DOES MAGNETIC RESONANCE IMAGING PROVIDE SUPERIOR RELIABILITY FOR ACHILLES AND PATELLAR TENDON CROSS-SECTIONAL AREA MEASUREMENTS COMPARED WITH ULTRASOUND IMAGING?

This study investigated the reliability of Achilles and patellar tendon cross-sectional area (CSA) measurement using ultrasound imaging (USI) and magnetic resonance imaging (MRI). Fifteen healthy adults were imaged twice on two occasions, interrupted by a tendon loading protocol. Tendon CSA segmentations were conducted by an experienced and an inexperienced rater blinded to information regarding subject, session and loading status. USI provided good test-retest reliability (intra-class correlation coefficient [ICC] 2,1 > 0.85, standard error of measurement [SEM] 5%-6%), while with MRI it was excellent (ICC 2,1 > 0.92, SEM 4%) for the experienced rater. This study suggests that MRI provides superior reliability for tendon CSA measurements compared with USI. However, the difference in reliability between the methods was small, and the results were inconclusive regarding objectivity and sensitivity to change when assessed based on the effect of loading. We concluded that both methods can be used for reliable CSA measurements of the Achilles and patellar tendons when using a highly standardized measurement protocol and when conducted by an experienced rater. (C) 2019 World Federation for Ultrasound in Medicine & Biology. All rights reserved.Peer reviewe

Slower Walking Speed in Older Men Improves Triceps Surae Force Generation Ability

Purpose Older adults walk slower than young adults, but it is not known why. Previous research suggests that ankle plantarflexors may have a crucial role in the reduction of walking speed. The purpose of this study was to investigate age-related differences in triceps surae muscle–tendon function during walking to further investigate the role of plantarflexors in the age-related reduction of walking speed. Methods Medial gastrocnemius and soleus muscle fascicle lengths were measured using ultrasound imaging during walking from 13 young (25 ± 4 yr) men at preferred walking speed and from 13 older (73 ± 5 yr) men at preferred speed and at the young men’s preferred speed. Muscle–tendon unit lengths were calculated from joint kinematics, and tendinous tissue lengths were calculated by subtracting muscle lengths from muscle–tendon unit lengths. In addition, ground reaction forces and electromyographic activity of medial gastrocnemius and soleus were measured. Results In both medial gastrocnemius and soleus, it was observed that at preferred walking speed, older men used a narrower muscle fascicle operating range and lower shortening velocity at the estimated time of triceps surae peak force generation compared with young men. Fascicles also accounted for a lower proportion of muscle–tendon unit length changes during the stance phase in older compared with young men. Significant differences in triceps surae muscle function were not observed between age groups when compared at matched walking speed. Conclusions In older men, walking at preferred speed allows triceps surae muscles to generate force with more favorable shortening velocity and to enhance use of tendinous tissue elasticity compared with walking at young men’s preferred speed. The results suggest that older men may prefer slower walking speeds to compensate for decreased plantarflexor strength

Open-source software library for real-time inertial measurement unit data-based inverse kinematics using OpenSim

Background Inertial measurements (IMUs) facilitate the measurement of human motion outside the motion laboratory. A commonly used open-source software for musculoskeletal simulation and analysis of human motion, OpenSim, includes a tool to enable kinematics analysis of IMU data. However, it only enables offline analysis, i.e., analysis after the data has been collected. Extending OpenSim’s functionality to allow real-time kinematics analysis would allow real-time feedback for the subject during the measurement session and has uses in e.g., rehabilitation, robotics, and ergonomics. Methods We developed an open-source software library for real-time inverse kinematics (IK) analysis of IMU data using OpenSim. The software library reads data from IMUs and uses multithreading for concurrent calculation of IK. Its operation delays and throughputs were measured with a varying number of IMUs and parallel computing IK threads using two different musculoskeletal models, one a lower-body and torso model and the other a full-body model. We published the code under an open-source license on GitHub. Results A standard desktop computer calculated full-body inverse kinematics from treadmill walking at 1.5 m/s with data from 12 IMUs in real-time with a mean delay below 55 ms and reached a throughput of more than 90 samples per second. A laptop computer had similar delays and reached a throughput above 60 samples per second with treadmill walking. Minimal walking kinematics, motion of lower extremities and torso, were calculated from treadmill walking data in real-time with a throughput of 130 samples per second on the laptop and 180 samples per second on the desktop computer, with approximately half the delay of full-body kinematics. Conclusions The software library enabled real-time inverse kinematical analysis with different numbers of IMUs and customizable musculoskeletal models. The performance results show that subject-specific full-body motion analysis is feasible in real-time, while a laptop computer and IMUs allowed the use of the method outside the motion laboratory

Exploration of muscle–tendon biomechanics one year after Achilles tendon rupture and the compensatory role of flexor hallucis longus

Achilles tendon (AT) rupture leads to long-term structural and functional impairments. Currently, the predictors of good recovery after rupture are poorly known. Thus, we aimed to explore the interconnections between structural, mechanical, and neuromuscular parameters and their associations with factors that could explain good recovery in patients with non-surgically treated AT rupture. A total of 35 patients with unilateral rupture (6 females) participated in this study. Muscle-tendon structural, mechanical, and neuromuscular parameters were measured 1-year after rupture. Interconnections between the inter-limb differences (Δ) were explored using partial correlations, followed by multivariable linear regression to find associations between the measured factors and the following markers that indicate good recovery: 1) tendon length, 2) tendon non-uniform displacement, and 3) flexor hallucis longus (FHL) normalized EMG amplitude difference between limbs. Δmedial gastrocnemius (MG) (β = −0.12, p = 0.007) and Δlateral gastrocnemius (β = −0.086, p = 0.030) subtendon lengths were associated with MG tendon Δstiffness. MG (β = 11.56, p = 0.003) and soleus (β = 2.18, p = 0.040) Δsubtendon lengths explained 48 % of variance in FHL EMG amplitude. Regression models for tendon length and non-uniform displacement were not significant. Smaller inter-limb differences in Achilles subtendon lengths were associated with smaller differences in the AT stiffness between limbs, and a smaller contribution of FHL muscle to the plantarflexion torque. In the injured limb, the increased contribution of FHL appears to partially counteract a smaller contribution from MG due to the elongated tendon, however the role of FHL should not be emphasized during rehabilitation to allow recovery of the TS muscles

An EMG-Assisted Muscle-Force Driven Finite Element Analysis Pipeline to Investigate Joint- and Tissue-Level Mechanical Responses in Functional Activities : Towards a Rapid Assessment Toolbox

Publisher Copyright: © 1964-2012 IEEE.Joint tissue mechanics (e.g., stress and strain) are believed to have a major involvement in the onset and progression of musculoskeletal disorders, e.g., knee osteoarthritis (KOA). Accordingly, considerable efforts have been made to develop musculoskeletal finite element (MS-FE) models to estimate highly detailed tissue mechanics that predict cartilage degeneration. However, creating such models is time-consuming and requires advanced expertise. This limits these complex, yet promising, MS-FE models to research applications with few participants and makes the models impractical for clinical assessments. Also, these previously developed MS-FE models have not been used to assess activities other than gait. This study introduces and verifies a semi-automated rapid state-of-the-art MS-FE modeling and simulation toolbox incorporating an electromyography- (EMG) assisted MS model and a muscle-force driven FE model of the knee with fibril-reinforced poro(visco)elastic cartilages and menisci. To showcase the usability of the pipeline, we estimated joint- and tissue-level knee mechanics in 15 KOA individuals performing different daily activities. The pipeline was verified by comparing the estimated muscle activations and joint mechanics to existing experimental data. To determine the importance of the EMG-assisted MS analysis approach, results were compared to those from the same FE models but driven by static-optimization-based MS models. The EMG-assisted MS-FE pipeline bore a closer resemblance to experiments compared to the static-optimization-based MS-FE pipeline. Importantly, the developed pipeline showed great potential as a rapid MS-FE analysis toolbox to investigate multiscale knee mechanics during different activities of individuals with KOA.Peer reviewe

Near infrared spectroscopic evaluation of biochemical and crimp properties of knee joint ligaments and patellar tendon

Knee ligaments and tendons play an important role in stabilizing and controlling the motions of the knee. Injuries to the ligaments can lead to abnormal mechanical loading of the other supporting tissues (e.g., cartilage and meniscus) and even osteoarthritis. While the condition of knee ligaments can be examined during arthroscopic repair procedures, the arthroscopic evaluation suffers from subjectivity and poor repeatability. Near infrared spectroscopy (NIRS) is capable of non-destructively quantifying the composition and structure of collagen-rich connective tissues, such as articular cartilage and meniscus. Despite the similarities, NIRS-based evaluation of ligament composition has not been previously attempted. In this study, ligaments and patellar tendon of ten bovine stifle joints were measured with NIRS, followed by chemical and histological reference analysis. The relationship between the reference properties of the tissue and NIR spectra was investigated using partial least squares regression. NIRS was found to be sensitive towards the water (R2CV = .65) and collagen (R2CV = .57) contents, while elastin, proteoglycans, and the internal crimp structure remained undetectable. As collagen largely determines the mechanical response of ligaments, we conclude that NIRS demonstrates potential for quantitative evaluation of knee ligaments.publishedVersionPeer reviewe

Circulating levels of adipokines and IGF-1 are associated with skeletal muscle strength of young and old healthy subjects

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Effects of ageing on Achilles tendon properties and triceps surae muscle architecture in vivo

Achilles tendon is the largest tendon in human body and it has an important role in human locomotion. Ageing is associated with lowered muscle function and the changes in tendon properties could have a major role in modulating the muscle function with ageing. The aim of this study was to identify the changes in triceps surae muscle-tendon complex with ageing. Achilles tendon mechanical properties and triceps surae muscle architecture were measured from total of 100 subjects [33 young (24 ± 2 yr.) and 67 old (75 ± 3 yr.)]. Motion analysis assisted ultrasonography was used to determine Achilles tendon stiffness, Young’s modulus and hysteresis during isometric ramp contractions. Ultrasonography was used to measure muscle architectural features from triceps surae muscles. The main findings of the study were that Achilles tendon stiffness was decreased by 17 % (p < 0.001) and Young’s modulus by 32 % (p < 0.001) with ageing. There was no difference in hysteresis between young and old. Achilles tendon stiffness and Young’s modulus were found to be associated with the triceps surae muscles force producing capacity (r = 0.612, p < 0.001 and r = 0.625, p < 0.001 for stiffness and Young’s modulus, respectively) in combined data of young and old subjects. Achilles tendon crosssectional area was 20 % higher (p < 0.001, n = 71) in old than young subjects measured from the middle of the free Achilles tendon but the muscle cross-sectional area measured from the both heads of gastrocnemius muscle was lowered by 15 % (p < 0.001) in old compared to young subjects. The triceps surae muscle force was 39 % (p < 0.001) lower in old compared to young. Gastrocnemius medialis and soleus muscle thickness and gastrocnemius medialis muscle fascicle length was lower in old compared to young (for all p < 0.05). There were no other differences in muscle architecture in old compared to young subjects. The data suggests that Achilles tendon mechanical properties are modulated to match the level of muscle performance even at old age. The functional consequence of these findings is that the Achilles tendon of old individuals seem to be more suitable for normal daily activities of old people like walking than the Achilles tendon of young individuals. The changes in the Achilles tendon mechanical properties can counteract the lowered muscle performance in order to keep the functional capacity of the muscletendon complex as good as possible.Akillesjänne on ihmiskehon suurin jänne ja sillä merkittävä rooli ihmisen liikkumisessa. Ikääntymiseen liittyy heikentynyt lihasten toimintakyky ja muutoksilla jänteen ominaisuuksissa voi olla merkittävä rooli lihaksen toimintakyvyn muutoksissa ikääntyessä. Tämän tutkimuksen tarkoitus oli tunnistaa muutokset kolmipäisen kantalihaksen lihasjännekompleksissa. Akillesjänteen ominaisuudet ja kolmipäisen kantalihaksen lihasarkkitehtuuri mitattiin 100 koehenkilöltä [33 nuorta (ikä 24 ± 2 vuotta) ja 67 ikääntynyttä (ikä 75 ± 3 vuotta)]. Akillesjänteen mekaaniset (jäykkyys) ja materiaaliset ominaisuudet (Youngin moduli), sekä hystereesi mitattiin käyttäen liikeanalyysiavusteista ultraäänikuvantamista isometristen plantaarifleksioiden aikana. Ultraäänikuvantamista käytettiin määrittämään lihaksen arkkitehtuurisia tekijöitä kolmipäisestä kantalihaksesta. Tutkimuksen päätulokset olivat, että akillesjänteen jäykkyys oli vähentynyt 17 % (p < 0,001) ja Youngin moduli 32 % (p < 0,001) ikääntymisen seurauksena. Hystereesissä ei havaittu eroja nuorten ja ikääntyneiden välillä. Akillesjänteen poikkipinta-ala oli 20 % suurempi (p < 0,001, n = 71) ikääntyneillä verrattuna nuoriin puhtaan jänteen puolivä- lissä. Akillesjänteen jäykkyys ja Youngin moduli olivat yhteydessä kolmipäisen kantalihaksen voimantuottokykyyn (jäykkyydelle: r = 0.612, p < 0.001 ja Youngin modulille: r = 0.625, p < 0.001) yhdistetyssä aineistossa. Kaksoiskantalihasten poikkipinta-ala oli 15 % (p < 0,001) pienempi ikääntyneillä verrattuna nuoriin. Kolmipäisen kantalihaksen lihasvoima oli 39 % (p < 0,001) alhaisempi ikääntyneillä verrattuna nuoriin. Kasipäisen kantalihaksen sisemmän osan lihaksen paksuus ja lihassolukimppujen pituus, sekä leve- än kantalihaksen paksuus oli pienempi ikääntyneillä verrattuna nuoriin (p < 0,05 kaikille). Muita eroja lihasarkkitehtuurissa nuorten ja ikääntyneiden välillä ei löydetty. Tulokset osoittavat, että akillesjänteen mekaaniset ominaisuudet mukautuvat lihaksen voimantuottokyvyn mukaan niin ikääntyneillä, kuin nuorillakin. Näiden löydösten toiminnallinen seuraus on se, että ikääntyneiden ihmisten akillesjänne näyttää olevan paremmin soveltuva heidän päivittäisiin liikkumismuotoihin, kuten kävelyyn verrattuna nuorten ihmisten akillesjänteeseen. Akillesjänteen mekaanisten ominaisuuksien muutokset ikääntyessä voivat vähentää lihaksessa tapahtuvia toimintakykyä heikentäviä muutoksia pitäen lihas-jännekompleksin toimintakyvyn niin hyvänä, kuin mahdollista

Biplanar ultrasound investigation of in vivo Achilles tendon displacement non-uniformity

The Achilles tendon is a common tendon for the medial and lateral gastrocnemius and soleus muscles. Non‐uniform Achilles tendon regional displacements have been observed in vivo which may result from non‐uniform muscle loading and intratendinous shearing. However, prior observations are limited to the sagittal plane. This study investigated Achilles tendon tissue displacement patterns during isometric plantarflexor contractions in the coronal and sagittal planes. Fourteen subjects (5 female, 9 male, 26 ± 3 year) performed maximal isometric plantarflexor contractions with the knee in full extension and flexed to 110°. An ultrasound transducer positioned over the free Achilles tendon collected beam formed radio frequency (RF) data at 70 frames/s. Localized tissue displacements were analyzed using a speckle tracking algorithm. We observed non‐uniform Achilles tendon tissue displacements in both imaging planes. Knee joint posture had no significant effect on tissue displacement patterns in either imaging plane. The non‐uniform Achilles tendon tissue displacements during loading may arise from the anatomical organization of the sub‐tendons associated with the three heads of the triceps surae. The biplanar investigation suggests that greatest displacements are localized to tissue likely to belong to soleus subtendon. This study adds novel information with possible implications for muscle coordination, function, and muscle‐tendon injury mechanisms.peerReviewe