Franck Barbier

Gait pattern classification of healthy elderly men based on biomechanical data

OBJECTIVES To distinguish the gait patterns of young subjects from those of elderly men using three-dimensional (3D) gait data, to determine if elderly subjects displayed other than a typical gait pattern, and to identify which parameters best describe them. DESIGN Nonrandomized study in which video and force plate data were collected at the subjects own free walking speed and used in a 3D inverse dynamic model. Cluster analysis was chosen to identify the gait families, and analyses of variance were performed to determine which parameters were different. SETTING A gait laboratory. PARTICIPANTS The sample of convenience involved a single but mixed group consisting of 16 able-bodied elderly subjects (mean age, 62yrs) and 16 able-bodied young subjects aged between 20 and 35 years. MAIN OUTCOME MEASURES Phasic and temporal gait parameters, as well as the 3D muscle powers developed in the joints of the right lower limb during the gait cycle. RESULTS The walking patterns in elderly subjects were found to be different from those of the young adults. Three elderly gait families or groups forming a specific gait pattern were identified, and differences were found in the phasic and temporal parameters as well as in 6 peak muscle powers. Four of the peak powers occurred in the sagittal plane, and half of them were related to the hip. CONCLUSIONS Biomechanical parameters can be used to classify the gait patterns of young and elderly men using cluster analysis rather than age alone. The muscle powers in elderly subjects are perturbed throughout the gait cycle and not only at push-off. It appears that the plane in which the peak powers occurred was related to their occurrence in the gait cycle. Variability in the gait patterns of elderly subjects could reflect natural adaptations or compensations. These should not be indicative of a deficient gait or be misconstrued as some age-related pathology.

Effect of trunk inclination on lower limb joint and lumbar moments in able men during the stance phase of gait

BACKGROUND Though the effect of imposed trunk posture affects walking patterns little is known about the effect of natural orientation of the trunk on gait. The objectives of this study are to test if the lower limb joint and thoraco-lumbar moments are similar in subjects who maintain an average natural forward or backward trunk inclination during gait and verify if the lower limbs are equally affected. METHODS Twenty-five young men were divided according to their natural backward or forward trunk inclination during level walking. Ankle, knee, hip and thoraco-lumbar moments were calculated by an inverse dynamic approach for the two limbs. A two-way ANOVA was performed on peak lower limb moments. A one-way ANOVA was performed on thoraco-lumbar peak moments. FINDINGS There was a main effect for both trunk inclinations and lower limb sides but no interaction. For the forward leaners, the duration of hip extension moment was longer (P<0.001) while the hip flexion moment was 1.3 times smaller (P<0.001). Differences between the lower limb sides were noted in all joints but at push-off of the stance phase only. The two thoraco-lumbar extension moments were, respectively, 1.4 times higher for the forward leaners while the two flexion moments were approximately 1.4 times higher for the backward leaners. INTERPRETATIONS The backward leaners propel themselves with a strong hip flexor activity at push-off while the forward leaners use their hip muscles throughout stance. These results support the idea that trunk inclinations and moment variations are associated with the type of walking patterns.

Lower Limb Coordination in Hemiparetic Subjects: Impact of Botulinum Toxin Injections Into Rectus Femoris

Background. Botulinum toxin (BTX) injection into rectus femoris (RF) is a therapeutic modality used to improve knee flexion during the swing phase of gait in hemiparesis. The impact of this treatment on lower limb coordination is unknown. The authors evaluated whether BTX injection into RF is associated with modifications of intersegmental coordination in hemiparesis. Methods. The authors evaluated gait in 10 control and 14 hemiparetic subjects with low peak knee flexion associated with inappropriate RF activity in mid-swing, using 3-dimensional analysis before and 1 month after BTX injection into RF (Botox, 200 units). Thigh—shank coordination was measured in the sagittal plane by averaging the continuous relative phase (CRPThigh— Shank) during each phase of the gait cycle in both lower limbs. The CRP is a validated metric that integrates angle positions and velocities of 2 limb segments to quantify their temporal—spatial coordination. Results. Before treatment, the low peak knee flexion in hemiparetic subjects (paretic limb 29 ± 9°) was associated with a decreased CRP Thigh—Shank in the paretic limb in swing (paretic limb 26.0 ± 16.6° vs controls 73.5 ± 7.4°, P < .001) and with a trend of an increased CRPThigh —Shank in the nonparetic limb over the full gait cycle (nonparetic limb 77.9 ± 14.1° vs controls 66.2 ± 19.8°, P = .083). After treatment, the CRPThigh— Shank increased by 11.9° in the swing phase of the paretic limb (P = .002) and decreased by 8.0° over the full gait cycle ( P = .002) in the nonparetic limb. Conclusions. BTX injection into RF was associated with improved thigh—shank coordination in parts of the gait cycle, in both injected paretic and noninjected nonparetic limbs.

Does lower limb preference influence gait initiation

Gait initiation (GI) has been the focus of many investigations in order to determine the kinematic and kinetic parameters associated with this process. In these studies, the parameters are observed during GI with the preferential lower limb. However, none of these studies have looked at the impact on GI parameters when the start is achieved with the non-preferential limb. This investigation focused on the effects of lower limb preference on the kinematic and kinetic parameters of GI. Upon display of a visual cue, subjects stepped with preferential limb or non-preferential limb at natural speed. The duration of GI phases, the medio-lateral component of the center of mass (CM) displacement, the medio-lateral distance between the center of pressure and the CM, the step width as well as the medio-lateral impulse, were observed. When subjects started with the non-preferential limb, the bodyweight transfer was facilitated by a greater impulse during the anticipatory postural adjustment (APA) phase. Conversely, a more lateral CM displacement during the execution phase and a more lateral step in preferential start were observed. Asymmetry in frontal plane body motion was observed during weight transfer following APA, as well as during assistive control of ballistic body motion during the execution phase of the first step. In both conditions, the non-preferential limb provided the greater lateral impulse on the ground. This may have clinical relevance especially in individuals with unilateral limb dyscontrol and postural asymmetry that may require rehabilitation.

Lower limb coordination patterns in hemiparetic gait: factors of knee flexion impairment.

BACKGROUND The mechanisms altering knee flexion in hemiparetic gait may be neurological (muscle overactivity) or orthopedic (soft tissue contracture) in nature, a distinction which is difficult to ascertain clinically during gait. This study aimed to distinguish the 2 mechanisms in evaluating thigh-shank coordination, which may show instability across the gait cycle in the case of bursting rectus femoris overactivity. METHODS We measured thigh-shank coordination in the sagittal plane using the continuous relative phase during gait in 15 healthy subjects without and with an orthotic knee constraint (control and constrained) and 14 subjects with hemiparesis and rectus femoris overactivity before (pre) and after botulinum toxin injection. FINDINGS Compared with the control group, both orthopedic and neurological knee flexion limitations were associated with decreased root-mean square of continuous relative phase over swing (control, 72.9; constrained, 26.0, P<0.001; pre, 31.3, P<0.001). However, only the neurological limitation was characterized by a higher number of continuous relative phase reversals over swing (control, 2.3; pre, 4.0; P=0.001) and late stance (control, 0.6; pre, 1.7; P<0.001). Botulinum toxin injection was associated with a 40% increase in root-mean square of continuous relative phase during swing and a 41% decrease in number of continuous relative phase reversals during late stance, while peak knee flexion was increased by 31%. INTERPRETATION In hemiparesis, rectus femoris overactivity at swing phase is associated with alternating thigh-shank coordination in swing and late stance, which improves after botulinum toxin injection. Coordination analysis may help to distinguish neurological from orthopedic factors in knee flexion impairment.

Estimation of the 3-D center of mass excursion from force-plate data during standing

Biomechanical models are used with force-plate information to determine the center of mass (COM) trajectory during standing. They are usually based on simplifying assumptions and are often limited to a single-plane analysis. The objectives of this study were to present a three-dimensional (3-D) model to calculate the excursion of the COM of the human body, validate it and compare its performance to a video-based system during quiet standing and antero-posterior (AP) and medio-lateral (ML) self-imposed oscillations. In addition to the vertical displacements of the COM, the originality of the method lies in eliminating the accelerations terms in the model and their related assumptions. The model was able to estimate closely the COM displacements in quiet standing [a root mean square (RMS) of 0.9 mm or less]. For the self-imposed oscillations, the RMS differences were 6.6 mm in the AP and ML directions and 1.6 mm along the vertical axis. For all three testing conditions, the coefficients of correlation of the COM displacements between the model and the video methods were above 0.8 with the exception of the vertical direction, where the values were more variable.

Walking velocity and lower limb coordination in hemiparesis

BACKGROUND/OBJECTIVE Gait training at fast speed has been suggested as an efficient rehabilitation method in hemiparesis. We investigated whether maximal speed walking might positively impact inter-segmental coordination in hemiparetic subjects. METHODS We measured thigh-shank and shank-foot coordination in the sagittal plane during gait at preferred (P) and maximal (M) speed using the continuous relative phase (CRP), in 20 healthy and 27 hemiparetic subjects. We calculated the root-mean square (CRP(RMS)) and its variability (CRP(SD)) over each phase of the gait cycle. A small CRP(RMS) indicates in-phasing, i.e. high level of synchronization between two segments along the gait cycle. A small CRP(SD) indicates high stability of the inter-segmental coordination across gait cycles. RESULTS Increase from preferred to maximal speed was 57% in healthy and 49% in hemiparetic subjects (difference NS). In healthy subjects, the main change was shank-foot in-phasing at stance (CRP(Shank-Foot/RMS), P, 98±10; M, 67±12, p<0.001). In hemiparetic subjects, we also found shank-foot in-phasing at late stance bilaterally (non-paretic CRP(Shank-Foot/RMS), P, 37±9; M, 29±8, p<0.001; paretic CRP(Shank-Foot/RMS), P, 38±13; M, 32±12, p<0.001), and thigh-shank in-phasing at mid-stance in the non-paretic limb (CRP(Thigh-Shank/RMS), P, 57±9; M, 49±9, p<0.001). CRP(Thigh-Shank) variability diminished in the paretic limb (CRP(Thigh-Shank/SD), P, 18.3±6.3; M, 16.1±5.2, p<0.001). CONCLUSION During gait velocity increase in hemiparesis, there is improvement of thigh-shank coordination stability in the paretic limb and of shank-foot synchronization at late stance bilaterally, which optimizes the propulsive phase similarly to healthy subjects. These findings may add incentive for rehabilitation clinicians to explore maximal velocity gait training in hemiparesis.

Trunk's Natural Inclination Influences Stance Limb Kinetics, but Not Body Kinematics, during Gait Initiation in Able Men

The imposing mass of the trunk in relation to the whole body has an important impact on human motion. The objective of this study is to determine the influence of trunks natural inclination - forward (FW) or backward (BW) with respect to the vertical - on body kinematics and stance limb kinetics during gait initiation. Twenty-five healthy males were divided based on their natural trunk inclination (FW or BW) during gait initiation. Instantaneous speed was calculated at the center of mass at the first heel strike. The antero-posterior impulse was calculated by integrating the antero-posterior ground reaction force in time. Ankle, knee, hip and thoraco-lumbar (L5) moments were calculated using inverse dynamics and only peaks of the joint moments were analyzed. Among all the investigated parameters, only joint moments present significant differences between the two groups. The knee extensor moment is 1.4 times higher (P<0.001) for the BW group, before the heel contact. At the hip, although the BW group displays a flexor moment 2.4 times higher (P<0.001) before the swing limbs heel-off, the FW group displays an extensor moment 3.1 times higher (P<0.01) during the swing phase. The three L5 extensor peaks after the toe-off are respectively 1.7 (P<0.001), 1.4 (P<0.001) and 1.7 (P<0.01) times higher for the FW group. The main results support the idea that the patterns described during steady-state gait are already observable during gait initiation. This study also provides reference data to further investigate stance limb kinetics in specific or pathologic populations during gait initiation. It will be of particular interest for elderly people, knowing that this population displays atypical trunk postures and present a high risk of falling during this forward stepping.

Bilateral Strength Deficit Is Not Neural in Origin; Rather Due to Dynamometer Mechanical Configuration.

During maximal contractions, the sum of forces exerted by homonymous muscles unilaterally is typically higher than the sum of forces exerted by the same muscles bilaterally. However, the underlying mechanism(s) of this phenomenon, which is known as the bilateral strength deficit, remain equivocal. One potential factor that has received minimal attention is the contribution of body adjustments to bilateral and unilateral force production. The purpose of this study was to evaluate the plantar-flexors in an innovative dynamometer that permitted the influence of torque from body adjustments to be adapted. Participants were identically positioned between two setup configurations where torques generated from body adjustments were included within the net ankle torque (locked-unit) or independent of the ankle (open-unit). Twenty healthy adult males performed unilateral and bilateral maximal voluntary isometric plantar-flexion contractions using the dynamometer in the open and locked-unit mechanical configurations. While there was a significant bilateral strength deficit in the locked-unit (p = 0.01), it was not evident in the open-unit (p = 0.07). In the locked-unit, unilateral torque was greater than in the open-unit (p<0.001) and this was due to an additional torque from the body since the electromyographic activity of the agonist muscles did not differ between the two setups (p>0.05). This study revealed that the mechanical configuration of the dynamometer and then the body adjustments caused the observation of a bilateral strength deficit.

Propulsion and braking in the study of asymmetry in able-bodied men's gaits.

The present study was designed to test functional differences between both lower limbs in able-bodied gait according to fore-aft force impulse analyses and to assess the existence of a preferential lower limb for forward propulsion and braking. The leg that did more of the braking (Most Braking Limb) and the leg that did more of the propulsion (Most Propulsive Limb) were defined by the higher negative and positive impulses calculated from the anterior-posterior component of the ground reaction force. 24 adult men free of pain and injury to their lower extremities (M age = 25.9 yr., SD = 4.5) performed 10 walking trials on a 10-m walkway with two force plates flush mounted in the middle. The anterior-posterior component of the velocity of the center of mass (VAP) was calculated with the VICON system. Results highlighted two forms of asymmetry behaviour: although significant bilateral differences between the legs concerning the propulsive and braking impulses were found in all participants, 70.8% of the participants displayed a different Most Braking Limb than Most Propulsive Limb, whereas 25% used the same leg to produce both more propulsion and braking. High consistency was found in the behavioural strategy. Bilateral differences in VAP according to the gait cycle (Most Propulsive Limb vs Most Braking Limb) suggested a functional division of tasks between the two lower limbs for 70.8% of the participants. The study provides support for the relevancy of a functional categorization to highlight different asymmetry strategies in able-bodied gait.