Jaap Harlaar

TWO STRATEGIES OF TRANSFERRING FROM SIT-TO-STAND ; THE ACTIVATION OF MONOARTICULAR AND BIARTICULAR MUSCLES

In this study, two different strategies of rising from a chair were compared, using integrated biomechanical and electromyographic analyses. Nine healthy subjects were instructed to rise using two different strategies: natural sit-to-stand transfer (NSTS) and a sit-to-stand transfer with full flexion of the trunk (FSTS). Sagittal kinematics and ground reaction forces were registered. Muscle activity of nine muscles of the right leg were recorded by means of surface EMG. All signals were synchronized at seat-off. The results show that no differences occur between the kinematics of knee and ankle, whereas the hip flexion is, as expected, higher during FSTS. The higher moment about the knee during NSTS is shifted to proportionally higher moments about the hip and ankle during FSTS. It is mainly the differences in the EMG-levels of the biarticular hip and knee muscles which might explain the differences in net moment. These results are in accordance with a theory about a particular role of biarticular muscles. On the other hand, the shift from knee to ankle cannot be associated with a particular increase in activity of the biarticular m.gastrocnemius. It is hypothesized that about the ankle, control of stability is preferred over movement control. An important conclusion for rehabilitation medicine is that a lower net moment about the knee in FSTS does not automatically imply that this reduces the load on the knee extensors.

Biomechanics and muscular activity during sit-to-stand transfer

In the present study 10 healthy subjects were measured, performing sit-to-stand transfers in a natural way. Starting position and speed of movement were standardized. Sagittal kinematics, the ground reaction force, and muscle activity of nine leg muscles were recorded. During sit-to-stand transfer the mass centre of the body was moved forward and upward. Based on the velocity of the mass centre of the body three phases were distinguished. In horizontal direction forward rotation of the upper body contributed to the velocity of the mass centre of the body, whereas extension of the legs contributed considerably in vertical direction. After seat-off most muscles were concentrically active, whereas the shortening velocity of the rectus femoris was very low. Thus hip and knee joints were extended and a relatively high knee moment was delivered to control the ground reaction force in a slightly backward direction. Co-contraction of hamstrings and rectus femoris in sit-to-stand transfer was judged to be efficient.

Recording scapular motion using an acromion marker cluster

Disorders of the shoulder complex can be accompanied by changes in the movement pattern of the scapula. However, scapular motion is difficult to measure. A possible non-invasive method for dynamic three-dimensional kinematic measurement of the human scapula is the use of a marker cluster placed on the flat part of the acromion. A small light-weight acromion marker cluster (AMC) is presented in this study. In order to assess validity, kinematics obtained with the AMC were compared to simultaneous scapula locator (SL) recordings in a series of postures. The test/retest variability of replacement of the AMC, was also assessed. Measurement errors appeared to be sensitive for the plane of movement, the degree of humerus elevation, and replacement of the AMC. The AMC generally under-estimated scapula motion, compared to the SL. Some significant differences were found between the two methods, although the absolute differences were small (maximum mean difference 8.4 degrees in extreme position). In humerus forward flexion and abduction the maximum mean differences were 6 degrees or lower. In conclusion, the AMC is a valid method of measuring scapular movement during arm elevation that could be used in shoulder pathologies. Placement and planes of movement should be carefully considered and elevation of the humerus should not exceed 100 degrees.

Anatomical information is needed in ultrasound imaging of muscle to avoid potentially substantial errors in measurement of muscle geometry

This study validates two‐dimensional (2D) ultrasound measurements of muscle geometry of the human medial gastrocnemius (GM) and investigates effects of probe orientation on errors in these measurements. Ultrasound scans of GM muscle belly were made both on human cadavers (n = 4) and on subjects in vivo (n = 5). For half of the cadavers, ultrasound scans obtained according to commonly applied criteria of probe orientation deviated 15° from the true fascicle plane. This resulted in errors of fascicle length and fascicle angle up to 14% and 23%, respectively. Fascicle‐like structures were detectable over a wide range of probe tilt and rotation angles, but they did not always represent true fascicles. Errors of measurement were either linear or quadratic functions of tilt angle. Similar results were found in vivo. Therefore, we conclude that similar errors are likely to occur for in vivo measurements. For all cadavers, at the distal end of GM, the true fascicle plane was shown to be perpendicular to the distal aponeurosis. Using transverse images of GM to detect the curvature of the deep aponeurosis at the distal end of the muscle belly is a simple strategy to help identify the fascicle plane. For subsequent longitudinal imaging, probe alignment within this plane will help minimize measurement errors of fascicle length, fascicle angle, and muscle thickness. Muscle Nerve, 2009

Electromyography in the biomechanical analysis of human movement and its clinical application.

This article introduces the area of scientific study of human movement. It is primarily intended for readers who wish to form a judgement on the usefulness of scientific movement analysis techniques in the treatment process of patients with abnormal movement patterns. With a focus on the analysis of human locomotion, the paper outlines the historical development of a biomechanical approach towards the understanding of human movement patterns. This approach alone proves to be inadequate in supplying reliable information on neuromuscular control of movement. It follows that electromyographic techniques are essential for this purpose. Scientific literature reveals relevant practical usability of such information. This is the rationale for a review of the historical, physiological, technical and methodological background of electromyographic analysis of movement. The field of management and rehabilitation of motor disability is identified as one important application area. On the basis of relevant literature, the present paper asserts that scientific analysis of human movement patterns can materially affect patient treatment. It provides evidence that patient management and rehabilitation processes in central neurological disorders can be improved through electromyographic techniques. In particular, this evidence supports the use of electromyography for surgical planning in children with cerebral palsy. The paper concludes with a view on future directions in research, development and applications of scientific analysis of human movement. Copyright 1998 Elsevier Science B.V.

EFFECT OF ANKLE-FOOT ORTHOSES ON WALKING EFFICIENCY ANd GAIT IN CHILdREN WITH CEREBRAL PALSY

OBJECTIVE To determine the effect of ankle-foot orthoses on walking efficiency and gait in a heterogeneous group of children with cerebral palsy, using barefoot walking as the control condition. DESIGN A retrospective study. METHODS Barefoot and ankle-foot orthosis data for 172 children with spastic cerebral palsy (mean age 9 years; hemiplegia: 21, diplegia: 97, and quadriplegia: 54) were compared. These data consisted of non-dimensional speed, net non- dimensional energy cost of walking (NN-cost), and NN-cost as a percentage of speed-matched controls (NN-cost(pct)). For 80 of these children the Gillette Gait Index and data for 3D gait kinematics and kinetics were also analyzed. RESULTS Speed was 9% faster (p<0.001), NN-cost was 6% lower (p=0.007), and NN-cost(pct) was 9% lower (p=0.022) when walking with an ankle-foot orthosis. The Gillette Gait Index remained unchanged (p=0.607). Secondary subgroup analysis for involvement pattern showed a significant improvement in NN-cost(pct) only for quadriplegics (20%, p=0.004), whereas it remained unchanged for patients with hemiplegia and diplegia. Changes in the minimum knee flexion angle in stance phase and in terminal swing were found to be significantly related to the change in NN-cost(pct) (p=0.013 and p=0.022, respectively). CONCLUSION The use of an ankle-foot orthosis resulted in a significant decrease in the energy cost of walking of quadriplegic children with cerebral palsy, compared with barefoot walking, whereas it remained unchanged in hemiplegic and diplegic children with cerebral palsy. Energy cost reduction was related to both a faster and more efficient walking pattern. The improvements in efficiency were reflected in changes of stance and swing phase knee motion, i.e. those children whose knee flexion angle improved toward the typical normal range demonstrated a decrease in energy cost of walking, and vice versa.

Quadriceps muscle endurance in patients with chronic obstructive pulmonary disease

The purpose of this study was to compare quadriceps muscle strength (maximal voluntary contraction, MVC), endurance (TLIM), and dynamic work capacity (WLIM) in 89 patients (57 men and 32 women) with chronic obstructive pulmonary disease (COPD) to 31 healthy controls (20 men and 11 women). Compared with the healthy subjects, COPD patients demonstrated statistically significant (P < 0.05) lower values for MVC, TLIM and WLIM. The MVC was 20–30% lower, whereas TLIM and WLIM were 70–80% lower in the patients. Stepwise multiple regression analysis revealed that pulmonary function variables contributed only partially to the explanation of variance in MVC, TLIM, and WLIM. Our results indicate that in patients with COPD, quadriceps muscle endurance and dynamic work capacity are impaired to a greater extent than is quadriceps muscle strength. For rehabilitation purposes, the findings may lead to more specific exercise programs, further enhancing rehabilitation outcomes in terms of functional abilities and social participation. Muscle Nerve 29: 267–274, 2004

Validation of the portable VmaxST system for oxygen-uptake measurement.

The aim of this study was to validate the accuracy of a new type of portable gas-analysis system (Sensormedics VmaxST) for the measurement of oxygen-uptake at expenditure levels that are reached during walking in patients with movement disorders. The criterion method was the Douglas Bag (DB) method, which is considered to be the gold standard. Accuracy evaluations were made in two trials, randomly using the VmaxST (ST) and the Douglas Bag method. Ten healthy adult subjects participated in the trials (age: 28.8 (4.3) years; body mass: 75 (13.3)kg; height: 179.3 (8.9)cm). Each trial consisted of two time periods: 5 min of resting in a comfortable chair and 5 min of cycling at an 80 W workload. During the fifth minute of each block, mean minute ventilation (VE), oxygen-uptake (VO2), and carbon dioxide production (VCO2) were measured or calculated for both systems. Energy expenditure (EE) values were calculated and net values calculated by subtracting resting measurements from gross measurements. The results show that no significant differences were found between the VmaxST and the Douglas Bag method for the primary parameters: EEnet and VO2net. Significantly higher values were found for rest and exercise values. However, these differences were very small. Therefore, the validity of the VmaxST is sufficient for use in gait studies to determine the energy cost of walking, especially when net values are calculated.

Passive stiffness characteristics of ankle plantar flexors in hemiplegia

OBJECTIVE To assess the feasibility and reliability of ankle plantar flexor stiffness measurements in hemiplegia. DESIGN Repeated measurements in five consecutive weeks. BACKGROUND In hemiplegia, an equinovarus positioning of the foot might be caused by an increased stiffness of the m. triceps surae. METHODS In eight hemiplegic patients the net joint torque of passive muscle stretch was measured as a function of ankle-angle by a dynamometer, at both sides. Ankle-stiffness was characterised and also a biomechanical model of the passive muscle was fitted. RESULTS In the vast majority of measurements it was possible to obtain measurements that were not distorted by involuntary muscle contraction. These measurements showed for the angle at which a passive plantar moment of 10 N m was reached a standard error of measurement of less than 2.7 degrees. The muscle model showed the increased stiffness as a shortening of the muscle-fibre-length. CONCLUSION The feasibility of this method to measure muscle stiffness was fair to good in hemiplegic patients. Provided the abandoning of involuntary muscle activity, the reproducibility warrants application in clinical practice at an individual level. The use of the model relates this changes to a shortened m. soleus and/or m. gastrocnemius. RelevanceEffective clinical decisions for treatment of equinovarus positioning of the foot in the hemiplegic individual, should consider excessive involuntary contractions of the m. triceps surae complex (i.e., spasticity), as well as shortened muscle tissue resulting in high stiffness. Despite the importance of increased stiffness there have been no validated methods of measurement.

Reliability assessment of isometric knee extension measurements with a computer-assisted hand-held dynamometer

OBJECTIVE To assess clinically relevant indexes of measurement error of hand-held dynamometer measurements using a computer-assisted hand-held dynamometer (CAHN-DY). DESIGN In separate sessions, different physical therapists performed repeated measurements of maximal isometric knee extension. SETTING Four physical therapy practices and outpatient departments. PATIENTS Consecutive samples of 30 male and 28 female patients aged 13 to 77 years, with isolated orthopedic knee disorders participated in this study. MAIN OUTCOME MEASURES For intrarater and interrater applications, the standard error of measurement (SEM) and related 95% confidence intervals and minimal detectable changes were assessed. RESULTS Sixty percent of the patients performed within the therapists upper force limit. Variance between sessions performed by the same or different therapists accounted for a large percentage of the measurement error (70% to 81%). For single measurements, the standard error of measurement was assessed not to exceed 10N x m. Minimal detectable changes for different designs varied from 13.8 to 28.2N x m. CONCLUSIONS The CAHN-DY facilitated standardization of test performance in a satisfactory manner, resulting in less measurement error compared with simple hand-held dynamometry.