Spatial Neglect: An Exploration of Clinical Assessment Behaviour in Stroke Rehabilitation.

OBJECTIVE: There is a large gap between evidence-based recommendations for spatial neglect assessment and clinical practice in stroke rehabilitation. We aimed to describe factors that may contribute to this gap, clinician perceptions of an ideal assessment tool, and potential implementation strategies to change clinical practice in this area. DESIGN: Qualitative focus group investigation. Focus group questions were mapped to the Theoretical Domains Framework and asked participants to describe their experiences and perceptions of spatial neglect assessment. SETTING: Online stroke rehabilitation educational bootcamp. PARTICIPANTS: A sample of 23 occupational therapists, three physiotherapists, and one orthoptist that attended the bootcamp. INTERVENTION: Prior to their focus group, participants watched an hour-long educational session about spatial neglect. MAIN MEASURES: A deductive analysis with the Theoretical Domains Framework was used to describe perceived determinants of clinical spatial neglect assessment. An inductive thematic analysis was used to describe perceptions of an ideal assessment tool and practice-change strategies in this area. RESULTS: Participants reported that their choice of spatial neglect assessment was influenced by a belief that it would positively impact the function of people with stroke. However, a lack of knowledge about spatial neglect assessment appeared to drive low clinical use of standardised functional assessments. Participants recommended open-source online education involving a multidisciplinary team, with live-skill practice for the implementation of spatial neglect assessment tools. CONCLUSIONS: Our results suggest that clinicians prefer functional assessments of spatial neglect, but multiple factors such as knowledge, training, and policy change are required to enable their translation to clinical practice.

History-dependence of muscle slack length following contraction and stretch in the human vastus lateralis.

KEY POINTS: In reduced muscle preparations, the slack length and passive stiffness of muscle fibres have been shown to be influenced by previous muscle contraction or stretch. In human muscles, such behaviours have been inferred from measures of muscle force, joint stiffness and reflex magnitudes and latencies. Using ultrasound imaging, we directly observed that isometric contraction of the vastus lateralis muscle at short lengths reduces the slack lengths of the muscle-tendon unit and muscle fascicles. The effect is apparent 60 s after the contraction. These observations imply that muscle contraction at short lengths causes the formation of bonds which reduce the effective length of structures that generate passive tension in muscles. ABSTRACT: In reduced muscle preparations, stretch and muscle contraction change the properties of relaxed muscle fibres. In humans, effects of stretch and contraction on properties of relaxed muscles have been inferred from measurements of time taken to develop force, joint stiffness and reflex latencies. The current study used ultrasound imaging to directly observe the effects of stretch and contraction on muscle-tendon slack length and fascicle slack length of the human vastus lateralis muscle in vivo. The muscle was conditioned by (a) strong isometric contractions at long muscle-tendon lengths, (b) strong isometric contractions at short muscle-tendon lengths, (c) weak isometric contractions at long muscle-tendon lengths and (d) slow stretches. One minute after conditioning, ultrasound images were acquired from the relaxed muscle as it was slowly lengthened through its physiological range. The ultrasound image sequences were used to identify muscle-tendon slack angles and fascicle slack lengths. Contraction at short muscle-tendon lengths caused a mean 13.5 degree (95% CI 11.8-15.0 degree) shift in the muscle-tendon slack angle towards shorter muscle-tendon lengths, and a mean 5 mm (95% CI 2-8 mm) reduction in fascicle slack length, compared to the other conditions. A supplementary experiment showed the effect could be demonstrated if the muscle was conditioned by contraction at short lengths but not if the relaxed muscle was held at short lengths, confirming the role of muscle contraction. These observations imply that muscle contraction at short lengths causes the formation of bonds which reduce the effective length of structures that generate passive tension in muscles.

Reducing redundant testing using the Functional Independence Measure and Early Functional Abilities scale during rehabilitation in patients with brain injury.

PRIMARY OBJECTIVE: Rehabilitation scales following neurological injury can be useful for monitoring patient progress. However, too often, rehabilitation scales are administered unnecessarily placing an extra burden on clinicians and patients. The primary objective was to reduce redundant testing by providing guidelines for the concurrent use of the Functional Independence Measure (FIM) and Early Functional Abilities (EFA) scales during rehabilitation in patients with brain injury. METHODOLOGY: In total, 3289 concurrent FIM and EFA scores from 929 patients were examined. We proposed, using clinically sound and operational criterion, that the FIM should be used throughout rehabilitation, EFA should be used as a supplement when the FIM is ≤36 and FIM should be administered before the EFA on each testing occasion. RESULTS: Around 24% of patients should be measured with the FIM and EFA throughout rehabilitation, 35% of patients should be measured with the EFA and FIM initially but not require EFA measurements when there is an increase in function and 39% of patients should only be measured with the FIM. According to these guidelines, the EFA was administered unnecessarily 53% of the time. CONCLUSIONS AND IMPLICATIONS: These guidelines ensure that the EFA is used when it is sensitive. This will optimize clinician time and minimize redundant testing, without compromising the measurement of clinical progress.

The Effectiveness of Pain Science Education on Caregiver and Children's Knowledge, Beliefs, Attitudes, and Behaviors-A Systematic Review and Meta-Analysis.

Pain science education (PSE) can be used as part of treatment and prevention for chronic pain in children. We assessed the effectiveness of PSE on knowledge, beliefs, attitudes, and behaviors in children and the people that care for children. We set a minimum criterion for education to address pain biology knowledge. We included studies aimed at both treatment and prevention of chronic pain. We conducted searches using 5 databases. We assessed the risk of bias using the Cochrane Risk of Bias 2 tool. Data were pooled using a random-effects meta-analysis or assessed using a narrative synthesis. The certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation. We screened 14,505 records and included 7 studies involving 351 caregivers and 1,285 children. Four studies were included in meta-analyses. We found low-certainty evidence that PSE has a large beneficial effect on caregiver knowledge and beliefs compared with alternative education (standardized mean difference = 1.14 [95% confidence interval: .88-1.42]; I2 = 0%). We found no difference in functional disability in children with chronic pain after PSE (Functional Disability Inventory score mean difference = .73 [95% confidence interval: -.81 to 2.27; I = 0%]). Narrative syntheses showed low-certainty evidence for improved knowledge and beliefs in children with preventative and treatment effects. Overall, we found few studies, and along with high risk of bias, this significantly contributed to the low certainty of findings. The effect of learning pain science for both preventative and treatment effects in children, carers, and the child/carer dyad remains mostly unknown. This review was prospectively registered with The international Prospective register of systematic reviews (CRD42022344382) on July 22, 2022. PERSPECTIVE: This review examines the effect of PSE on pain-related knowledge, beliefs, attitudes, and behaviors in children and the people that care for children (0-18). The findings contribute to knowledge about pain treatments and health promotion for caregivers and their children with and without chronic pain.

Regression-based prognostic models for functional independence after postacute brain injury rehabilitation are not transportable: a systematic review.

BACKGROUND AND OBJECTIVES: To identify and summarize validated multivariable prognostic models for the Functional Independence Measure® (FIM®) at discharge from post-acute inpatient rehabilitation in adults with acquired brain injury (ABI). METHODS: This review was conducted based on the recommendations of the Cochrane Prognosis Methods Group and adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Three databases were systematically searched in May 2021 and updated in April 2022. Main inclusion criteria were: a) adult patients with ABI, b) validated multivariable prognostic model, c) time of prognostication within 1-week of admission to post-acute rehabilitation, and d) outcome was the FIM® at discharge from post-acute rehabilitation. RESULTS: The search yielded 3,169 unique articles. Three articles fulfilled the inclusion criteria, accounting for n = 6 internally and n = 2 externally validated prognostic models. Discrimination was estimated as an area under the curve between 0.76 and 0.89. Calibration was deemed to be assessed insufficiently. The included models were judged to be of high risk of bias. CONCLUSION: Current prognostic models for the FIM® in post-acute rehabilitation for patients with ABI lack the methodological rigor to support clinical use outside the development setting. Future studies addressing functional independence should ensure appropriate model validation and conform to uniform reporting standards for prognosis research.

Clinical trial registration has become more prevalent in physical therapy but it is still inadequate: A meta-research study.

BACKGROUND: A study using data from 2009 showed low prevalence and inadequate trial registration in physiotherapy. In 2013, a joint editorial recommended prospective registration in physiotherapy journals. Ten years later it is unclear whether the joint editorial achieved its intended benefit. OBJECTIVES: To investigate the proportion of randomized trials adequately registered and the extent of selective reporting of outcomes in trials of physiotherapy interventions published in 2019 and to compare these data with equivalent published data from 2009. DESIGN: Meta-research study. METHOD: A random sample of 200 trials published in 2019 was used. Evidence of registration was sought on trial registers and by contacting authors. Data from the article was compared with data from the trial registration. Data from this sample of trial published in 2019 were compared with equivalent published data from 2009. RESULTS: In 2019, the proportion of trials that were registered was 63% versus 34% in 2009 (absolute difference 29%). In 2019, 18% of the trials were prospectively registered compared to 6% in 2009 (absolute difference 12%). Unambiguous primary outcomes (i.e., method and timepoints of measurement clearly defined in the trial registry entry) were registered for 30% in 2019. Registration was adequate (i.e., prospective with unambiguous primary outcomes) for 8%, compared with 3% in 2009 (absolute difference 5%). Selective outcome reporting occurred in 73% of the trials in which it was assessable; in 2009 this proportion was 47% (absolute difference 26%). CONCLUSIONS: Registration of randomized trials in physiotherapy increased in the past decade, but it is still inadequate. More effort is still required to implement and enforce adequate registration.

Assessing the Reconceptualization of Pain in Graduate-Entry Physiotherapy Students Using the Concept of Pain Inventory for Adults: The University of Technology Sydney Physiotherapy Student Surveys Project.

INTRODUCTION: Validly and reliably assessing conceptual change is essential for evaluating the effectiveness of pain science education for physiotherapy students. We aimed to 1) evaluate concept of pain before and after a 14-week pain science education university subject, 2) assess structural validity of the Concept of Pain Inventory for Adults (COPI-Adult) in postgraduate entry-level physiotherapy students, and 3) explore possible relationships between baseline variables and baseline COPI-Adult scores. REVIEW OF LITERATURE: As the COPI-Adult is a newly developed questionnaire, there is a lack of data regarding its psychometric properties. SUBJECTS: Of 129 enrolled students at an Australian university, 124 (96%) and 114 (88%) completed the baseline and follow-up questionnaires, respectively. METHODS: In this prospective cohort study, students who commenced the degree in 2020 or 2021 completed online questionnaires, including the COPI-Adult, at the start and end of their first semester. This semester included a 14-week pain science education subject and other physiotherapy-related subjects. Higher COPI-Adult scores (range = 0-52) indicate better alignment with contemporary pain science. We 1) compared differences in concept of pain before and after the semester, 2) performed a confirmatory factor analysis on the COPI-Adult, and 3) performed exploratory regression analyses. RESULTS: Concept of Pain Inventory for Adults scores increased from baseline (median [interquartile range]: 39 [36-44]) to follow-up (48 [44-51]). The COPI-Adult retained its 1-factor structure, with acceptable internal consistency (Cronbach's alpha = 0.80). Exploratory analysis showed that previously completing a subject on pain was related to higher COPI-Adult baseline scores. Age, gender, and mental health diagnosis did not relate to baseline COPI-Adult scores. DISCUSSION AND CONCLUSION: Following a 14-week pain science education subject embedded within a physiotherapy degree, students improved their concept of pain. The COPI-Adult maintains a 1-factor structure in this population. Completing a previous subject on pain was associated with higher COPI-Adult scores.

Motor adaptation following split-belt treadmill walking.

Malone L, Vasudevan E, and Bastian A (J Neurosci 31: 15136-15143, 2011) investigated the effects of different training paradigms on the day-by-day retention of learned motor patterns. In this Neuro Forum, a description and assessment of the methods used will be presented. The interpretation of the findings will be extended and the possible implications will be discussed. Finally, alternative explanations of the possible regions involved in motor pattern relearning will be provided.

Identifying common core outcome domains from core outcome sets of musculoskeletal conditions: protocol for a systematic review.

BACKGROUND: Core outcome sets (COSs) aim to reduce outcome heterogeneity in clinical practice and research by suggesting a minimum number of agreed-upon outcomes in clinical trials. Most COSs in the musculoskeletal field are developed for specific conditions. We propose that there are likely to be common core domains within existing musculoskeletal COSs that may be used as a starting point in the development of future COSs. We aim to identify common core domains from existing COSs and to facilitate the development of new COSs for musculoskeletal conditions. As a secondary aim, we will assess the development quality of these COSs. METHODS: A systematic review including musculoskeletal COSs. We will search Core Outcome Measures in Effectiveness Trials (COMET) database, MEDLINE, EMBASE, Scopus, Cochrane Methodology Register and International Consortium for Health Outcome Measurement (ICHOM). Studies will be included if related to the development of a COS in adults with musculoskeletal conditions and for any type of intervention. Quality will be assessed using the Core Outcome Set-Standards for Development (COS-STAD) recommendations. Data extracted will include scope of the COS, health condition, interventions and outcome domains. Primary outcomes will be all core domains recommended within each COS. We define a common core outcome domain as one present in at least 67% of all COSs. All findings will be summarized and presented using descriptive statistics. DISCUSSION: This systematic review of COSs will describe the core domains recommended within each musculoskeletal COS. Common domains found may be used in the initial stages of development of future musculoskeletal COSs. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42021239141.

Phase modulation of the short-latency crossed spinal response in the human soleus muscle.

Short-latency spinally mediated interlimb reflex pathways were recently reported between the left and right soleus muscles in the human lower-limb during sitting. The aim of the current study was to establish if these pathways were observed during a functional motor task such as human gait and modulated by the gait cycle phase and/or electrical stimulation intensity. The second aim was to elucidate on the afferents involved. Two interventions were investigated. First was ipsilateral tibial nerve (iTN) stimulation at motor threshold (MT), 35% of the maximal peak-to-peak M-wave(M-Max) and 85% M-Max (85M-Max) with stimuli applied at 60%, 70%, 80%, 90%, and 100%of the gait cycle of the ipsilateral leg. Second was ipsilateral sural nerve (SuN) and medial plantar nerve (MpN) stimulation at 1, 2, and 3X perceptual threshold at 90% of the gait cycle [corrected]. The root mean squared (RMS) of the contralateral soleus (cSOL) responses were analyzed in a time window, 40-55 ms (or 45-60 ms for subjects >50 y/o) following iTN stimulation. The most consistent responses occurred at 90 and 100% of the gait cycle at higher stimulation intensities of the iTN. Significantly inhibitory responses (P = 0.006) were reported at 60 versus 80% (P = 0.03), 90% (P = 0.006), and 100% (P = 0.002) and 70 versus 90% (P = 0.02) and 100% (P = 0.009) of the gait cycle at 85M-Max. The responses became more inhibitory with increasing stimulation intensities at 80% (P = 0.01), 90% (P = 0.001), and 100% (P = 0.004) of the gait cycle. Stimulation of the MpN and SuN at all stimulation intensities demonstrated no short-latency responses. Therefore, it is unlikely that afferents within these nerves contribute to the response. This is the first study to show short-latency spinally mediated responses in the cSOL following iTN stimulation, during walking. It provides evidence for a new spinal pathway contributing to motor control and demonstrates that the response likely has functional relevance.

Crossed spinal soleus muscle communication demonstrated by H-reflex conditioning.

INTRODUCTION: A conditioning volley to the ipsilateral tibial nerve (iTN) inhibits contralateral soleus (cSOL) electromyographic activity at latencies of 37-41 ms. This is evidence for spinal muscular communication in opposing limbs. The aim of our study was to determine whether the cSOL H-reflex would be inhibited in a similar manner. METHODS: Thirteen subjects participated in two experiments: (1) stimuli delivered to the iTN at 85% of the maximal peak-to-peak M-wave (85% M-max) with a pre-contracted cSOL; (2) 510 stimuli delivered at 85% M-max to the iTN with a test volley delivered to the contralateral tibial nerve at interstimulus intervals of -6 to 100 ms. RESULTS: Significant inhibition was observed in the cSOL H-reflex when conditioning stimuli were delivered 3-33 ms before the test H-reflex. CONCLUSIONS: The activity of this spinal pathway can be quantified using H-reflex conditioning to provide a controlled model for further studies of this response.

Has Reporting on Physical Therapy Interventions Improved in 2 Decades? An Analysis of 140 Trials Reporting on 225 Interventions.

OBJECTIVES: To investigate the completeness of reporting of physical therapy interventions in randomized controlled trials before and after publication of the Template for Intervention Description and Replication (TIDieR) checklist (a reporting guideline for interventions). DESIGN: Meta-research. METHODS: We searched 6 journals for trials using physical therapy interventions that were published in 2000 and 2018. Two independent assessors scored the TIDieR checklist and extracted descriptive information, including Physiotherapy Evidence Database (PEDro) scale scores. We identified control or treatment interventions, exercise-based interventions, and area of physical therapy. We performed a descriptive analysis and defined a priori a 20% difference between studies published in 2000 and 2018 as meaningful. We assessed correlations between TIDieR and PEDro scale scores for all interventions. RESULTS: In total, 140 articles that met selection criteria evaluated 225 interventions (2000, n = 61; 2018, n = 164). Mean ± SD TIDieR score (2000, 7.52 ± 2.62; 2018, 8.26 ± 2.26) did not show a meaningful difference between years for all interventions (+5%), controls (+6%), treatment interventions (+6%), exercise-based interventions (+9%), or musculoskeletal (+4%) or neurological (+7%) physical therapy. For exercise interventions, number of sessions was reported more (+21%) in 2018 than in 2000. For musculoskeletal trials, 2 items were reported more completely in 2018 than in 2000 (materials, +29%; individual versus group, +22%) and 3 items were reported more completely in neurological trials (mode of delivery, +20%, [item 8.1] when +45%, and assessment of fidelity, +20%). The item "Who delivered the intervention?" was reported less completely (-23%) in 2018 than in 2000 in neurological trials. We found no correlation (r = 0.12) between PEDro scale score and TIDieR score. CONCLUSION: There were few meaningful improvements in how physical therapy interventions were described after publication of the TIDieR reporting guideline. J Orthop Sports Phys Ther 2021;51(10):503-509. doi:10.2519/jospt.2021.10642.

Therapist perceptions of the Danish Physiotherapy Research Database for assessing patients with chronic disease.

BACKGROUND: The Danish Physiotherapy Research Database for chronic patients receiving Free of Charge Physiotherapy (PhysDB-FCP) was piloted over a 1-year period. The purpose of the PhysDB-FCP is to provide a user friendly digital online structured tool that standardizes initial and follow up clinical assessments generating data that can be used for clinical decision making and support future research in physiotherapy for patients with chronic disease. Although initial assessments were completed, the attrition rate was 73% and 90% at 3- and 6- months, respectively, which suggests problems with the current tool. OBJECTIVE: To evaluate the perspectives of the physiotherapists that used the PhysDB-FCP and propose changes to the tool based on this feedback. MATERIALS AND METHODS: Fifty of the 103 physiotherapists introduced to the PhysDB-FCP completed an anonymous online survey. Physiotherapists were asked Likert/categorical and yes/no questions on experiences with the PhysDB-FCP within their practice, perceptions of patient experiences, suitability of the resources and support provided by the PhysDB-FCP working group and the ideal administration frequency of the assessments within the PhysDB-FCP. Open ended feedback on possible improvements to the PhysDB-FCP was also collected. RESULTS: Physiotherapists agreed that the PhysDB-FCP was useful for taking a physiotherapy assessment (74%) and the patient survey was useful for goal setting (72%). Although physiotherapists felt the PhysDB-FCP was well-defined (82%), only 36% would like to use a similar tool again. Generally, the PhysDB-FCP was too time-consuming, administered too frequently and included irrelevant items. For example, 72% of physiotherapists took >45 min to administer the assessment in the first consultation which was performed over multiple sessions. CONCLUSIONS: The perspectives of physiotherapists using The PhysDB-FCP suggest specific changes that will ensure better use of the tool in future practice. Changes will likely involve administering the assessment less frequently (every 6-months to 1-year), shortening the assessment, and using diagnosis-specific assessment items.

Externally validated model predicting gait independence after stroke showed fair performance and improved after updating.

OBJECTIVE: To externally validate recent prognostic models that predict independent gait following stroke. STUDY DESIGN AND SETTING: A systematic search identified recent models (<10 years) that predicted independent gait in adult stroke patients, using easily obtainable predictors. Predictors from the original models were assigned proxies when required, and model performance was evaluated in the validation cohort (n = 957). Models were updated to determine if performance could be improved. RESULTS: Three prognostic models met our criteria, all with high Risk of Bias. Validation data was only available for the Australian model. This model used National Institute of Health Stroke Scale (NIHSS) and age to predict independent gait, using Motor Assessment Scale (MAS) walking item. For validation, Scandinavian Stroke Scale (SSS) was a proxy for NIHSS, and Functional Independence Measure (FIM) locomotion item was a proxy for MAS. The Area Under the Curve was 0.77 (0.74-0.80) and had good calibration in the validation dataset. Adjustment of the intercept and regression coefficients slightly improved discrimination. By adding paretic leg strength, the model further improved (AUC 0.82). CONCLUSION: External validation of the Australian model with proxies showed fair discrimination and good calibration. Updating the model by adding paretic leg strength further improved model performance.

Short-latency crossed inhibitory responses in the human soleus muscle.

Even though interlimb coordination is critical in bipedal locomotion, the role of muscle afferent mediated feedback is unknown. The aim of this study was to establish if ipsilateral muscle generated afferent feedback can influence contralateral muscle activation patterns in the human lower limb and to elucidate the mechanisms involved. The effect of ipsilateral tibial nerve stimulation on contralateral soleus (cSOL) responses were quantified. Three interventions were investigated, 1) electrical stimulation applied to the tibial nerve at stimulation intensities from 0 to 100% of maximal M-wave (M-max) with the cSOL contracted from 5 to 15% of maximal voluntary contraction (MVC) and 15 to 30% MVC, 2) ispsilateral tibial nerve stimulation at 75% M-max prior to, during, and following the application of ischemia to the ipsilateral thigh. 3) Electrical stimulation applied to the ipsilateral sural (SuN) and medial plantar nerves at stimulation intensities from 1 to 3 times perceptual threshold. A short-latency depression in the cSOL electromyogram (EMG; onset: 37-41 ms) was observed following ipsilateral tibial nerve stimulation. The magnitude of this depression increased (P = 0.0005 and P = 0.000001) with increasing stimulus intensities. Ischemia delayed the time of the minimum of the cSOL depression (P = 0.04). SuN and medial plantar nerve stimulation evoked a longer latency depression [average; 91.2 ms (SuN); 142 ms (medial plantar nerve)] and therefore do not contribute to the response. This is the first study to demonstrate a short-latency depression in the cSOL following ipsilateral tibial nerve stimulation. Due to its short latency, the response is spinally mediated. The involvement of crossed spinal interneurons receiving input from low-threshold muscle afferents is discussed.

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.

Passive elongation of muscle fascicles in human muscles with short and long tendons.

This study tested the hypothesis that the ratio of changes in muscle fascicle and tendon length that occurs with joint movement scales linearly with the ratio of the slack lengths of the muscle fascicles and tendons. We compared the contribution of muscle fascicles to passive muscle-tendon lengthening in muscles with relatively short and long fascicles. Fifteen healthy adults participated in the study. The medial gastrocnemius, tibialis anterior, and brachialis muscle-tendon units were passively lengthened by slowly rotating the ankle or elbow. Change in muscle fascicle length was measured with ultrasonography. Change in muscle-tendon length was calculated from estimated muscle moment arms. Change in tendon length was calculated by subtracting change in fascicle length from change in muscle-tendon length. The median (IQR) contribution of muscle fascicles to passive lengthening of the muscle-tendon unit, measured as the ratio of the change in fascicle length to the change in muscle-tendon unit length, was 0.39 (0.26-0.48) for the medial gastrocnemius, 0.51 (0.29-0.60) for tibialis anterior, and 0.65 (0.49-0.90) for brachialis. Brachialis muscle fascicles contributed to muscle-tendon unit lengthening significantly more than medial gastrocnemius muscle fascicles, but less than would be expected if the fascicle contribution scaled linearly with the ratio of muscle fascicle and tendon slack lengths.

Behavior of human gastrocnemius muscle fascicles during ramped submaximal isometric contractions.

Precise estimates of muscle architecture are necessary to understand and model muscle mechanics. The primary aim of this study was to estimate continuous changes in fascicle length and pennation angle in human gastrocnemius muscles during ramped plantar flexor contractions at two ankle angles. The secondary aim was to determine whether these changes differ between proximal and distal fascicles. Fifteen healthy subjects performed ramped contractions (0-25% MVC) as ultrasound images were recorded from the medial (MG, eight sites) and lateral (LG, six sites) gastrocnemius muscle with the ankle at 90° and 120° (larger angles correspond to shorter muscle lengths). In all subjects, fascicles progressively shortened with increasing torque. MG fascicles shortened 5.8 mm (11.1%) at 90° and 4.5 mm (12.1%) at 120°, whereas LG muscle fascicles shortened 5.1 mm (8.8%) at both ankle angles. MG pennation angle increased 1.4° at 90° and 4.9° at 120°, and LG pennation angle decreased 0.3° at 90° and increased 2.6° at 120°. Muscle architecture changes were similar in proximal and distal fascicles at both ankle angles. This is the first study to describe continuous changes in fascicle length and pennation angle in the human gastrocnemius muscle during ramped isometric contractions. Very similar changes occurred in proximal and distal muscle regions. These findings are relevant to studies modeling active muscle mechanics.