Brief report: Passive mechanical properties of gastrocnemius in multiple sclerosis and ankle contracture.

BACKGROUND: Ankle contracture is common in people with multiple sclerosis (MS) but the mechanisms of contracture are not clear. This study aimed to identify the mechanisms of contracture in MS by comparing passive muscle length and stiffness at known tension, separated into contributions by muscle fascicles and tendons, between people with MS who had contracture and healthy people. METHODS: Passive length-tension curves of the gastrocnemius muscle-tendon unit were derived from passive ankle torque and angle using a published biomechanical method. Ultrasound images of medial gastrocnemius muscle fascicles were used to partition length-tension curves into fascicle and tendon components. Lengths and stiffness of the muscle-tendon unit, muscle fascicles and tendons were compared between groups with linear regression. FINDINGS: Data were obtained from 15 participants with MS who had contracture [age 53 (12) years, mean (SD)] and 25 healthy participants [48 (20) years]. Participants with MS had clinically significant ankle contracture, and had shorter fascicles at slack length (between-groups mean difference -0.8 cm, 95% CI -1.2 to -0.4 cm, p < 0.001) and at 100 N (-0.7 cm, 95% CI -1.3 to -0.1 cm, p = 0.02) compared to healthy participants. There were no differences between groups in all other outcomes. INTERPRETATION: Tension-referenced comparisons of passive muscle length and stiffness show that people with MS who had contracture had shorter fascicles at low and high tension compared to healthy people, but there were no changes to the muscle-tendon unit or tendon. Further studies are needed to identify the causes and mechanisms of contracture in neurological conditions.

Safety, Feasibility, and Efficacy of an Eccentric Exercise Intervention in People with Multiple Sclerosis with Ankle Contractures.

BACKGROUND: The primary aim of this study was to investigate the safety and feasibility of an eccentric exercise program for people with multiple sclerosis (MS) who have ankle contractures, ie, reduced ankle range of motion (ROM). Secondary aims were to explore the efficacy of this eccentric exercise on ankle joint ROM and functional mobility. METHODS: Five adults with MS with ankle contractures (three women and two men; mean ± SD age, 50.8 ± 9.4; MS duration, 7.6 ± 5.6 years) completed two eccentric exercise training sessions (10-45 minutes) per week for 12 weeks. The training involved walking backward downhill on an inclined treadmill (gradient, 10°-14°) at a self-selected pace. The intervention was assessed for safety (adverse events), feasibility (recruitment rates, adherence rates, enjoyment levels, difficulty, and discomfort), and clinical outcomes, including passive/active ankle ROM and distance walked in 6 minutes. RESULTS: There were no adverse events during or after the eccentric exercise training. There was a 100% adherence rate. All participants enjoyed the training and experienced low levels of muscle soreness/discomfort. The training program improved passive/active ankle ROM in all participants; however, improvements did not translate to improvements in walking for all participants. CONCLUSIONS: Walking backward and downhill is a safe and feasible training modality for people with MS with ankle contractures. Clinical outcomes (greater passive/active ankle ROM) after this eccentric exercise training were evident. However, translation to clinically meaningful changes in walking function requires further examination.

Between session reliability of heel-to-toe progression measurements in the stance phase of gait.

The objective of the current study was to determine the test-retest reliability of heel-to-toe progression measures in the stance phase of gait using intraclass correlation coefficient (ICC) analysis. It has been proposed that heel-to-toe progression could be used as a functional measure of ankle muscle contracture/weakness in clinical populations. This was the first study to investigate the test-retest reliability of this measure. Eighteen healthy subjects walked over the GAITRite® mat three times at a comfortable speed on two sessions (≥ 48 hours apart). The reliability of the heel-to-toe progression measures; heel-contact time, mid-stance time and propulsive time were assessed. Also assessed were basic temporal-spatial parameters; velocity, cadence, stride length, step length, stride width, single and double leg support time. Reliability was determined using the ICC(3,1) model and, fixed and proportional biases, and measures of variability were assessed. Basic gait temporal-spatial parameters were not different between sessions (p > 0.05) and had excellent reliability (ICC(3,1) range: 0.871-0.953) indicating that subjects walked similarly between sessions. Measurement of heel-to-toe progression variables were not different between sessions (p > 0.05) and had excellent reliability (ICC(3,1) range: 0.845-0.926). However, these were less precise and more variable than the measurement of standard temporal-spatial gait variables. As the current study was performed on healthy populations, it represents the 'best case' scenario. The increased variability and reduced precision of heel-to-toe progression measurements should be considered if being used in clinical populations.

Wearable technology reveals gait compensations, unstable walking patterns and fatigue in people with multiple sclerosis.

OBJECTIVE: People with multiple sclerosis (PwMS) often experience a decline in gait performance, which can compromise their independence and increase falls. Ankle joint contractures in PwMS are common and often result in compensatory gait patterns to accommodate reduced ankle range of motion (ROM). APPROACH: Using advances in wearable technology, the aim of this study was to quantify head and pelvis movement patterns that occur in PwMS with disability and determine how these secondary gait compensations impact on gait stability. Twelve healthy participants and 12 PwMS participated in the study. Head and pelvis movements were measured using two tri-axial accelerometers. Measures of gait compensation, mobility, variability, asymmetry, stability and fatigue were assessed during a 6 min walking test. MAIN RESULTS: Compared to healthy controls, PwMS had greater vertical asymmetry in their head and pelvic movements (Cohen's d = 1.85 and 1.60). Lower harmonic ratios indicated that PwMS were more unstable than controls (Cohen's d = -1.61 to -3.06), even after adjusting for their slower walking speeds. In the PwMS, increased compensatory movements were correlated with reduced ankle active ROM (r = -0.71), higher disability (EDSS) scores (r = 0.58), unstable gait (r = -0.76), reduced mobility (r = -0.76) and increased variability (r = 0.83). SIGNIFICANCE: Wearable device technology provides an efficient and reliable way to screen for excessive compensatory movements often present in PwMS and provides clinically important information that impacts on mobility, stride time variability and gait stability. This information may help clinicians identify PwMS at high risk of falling and develop better rehabilitation interventions that, in addition to improving mobility, may help target the underlying causes of unstable gait.

Impaired heel to toe progression during gait is related to reduced ankle range of motion in people with Multiple Sclerosis.

BACKGROUND: Gait impairment in people with Multiple Sclerosis results from neurological impairment, muscle weakness and reduced range of motion. Restrictions in passive ankle range of motion can result in abnormal heel-to-toe progression (weight transfer) and inefficient gait patterns in people with Multiple Sclerosis. The purpose of this study was to determine the associations between gait impairment, heel-to-toe progression and ankle range of motion in people with Multiple Sclerosis. METHODS: Twelve participants with Multiple Sclerosis and twelve healthy age-matched participants were assessed. Spatiotemporal parameters of gait and individual footprint data were used to investigate group differences. A pressure sensitive walkway was used to divide each footprint into three phases (contact, mid-stance, propulsive) and calculate the heel-to-toe progression during the stance phase of gait. FINDINGS: Compared to healthy controls, people with Multiple Sclerosis spent relatively less time in contact phase (7.8% vs 25.1%) and more time in the mid stance phase of gait (57.3% vs 33.7%). Inter-limb differences were observed in people with Multiple Sclerosis between the affected and non-affected sides for contact (7.8% vs 15.3%) and mid stance (57.3% and 47.1%) phases. Differences in heel-to-toe progression remained significant after adjusting for walking speed and were correlated with walking distance and ankle range of motion. INTERPRETATION: Impaired heel-to-toe progression was related to poor ankle range of motion in people with Multiple Sclerosis. Heel-to-toe progression provided a sensitive measure for assessing gait impairments that were not detectable using standard spatiotemporal gait parameters.

Gyroscopic corrections improve wearable sensor data prior to measuring dynamic sway in the gait of people with Multiple Sclerosis.

Accelerometers are incorporated into many consumer devices providing new ways to monitor gait, mobility, and fall risk. However, many health benefits have not been realised because of issues with data quality that results from gravitational 'cross-talk' when the wearable device is tilted. Here we present an adaptive filter designed to improve the quality of accelerometer data prior to measuring dynamic pelvic sway patterns during a six minute walk test in people with and without Multiple Sclerosis (MS). Optical motion capture was used as the gold standard. Improved wearable device accuracy (≤4.4% NRMSE) was achieved using gyroscopic corrections and scaling filter thresholds by step frequency. The people with MS presented significantly greater pelvis sway range to compensate for their lower limb weaknesses and joint contractures. The visualisation of asymmetric pelvic sway in people with MS illustrates the potential to better understand their mobility impairments for reducing fall risk.