Single Stance Phase Research Articles

Centre of gravity of the body during the ontogeny of chimpanzee bipedal walking.

Bipedal walking was studied in chimpanzees between 1 and 19 years of age by measuring the external energy generated by the movement of the centre of gravity of the body. The 'recovery' of external energy in infant chimpanzees less than five years of age is smaller than in juveniles from 5 to 19 years of age. During the single stance phase, the short, flexed hindlimb of chimpanzees younger than 5 years is not able to lift the body centre of gravity high enough, so that these infants have a considerable energy output during bipedal walking. Extension of the hindlimb is one of the bases for energy economy in human bipedalism. The development of this low-energy-cost mechanism is an important component of the evolution of human bipedalism.

A biomechanical model to determine lumbosacral loads during single stance phase in normal gait

A dynamic biomechanical model to determine loads (joint forces) attained at the lumbosacral joint-centre during the stance phase of normal level walking was developed. The biomechanical model was based on rigid free body-segments; namely, the foot, shank, thigh, pelvis and head, arms and trunk (HAT) segments. In this biomechanical model, the forces and moments acting on the lumbar spine are derived from body-segment mass and movements of the trunk. These external forces and their moments must be equilibrated by internal forces, that is, contributions from the erector spinae or rectus abdominus muscle group, and abdominal pressures from within the trunk together with spine forces. Three-dimensional co-ordinate and ground-reaction force data were captured from five healthy young male subjects performing normal level walking in the motion analysis laboratory of the Department of Orthopaedic Surgery, National University of Singapore. These data were captured using the VICON motion analysis system. Both of these data sets were pre-processed, and together with relevant anthropometric parameters and physical measurements of the subject, were passed into the biomechanical model to compute the resultant loads at the lumbosacral joint-centre. The results of this study showed that the peak resultant loads at the lmbosacral joint-centre were between 1.45 and 2.07 times body-weight.

Gait adaptations of young adult females to hand-held loads determined from ground reaction forces

Abstract Although walking with hand-held loads is a fairly mundane activity performed by all sections of the ambulant population, very few studies have been made of the possible consequences for the gait. In this study we investigated a group of young adult females while walking without load, asymmetrically loaded with 15% body weight either in the left hand or in the right hand, or symmetrically loaded with 15% body weight in each hand. Walking speed over a distance of 3.5 m was measured, together with data from two force plates. The latter were used to determine durations of the walking cycle and its phases. The ground reaction forces were incorporated in simple equations of motion to determine the oscillations of movement of the centre of mass of the body, or body plus load, during the walking cycle. Group mean values of measurements made in the loaded situations were compared with the corresponding values for the unloaded situation. Values obtained for the asymmetric loading were used to investigate the effects upon gait symmetry. Our main findings were that loading tended to decrease the cycle duration, increase double support and decrease single stance phase, but the stance phase was not affected. The amplitudes of the lateral and fore-aft oscillations of the centre of mass were reduced by loading. Consistent asymmetries were seen in the body centre of mass oscillations as a result of asymmetric loading. Where comparisons are possible, our results tend to match those of other authors who performed studies under other sorts of loading conditions. The overall conclusion is that the changes even when significant are quite small, indicating that the gait adapts well to loading, at least for the group of subjects we studied and for the loads we used.

Function of mono- and biarticular muscles in running

In this study the function of leg muscles during stretch-shortening cycles in fast running (6 m.s-1) was investigated. For a single stance phase, kinematics, ground reaction forces, and EMG were recorded. First, rough estimates of muscle force, obtained by shifting the EMG curves +90 ms, were correlated with origin-to-insertion velocity (VOI). Second, active state and internal muscle behavior were estimated by using a muscle model that was applied for soleus and gastrocnemius. High correlations were found between estimates of muscle force and VOI time curves for mono-articular hip, knee, and ankle extensor muscles. The correlation coefficients for biarticular muscles were low. The model results showed that active state of gastrocnemius was high during increase of origin-to-insertion length (LOI), whereas active state of soleus was low during the start of increase of LOI and rose to a plateau at the time lengthening ended and shortening started. It seems that the difference in stimulation between gastrocnemius and soleus is a compromise between minimizing energy dissipation and using the stretch-shortening cycle optimally. Furthermore, it was found that the net plantar flexion moment during running reached a value of 302 Nm, which was 158% and 127% higher than the peak values reached in maximal jump and sprint push-offs, respectively. It was argued that the higher mechanical output in running than in jumping could be ascribed to the utilization of the stretch-shortening cycle in running. The higher values in running compared with sprinting, however, may lie in a difference in muscle stimulation.

Effects of arch height of the foot on angular motion of the lower extremities in running

It has been suggested that a relationship exists between the height of the medial longitudinal arch of the foot and athletic injuries to the lower extremities. However, the functional significance of arch height in relation to injury is not well understood. The purpose of this study was to determine the influence of arch height on kinematic variables of the lower extremities that have been associated with the incidence of injury in running in an attempt to gain some insight into a functional relationship between arch height and injury. The three-dimensional kinematics of the lower extremities were measured during running for 30 subjects using high-speed video cameras. A joint coordinate system was used to calculate the three-dimensional orientation of the ankle joint complex for a single stance phase. Simple, linear regression analyses showed that arch height does not influence either maximal eversion movement or maximal internal leg rotation during running stance. However, assuming that knee pain in running can result from the transfer of foot eversion to internal rotation of the tibia, a functional relationship between arch height and injury may exist in that the transfer of foot eversion to internal leg rotation was found to increase significantly with increasing arch height. A substantial (27%), yet incomplete, amount of the variation in the transfer of movement between subjects was explained by arch height, indicating that there must be factors other than arch height that influence the kinematic coupling at the ankle joint complex. Additionally, the transfer of movement is only one factor of many associated with the etiology of knee pain in running. Therefore, it is suggested that a running-injury-related foot typology based on arch height is not possible at this time.

Clinical meaning of the torque between stance leg and ground for the analysis of gait mechanism.

Transversal torque between the stance leg and the ground was measured in 169 test persons with normal gait (91 women, 78 men; ages 15-79 years) using three-dimensional force plates. Taking the average of six to ten single steps produces reproducible person- and group-specific data. This permits the isolation and study of individual solutions to specific problems of locomotion, so-called gait mechanisms. The relatively great torque during the double-stance phase is caused mainly by the medially directed, short-term impact peak at heel strike, with the stride length as lever arm. Double-stance torque is therefore determined by motion dynamics and does not help in understanding individual gait mechanisms. Torque measured during the single-stance phase is, in comparison, rather small and is interindividually relatively variable. Experimentally measured torque is considered in terms of various hypotheses concerning the creation of torque in the human gait. Men obviously tend, for reasons of equilibrium and stability, to compensate the various torques. Better than the more known vertical, sagittal, and frontal force components, the remaining torque represents the individual problem solution and therefore permits the study of specific gait mechanisms, both physiological and pathological. Using the characteristic gait of patients with hemiplegia as an example, it is shown that pathological torque observed systematically on the nonaffected side in such patients is a quantitative measure of the trunk rotation necessary to move the plegic side forward. Measurement of this torque therefore permits precise determination of the degree of damage, as well as quantitative control and objective documentation of the rehabilitation progress.

Improvement in gait one year after surgery for knee osteoarthrosis: a comparison between high tibial osteotomy and prosthetic replacement in a prospective randomized study

The aim of this study was to analyse gait improvement one year after high tibial osteotomy and unicompartmental knee arthroplasty in patients with strictly unilateral osteoarthrosis of the medial compartment of the knee. Thirty-six patients, 18 men and 18 women, received a unicompartmental Brigham knee prosthesis and 23 patients, 10 men and 13 women, were operated on with a high tibial osteotomy. Clinical and radiographical assessments were supplemented by a functional test, measurements of thigh muscle torque with a Cybex II dynamometer and analysis on a force plate walkway with electrogoniometers. All patients were assessed prior to, and one year after surgery. Both groups showed overall clinical improvement, as assessed by the British Orthopaedic Association (BOA) score. Pain during walking decreased. The range of knee flexion remained unchanged. The ability to ascend and descend steps improved. The isokinetic thigh muscle torque remained unchanged. In the prosthetic group free walking speed increased from 1.03 to 1.09 m/s (p < 0.001). Step frequency and step length increased (p < 0.001). Single stance phase ratio increased from 0.96 to 0.99 (p < 0.01), indicating a more symmetrical gait. Double stance phase (% gait cycle) of both legs decreased (p < 0.001), indicating a faster transfer of weight during walking. In the osteotomy group, free walking speed did not increase. Step length of the uninvolved leg increased (p < 0.01). Double stance phase of the involved leg decreased (p < 0.001) and double stance phase of the uninvolved leg decreased (p < 0.01). Both groups improved after surgery and there was no difference between the groups.

片麻痺患者の歩行の連続計測 : 短下肢装具の矯正モーメントの影響を中心として

The ankle joint moment in the saggital plane, dorsi and plantar flexion of the ankle joint, flexion and extension of the knee joint, and temporal factors of gait were measured continuously for 10 hemiplegic patients under two conditions: with and without AFO. The ankle joint moment was measured by a capacitive transducer which detected vertical floor reaction forces during the gait. All devices were attached to the subject's body, so that 8 to 20 strides could be measured continuously during 30 seconds. A specially disigned AFO was used in order to decompose the total ankle joint moment into two factors, the moment due to muscle forces and the moment due to the corrective forces generated by the AFO. The data were analyzed with special focus on the corrective moment of the AFO. The maximum dorsi-flexion moment due to the AFO in the early stage of the stance phase was less than 5Nm, and the maximum plantar-flexion moment in the late stage of the stance phase was less than 8Nm. These values were small in comparison with the total ankle joint moment, which ranged up to 70Nm. In regard to the effect of the AFO, the following general tendencies were statistically found. 1. The gait cycle decreased. 2. The single stance phase duration of the affected leg increased. 3. The swing phase duration of the affected leg decreased. 4. The maximum dorsi-flexion angle of the ankle joint during stance phase decreased. 5. The maximum plantar-flexion angle during swing phase of the ankle joint decreased. 6. The maximum dorsi-flexion of the ankle joint occurred in the ealier stage of the stance phase. 7. The maximum extension of the knee joint occurred in the later stage of the stance phase. 8. The maximum dorsi-flexion moment increased. 9. The maximum plantar-flexion moment increased. 10. The maximum dorsi-flexion moment occurred later. 11. The activities of dorsi-flexor muscles and plantar-flexor muscles decreased. However, hemiplegic gait showed extremely large variation depending on the subject. Thus, a case where the ankle joint moment increased with the AFO, a case where the ankle joint moment decreased with the AFO, and cases that showed a change in the knee joint angular pattern are reported and examined in more detail individually.

Voluntary bipedal walking of infant chimpanzees

The voluntary bipedal walking of infant chimpanzees was studied by the analysis of foot force and by motion analysis. The infants were trained to locomote on a level platform without any restrictions on the locomotor pattern. The voluntary bipedal walking was compared with the other types of locomotion at the same age and with the trained bipedal walking performed by other chimpanzees, including adult chimpanzees. The characteristics of voluntary bipedal walking in the infant until one year of age were: (1) high-speed walking with short cycle duration; (2) short stance phase duration; (3) small braking component of the preceding leg and large acceleration of the following leg; (4) one downward peak in the vertical component; and (5) a relatively small transverse component. Bipedal walking usually continued for less than one second and ended in quadrupedal locomotion. During walking, the preceding foot touched the floor, heel first, as in the case of older chimpanzees and humans. At this age, bipedal walking was similar to high-speed locomotion. The voluntary bipedal walking of the two-year-old and frour-yearold chimpanzees was characterized as follows: (1) slower speed than during quadrupedal locomotion, (2) relatively long periods and distances; (3) well balanced accelerating and braking components; and (4) a vertical component showing two downward peaks and a trough in between during numerous trials. The last characteristic means that the body center of gravity is higher in the single stance phase, just as in the bipedal walkinbg of the adult chimpanzees and humans. The bipedal walking of infant chimpanzees was discussed in comparison with the walking of humans, including infants.

Performance objectives in human movement: A review and application to the stance phase of normal walking

That some form of optimisation takes place in skilled human movements may be inferred from metabolic, electromyographic and perceptual experimental results. However, the parameter(s) or function(s) minimised in activities such as walking has not been satisfactorily identified. This work used non-linear optimal control and multiple-segment simulation software to evaluate the predictive ability of seven performance objective functions. The results indicated that minimisation of the time integrals of the sums of the joint torques, the segmental angular accelerations, or the segmental mechanical energies produced the best simulations of the single stance phase of walking. Strong support was also provided for the existence of simultaneous multiple performance objectives in complex movements.

Disarticulation of the knee in children. A functional assessment.

We assessed the functional abilities of six patients who had had disarticulation of nine knees during childhood by analyzing their gait using electrocardiographic telemetry. Those who were more than five years old were further studied by timing them as they ran the fifty-yard (45.7-meter) dash and by testing the strength of the musculature of the hip girdle using a Cybex dynamometer. The physiological cost-index of Butler et al. was used to assess energy consumption. Three patients had had unilateral disarticulation and three had had bilateral disarticulation. Kinematic studies showed persistent bilateral abduction of the hip throughout the gait cycle in all six patients. The flexion-extension arc of the hip was decreased in the three who had had bilateral disarticulation. Increased flexion of the hip was noted on the normal side and decreased flexion, on the affected side in those who had had unilateral disarticulation. Phase reversal of pelvic obliquity was noted in the amputees who had had bilateral disarticulation. The prosthetic knee showed good flexion during the swing phase. All patients showed a mild decrease in the velocity of gait and in the length of step and stride. The patients who had had unilateral disarticulation showed decreased duration of the bilateral stance and single stance phases and increased duration of the swing phase. Those who had had bilateral disarticulation of the knee had a normal distribution of the components of the gait cycle: bilateral stance, single stance, and swing. The physiological cost-index for all six was within the normal range, indicating minimum energy handicap.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of hip joint forces in sheep, dog and man

The hip joint forces of sheep and dogs were measured with instrumented endoprostheses and the results were compared with reported data concerning these forces in man. In all animals load directions with 0 to 30° inclinations relative to the femoral axis predominated. The transverse components mostly acted from medio-ventral directions. While the force orientations varied little during each single stance phase, they changed rapidly during the swing phase. Strong inter-and intra-individual differences of load directions were found in all animals. Irregular forces, acting upwards or transverse to the femur, were frequently observed. Maximum joint forces were up to 110% of body weight and depended more on the postoperative time than on the walking speed. Load orientations in the animals were similar to those reported for man. In this regard sheep and dogs appear equally well suited for tests of hip endoprostheses for man.

The use of a four-channel electrical stimulator as an ambulatory aid for paraplegic patients.

This article reports the use of electrical stimulation to provide paraplegic patients with complete lesions of the spinal cord the ability to rise from sitting to standing, to maintain a standing position, and to walk with a reciprocal gait. Four channels of electrical stimulation are sufficient for synthesis of a simple reciprocal gait pattern in these patients. During the double-stance phase, knee extensor muscles of both knees are stimulated, providing sufficient support for the body. Only one knee extensor muscle group is excited during the single-stance phase. The swing phase of the contralateral lower extremity is accomplished by eliciting the synergistic flexor muscle response through electrical stimulation of afferent nerves. The transition from the double-stance phase to the swing phase is controlled by two hand switches used by the therapist or built into the handles of the walking frame or crutches for use by the patient.