost penalties associated with walking on a flexed knee were evaluated in normal subjects [65]. A specially designed hinged knee orthosis restricted right knee extension to 15, 30, and 45°, but allowed full flexion. Progressively greater O2 cost and rates of O2
Ambulation with crutch-assisted gait patterns
Both swing-through and unilateral non-weight bearing crutch locomotion require a high rate of physical effort in comparison to normal walking. The arms and shoulder girdle musculature must lift and then swing the entire body weight forward with each step. Swing-through crutch-assisted gait, when both lower extremities make floor contact during stance phase and leave floor contact simultaneously during swing, is a gait pattern sometimes adopted following paraplegia. Unilateral non-weight bearing
Amputation
Lower extremity amputation with or without prosthetic replacement imposes energy penalties for ambulation. The patient must choose between walking without a prosthesis which would require increased energy for upper extremity weight bearing on crutches, or using a prosthesis which increases energy demands from utilizing the remaining proximal muscles to substitute for lost muscle function distal to the amputation.
A special problem confronting many older patients with vascular amputations is
Swing-through crutch assisted gait pattern
The typical person with complete paraplegia using a swing-through gait requires bilateral knee–ankle–foot orthoses (KAFO’s) to stabilize the knees and lacks abductor and extensor muscle function to stabilize the hips. Not only must the arms lift and swing the body forward in the swing phase, but they must also provide antigravity support during the stance phase to control the hip and trunk. Persons with thoracic and high lumbar paraplegia also commonly have deficient trunk and hip flexors,
Myelodysplasia
The child with myelodysplasia has a pattern of motor paralysis which parallels that observed following traumatic SCI, in the absence of brain dysfunction secondary to hydrocephalus or Arnold–Chiari malformation. Following a preliminary report on 15 children with myelodysplasia, we have tested 22 children averaging 12.1 years of age [131]. Patients with clinically significant neurologic impairment above the level of their spinal lesion, impairing use of the upper extremities, or clinically
Hemiplegia (stroke)
Energy expenditure of walking for persons with hemiplegia is variable, depending on the extent of neurologic dysfunction and spasticity. The hemiplegic population generally consists of older individuals with a high prevalence of cardiovascular disease, who are often further deconditioned by the effects of acute illness and bed rest prior to active rehabilitation. Exercise capacity is therefore typically reduced.
Spasticity and primitive patterns of motion characterize hemiplegic gait [136]. Bard
Spastic diplegia (cerebral palsy)
The child with spastic diplegia has spasticity and a pervasive loss of motor control throughout both lower limbs which depend on the degree of involvement. Campbell and Ball evaluated 35 children with spastic diplegia between the ages of 5 and l7 years [145]. All had spasticity and varying degrees of impaired motor control. Upright balance reactions were present in six subjects, delayed or absent in 17 subjects, and absent in 12. Six children wore bilateral AFO’s and six wore unilateral AFO’s.
Summary
Measurement of physiological energy expenditure provides a method to determine the energetic penalty of gait disability and a patient’s functional performance ability. The O2 cost per meter is directly related to the extent of the patient's gait disability. The O2 rate indicates the physiological effort of walking at the selected speed.
The use of upper extremity assistive devices (cane, crutches or walker) for weightbearing requires significant arm work. This results in an elevated rate of
Acknowledgements
The staff of the Pathokinesiology Laboratory Rancho Los Amigos Medical Center, Jacquelin Perry, Medical Consultant, and the students in the Department of Physical Therapy, University of Southern California who assisted in patient testing.
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