Locomotor patterns in cerebellar ataxia

Several studies demonstrated how cerebellar ataxia (CA) affects gait, resulting in deficits in multi-joint coordination and stability. Nevertheless, how lesions of cerebellum influence the locomotor muscle pattern generation is still unclear. To better understand the effects of CA on locomotor output, here we investigated the idiosyncratic features of the spatiotemporal structure of leg muscle activity and impairments in the biomechanics of CA gait. To this end, we recorded the electromyographic (EMG) activity of 12 unilateral lower limb muscles and analyzed kinematic and kinetic parameters of 19 ataxic patients and 20 age-matched healthy subjects during overground walking. Neuromuscular control of gait in CA was characterized by a considerable widening of EMG bursts and significant temporal shifts in the center of activity due to overall enhanced muscle activation between late swing and mid-stance. Patients also demonstrated significant changes in the intersegmental coordination, an abnormal transient in the vertical ground reaction force and instability of limb loading at heel strike. The observed abnormalities in EMG patterns and foot loading correlated with the severity of pathology (clinical ataxia scale, ICARS) and the changes in the biomechanical output. The findings provide new insights into the physiological role of cerebellum in optimizing the duration of muscle activity bursts and the control of appropriate foot loading during locomotion

Biomechanical, muscle activation and clinical characteristics of chronic exertional compartment syndrome

Chronic exertional compartment syndrome (CECS) is a common problem within both military and athletic populations that can be difficult to diagnose. Furthermore, it is unclear what causes the development of CECS, particularly in the military population, as personnel undertake a variety of activities that can cause pain with CECS such as fast walking, marching and running. Chronic exertional compartment syndrome has been hypothesised to develop due to excessive muscle activity, foot pronation and abnormal biomechanics predominantly at the ankle. Treatment of CECS through running re-education to correct these abnormalities has been reported to improve symptoms. However no primary research has been carried out to investigate the biomechanical, muscle activation and clinical characteristics of military patients with CECS. The purpose of this thesis was to provide an original contribution to the knowledge through the exploration of these characteristics; and the development of insights into the development of CECS, with implications for prevention and treatment. Study one investigated the clinical characteristics of 93 service personnel with CECS. Plantar pressure variables, related to foot type and anterior compartment muscle activity, and ankle joint mobility were compared during walking between 70 cases and 70 controls in study two. Study three compared three-dimensional whole body kinematics, kinetics and lower limb muscle activity during walking and marching between 20 cases and 20 controls. Study four compared kinematics and lower limb muscle activity during running in a separate case-control cohort (n=40). Differences in electromyography (EMG) intensity during the gait cycle were compared in the frequency and time domain using wavelet analysis. All studies investigated subject anthropometry. Cases typically presented with bilateral, ‘tight’ or ‘burning’ pain in the anterior and lateral compartments of the lower leg that occurred within 10 minutes of exercise. This pain stopped all cases from exercising during marching and/or running. As such subsequent studies investigated the biomechanics of both ambulatory and running gaits. Cases in all case-control studies were 2-10 cm shorter; and were typically overweight resulting in a higher body mass index (BMI) than controls. There was strong evidence from study 3 that cases had greater relative stride lengths than controls during marching gait. This was achieved through an increase in ankle plantarflexion during late stance and a concomitant increase in the gastrocnemius medialis contraction intensity within the medium-high frequency wavelets. Given the differences in height observed, this may reflect ingrained alterations in gait resulting from military training; whereby all personnel are required to move at an even cadence and speed. These differences in stride length were also observed in walking and running gaits although to a lesser extent. There was no evidence from the EMG data that cases had greater tibialis anterior activation than controls during any activity tested, at any point in the gait cycle or in any frequency band. In agreement, there was also no evidence of differences between groups in plantar pressure derived measures of foot type, which modulate TA activity. Toe extensor - related plantar pressure variables also did not differ between groups. In summary, contrary to earlier theories, increased muscle activity of the anterior compartment musculature does not appear to be associated with CECS. The kinematic differences observed during running only partially matched the clinical observations previously described in the literature. Cases displayed less anterior trunk lean and less anterior pelvic tilt throughout the whole gait cycle and a more upright shank inclination angle during late swing (peak mean difference 3.5°, 4.1° and 7.3° respectively). However, no consistent differences were found at the ankle joint suggesting that running is unlikely to be the cause of CECS in the military; and that the reported success of biomechanical interventions may be due to reasons other than modifying pathological aspects of gait. In summary, the data presented in the thesis suggest that CECS is more likely to develop in subjects of shorter stature and that this is associated with marching at a constant speed and cadence. Biomechanical interventions for CECS, such as a change in foot strike or the use of foot orthotics, are unlikely to be efficacious for the military as personnel will continue to be required to march at prescribed speeds to satisfy occupational requirements. Preventative strategies that allow marching with a natural gait and/or at slower speeds may help reduce the incidence of CECS. The lack of association with foot type or muscle activity suggests that foot orthoses would not be a useful prevention strategy or treatment option for this condition.Headley Court Trustees - funding of student fee

Kinematics, Kinetics, and Modeling of Fatigue in Young Distance Runners

In recent years, organized distance races have reported increases in children and young adult participants. In addition, female high school athletes generally experience higher rates of injury, including those due to overuse and specialization. These early injuries can lead to a higher likelihood of future injuries, growth plate disruption, and psychological outcomes like burnout. However, there is no general consensus among coaches, physicians, or athletic bodies about safe cumulative running loads at younger ages. The purpose of this study was to investigate how kinematics, kinetics, and muscle activations changed with fatigue in a group of young female distance runners. Motion and ground reaction force data was collected before and after a 5-kilometer run at the subjects’ personal best pace for eleven healthy girls aged 8-17. The resultant data was processed and characteristics such as joint angles, moments, and powers, ground reaction forces, and muscle forces were compared for pre and post run, as well as for the younger runners compared to the older runners. Ankle joint mechanics were most significantly altered by fatigue, and knee kinetic changes were most dependent on the runners’ age. In addition, knee flexor forces increased and extensor forces decreased with fatigue, while changes to muscle forces around the hip and ankle were more dependent on the age of the runner. These results suggest that performance and injury avoidance in these young runners can be aided by strength programs including the involved muscles to avoid imbalances

歩行制御の加齢変化におけるバイオメカニクス研究

博士（学術）神戸大

Immature Spinal Locomotor Output in Children with Cerebral Palsy

Cappellini G, P. Ivanenko Y, Martino G, et al. Immature Spinal Locomotor Output in Children with Cerebral Palsy. Frontiers in Physiology. 2016;7:478

Lower limb co-contraction during walking in subjects with stroke: A systematic review

a b s t r a c t Purpose: The aim of this paper was to identify and synthesise existing evidence on lower limb muscle cocontraction (MCo) during walking in subjects with stroke. Methods: An electronic literature search on Web of Science, PubMed and B-on was conducted. Studies from 1999 to 2012 which analysed lower limb MCo during walking in subjects with stroke, were included. Results: Eight articles met the inclusion criteria: 3 studied MCo in acute stage of stroke, 3 in the chronic stage and 2 at both stages. Seven were observational and 1 had a pretest-posttest interventional design. The methodological quality was ''fair to good'' to ''high'' quality (only 1 study). Different methodologies to assess walking and quantify MCo were used. There is some controversy in MCo results, however subjects with stroke tended towards longer MCo in both lower limbs in both the acute and chronic stages, when compared with healthy controls. A higher level of post-stroke walking ability (speed; level of independence) was correlated with longer thigh MCo in the non-affected limb. One study demonstrated significant improvements in walking ability over time without significant changes in MCo patterns. Conclusions: Subjects with stroke commonly present longer MCo during walking, probably in an attempt to improve walking ability. However, to ensure recommendations for clinical practice, further research with standardized methodologies is needed

Changes in joint coupling and variability during walking following tibialis posterior muscle fatigue

<p>Abstract</p> <p>Background</p> <p>The tibialis posterior muscle is believed to play a key role in controlling foot mechanics during the stance phase of gait. However, an experiment involving localised tibialis posterior muscle fatigue, and analysis of discrete rearfoot and forefoot kinematic variables, indicated that reduced force output of the tibialis posterior muscle did not alter rearfoot and forefoot motion during gait. Thus, to better understand how muscle fatigue affects foot kinematics and injury potential, the purpose of this study was to reanalyze the data and investigate shank, rearfoot and forefoot joint coupling and coupling variability during walking.</p> <p>Methods</p> <p>Twenty-nine participants underwent an exercise fatigue protocol aimed at reducing the force output of tibialis posterior. An eight camera motion analysis system was used to evaluate 3 D shank and foot joint coupling and coupling variability during treadmill walking both pre- and post-fatigue.</p> <p>Results</p> <p>The fatigue protocol was successful in reducing the maximal isometric force by over 30% and a concomitant increase in coupling motion of the shank in the transverse plane and forefoot in the sagittal and transverse planes relative to frontal plane motion of the rearfoot. In addition, an increase in joint coupling variability was measured between the shank and rearfoot and between the rearfoot and forefoot during the fatigue condition.</p> <p>Conclusions</p> <p>The reduced function of the tibialis posterior muscle following fatigue resulted in a disruption in typical shank and foot joint coupling patterns and an increased variability in joint coupling. These results could help explain tibialis posterior injury aetiology.</p

CHANGES IN LONGITUDINALLY ASSESSED BIOMECHANICAL PARAMETERS RELATED TO INCREASED RISK OF ANTERIOR CRUCIATE LIGAMENT (ACL) INJURIES IN ADOLESCENT FEMALE AND MALE ATHLETES

Females suffer anterior cruciate ligament (ACL) injuries at a 2 to 10-fold greater rate compared to male athletes participating in similar sports. Altered movement patterns and inadequate knee stiffness are two interrelated factors that may increase ACL injury risk. Onset of these neuromuscular risk factors may coincide with the rapid adolescent growth that results in the divergence of a multitude of neuromuscular parameters between sexes. The overall purpose of this dissertation was to determine if neuromuscular ACL injury risk factors in female athletes increase following rapid growth and development compared to males. Male and female athletes were tested with three-dimensional motion analysis techniques during a drop vertical jump over two consecutive years to determine if ACL injury risk factors increased. Pubertal females showed a significant longitudinal increase in knee abduction angle compared to post-pubertal females and both male groups. The increase in knee abduction angle appeared to remain consistent, as the post pubertal female cohort had greater overall knee abduction compared to post-pubertal males. Similar results were found with a greater magnitude of knee abduction moment in post-pubertal females compared to males. Males and females increased ankle, knee and hip active stiffness from the first to second year of testing. Ankle and hip stiffness were increased significantly more in the pubertal group compared to post-pubertal. Sex and maturational group differences were found in hip and ankle joint stiffness. Post-pubertal males had significantly greater hip stiffness than the other groups (even when normalized to body mass). This indicates that post-pubertal males utilized a different neuromuscular strategy during landing. Males had a significantly greater increase from year to year in vertical jump height compared to females. Vertical jump height is often related to a measure of whole body power and indicates that males had a significant neuromuscular spurt compared to females. Early puberty appears to be a critical phase related to the divergence of increased ACL injury risk factors. Injury prevention programs that focus on neuromuscular training may be beneficial to help address the development of ACL injury risk factors that occur in female athletes during maturation