Double Leg Support Research Articles

Alterations in over-ground walking patterns in obese and overweight adults

Obesity has been associated with negative effects on postural control, including falls. Previous studies revealed different outcomes regarding the effects of obesity on gait features, and the use of BMI may lead to bias in assessing the true effects of obesity on gait. To better understand the effects of obesity on gait, it is important to examine gait features and associated body composition measures. The purpose of this study was: (1) to assess gait features of normal weight, overweight and obese adults, and (2) to assess the relationship between body composition measures and gait features. Thirty participants were assigned to one of three groups based upon their BMI at the onset of the study: healthy weight (BMI: 18.5–24.9kg/m2), overweight (BMI: 25–29.9kg/m2), or obese (BMI: 30–40kg/m2). Participants performed straight-line over-ground walking through a 200m hallway at their natural preferred speed while wearing their own shoes. The angular displacements, range of motion (ROM), and approximate entropy of kinematic data of the bilateral hips, knees, and ankles in the sagittal plane were computed. Walking speed, step length, stride length, single leg support phase, double leg support phase, swing phase and bilateral stance phase times were extracted from the GaitRite data. Overall, body mass and BMI were associated with peak flexion and ROM in the knees as well as single support, double support, stance, and swing phases. Body fat percentage did not exhibit correlations with measured gait features. Gait variables were more highly correlated with BMI and body mass instead of percent body fat, suggesting that absolute mass is more influential on gait features rather than amount of fat tissue.

The influence of passive-dynamic ankle-foot orthosis bending axis location on gait performance in individuals with lower-limb impairments

BackgroundPassive-dynamic ankle-foot orthoses are commonly prescribed to augment impaired ankle muscle function, however their design and prescription are largely qualitative. One design includes a footplate and cuff, and flexible strut connecting the two. During gait, deflection occurs along the strut, with the greatest deflection at a central bending axis. The vertical location of the axis can affect lower extremity biomechanics. The goal of this study was to investigate the influence of bending axis location on gait performance. MethodsFor thirteen participants with unilateral ankle muscle weakness, an additive manufacturing framework was used to fabricate passive-dynamic ankle-foot orthosis struts with central and off-center bending axes. Participants walked overground while electromyographic, kinetic and kinematic data were collected for three different bending axes: proximal (high), central (middle) and distal (low), and the participants indicated their order of bending axis preference after testing. Gait measures and preference effect sizes were examined during six regions of the gait cycle. FindingsA few differences between bending axes were observed: in the first double-leg support peak plantarflexion angle, peak dorsiflexion moment and positive hip work, in the early single-leg support peak knee extension moment and positive ankle and knee work, and in the late single-leg support gastrocnemius activity and vertical ground reaction force impulse. In addition, preference was strongly related to various gait measures. InterpretationDespite the observed statistical differences, altering bending axis location did not produce large and consistent changes in gait performance. Thus, individual preference and comfort may be more important factors guiding prescription.

A musculoskeletal model of the ankle joint complex for the analysis of the dynamic behavior of an ankle prosthesis

Introduction: The ankle joint complex constitutes a biomechanical system of extreme complexity. Both in case of joint arthrodesis and joint replacement, the analysis of the forces generated under dynamic conditions is crucial. In the present work, we developed a musculoskeletal model of the ankle joint complex in order to: (a) analyze the physiological movements of the ankle joints, (b) evaluate the forces experienced by ligaments, muscles and at the contacts between tibia and talus, and (c) evaluate the effects of the insertion of a modern ankle prosthesis. Methods: The adopted software (SimWise4D) allows to perform dynamic simulations of the interaction between solid objects bound to each other, and under various loading conditions. The models of the foot bones were imported from MRI acquisitions performed on a healthy person of 37 years, mass 68kg and height 1.70m. The joints considered were: tibio-talar, subtalar, calcaneo-cuboid and talo-navicular. To represent the muscles, linear actuators were used, as controlled in terms of force or length. The geometric constraints of their lines of action (via points) were defined. The ligaments were represented by springs with nonlinear characteristics [1]. To verify themodel’s response to various muscle contractions, simulations were performed with the foot in non weight-bearing (movement against gravity) and in weight-bearing (double leg support), activating actuators individually according to their theoretical function. Different synergistic activations of muscles were simulated, in order to reproduce plantarflexion, dorsiflexion, pronationandsupination jointmovements. For each condition, muscle forces, ligament forces and contact forces between the tibia and talus were analyzed. The CAD model Fig. 1.

Differences of Ballet Turns (Pirouette) Performance Between Experienced and Novice Ballet Dancers

Purpose: This study investigated the different postural control strategies exhibited by experienced and novice dancers in ballet turns (pirouettes). Method: Thirteen novice and 13 experienced dancers performed ballet turns with dominant-leg support. The peak push force was measured in the double-leg support phase. The inclination angles of rotation axis with respect to vertical axis were calculated in the early single-leg support phase as well as the initiation sequence of ankle, knee, and hip joints on the supporting leg. Moreover, the anchoring index of the head was computed in the transverse plane during turning. Results: The novice dancers applied a greater push force, an increased inclination angle of rotation axis, and an insufficient proximal-to-distal extension sequence pattern. The novice dancers also had a smaller head-anchoring index compared with experienced dancers, which meant novice dancers were not using a space target as a stability reference. Conclusions: A poorer performance in novice dancers could result from higher push force in propulsion, lack of a “proximal-to-distal extension sequence” pattern, and lack of visual spotting for postural stability. Training on sequential initiation of lower-extremity joints and rehearsal of visual spotting are essential for novice dancers to obtain better performance on ballet turns.

Lumbopelvic muscle activation patterns in three stances under graded loading conditions: Proposing a tensegrity model for load transfer through the sacroiliac joints

According to the conventional arch model of the pelvis, stability of the sacroiliac joints may require a predominance of form and force closure mechanisms: the greater the vertical shear force at the sacroiliac joints, the greater the reliance on self-bracing by horizontally or obliquely oriented muscles (such as the internal oblique). But what happens to the arch model when a person stands on one leg? In such cases, the pelvis no longer has imposts, leaving both the arch, and the arch model theory, without support. Do lumbopelvic muscle activation patterns in one-legged stances under load suggest compatibility with a different model? This study compares lumbopelvic muscle activation patterns in two-legged and one-legged stances in response to four levels of graded trunk loading in order to further our understanding the stabilization of the sacroiliac joints. Thirty male subjects experienced four levels of trunk loading (0%, 5%, 10% and 15% of body weight) by holding a bucket at one side, at three conditions: 1) two-legged standing with the bucket in the dominant hand, 2) ipsilateral loading: one-legged standing with the bucket in the dominant hand while using the same-side leg, and 3) contralateral loading: one-legged standing using the same leg used in condition 2, but with the bucket in the non-dominant hand. During these tasks, EMG signals from eight lumbopelvic muscles were collected. ANOVA with repeated design was performed on normalized EMG's to test the main effect of load and condition, and interaction effects of load by condition. Latissimus dorsi and erector spinae muscles showed an antagonistic pattern of activity toward the direction of load which may suggest these muscles as lateral trunk stabilizers. Internal oblique muscles showed a co-activation pattern with increasing task demand, which may function to increase lumbopelvic stability (P < 0.05). No unilateral pattern of the internal obliques was observed during all trials. Our results suggest that the lumbopelvic region uses a similar strategy for load transfer in both double and single leg support positions which is not compatible with the arch analogy. Our findings are more consistent with a suspensory system (wire-spoke wheel model). If our proposed model holds true, the pelvic ring can only be integrated by adjusting tension in the spokes and by preserving rim integrity or continuity. Thus, we propose that in order to restore tension integrity throughout the pelvic ring, efforts to unlock restrictions, muscular correction of positional faults and lumbopelvic or even respiratory exercises following sacroiliac joint dysfunctions must be taken into consideration. Our hypothetical model may initiate thinking and act as a guide to future work based on a biomechanical approach to the problem of sacroiliac joint dysfunction.

Exercícios de estabilização do tronco para indivíduos saudáveis

The aim of this study was to analyze the trunk muscular response during different variations of some of the most popular stabilization exercises: front-bridge, back-bridge, side-bridge, and bird-dog. Surface electromyography was bilaterally re-corded from rectus abdominis, external and internal oblique and erector spinae during 25 variations of the aforementioned exercises. Compared to the conventional form of the front- and side-bridge, performing these exercises kneeling on a bench or with elbows extended reduced the muscular challenge. Conversely, performing the back-bridge with elbows extended elicited higher muscular activation than the conventional exercise. While bridge exercises with double leg support produced the highest activation levels in those muscles that counteracted gravity, single leg support while bridging increased the activation of the trunk rotators, especially internal oblique. The highest activation levels were found in three exercises: sagittal walkout in a front-bridge position, rolling from right side-bridge into front-bridge position, and side-bridge with single leg support on a BOSUTMbalance trainer. Although the exercises performed on unstable surfaces usu-ally enhanced the muscle activation, performing the exercises on the BOSUTMbalance trainer did not always increase the trunk muscle activity. Overall, this information may be useful to guide fitness instructors and clinicians when establishing stabilization exercise progressions for the trunk musculature.

Kinematic assessment of postural control during simulated slips while walking: a comparison with and without carrying a handbag

【Objective】The purpose of this study was to identify the factors that increase the risk of falling when carrying a handbag. Postural responses were compared with and without a handbag when the subjects were given a simulated slip stimulus during walking on a split-belt treadmill.【Subjects and Methods】The subjects of this study were 20 healthy adult males. The simulated slip stimulation was given to the right foot at heel contact. The three measurement conditions were left handbag, right handbag, and empty-handed walking. A three-dimensional motion analysis system was used to record the positional and temporal information of body landmarks, and the body axis and virtual center of mass were calculated from the position data.【Results】The postural response to the simulated slip stimulation was classified into two categories: single leg support response (S-response) and double leg support response (DS-response). In the S-response, the subjects stepped on the opposite foot of the stimulated lower limb. In the DS-response, the subjects stood on both legs without a step. The subjects tilted the trunk more to the posterior, and the virtual center of mass showed larger backward displacement in the S-response than in the DS-response. The subjects tilted the trunk more to the right, and the virtual center of mass showed larger rightward displacement in the DS-response than in the S-response. A larger number of DS-responses occurred when the handbag was held with the right hand. The start timing of stepping in the S-responses was delayed when the handbag was held with the right hand.【Conclusion】Slips of the foot on the handbag side at heel contact during walking are more dangerous than slips that happen on the other side, and the start timing of stepping was delayed. However, it is not possible to predict which foot will slip. Therefore, holding a handbag may increase the fall risk during walking compared to walking empty-handed. Language: ja

Turning in a Bipedal Robot

We report the development of turning behavior on a child-size bipedal robot that addresses two common scenarios: turning in place and simultaneous walking and turning. About turning in place, three strategies are investigated and compared, including body-first, leg-first, and body/leg-simultaneous. These three strategies are used for three actions, respectively: when walking follows turning immediately, when space behind the robot is very tight, and when a large turning angle is desired. Concerning simultaneous walking and turning, the linear inverted pendulum is used as the motion model in the single-leg support phase, and the polynomial-based trajectory is used as the motion model in the double-leg support phase and for smooth motion connectivity to motions in a priori and a posteriori single-leg support phases. Compared to the trajectory generation of ordinary walking, that of simultaneous walking and turning introduces only two extra parameters: one for determining new heading direction and the other for smoothing the Center of Mass (COM) trajectory. The trajectory design methodology is validated in both simulation and experimental environments, and successful robot behavior confirms the effectiveness of the strategy.

Effect of leg support on muscle cross-correlation of bilateral erector spinae during trunk flexion–extension performance

Investigations corresponding to the affected factors of the cross-correlation of pair muscles are limited though muscle activation patterns of bilateral erector spinae (ES) during trunk flexion–extension performance in standing have been utilized as an indicator in the evaluation of low back pain condition. The purpose of the study is to evaluate the effect of leg support on the cross-correlation of bilateral ES, and to test if the average of bilateral ES could weaken this effect. Twenty male university students volunteered for this study. Each performed the trunk flexion–extension in three leg support conditions randomly with the condition of single left leg support, double leg support and single right leg support, respectively. Each condition included three trials of trunk flexion–extension with the cycle of 5s flexion and 5s extension in standing. Surface electromyography from the right ES muscle as well as from the left one was recorded. The cross-correlation both in pair muscle of right–left ES and in pair muscle of right-average of bilateral ES was calculated in the flexion as well as extension period. A one-way ANOVA with repeated measures was used. The results showed that leg support has some effect on cross-correlation of bilateral ES, which causes the absolute value of phase lag to be significantly larger in flexion period. It is suggested that this effect could be weakened by the average of bilateral ES through significantly increasing the cross-correlation coefficient, and decreasing the absolute value of phase lag.

Spatial and Temporal Variability of Movement Parameters in Individuals with down Syndrome

This investigation compared spatial and temporal gait movement parameters of a sample of individuals with Down syndrome (n=12) and one of individuals without disabilities (n=12). All participants were evaluated on responses to a preferred pace and fast walk with the GAITRite Electronic Walkway. Spatial outcomes included step and stride length, step and stride width, toe-in/toe-out, and base of support. Temporal outcomes included step time, velocity, single and double leg support time, stance, and swing time. There were significant group differences for step length, step width, stride length, and velocity in the preferred walk condition. Significant group differences for step length, step width, and stride length were observed in the fast walk condition. Percentage differences also indicated lower scores for all spatial and temporal variables in relation to the control group. The ability to control gait movements appears to reflect earlier movement experiences, so it may be possible to use variable sensory feedback and specific training to modify and adjust movement responses and improve gait performance in Down syndrome.

Trunk muscle activation during stabilization exercises with single and double leg support

The aim of this study was to analyze trunk muscle activity during bridge style stabilization exercises, when combined with single and double leg support strategies. Twenty-nine healthy volunteers performed bridge exercises in 3 different positions (back, front and side bridges), with and without an elevated leg, and a quadruped exercise with contralateral arm and leg raise (“bird-dog”). Surface EMG was bilaterally recorded from rectus abdominis (RA), external and internal oblique (EO, IO), and erector spinae (ES). Back, front and side bridges primarily activated the ES (approximately 17% MVC), RA (approximately 30% MVC) and muscles required to support the lateral moment (mostly obliques), respectively. Compared with conventional bridge exercises, single leg support produced higher levels of trunk activation, predominantly in the oblique muscles. The bird-dog exercise produced greatest activity in IO on the side of the elevated arm and in the contralateral ES. In conclusion, during a common bridge with double leg support, the antigravity muscles were the most active. When performed with an elevated leg, however, rotation torques increased the activation of the trunk rotators, especially IO. This information may be useful for clinicians and rehabilitation specialists in determining appropriate exercise progression for the trunk stabilizers.

Perceived impact of spasticity is associated with spatial and temporal parameters of gait in multiple sclerosis.

Background. Spasticity is prevalent and disabling in persons with multiple sclerosis (MS), and the development of the Multiple Sclerosis Spasticity Scale-88 (MSSS-88) provides an opportunity for examining the perceived impact of spasticity and its association with gait in this population. Purpose. This study examined the association between the perceived impact of spasticity and spatio-temporal parameters of gait in persons with MS. Methods. The sample included 44 adults with MS who completed the MSSS-88 and 4 walking trials on a 26-foot GAITRiteTM electronic walkway for measurement of spatio-temporal components of gait including velocity, cadence, base of support, step time, single support, double support, and swing phase. Results. The overall MSSS-88 score was significantly associated with velocity (r = −0.371), cadence (r = −0.306), base of support (r = 0.357), step time (r = 0.305), single leg support (r = −0.388), double leg support (r = 0.379), and swing phase (r = −0.386). Conclusions. The perceived impact of spasticity coincides with alterations of the spatio-temporal parameters of gait in MS. This indicates that subsequent interventions might target a decrease in spasticity or its perceived impact as an approach for improving mobility in MS.

Wheel Locomotion of a Biped Robot Using Passive Rollers – Large Biped Robot Roller Walking Using a Variable-Curvature Truck –

This paper proposes the leg-wheel locomotion of a biped robot. The feet of the robot consist of wheels that move forward with the periodic motion of a leg under a double-leg support. There are many types of approach leg-wheel hybrid systems; however, biped system with passive wheels is rarely used. A special axle mechanism is introduced so that the wheels could smoothly track a curved path for propulsive motion. Finally, the robot achieves not only straight and circular motion but also pivoting motion that is significantly faster than walking, while implementing a minimal number of simple components. The concept of locomotion, function of the mechanism, and experimental results are described in this paper.

MEASUREMENT OF TEMPORAL PARAMETERS OF GAIT: COMPARISON OF A STOPWATCH AND A FRAME COUNTING TECHNIQUE

1686 The purpose of this study was to compare two methods of measuring temporal parameters of gait in subjects with and without low back pain. A total of ten subjects with low back pain and 12 normal subjects participated in this study. Each subject was videotaped while walking twice at two speed conditions(preferred and fastest) over a 6-meter walkway. A stopwatch and frame counting technique were used to measure the gait parameters from the videotapes. The parameters measured in seconds were; stance phase, swing phase, single leg support, and double leg support. All stopwatch measures underestimated double leg support time. In the patient group, the mean and SD of stopwatch measures was 0.12 ± 0.02 and 0.08 ± 0.01 for preferred and fastest speed respectively. This compared to a mean and SD of 0.15 ± 0.02 and 0.10± 0.03 measured with counting frames technique. In the normal group the mean and SD of stopwatch measures was 0.12 ± 0.02 and 0.08 ± 0.01 for preferred and fastest speed respectively. This compared to the mean and SD of 0.15 ± 0.02 and 0.11 ± 0.01 with frame counting technique. In contrast, stopwatch measures overestimated the swing time. In the patient group, the mean and SD of stopwatch measures was 0.42 ± 0.04 and 0.39 ± 0.03 for preferred and fastest speed respectively. This compared to the mean and SD of 0.32 ± 0.02 and 0.38 ± 0.03 measured with frame counting technique. In the normal group the mean and SD of stopwatch measures was 0.45 ± 0.02 and 0.39 ± 0.03 for preferred and fastest speed respectively. This compared to the mean and SD of 0.38± 0.02 and 0.34 ± 0.02 measured with frame counting technique. Paired t-tests revealed a significant difference between methods on all parameters in each group and in each speed condition ( P values < 0.01). Comparison of the two clinical techniques showed systematic differences. Frame counting technique is simple, and easy to use, therefore has potential for greater clinical utility.

ECCENTRIC EXERCISE ALTERS GAIT IN OLDER INDIVIDUALS 908

The objective of this study was to determine if novel eccentric exercise, which evoked the classical responses of pain and reduced strength, altered gait in healthy, older individuals. 3 females and 3 males aged 55 to 64 (mean± SD; 59 ± 3 yr, 77 ± 11 kg) performed 8 sets of 8 unilateral eccentric (ECC) actions with the right quadriceps femoris muscle group (QF) with a load equal to 75% of the ECC one repetition maximum. Before and 3 days after ECC exercise the maximum load that could be lifted once (1 RM) and muscular pain, self-assessed with a 100 mm visual analog scale, were measured. Prior to these tests, subjects were videotaped from a lateral perspective (120Hz, 8Hz filter) during each of 5 walks (20 feet) at self-selected pace down a 16% decline. 1 RM was decreased 18% (p = 0.047) by ECC exercise while pain in the involved QF while rising from the seated position increased (p = 0.001) from none (0 mm) before ECC exercise to 50 mm. Subjects presented no changes in pain or strength for the left, uninvolved QF. Self-selected walking pace and maximal downward velocity of the body's center of mass (COM) during stance on the involved QF were reduced 9 and 14%, respectively p ≤ 0.046). Stride length for the uninvolved leg was also reduced 11% (p = 0.031). Time spent in double leg support increased 11% (p = 0.041) after ECC exercise, while the horizontal COM coordinate relative to the length of the base of support at heel strike shifted posteriorly 25% (p = 0.014) for the involved leg and 13% for the uninvolved leg (p = 0.005). These preliminary results indicate that unilateral eccentric exercise which induced moderate pain and reduced strength also altered downhill gait in older individuals. Subjects favored their involved leg, spent more time with both feet on the ground, walked more slowly with shorter steps, and shifted their center of mass backward. It is suggested, on the one hand, that muscle pain and reduced strength likely increase the risk of injurious falls in older individuals. However, on the other hand, responses to novel eccentric exercise evoke gait adaptations which may reduce this risk.

WALKING PATTERN ANALYSIS OF PRIMARY SCHOOL CHILDREN DURING LOAD CARRIAGES ON TREADMILL 492

The effect of carrying school bags on children was investigated so as to supply a picture of recommended weight of school bag and prevent vertebral problems. Two dimensional video filming and heart rate measurement were carried out in 10 male students of Primary Six (average 11.6 years) during walking on a treadmill with backpack of 0%, 10%, 15%, and 20% of body weight respectively. The body height and weight of the subjects were 149.95 ± 5.55 cm and 44.45 ± 11.41 kg respectively. The subjects were requested to walk at a speed of 1.1m/s for 15 minutes on a treadmill, at each condition of carrying. Loads were put inside the backpack placed on the mid back of the subject. 0% body weight was used as a control for carrying. Video tapes were then digitized and analyzed on Peak Motion Measurement System. Results showed no statistically significant difference between different load conditions in stride length, stride rate, double leg support time, swing time and center of gravity height as well as in heart rate. It was found there was significant difference in single leg support time among different load condition. The F-ratio was F(3.36)=3.461, P<0.05. One-way Scheffe Test indicated that there was significant difference in single leg support time only at between 0% and 20% body weight load conditions. Significant difference was found in inclination of trunk between 0% and the other three load conditions. The F-ratio was F(3.36)=11.64, p<0.01, showing there were significant differences in inclination of trunk between 0% and the other three load conditions. The study could not provide any support to the recommendation of 10% body weight as the guideline for carrying school bag among children. It was also found that heart rate could not be used as the only physiological testing parameter of carrying school bag on children. It was suggested that longitudinal study and the study with EMG testing should be carried out in order to provide information on the causes of vertebral problems related to the load of school bags.

Impact of knee extensor strength deficits on stair ascent performance in patients after medial meniscectomy

After arthroscopic meniscectomy the relationship between the magnitude of knee extensor strength deficits and locomotor performance during stair ascent unloaded and when carrying a 22 kg load has been tested in 31 patients. The specific locomotor adaptations related to large strength deficits were also studied. The results indicate that large deficits were significantly associated to: 1) reduced activation of the knee extensor muscles (vastus medialis and lateralis) during the first double leg support and single leg support phases, and of the hip extensors (medial hamstrings) during the second double leg support of stair ascent, 2) overactivations of the hip extensors (gluteus maximus and medial hamstrings) during single leg support, and 3) longer cycle and step durations and lower cadences. Locomotor abnormalities in movements and muscle activations were generally found in patients with strength deficits greater than 25% while patients with smaller strength deficits (less than 25%) usually could climb stairs with normal performance. These results support the use of knee extensor strength measures to predict locomotor capacities, and also highlight the importance of postoperative knee strength rehabilitation.

Body Segment and Release Parameter Contributions to New-Rules Javelin Throwing

Eight male javelin throwers were filmed while throwing new-rules javelins during competition at five meets over a 2-year period. Body segment kinematics and javelin release parameters were assessed relative to their contribution to throwing performance. The data suggest that successful throws, as judged by distance thrown, are characterized by higher release speeds, longer last-step lengths, less flexion of the front-leg knee during the final plant phase, and an orderly progression of peak speeds at the hip, shoulder, and elbow from the onset of double leg support until release. Individual variability in performance was associated with differences measured between several throwing variables. Limitations inherent to two-dimensional analysis were identified that highlighted the need for three-dimensional investigation of the javelin throw.

Biped gait stabilization via foot placement

It is shown that stable biped gaits can be achieved by discrete foot placement based on feedback of information available at the time of foot placement. The model, developed by Townsend (1981, J. Biomechanics 14, p. 727) to evaluate the coordinations of torso motions, subsumes most of the salient body members and motions. The modeling yielded a generalized inverted pendulum with a movable support point which physically defines lateral foot placement. The principla result is that stable gaits can be defined by foot placements which are a linear function of the system center of mass position and vleocity at the time of foot placement (only). Gaits may be ‘smooth’ or may have impulsive corrections to adjust the character of the motions and foot placement. Several general algorithms and specific simulations are presented, and calculations for non-impulsive gaits and impulsive corrections are presented. The model predictions are compared with published data. The predictions are sufficiently close to the data such that the general algorithms appear to be validated. Of particular interest are the non-sinusoidal character of the motions and the relatively simple algorithms. Indeed, the simplicity of the algorithms suggests the practical possibility of legged mobile robots. Accordingly, further investigation seems warranted for determining the parametric variation and control of gait. Some attention is also given to continuous-feedback control such as would exist during double-leg support and in specialized tasks such as rope walking or skating. Subsequent investigation will consider superposition of single and double leg support, although clearly the discrete gaits pose the more restrictive stability problem.

正常歩行中の下肢筋活動様式に関する筋電図学的研究

Objectives of this paper were to elucidate essential electrical discharge patterns of lower limb muscles and their variabilities during a normal gait cycle.Subjects employed in the experiments were 217 healthy adults of both sexes, ranging in age from 18 to 22 years, and they had no disorder in the lower limb or the central nervous system in their medical history. Electromyograms (EMGs) were recorded from the Tibialis anterior (Ta), the Gastrocnemius lateral head (Gl), the Vastus medialis (Vm), the Gluteus maximus (Gm), the Rectus femoris (Rf), the Medial Hastrings (MH), and the Biceps femoris (Bf) by conventional method using surface electrodes. Angular changes of the ankle, knee and hip joints and time signals at the heel and the toe contacts with the ground were simultaneously recorded with the EMGs.The essential EMG pattern s of the lower limb muscles during a normal gait cycle were conclusively summarized: 1) The ankle joint muscles; i) The marked discharge of the Ta was observed in the period from the end of the swing phase to the early part of the stance phase, and in the period from the end of the stance phase to the early part of the swing phase. ii) The Gl showed the main discharge in the latter half of the stance phase, and showed almost complete electrical silence in the former half of the swing phase.2) The knee and hip joint muscles; i) The discharge of the Vm started at the latter half of the swing phase and increased abruptly just before or after the heel contact. The marked discharge of the Vm lasted into the first double leg support period. ii) The discharge of the Gm started at the latter half of the swing phase and increased just before or after the heel contact. The Gm showed the continuous discharge during the former half of the stance phase. iii) The main discharge of th Rf was similar to that of the Vm, and the Rf did not show distinguished activity in the former half of the swing phase. iv) The MH and the Bf showed the marked discharges from the the latter half of the swing phase to just before or after the heel contact, but little or no discharge in the former half of the swing phase.In addition to the essential EMG pattern s, the variations in the EMG patterns which were found to be within ranges of the normal activities were as follows: 1) The ankle joint muscles ; i) The distinguished discharge of the Ta at about the mid-swing phase appeared in about 85% of the subjects. ii) The discharge variation of the G1 was hardly observed during the gait cycle.2) The knee and hip joint muscles; i) The discharge of the Vm was seen around the mid-stance phase and in the second double leg support period in about 20% of the subjects. ii)The discharge variations of the Gm were similar to those of the Vm. iii) The discharge of the Rf appeared around the mid-stance phase in less than 20% of the subjects and at the end of the stance phase in about 80%. iv) In about 60% of the subjects the marked discharges of the MH and the Bf in the latter half of the swing phase decreased or disappeared abruptly around the heel contact; however, in the other 40%, the discharges continued until the midstance phase. The discharges of the MH and the Bf at the end of the stance phase were observed in less than 20% of the subjects.The marked discharges of the MH and the Bf decreased or disappeared abruptly at the moment when the Rf abruptly increased its electrical activity around the heel contact, and the spike sessation lasted until the moment when the Rf decreased its activity. It was suggested that the spike inhibition in the MH and the Bf might be due to an antagonistic inhibition caused by facilitation of the Rf.