Development of Postural Adjustment During Gait Initiation: Kinematic and EMG Analysis

The authors studied the development of postural adjustments associated with the initiation of gait in children by using kinematic and electromyographic (EMG) analysis. Participants (N = 28) included infants with 1-4 and 9-17 months of walking experience, children 4-5 years of age, and adults. Anticipatory postural adjustments (APA) were present in the youngest age groups, including a clear anticipatory lateral tilt of the pelvis and the stance leg, which enabled the child to unload the opposite leg shortly before its swing phase. An anticipatory activation of the hip abductor of the leg in stance phase prior to heel-off was found, suggesting pelvis stabilization. APA did not appear consistently until 4-5 years of age. A decrease in segmental oscillations occurred across the ages, indicating better control of intersegmental coordination in the frontal and sagittal planes during the postural phase of gait initiation. Young walkers presented APA involving movements of both the upper and the lower parts of the body, whereas, like adults, 4- to 5-year-olds were able to laterally shift only the pelvis and the stance leg. The oldest children and the adults also showed lower activation levels of hip and knee muscles but higher activation at the ankle level. Those kinematic and EMG results taken together suggest a clear developmental sequence from an en bloc operation of the body through an articulated operation with maturation, walking experience, or both.     

Increased forefoot loading is associated with an increased plantar flexion moment

The aim of this study was to identify the cascade of effects leading from alterations in force generation around the ankle joint to increased plantar pressures under the forefoot. Gait analysis including plantar pressure measurement was performed at an individually preferred and a standardized, imposed gait velocity in diabetic subjects with polyneuropathy (n = 94), without polyneuropathy (n = 39) and healthy elderly (n = 19). The plantar flexion moment at 40% of the stance phase was negatively correlated with the displacement rate of center of pressure (r = ?.749, p < .001 at the imposed, and r = ?.693, p < .001 at the preferred gait velocity). Displacement rate of center of pressure was strongly correlated with forefoot loading (r = ?.837, p < .001 at the imposed, and r = ?.731, p < .001 at the preferred gait velocity). People with a relatively high plantar flexion moment at 40% of the stance phase, have a faster forward transfer of center of pressure and consequently higher loading of the forefoot. This indicates that interventions aimed at increasing the control of the roll-off of the foot may contribute to a better plantar pressure distribution.     

Walking impairs cognitive performance among people with multiple sclerosis but not controls

People with multiple sclerosis (MS) complain of problems completing two tasks simultaneously; sometimes called ‘dual-tasking’ (DT). Previous research in DT among people with MS has focused on how adding a cognitive task interferes with gait and few have measured how adding a motor task could interfere with cognition. We aimed to determine the extent to which walking affects a concurrent working memory task in people with MS compared to healthy controls. We recruited MS participants (n = 13) and controls (n = 10) matched by age (±3 years), education (±3 years) and gender. Participants first completed the cognitive task (subtracting 7’s from the previous number) and then again while walking on an instrumented walkway. Although there were no baseline differences in cognition or walking between MS participants and controls, MS participants demonstrated a 52% decrease in number of correct answers during DT (p < 0.001). Mental Tracking Rate (% correct answers/min) correlated strongly with MS-related disability measured using the Expanded Disability Status Scale (EDSS; r(11) = −0.68, p < 0.01). We propose that compromised mental tracking during walking could be related to limited neural resource capacity and could be a potentially useful outcome measure to detect ecologically valid dual tasking impairments.     

Investigation of factors impacting mobility and gait in Parkinson disease

Mobility and gait limitations are major issues for people with Parkinson disease (PD). Identification of factors that contribute to these impairments may inform treatment and intervention strategies. In this study we investigated factors that predict mobility and gait impairment in PD. Participants with mild to moderate PD and without dementia (n = 114) were tested in one session ‘off’ medication. Mobility measures included the 6-Minute Walk test and Timed-Up-and-Go. Gait velocity was collected in four conditions: forward preferred speed, forward dual task, forward fast as possible and backward walking. The predictors analyzed were age, gender, disease severity, balance, balance confidence, fall history, self-reported physical activity, and executive function. Multiple regression models were used to assess the relationships between predictors and outcomes. The predictors, in different combinations for each outcome measure, explained 55.7% to 66.9% of variability for mobility and 39.5% to 52.8% for gait velocity. Balance was the most relevant factor (explaining up to 54.1% of variance in mobility and up to 45.6% in gait velocity). Balance confidence contributed to a lesser extent (2.0% to 8.2% of variance) in all models. Age explained a small percentage of variance in mobility and gait velocity (up to 2.9%). Executive function explained 3.0% of variance during forward walking only. The strong predictive relationships between balance deficits and mobility and gait impairment suggest targeting balance deficits may be particularly important for improving mobility and gait in people with PD, regardless of an individual’s age, disease severity, fall history, or other demographic features.     

Postural control after unexpected external perturbation: Effects of Parkinson’s disease subtype

Different clinical subtypes of Parkinson’s disease (PD) have long been recognized. Recent studies have focused on two PD subtypes: Postural Instability and Gait Difficulty (PIGD) and Tremor Dominant (TD). PIGD patients have greater difficulties in postural control in relation to TD. However, knowledge about the differences in reactive adjustment mechanisms following a perturbation in TD and PIGD is limited. This study aimed to compare reactive postural adjustments under unexpected external perturbation in TD, PIGD, and control group (CG) subjects. Forty-five individuals (15 TD, 15 PIGD, and 15 CG) participated in this study. Postural perturbation was applied by the posterior displacement of the support surface in an unexpected condition. The velocity (15 cm/s) and displacement (5 cm/s) of perturbation were the same for all participants. Center of pressure (CoP) and center of mass (CoM) were analyzed for two reactive windows after the perturbation (0–200 ms and 200–700 ms). The Bonferroni post hoc test indicated a higher range of CoP in the PIGD when compared to the CG (p = 0.021). The PIGD demonstrated greater time to recover the stable posture compared to the TD (p = 0.017) and CG (p = 0.003). Furthermore, the TD showed higher AP-acceleration peak of CoM when compared to the PIGD (p = 0.048) and CG (p = 0.013), and greater AP-acceleration range of CoM in relation to the CG (p = 0.022). These findings suggest that PD patients present worse reactive postural control after perturbation compared to healthy older individuals. CoP and CoM parameters are sensitive to understand and detect the differences in reactive postural mechanisms in PD subtypes.     

Minimal detectable change of kinematic and spatiotemporal parameters in patients with chronic stroke across three sessions of gait analysis

Three-dimensional gait analysis is the gold standard for gait-assessment in patients with stroke. This technique is commonly used to assess the effect of treatment on gait parameters. In clinical practice, three gait analyses are usually carried out (baseline, after treatment and follow-up), the objectives were to define the reproducibility and the Minimum Detectable Change (MDC) for gait parameters in stance and swing measured using 3D-gait analysis, and to assess changes in MDC across three repeated 3D-gait analyses. Three gait analyses (V1, V2 and V3) were performed at 7-day intervals in twenty-six patients with chronic stroke. Kinematic data (in the sagittal plane, during swing and stance) and spatiotemporal data were evaluated for the paretic limb. Reliability was tested using repeated measures ANOVA with a Tukey post hoc test, and the MDC values were calculated for each parameter. Only the range of hip motion during swing changed significantly between V1 and V2, but no other kinematic parameters changed. No significant differences were observed for the spatiotemporal parameters. MDC values were always higher during the V1vsV2 comparison for both kinematic and spatiotemporal parameters. This is the first study to evaluate the MDC for kinematic and spatiotemporal parameters during stance and swing. Reliability of kinematic and spatiotemporal data across sessions was very good over the three sessions. MDC values were the lowest between V2 and V3 for most parameters. Use of the MDC will allow clinicians to more accurately determine the effect of treatments.     

Self-reported walking difficulty and knee osteoarthritis influences limb dynamics and muscle co-contraction during gait

Knee osteoarthritis (OA) gait is characterized by simultaneous flexor and extensor use, or co-contraction. Co-contraction can stabilize and redirect joint forces. However, co-contraction can push and pull on the femur and tibia that exacerbate OA symptoms and make walking difficult. Such movements are quantifiable by limb dynamics (i.e., linear acceleration and jerk); thus, this study examines limb dynamics and its relationship with co-contraction and OA related walking difficulty.Three groups of age-and-sex-matched subjects with and without OA and walking difficulty (N = 13 per group) walked with electromyography (EMG) on the knee extensors and flexors and inertial measurement units (IMUs) at the femur and tibia. We calculated co-contraction from antagonistic EMG signals and linear acceleration and its derivative jerk from IMUs. We determined group differences using one-way ANOVAs, nonparametric equivalence, and effect sizes, and main and interaction effects of walking difficulty with regression modeling.Medium effect sizes and differences for femoral acceleration (d = 0.64; P = .02) and jerk (d = 0.51; P = .01) were observed between with and without knee OA. Medium to large effect sizes (r = 0.33 to 0.51 and d = 0.81 to 0.97) and differences (P = .01 to 0.05) for tibial acceleration and jerk were obsevered between with and without walking difficulty. Walking difficulty moderated the relationship between tibial jerk and co-contraction (p < .05).Tibial jerk differences were observed based on walking difficulty. The significant interaction effect suggested that walking difficulty explained the relationship between limb dynamics and co-contraction. Perhaps co-contraction levels used by those with knee OA and no walking difficulty are optimal as compared to those with walking difficulty.     

Rhythmic priming across effector systems: A randomized controlled trial with Parkinson’s disease patients

This study investigated the immediate effects of auditory-motor entrainment across effector systems by examining whether Rhythmic Auditory Stimulation training of arm or finger movements would modulate gait speed. Forty-one participants with idiopathic Parkinson’s Disease were randomly assigned to 3 groups. Participants in the finger-tapping group tapped in synchrony with a metronome set to 20% faster pace than the pre-training walking cadence, whereas participants in the other group were asked to swing both arms in an alternating motion in synchrony with the metronome. Participants in the control condition did not receive training. To assess gait parameters pre- and post-training, participants walked on a 14-meter flat walkway at his/her preferred walking cadence with no auditory cueing. Results indicated that there was a significant increase in gait velocity after the finger tapping training (p < .005), whereas no differences were observed in the arm swing (p = .802) and in the control conditions (p = .525). Similarly, there were significant changes in gait cadence post-training in the finger tapping group (p < .005), but not after arm swing training (p = .879) or control (p = .759). There were no significant changes in stride length post-training in none of the groups. These findings suggest that auditory-motor entrainment in one effector system may prime a second effector system. Interestingly, however, the priming effect on gait was only observed in the finger tapping condition and not with synchronized arm swing movements. These findings have significant implications for motor rehabilitation and open new avenues for further investigation of the mechanisms underlying cross-effector coupling.     

Dynamic angular stiffness about the metatarsophalangeal joint increases with running speed

Altering the longitudinal bending stiffness of footwear has the potential to affect mechanics of the metatarsophalangeal (MTP) joint. Recent efforts have been put forth to identify an optimal bending stiffness of footwear to improve running performance. However, little is known about how this optimal bending stiffness may change with running speed. The purpose of this study was to investigate how dynamic angular stiffness about the MTP joint changes across running speeds. Eighteen participants ran at five speeds from 3.89 to 6.11 m/s. Metatarsophalangeal joint angles, moments, and stiffness were estimated for each speed. Two MTPJ load-displacement metrics were defined, active and critical stiffness. Instantaneous stiffness of the MTP joint was also quantified. There was a significant main effect of speed on critical stiffness (p < .001), maximum MTP moment (p < .001), MTP moment at maximum dorsiflexion (p < .001), and MTP range of motion (p = .013). There was no effect of speed on active stiffness (p = .094). These results support the notion that involvement of the MTP joint increases with running speed. Individual contributions of the foot and shoe to the MTP joint moment and stiffness suggest that the foot appears to dominate the stiffness of the foot-shoe complex and torque generation about the MTP joint. Instantaneous stiffness fluctuated throughout stance phase, suggesting that foot-shoe complex stiffness is time dependent. The ratio by which critical stiffness and MTP joint range of motion increase with running speed may provide insight for how to guide construction of performance footwear. These results suggest that when utilizing MTP joint mechanics for insights into designing a shoe for performance purposes, the effect of speed should be taken into consideration.     

Joint range of motion entropy changes in response to load carriage in military personnel

BackgroundOveruse accounts for 82% of injuries in military personnel, and these occur predominantly in the spine and lower limbs. While non-linear analyses have shown changes in overall stability of the movement during load carriage, individual joint contributions have not been studied. The concept of entropy compensation between task, organism and environmental constraints is studied at a joint level.Research questionThe aim of this study was to investigate whether using different methods of loading by military personnel would have an effect on the sample entropy of the joint ranges of motion.MethodsEleven male reserve infantry army soldiers (age: 22 ± 2 years; height: 1.80 ± 0.06 m; mass: 89.3 ± 14.4 kg) walked an outdoor, 800 m course under 5 load conditions: unloaded, 15 kg backpack, 25 kg backpack, 15 kg webbing and backpack and 25 kg webbing and backpack. Kinematic data was recorded at 240 Hz using the Xsens motion capture system. The ranges of motion (ROM) of the spine, hips and knee were calculated for each gait cycle. Mean ROM, coefficient of variation (CV) of the ROM and the sample entropy of the ROM were compared between conditions.ResultsSpine side flexion ROM decreased significantly from the control condition in all loaded conditions, while sample entropy of the spine side flexion ROM increased in some conditions with no significant change in CV. Conversely, the hip flexion ROM increased significantly from the control, while sample entropy of the hip flexion ROM decreased.SignificanceThese results suggest that entropy compensation may propagate at a joint level. Understanding that a decrease in certainty with which a joint angle is selected, may be accompanied by an increase at a neighbouring joint. This could be significant in monitoring injuries as a result of environmental or task constraints.