Charlotte Häger

Somatosensory control of precision grip during unpredictable pulling loads. II. Changes in load force rate.

SummaryIn manipulating ‘passive’ objects, for which the physical properties are stable and therefore predictable, information essential for the adaptation of the motor output to the properties of the current object is principally based on ‘anticipatory parameter control’ using sensorimotor memories, i.e., an internal representation of the objects properties based on previous manipulative experiences. Somatosensory afferent signals only intervene intermittently according to an ‘event driven’ control policy. The present study is the first in a series concerning the control of precision grip when manipulating ‘active’ objects that exert unpredictable forces which cannot be adequately represented in a sensorimotor memory. Consequently, the manipulation may be more reliant on a moment-to-moment sensory control. Subjects who were prevented from seeing the hand used the precision grip to restrain a manipulandum with two parallel grip surfaces attached to a force motor which produced distally directed (pulling) loads tangential to the finger tips. The trapezoidal load profiles consisted of a loading phase (4 N/s), plateau phase and an unloading phase (4 N/s) returning the load force to zero. Three force amplitudes were delivered in an unpredictable sequence; 1 N, 2 N and 4 N. In addition, trials with higher load rate (32 N/s) at a low amplitude (0.7 N), were superimposed on various background loads. The movement of the manipulandum, the load forces and grip forces (normal to the grip surfaces) were recorded at each finger. The grip force automatically changed with the load force during the loading and unloading phases. However, the grip responses were initiated after a brief delay. The response to the loading phase was characterized by an initial fast force increase termed the ‘catch-up’ response, which apparently compensated for the response delay — the grip force adequately matched the current load demands by the end of the catch-up response. In ramps with longer lasting loading phases (amplitude ≥ 2 N) the catch-up response was followed by a ‘tracking’ response, during which the grip force increased in parallel with load force and maintained an approximately constant force ratio that prevented frictional slips. The grip force during the hold phase was linearly related to the load force, with an intercept close to the grip force used prior to the loading. Likewise, the grip force responses evoked by the fast loadings superimposed on existing loads followed the same linear relationship. The grip force response to the unloading phase showed a rather smooth, nearly bell shaped, rate profile that suggested it was programmed for the inter-trial grip force. The stiffness in the loading direction increased with the load force in a manner suggesting that the two forces were subjected to similar coordinative constraints as in the manipulation of ‘passive’ objects.

Using motion interactive games to promote physical activity and enhance motor performance in children with cerebral palsy

Objective: To explore the feasibility of using low-cost motion interactive games as a home-based intervention for children with cerebral palsy (CP). Methods: Fourteen children with CP, 6–16 years old, practiced with the EyeToy for PlayStation2® in their homes during 4 weeks. Outcome measures were physical activity monitors, Movement Assessment Battery for Children-2 (mABC-2), Bruininks-Oseretsky Test of Motor Proficiency (sub-test 5 : 6), 1 Minute Walk Test and gaming diaries. Results: Motivation for practice and compliance of training were high. The childrens physical activity increased during the intervention and activity monitors were feasible to use, although data loss may be a concern. According to mABC-2 the childrens motor performance improved, but there were both floor and ceiling effects. The two additional motor tests showed only non-significant progress. Conclusion: It is highly feasible to use motion interactive games in home rehabilitation for children with CP. Specific motor effects need to be further explored.

Anterior cruciate ligament injury after more than 20 years: I. Physical activity level and knee function

Little is known about physical activity level and knee function including jump capacity and fear of movement/reinjury more than 20 years after injury of the anterior cruciate ligament (ACL). Seventy persons with unilateral ACL injury participated (23 ± 2 years post‐injury): 33 treated with physiotherapy in combination with surgical reconstruction (ACLR), and 37 treated with physiotherapy alone (ACLPT). These were compared with 33 age‐ and gender‐matched controls. Assessment included knee‐specific and general physical activity level [Tegner activity scale, International Physical Activity Questionnaire (IPAQ)], knee function [Lysholm score, Knee injury and Osteoarthritis Outcome Score (KOOS)], jump capacity (one‐leg hop, vertical jump, side hops), and fear of movement/reinjury [Tampa Scale for Kinesiophobia (TSK)]. Outcomes were related to degree of osteoarthritis (OA). ACL‐injured had lower Lysholm, KOOS, and Tegner scores than controls (P < 0.001), while IPAQ score was similar. ACL‐injured demonstrated inferior jump capacity in injured compared with noninjured leg (6–25%, P < 0.001–P = 0.010 in the different jumps), while noninjured leg had equal jump capacity as controls. ACL groups scored 33 ± 7 and 32 ± 7 of 68 on TSK. Lower scores on Lysholm and KOOS symptom were seen for persons with moderate‐to‐high OA than for no‐or‐low OA, while there were no differences for physical activity and jump capacity. Regardless of treatment, there are still negative knee‐related effects of ACL injury more than 20 years later.

Kinematic analysis of the upper extremity after stroke – how far have we reached and what have we grasped?

Abstract Background: Consequences of stroke frequently comprise reduced movement ability of the upper extremity (UE) and subsequent long-term disability. Clinical scales are used to monitor and evaluate rehabilitation but are often insufficient, while technological advances in 3D motion capture provide detailed kinematics to more objectively quantify and interpret movement deficits. Objectives: To provide a comprehensive overview of research using kinematic movement analysis of the UE in individuals post-stroke with focus on objectives, methodology and findings while highlighting clinical implications and future directions. Major Findings: A literature search yielded 93 studies categorised into four groups: comparative (healthy, stroke, task condition), intervention (clinical trials), methodological and longitudinal. The majority of studies used optoelectronic systems, investigated discrete reaching and involved mainly individuals with moderate or mild stroke impairment in chronic stage. About 80% of the studies were published after year 2004. Speed-related variables were most frequently addressed followed by smoothness indicators, joint angles and trunk displacement. Movements in the hemiparetic side are generally slower, less smooth and show a compensatory movement pattern. Task specificity is crucial for kinematic outcomes. Tables summarising the main characteristics, objectives and results of all included studies are provided. Conclusions: There is still a lack of studies addressing reliability and responsiveness and involving more complex, everyday UE tasks with ecological validity. To facilitate the use of UE kinematic movement analysis in clinics, a research-based simpler data handling with pre-defined output for the results, as commonly used in gait analysis, is warranted.

A new approach to measure functional stability of the knee based on changes in knee axis orientation

There is a lack of measures that quantify functional knee stability, which is of particular relevance in knee rehabilitation. Therefore, the aim of this study was to investigate the usefulness of knee finite helical axis (FHA) variables in 33 healthy subjects during two different functional tasks; One leg side hop (SH) and Two Leg Squat (TLS), and to investigate correlations of these variables with laxity. Laxity was assessed with a KT-1000 arthrometer and the Beighton Hypermobility Score. Movements were registered with an optical motion capture system. Knee rotation and translation were defined by a six degree of freedom segment model. FHA was calculated for finite steps of 20° knee flexion, based on error simulations. We computed the FHA inclination, the translation along FHA and an FHA Direction Index quantifying directional changes. All variables were repeatable (average ICCs ~0.97 during TLS and ~0.83 during SH). The lower functional knee stability in SH was reflected by a significantly higher FHA Direction Index and a larger medio-lateral FHA inclination compared to those in TLS. The superior-inferior inclination was smaller during Landing in SH compared to Take-Off and TLS. Translation along FHA was generally small as expected in healthy subjects. Beighton Hypermobility Score and KT-1000 values had weak but significant correlations with FHA Direction Index and FHA translation, which show that laxity influences the functional knee stability. We conclude that FHA measures were sensitive enough to discriminate between SH and TLS. The next step is to investigate the usability of these measures in subjects with knee injury.

Anterior cruciate ligament injury after more than 20 years. II. Concentric and eccentric knee muscle strength.

The long‐term consequences on knee muscle strength some decades after rupture of the anterior cruciate ligament (ACL) are not established. The aims of our study were to examine peak torque more than 20 years after ACL injury and to compare their knee muscle strength to that of healthy controls. We tested 70 individuals with unilateral ACL injury 23 ± 2 years after injury, whereof 33 (21 men) were treated with physiotherapy in combination with ACL reconstruction (ACLR) and 37 (23 men) with physiotherapy alone (ACLPT). These were compared with 33 age‐ and gender‐matched controls (21 men). A Kin‐Com® dynamometer (90°/s) was used to measure peak torque in knee flexion and extension in both concentric and eccentric contractions. Knee extension peak torque, concentric and eccentric, was ∼10% lower for the injured leg compared with the non‐injured leg for both ACLR (P < 0.001; P < 0.001) and ACLPT (P = 0.007; P = 0.002). The ACLPT group also showed reduced eccentric knee flexion torque of the injured leg (P = 0.008). The strength of the non‐injured leg in both ACL groups was equal to that of controls. No difference was seen for those with no‐or‐low degree of knee osteoarthritis compared to those with moderate‐to‐high degree of osteoarthritis. ACL injury may lead to a persistent reduction of peak torque in the injured leg, which needs to be considered across the lifespan.

Training of goal directed arm movements with motion interactive video games in children with cerebral palsy – A kinematic evaluation

Abstract Objective: The main aim of this study was to evaluate the quality of goal-directed arm movements in 15 children with cerebral palsy (CP) following four weeks of home-based training with motion interactive video games. A further aim was to investigate the applicability and characteristics of kinematic parameters in a virtual context in comparison to a physical context. Method: Kinematics and kinetics were captured while the children performed arm movements directed towards both virtual and physical targets. Results: The children’s movement precision improved, their centre of pressure paths decreased, as did the variability in maximal shoulder angles when reaching for virtual objects. Transfer to a situation with physical targets was mainly indicated by increased movement smoothness. Conclusion: Training with motion interactive games seems to improve arm motor control in children with CP. The results highlight the importance of considering both the context and the task itself when investigating kinematic parameters.

Anterior cruciate ligament injury about 20 years post-treatment : a kinematic analysis of one-leg hop

Reduced dynamic knee stability, often evaluated with one‐leg hops (OLHs), is reported after anterior cruciate ligament (ACL) injury. This may lead to long‐standing altered movement patterns, which are less investigated. 3D kinematics during OLH were explored in 70 persons 23 ± 2 years after ACL injury; 33 were treated with physiotherapy in combination with ACL reconstruction (ACLR) and 37 with physiotherapy alone (ACLPT). Comparisons were made to 33 matched controls. We analyzed (a) maximal knee joint angles and range of motion (flexion, abduction, rotation); (b) medio‐lateral position of the center of mass (COM) in relation to knee and ankle joint centers, during take‐off and landing phases. Unlike controls, ACL‐injured displayed leg asymmetries: less knee flexion and less internal rotation at take‐off and landing and more lateral COM related to knee and ankle joint of the injured leg at landing. Compared to controls, ACLR had larger external rotation of the injured leg at landing. ACLPT showed less knee flexion and larger external rotation at take‐off and landing, and larger knee abduction at Landing. COM was more medial in relation to the knee at take‐off and less laterally placed relative to the ankle at landing. ACL injury results in long‐term kinematic alterations during OLH, which are less evident for ACLR.

EffEctS of nEck cooRdInAtIon ExERcISE on SEnSoRIMotoR functIon In chRonIc nEck PAIn: A RAndoMIzEd contRollEd tRIAl

OBJECTIVE To evaluate the effect of neck coordination exercise on sensorimotor function in women with neck pain compared with best-available treatment and sham treatment. DESIGN Observer-blinded randomized controlled trial with short-term and 6-month follow-ups. SUBJECTS Women with chronic non-specific neck pain were randomized to 3 groups: neck coordination exercise with a novel training device; strength training for the neck and shoulders; or massage. Each group had 36 participants. METHODS The intervention period was 11 weeks with 22 individually supervised sessions. Primary outcomes were postural sway measures and precision of goal-directed arm movements. Secondary outcomes were range of motion for the neck, peak speed of axial rotation, and neck pain. A repeated measures multivariate analysis of variance (MANOVA) was conducted separately on the primary outcomes for the short-term and 6-month evaluations and on the sensorimotor secondary outcomes for the 6-month effect. The 6-month effect on pain was analysed with a repeated measures analysis of variance (ANOVA). RESULTS No significant treatment effects in favour of neck coordination exercise were found for short-term or 6-month evaluations. CONCLUSION Neck coordination exercise is no better than strength training and massage in improving sensorimotor function. Further research should investigate the use of cut-offs for sensorimotor dysfunctions prior to proprioceptive or coordinative training.

Measurement properties of the Motor Evaluation Scale for Upper Extremity in Stroke patients (MESUPES)

Purpose: To investigate inter-rater reliability of the Motor Evaluation Scale for Upper Extremity in Stroke patients (MESUPES), to provide estimates of the minimal detectable change (MDC) of the MESUPES and to investigate concurrent validity in relation to the arm scores of the Modified Motor Assessment Scale (M MAS). Methods: Forty-two stroke patients (mean age 56 ± 12 years) were independently assessed within a 48-hours window by two raters in different pairs (total available raters = 4). Results: Weighted κ analysis indicated good to very good agreement at item level (range 0.63–0.96). The relative and absolute reliability of the total score of MESUPES (maximum 58) was high according to the intraclass correlation coefficients (ICC = 0.98) and the standard error of measurement (SEM = 2.68). The MDC for three levels of confidence was calculated: A score change of 8, 7 and 5 is necessary for a MDC to have confidence of 95%, 90% and 80%, respectively, of a genuine change. Correlation between the MESUPES and M MAS was high (rs = 0.87). Conclusions: The MESUPES shows high inter-rater reliability, and our study provides useful estimates of MDC for different levels of certainty. Additional research to confirm concurrent validity and to examine other psychometric properties of the MESUPES such as sensitivity is needed. Implications for Rehabilitation This study shows that the Motor Evaluation Scale for Upper Extremity in Stroke patients (MESUPES) has high absolute and relative reliability. The MESUPES is suggested to be a useful tool to evaluate quality of movement in the upper extremity of stroke patients.