Elbow joint loads during simulated activities of daily living: implications for formulating recommendations after total elbow arthroplasty.

BACKGROUND: Overloading of the elbow joint prosthesis following total elbow arthroplasty can lead to implant failure. Joint moments during daily activities are not well contextualized for a prosthesis's failure limits, and the effect of the current postoperative instruction on elbow joint loading is unclear. This study investigates the difference in elbow joint moments between simulated daily tasks and between flexion-extension, pronation-supination, and varus-valgus movement directions. Additionally, the effect of the current postoperative instruction on elbow joint load is examined. METHODS: Nine healthy participants (age 45.8 ± 17 years, 3 males) performed 8 tasks; driving a car, opening a door, rising from a chair, lifting, sliding, combing hair, drinking, emptying cup, without and with the instruction "not lifting more than 1 kg." Upper limb kinematics and hand contact forces were measured. Elbow joint angles and net moments were analyzed using inverse dynamic analysis, where the net moments are estimated from movement data and external forces. RESULTS: Peak elbow joint moments differed significantly between tasks (P < .01) and movement directions (P < .01). The most and least demanding tasks were, rising from a chair (13.4 Nm extension, 5.0 Nm supination, and 15.2 Nm valgus) and sliding (4.3 Nm flexion, 1.7 Nm supination, and 2.6 Nm varus). Net moments were significantly reduced after instruction only in the chair task (P < .01). CONCLUSION: This study analyzed elbow joint moments in different directions during daily tasks. The outcomes question whether postoperative instruction can lead to decreasing elbow loads. Future research might focus on reducing elbow loads in the flexion-extension and varus-valgus directions.

Elbow joint biomechanics during ADL focusing on total elbow arthroplasty - a scoping review.

BACKGROUND: Overloading is hypothesized to be one of the failure mechanisms following total elbow arthroplasty (TEA). It is unclear whether the current post-operative loading instruction is compliant with reported failure mechanisms. Aim is therefore to evaluate the elbow joint load during activities of daily living (ADL) and compare these loads with reported failure limits from retrieval and finite element studies. METHODS: A scoping review of studies until 23 November 2021 investigating elbow joint load during ADL were identified by searching PubMed/Medline and Web of Science. Studies were eligible when: (1) reporting on the elbow joint load in native elbows or elbows with an elbow arthroplasty in adults; (2) full-text article was available. RESULTS: Twenty-eight studies with a total of 256 participants were included. Methodological quality was low in 3, moderate in 22 and high in 3 studies. Studies were categorized as 1) close to the body and 2) further away from the body. Tasks were then subdivided into: 1) cyclic flexion/extension, 2) push-up, 3) reaching, 4) self-care, 5) work. Mean flexion-extension joint load was 17 Nm, mean varus-valgus joint load 9 Nm, mean pronation-supination joint load 8 Nm and mean bone-on-bone contact force 337 N. CONCLUSION: The results of our scoping review give a first overview of the current knowledge on elbow joint loads during ADL. Surprisingly, the current literature is not sufficient to formulate a postoperative instruction for elbow joint loading, which is compliant with failure limits of the prosthesis. In addition, our current instruction does not appear to be evidence-based. Our recommendations offer a starting point to assist clinicians in providing informed decisions about post-operative instructions for their patients.

Correction: Rondinone et al. Extensive Placental Methylation Profiling in Normal Pregnancies. Int. J. Mol. Sci. 2021, 22, 2136.

In the original publication [...].

Age- and muscle-specific reliability of muscle architecture measurements assessed by two-dimensional panoramic ultrasound.

BACKGROUND: Age-related changes in muscle properties affect daily functioning, therefore a reliable assessment of such properties is required. We examined the effects of age on reliability, muscle quality and interrelation among muscle architecture (MA) parameters of the gastrocnemius medialis (GM), tibialis anterior (TA), and vastus lateralis (VL) muscles. METHODS: Three raters scored ultrasound (US) scans of 12 healthy younger and older adults, on fascicle length (FL), pennation angle (PA) and muscle thickness (MT). Intra- and inter-rater reliability of MA measures in rest and contraction was assessed by intraclass correlation coefficients (ICC) and standard error of measurements (SEM, SEM%). The relationship between MA parameters was examined using Pearson correlation coefficients. Muscle quality (MQ) was examined using mean pixel intensity. RESULTS: Reliability was moderate to excellent for TA in both groups (ICCs: 0.64-0.99, SEM% = 1.6-14.8%), and for VL in the younger group (ICCs: 0.67-0.98, SEM% = 2.0-18.3%). VL reliability was poor to excellent in older adults (ICCs: 0.22-0.99, SEM% = 2.7-36.0%). For GM, ICCs were good to excellent (ICCs: 0.76-0.99) in both groups, but GM SEM% were higher in older adults (SEM%Younger = 1.5-10.7%, SEM%Older = 1.6-28.1%). Muscle quality was on average 19.0% lower in older vs. younger adults. In both groups, moderate to strong correlations were found for VL FL and MT (r ≥ 0.54), and TA PA and MT (r ≥ 0.72), while TA FL correlated with MT (r ≥ 0.67) in younger adults only. CONCLUSIONS: In conclusion, age- and muscle-specificities were present in the relationships between MT and PA, and MT and FL at rest. Furthermore, the reliability of MA parameters assessed with 2D panoramic US is acceptable. However, the level of reliability varies with age, muscle and MA measure. In older adults notably, the lowest reliability was observed in the VL muscle. Among the MA parameters, MT appears to be the simplest and most easily reproducible parameter in all muscles and age groups.

In vitro-derived medium spiny neurons recapitulate human striatal development and complexity at single-cell resolution.

Stem cell engineering of striatal medium spiny neurons (MSNs) is a promising strategy to understand diseases affecting the striatum and for cell-replacement therapies in different neurological diseases. Protocols to generate cells from human pluripotent stem cells (PSCs) are scarce and how well they recapitulate the endogenous fetal cells remains poorly understood. We have developed a protocol that modulates cell seeding density and exposure to specific morphogens that generates authentic and functional D1- and D2-MSNs with a high degree of reproducibility in 25 days of differentiation. Single-cell RNA sequencing (scRNA-seq) shows that our cells can mimic the cell-fate acquisition steps observed in vivo in terms of cell type composition, gene expression, and signaling pathways. Finally, by modulating the midkine pathway we show that we can increase the yield of MSNs. We expect that this protocol will help decode pathogenesis factors in striatal diseases and eventually facilitate cell-replacement therapies for Huntington's disease (HD).

Age does not affect the relationship between muscle activation and joint work during incline and decline walking.

Older compared with younger adults walk with different configurations of mechanical joint work and greater muscle activation but it is unclear if age, walking speed, and slope would each affect the relationship between muscle activation and net joint work. We hypothesized that a unit increase in positive but not negative net joint work requires greater muscle activation in older compared with younger adults. Healthy younger (age: 22.1 yrs, n = 19) and older adults (age: 69.8 yrs, n = 16) ascended and descended a 7° ramp at slow (~1.20 m/s) and moderate (~1.50 m/s) walking speeds while lower-extremity marker positions, electromyography, and ground reaction force data were collected. Compared to younger adults, older adults took 11% (incline) and 8% (decline) shorter strides, and performed 21% less positive ankle plantarflexor work (incline) and 19% less negative knee extensor work (decline) (all p < .05). However, age did not affect (all p > .05) the regression coefficients between the muscle activation integral and positive hip extensor or ankle plantarflexor work during ascent, nor between that and negative knee extensor or ankle dorsiflexor work during descent. With increased walking speed, muscle activation tended to increase in younger but changed little in older adults across ascent (10 ± 12% vs. -1.0 ± 10%) and descent (3.6 ± 10.2% vs. -2.6 ± 7.7%) (p = .006, r = 0.47). Age does not affect the relationship between muscle activation and net joint work during incline and decline walking at freely-chosen step lengths. The electromechanical cost of joint work production does not underlie the age-related reconfiguration of joint work during walking.

Extensive Placental Methylation Profiling in Normal Pregnancies.

The placental methylation pattern is crucial for the regulation of genes involved in trophoblast invasion and placental development, both key events for fetal growth. We investigated LINE-1 methylation and methylome profiling using a methylation EPIC array and the targeted methylation sequencing of 154 normal, full-term pregnancies, stratified by birth weight percentiles. LINE-1 methylation showed evidence of a more pronounced hypomethylation in small neonates compared with normal and large for gestational age. Genome-wide methylation, performed in two subsets of pregnancies, showed very similar methylation profiles among cord blood samples while placentae from different pregnancies appeared very variable. A unique methylation profile emerged in each placenta, which could represent the sum of adjustments that the placenta made during the pregnancy to preserve the epigenetic homeostasis of the fetus. Investigations into the 1000 most variable sites between cord blood and the placenta showed that promoters and gene bodies that are hypermethylated in the placenta are associated with blood-specific functions, whereas those that are hypomethylated belong mainly to pathways involved in cancer. These features support the functional analogies between a placenta and cancer. Our results, which provide a comprehensive analysis of DNA methylation profiling in the human placenta, suggest that its peculiar dynamicity can be relevant for understanding placental plasticity in response to the environment.

User training for machine learning controlled upper limb prostheses: a serious game approach.

BACKGROUND: Upper limb prosthetics with multiple degrees of freedom (DoFs) are still mostly operated through the clinical standard Direct Control scheme. Machine learning control, on the other hand, allows controlling multiple DoFs although it requires separable and consistent electromyogram (EMG) patterns. Whereas user training can improve EMG pattern quality, conventional training methods might limit user potential. Training with serious games might lead to higher quality EMG patterns and better functional outcomes. In this explorative study we compare outcomes of serious game training with conventional training, and machine learning control with the users' own one DoF prosthesis. METHODS: Participants with upper limb absence participated in 7 training sessions where they learned to control a 3 DoF prosthesis with two grips which was fitted. Participants received either game training or conventional training. Conventional training was based on coaching, as described in the literature. Game-based training was conducted using two games that trained EMG pattern separability and functional use. Both groups also trained functional use with the prosthesis donned. The prosthesis system was controlled using a neural network regressor. Outcome measures were EMG metrics, number of DoFs used, the spherical subset of the Southampton Hand Assessment Procedure and the Clothespin Relocation Test. RESULTS: Eight participants were recruited and four completed the study. Training did not lead to consistent improvements in EMG pattern quality or functional use, but some participants improved in some metrics. No differences were observed between the groups. Participants achieved consistently better results using their own prosthesis than the machine-learning controlled prosthesis used in this study. CONCLUSION: Our explorative study showed in a small group of participants that serious game training seems to achieve similar results as conventional training. No consistent improvements were found in either group in terms of EMG metrics or functional use, which might be due to insufficient training. This study highlights the need for more research in user training for machine learning controlled prosthetics. In addition, this study contributes with more data comparing machine learning controlled prosthetics with Direct Controlled prosthetics.

Exploring the Relationship Between EMG Feature Space Characteristics and Control Performance in Machine Learning Myoelectric Control.

In myoelectric machine learning (ML) based control, it has been demonstrated that control performance usually increases with training, but it remains largely unknown which underlying factors govern these improvements. It has been suggested that the increase in performance originates from changes in characteristics of the Electromyography (EMG) patterns, such as separability or repeatability. However, the relation between these EMG metrics and control performance has hardly been studied. We assessed the relation between three common EMG feature space metrics (separability, variability and repeatability) in 20 able bodied participants who learned ML myoelectric control in a virtual task over 15 training blocks on 5 days. We assessed the change in offline and real-time performance, as well as the change of each EMG metric over the training. Subsequently, we assessed the relation between individual EMG metrics and offline and real-time performance via correlation analysis. Last, we tried to predict real-time performance from all EMG metrics via L2-regularized linear regression. Results showed that real-time performance improved with training, but there was no change in offline performance or in any of the EMG metrics. Furthermore, we only found a very low correlation between separability and real-time performance and no correlation between any other EMG metric and real-time performance. Finally, real-time performance could not be successfully predicted from all EMG metrics employing L2-regularized linear regression. We concluded that the three EMG metrics and real-time performance appear to be unrelated.

Daily Life Benefits and Usage Characteristics of Dynamic Arm Supports in Subjects with Neuromuscular Disorders.

Neuromuscular disorders cause progressive muscular weakness, which limits upper extremity mobility and performance during activities of daily life. Dynamic arm supports can improve mobility and quality of life. However, their use is often discontinued over time for unclear reasons. This study aimed to evaluate whether users of dynamic arm supports demonstrate and perceive quantifiable mobility benefits over a period of two months. Nine users of dynamic arm supports were included in this observational study. They had different neuromuscular disorders and collectively used four different arm supports. They were observed for three consecutive weeks during which they were equipped with a multi-sensor network of accelerometers to assess the actual use of the arm support and they were asked to provide self-reports on the perceived benefits of the devices. Benefits were experienced mainly during anti-gravity activities and the measured use did not change over time. The self-reports provided contextual information in domains such as participation to social life, in addition to the sensor system. However self-reports overestimated the actual use by up to three-fold compared to the accelerometer measures. A combination of objective and subjective methods is recommended for meaningful and quantifiable mobility benefits during activities of daily life.

Should Hands Be Restricted When Measuring Able-Bodied Participants to Evaluate Machine Learning Controlled Prosthetic Hands?

OBJECTIVE: When evaluating methods for machine-learning controlled prosthetic hands, able-bodied participants are often recruited, for practical reasons, instead of participants with upper limb absence (ULA). However, able-bodied participants have been shown to often perform myoelectric control tasks better than participants with ULA. It has been suggested that this performance difference can be reduced by restricting the wrist and hand movements of able-bodied participants. However, the effect of such restrictions on the consistency and separability of the electromyogram's (EMG) features remains unknown. The present work investigates whether the EMG separability and consistency between unaffected and affected arms differ and whether they change after restricting the unaffected limb in persons with ULA. METHODS: Both arms of participants with unilateral ULA were compared in two conditions: with the unaffected hand and wrist restricted or not. Furthermore, it was tested if the effect of arm and restriction is influenced by arm posture (arm down, arm in front, or arm up). RESULTS: Fourteen participants (two women, age = 53.4±4.05) with acquired transradial limb loss were recruited. We found that the unaffected limb generated more separated EMG than the affected limb. Furthermore, restricting the unaffected hand and wrist lowered the separability of the EMG when the arm was held down. CONCLUSION: Limb restriction is a viable method to make the EMG of able-bodied participants more similar to that of participants with ULA. SIGNIFICANCE: Future research that evaluates methods for machine learning controlled hands in able-bodied participants should restrict the participants' hand and wrist.

How age and surface inclination affect joint moment strategies to accelerate and decelerate individual leg joints during walking.

A joint moment also causes motion at other joints of the body. This joint coupling-perspective allows more insight into two age-related phenomena during gait. First, whether increased hip kinetic output compensates for decreased ankle kinetic output during positive joint work. Second, whether preserved joint kinetic patterns during negative joint work in older age have any functional implication. Therefore, we examined how age and surface inclination affect joint moment strategies to accelerate and/or decelerate individual leg joints during walking. Healthy young (age: 22.5 ±â€¯4.1 years, n = 18) and older (age: 76.0 ±â€¯5.7 years, n = 22) adults walked at 1.4 m/s on a split-belt instrumented treadmill at three grades (0%, 10%, -10%). Lower-extremity moment-induced angular accelerations were calculated for the hip (0% and 10%) and knee (0% and -10%) joints. During level and uphill walking, both age groups showed comparable ankle moment-induced ipsilateral (p = 0.774) and contralateral (p = 0.047) hip accelerations, although older adults generated lower ankle moments in late stance. However, ankle moment-induced contralateral hip accelerations were smaller (p = 0.001) in an older adult subgroup (n = 13) who showed larger hip extension moments in early stance than young adults. During level and downhill walking, leg joint moment-induced knee accelerations were unaffected by age (all p > 0.05). These findings suggest that during level and uphill walking increased hip flexor mechanical output in older adults does not arise from reduced ankle moments, contrary to increased hip extensor mechanical output. Additionally, results during level and downhill walking imply that preserved eccentric knee extensor function is important in maintaining knee stabilization in older age.

Users' and therapists' perceptions of myoelectric multi-function upper limb prostheses with conventional and pattern recognition control.

OBJECTIVE: To describe users' and therapists' opinions on multi-function myoelectric upper limb prostheses with conventional control and pattern recognition control. DESIGN: Qualitative interview study. SETTINGS: Two rehabilitation institutions in the Netherlands and one in Austria. SUBJECTS: The study cohort consisted of 15 prosthesis users (13 males, mean age: 43.7 years, average experience with multi-function prosthesis: 3.15 years) and seven therapists (one male, mean age: 44.1 years, average experience with multi-function prostheses: 6.6 years). Four of these users and one therapist had experience with pattern recognition control. METHOD: This study consisted of semi-structured interviews. The participants were interviewed at their rehabilitation centres or at home by telephone. The thematic framework approach was used for analysis. RESULTS: The themes emerging from prosthesis users and therapists were largely congruent and resulted in one thematic framework with three main themes: control, prosthesis, and activities. The participants mostly addressed (dis-) satisfaction with the control type and the prosthesis itself and described the way they used their prostheses in daily tasks. CONCLUSION: Prosthesis users and therapists described multi-function upper limb prostheses as more functional devices than conventional one-degree-of-freedom prostheses. Nonetheless, the prostheses were seldom used to actively grasp and manipulate objects. Moreover, the participants clearly expressed their dissatisfaction with the mechanical robustness of the devices and with the process of switching prosthesis function under conventional control. Pattern recognition was appreciated as an intuitive control that facilitated fast switching between prosthesis functions, but was reported to be too unreliable for daily use and require extensive training.

The Effect of Feedback During Training Sessions on Learning Pattern-Recognition-Based Prosthesis Control.

Human-machine interfaces have not yet advanced to enable intuitive control of multiple degrees of freedom as offered by modern myoelectric prosthetic hands. Pattern Recognition (PR) control has been proposed to make human-machine interfaces in myoelectric prosthetic hands more intuitive, but it requires the user to generate high-quality, i.e., consistent and separable, electromyogram (EMG) patterns. To generate such patterns, user training is required and has shown promising results. However, how different levels of feedback affect effectivity in training differently, has not been established yet. Furthermore, a correlation between qualities of the EMG patterns (the focus of training) and user performance has not been shown yet. In this study, 37 able-bodied participants (mean age 21 years, 19 males) were recruited and trained PR control over five days. Three levels of feedback were tested for their effectiveness: no external feedback, visual feedback and visual feedback with coaching. Training resulted in improved performance from pre- to post-test with no interaction effect of feedback. Feedback did however affect the quality of the EMG patterns where people who did not receive external feedback generated higher amplitude patterns. A weak correlation was found between a principal component, composed of EMG amplitude and pattern variability, and performance. Our results show that training is highly effective in improving PR control regardless of feedback and that none of the quality metrics correlate with performance. We discuss how different levels of feedback can be leveraged to improve PR control training.

Superficial Shoulder Muscle Synergy Analysis in Facioscapulohumeral Dystrophy During Humeral Elevation Tasks.

Facioscapulohumeral dystrophy (FSHD) is a progressive muscle-wasting disease which leads to a decline in upper extremity functionality. Although the scapulohumeral joint's stability and functionality are affected, evidence on the synergetic control of the shoulder muscles in FSHD individuals is still lacking. The aim of this paper is to understand the neuromuscular changes in shoulder muscle control in people with FSHD. Upper arm kinematics and electromyograms (EMG) of eight upper extremity muscles were recorded during shoulder abduction-adduction and flexion-extension tasks in eleven participants with FSHD and 11 healthy participants. Normalized muscle activities were extracted from EMG signals. Non-negative matrix factorization was used to compute muscle synergies. Maximum muscle activities were compared using non-parametric analysis of variance. Similarities between synergies were also calculated using correlation. The Biceps Brachii was significantly more active in the FSHD group (25±2%) while Trapezius Ascendens and Serratus Anterior were less active (32±7% and 39±4%, respectively). Muscle synergy weights were altered in FSHD individuals and showed greater diversity while controls mostly used one synergy for both tasks. The decreased activity by selected scapula rotator muscles and muscle synergy weight alterations show that neuromuscular control of the scapulohumeral joint is less consistent in people with FSHD compared to healthy participants. Assessments of muscle coordination strategies can be used to evaluate motor output variability and assist in management of the disease.

The Stabilizing Function of Superficial Shoulder Muscles Changes Between Single-Plane Elevation and Reaching Tasks.

OBJECTIVE: The goal of this study was to determine whether and how much the stabilizing role of the shoulder muscles changes as a function of humeral elevation and the plane of elevation. METHODS: A musculoskeletal model, comprising a personalized scapulohumeral rhythm, was used to calculate the ratio of shear over compressive force (stability ratio) of three rotator cuff muscles (supraspinatus, infraspinatus and subscapularis) and three superficial shoulder muscles (middle deltoid, clavicular part of pectoralis major and latissimus dorsi) during abduction, flexion and reaching movements in 10 healthy adults. RESULTS: The range of the stability ratios was [Formula: see text] for the rotator cuff muscles compared to [Formula: see text] for the superficial shoulder muscles. In the superior-inferior direction, the stability ratios of all muscles changed with humeral elevation and for infraspinatus, subscapularis, latissimus dorsi and deltoid also with the plane of elevation. In the anterior-posterior direction, the stability ratios of all muscles changed with humeral elevation, except for the deltoid, and with the plane of elevation, except for the supraspinatus, with interaction effects in all muscles. CONCLUSION: The rotator cuff muscles provide greater compression than shear forces during all tasks. The stabilizing function of the superficial shoulder muscles examined in this study varies during tasks. SIGNIFICANCE: The findings can be used to predict in which movements the shoulder joint becomes more unstable and can be applied to understand how shear and compressive forces change in populations with abnormal shoulder motion.

Advanced Age Redistributes Positive but Not Negative Leg Joint Work during Walking.

INTRODUCTION: Advanced age brings a distal-to-proximal redistribution of positive joint work during walking that is relevant to walking performance and economy. It is unclear whether negative joint work is similarly redistributed in old age. Negative work can affect positive work through elastic energy return in gait. We determined the effects of age, walking speed, and grade on positive and negative joint work in young and older adults. METHODS: Bilateral ground reaction force and marker data were collected from healthy young (age = 22.5 yr, n = 18) and older (age = 76.0 yr, n = 22) adults walking on a split-belt instrumented treadmill at 1.1, 1.4, and 1.7 m·s at each of three grades (0%, 10%, and -10%). Subjects also performed maximal voluntary eccentric, isometric, and concentric contractions for the knee extensors (120°·s, 90°·s, and 0°·s) and plantarflexors (90°·s, 30°·s, and 0°·s). RESULTS: Compared with young adults, older adults exhibited a distal-to-proximal redistribution of positive leg joint work during level (P < 0.001) and uphill (P < 0.001) walking, with larger differences at faster walking speeds. However, the distribution of negative joint work was unaffected by age during level (P = 0.150) and downhill (P = 0.350) walking. Finally, the age-related loss of maximal voluntary knee extensor (P < 0.001) and plantarflexor (P = 0.001) strength was smaller during an eccentric contraction versus concentric contraction for the knee extensors (P < 0.001) but not for the plantarflexors (P = 0.320). CONCLUSION: The distal-to-proximal redistribution of positive joint work during level and uphill walking is absent for negative joint work during level and downhill walking. Exercise prescription should focus on improving ankle muscle function while preserving knee muscle function in older adults trying to maintain their independence.

Effects of age and sex on shoulder biomechanics and relative effort during functional tasks.

Age-related decline in muscle strength can compromise shoulder function, which could increase the effort needed to perform activities of daily living (ADLs). The purpose of this cross-sectional study was to determine for the first time the relative shoulder effort during ADLs in healthy young and older adults. Ten healthy young adults and ten healthy older adults were tested for maximal isokinetic torque and on a set of ADL tasks. Using inverse dynamics, the shoulder torques during ADLs were referenced to the maximal isokinetic torque and relative effort was determined. Older compared to younger adults had >40% lower isokinetic shoulder abduction strength. The ratio of peak joint torque during six ADLs over the maximal isokinetic torque, i.e., relative effort, was higher in old (∼52%) compared with young adults (∼22%, p < 0.05). Relative effort in older adults was over 40% in overhead activities and particularly high in abduction and reaching tasks, over 60%. Healthy older compared with younger adults perform most ADL tasks involving the shoulder joint with nearly twice the level of relative effort. The concomitant reductions in maximal shoulder isokinetic torque and increases in relative effort may be related to the high prevalence of musculoskeletal pain and shoulder dysfunction in old age reported in epidemiological studies.

Effectiveness and feasibility of eccentric and task-oriented strength training in individuals with stroke.

BACKGROUND: Strength training can increase function in individuals with stroke. However it is unclear which type of strength training is most effective and feasible. OBJECTIVE: To assess the effect and feasibility of an intervention combining eccentric and task-oriented strength training in individuals with chronic stroke. METHODS: Eleven participants were randomly assigned to a group first receiving four weeks of eccentric strength training and then four weeks of task-oriented strength training (EST-TOST) or vice versa (TOST-EST). Strength and upper limb function were administered with a hand-held dynamometer (HHD) and the Action Research Arm Test (ARAT) respectively. Feasibility was evaluated with the Intrinsic Motivation Inventory (IMI), the adherence and drop-out rate. RESULTS: Significant increases were found in ARAT score (mean difference 7.3; p < 0.05) and in shoulder and elbow strength (mean difference respectively 23.96 N; p < 0.001 and 27.41 N; p < 0.003). Participants rated both EST and TOST with 81% on the IMI, the adherence rate was high and there was one drop-out. CONCLUSION: The results of this study show that a combination of eccentric and task-oriented strength training is an effective and feasible training method to increase function and strength in individuals with chronic stroke.

Functional Relevance of Relative Maintenance of Maximal Eccentric Quadriceps Torque in Healthy Old Adults.

BACKGROUND: Old referenced to young adults show a relative maintenance of maximal eccentric (RELM) compared to concentric muscle torque: ∼76 and ∼59%, respectively. However, it is unknown if RELM affords functional benefits in old adults. OBJECTIVE: We examined if there is specificity between the two types of peak quadriceps torque (i.e., concentric and eccentric) and timed gait performance measured during level, ramp, and stair walking and if gait performance was higher in old adults with high versus low RELM. METHODS: We measured peak concentric and eccentric quadriceps torque at 60 and 120°/s and timed gait at habitual and safe-fast speeds in healthy young (age 22.7 years, n = 24) and old (age 70.0 years, n = 21) adults. RESULTS: Comparable to previous studies, RELM was 21%, but instead of the anticipated specificity, we found that concentric compared with eccentric torque was more strongly associated with gait performance than eccentric torque, independently of walking direction and age (R2 = 0.16: eccentric vs. descending gaits; R2 = 0.17: eccentric vs. ascending gaits; R2 = 0.45: concentric vs. descending gaits; R2 = 0.56: concentric vs. ascending gaits, n = 45, all p < 0.01). Furthermore, old adults (n = 10) with ∼30% greater than normal levels of RELM (n = 11) ambulated at similar velocities measured on level and inclined surfaces. CONCLUSION: Normal and 30% above normal levels of RELM do not seem to increase or predict healthy old adults' gait performance on level and inclined surfaces. Future work should examine if RELM is associated with a heightened performance in other measures of neuromuscular function, such as gait biomechanics, muscle activation, as well as rate and control of voluntary force development in old adults with high or low mobility.