Advances in regenerative rehabilitation in the rehabilitation of musculoskeletal injuries.

In the rapidly advancing field of regenerative medicine, relying solely on cell transplantation alone may be insufficient for achieving functional recovery, and rehabilitation before and after transplantation is crucial. Regenerative rehabilitation functions by synergizing the therapeutic effects of regeneration and rehabilitation to maximize tissue regeneration and patient function. We used the keywords "regenerative rehabilitation" to search across the database for published works; this review discusses the development of regenerative rehabilitation for the treatment of musculoskeletal injuries. Rehabilitation has become a crucial component of regenerative medicine because it can enhance patients' functional activity and facilitate their early return to society. Experimental data increasingly demonstrates that rehabilitation interventions support the regeneration of transplanted tissues.

Regenerative medicine concepts can be incorporated into rehabilitation to help patients achieve a better functional recovery outcome. Rehabilitation therapy can help patients return to society sooner following an injury. Regenerative medicine concepts can also be integrated into regenerative therapy to maximize its benefits when compared with traditional rehabilitation or regenerative therapy alone. The development of regenerative rehabilitation for the treatment of skeletal muscle, bone and bone junction injuries is reviewed in this article.

A multi-resolution physics-informed recurrent neural network: formulation and application to musculoskeletal systems.

This work presents a multi-resolution physics-informed recurrent neural network (MR PI-RNN), for simultaneous prediction of musculoskeletal (MSK) motion and parameter identification of the MSK systems. The MSK application was selected as the model problem due to its challenging nature in mapping the high-frequency surface electromyography (sEMG) signals to the low-frequency body joint motion controlled by the MSK and muscle contraction dynamics. The proposed method utilizes the fast wavelet transform to decompose the mixed frequency input sEMG and output joint motion signals into nested multi-resolution signals. The prediction model is subsequently trained on coarser-scale input-output signals using a gated recurrent unit (GRU), and then the trained parameters are transferred to the next level of training with finer-scale signals. These training processes are repeated recursively under a transfer-learning fashion until the full-scale training (i.e., with unfiltered signals) is achieved, while satisfying the underlying dynamic equilibrium. Numerical examples on recorded subject data demonstrate the effectiveness of the proposed framework in generating a physics-informed forward-dynamics surrogate, which yields higher accuracy in motion predictions of elbow flexion-extension of an MSK system compared to the case with single-scale training. The framework is also capable of identifying muscle parameters that are physiologically consistent with the subject's kinematics data.

Incidence of knee and hip joint replacement associated with cumulative exposure to physical factors at work.

BACKGROUND: Knee osteoarthritis (OA) has been quite consistently associated with high physical workload and specific physical factors at work, while for hip OA, fewer studies are available, which still indicate possible associations with heavy lifting and physical workload. The objective of the study was to assess the association between exposure to workplace physical factors and incidence of knee and hip arthroplasty, as markers of severe OA in these joints. METHODS: The study population was composed of employees 25-60 years who participated in the Turin 2011 census. For each job held since 1995, exposure to physical factors was assigned to individuals in the cohort through a Job-Exposure Matrix constructed from the Italian O*NET database. Using Poisson regression models, the incidence of knee and hip arthroplasty for OA, identified through hospitalizations from 2012 to 2018, was examined in relation to cumulative exposure to 7 different physical hazards and a composite indicator of physical workload constructed from 17 physical factors (Ergo-Index). RESULTS: The risk of knee OA was significantly increased in the highest cumulative exposure quartile of physical workload (incidence rate ratio = 1.98, 95% confidence interval: 1.24-3.16) and of all single hazards examined, compared to the lowest quartile, with significant trends in risk with increasing exposure. In contrast, no association was found with hip OA, whose relative risks were close to or below one in all higher-exposure quartiles of physical workload and of each single hazard. CONCLUSIONS: Our results indicate that exposure to physical hazards at work increases the likelihood of developing knee OA, but not hip OA.

Dose Escalation Can Enhance the Therapeutic Potential of Radial Extracorporeal Shock-Wave Therapy in the Treatment of Plantar Fasciitis in Runners.

Background and Objectives: Treatment of chronic plantar fasciitis is challenging given that there are various of available treatment options with no clear gold standard. The aim of the study was to examine the dose-escalation effect of rESWT on the biomechanical parameters of the plantar fascia and pain ailments. Materials and Methods: In the experimental group (n = 30), the intensity of the shock wave was increased every two subsequent treatment sessions. In the control group (n = 32), the treatment parameters were not changed. In both groups, six treatments were performed, with two treatment sessions a week. In order to assess the biomechanical parameters of the plantar fascia, myotonometric measurements were performed. The pain intensity was assessed using the Visual Analog Scale (VAS). Results: The tension of the plantar fascia attachment in the experimental group decreased from 27.69 ± 2.06 [Hz] before treatment to 26.29 ± 1.69 [Hz] after treatment (p = 0.009) and to 26.03 ± 2.15 [Hz] 1 month after the beginning of treatment (p = 0.003). In the control group, the frequency results did not change significantly (p > 0.05). Flexibility increased in both groups. The test results before treatment and 1 month after the beginning of the treatment showed statistical significance in the experimental group (p = 0.001) vs. (p = 0.002) in the control group. The differences were not statistically significant between groups (p > 0.05). The assessment of pain intensity carried out 1 month after the end of treatment in the experimental group amounted to 3.14 ± 2.28 points, which was statistically significantly lower compared to that in the control group, where it amounted to 5.14 ± 1.92 points. (p < 0.001). Conclusions: The use of rESWT performed with an increasing intensity of impact during subsequent treatment procedures demonstrated greater effectiveness in improving the biomechanical parameters of the plantar fascia and was also more effective in reducing the pain ailments. Our results are encouraging. The dose escalation in the treatment cycle is worth considering. To prove that this method of treatment is more effective, a randomized controlled trial should be carried out on a representative sample.

Advances in the study of plant-derived extracellular vesicles in the skeletal muscle system.

Plant-derived extracellular vesicles (PDEV) constitute nanoscale entities comprising lipids, proteins, nucleic acids and various components enveloped by the lipid bilayers of plant cells. These vesicles play a crucial role in facilitating substance and information transfer not only between plant cells but also across different species. Owing to its safety, stability, and the abundance of raw materials, this substance has found extensive utilization in recent years within research endeavors aimed at treating various diseases. This article provides an overview of the pathways and biological characteristics of PDEV, along with the prevalent methods employed for its isolation, purification, and storage. Furthermore, we comprehensively outline the therapeutic implications of diverse sources of PDEV in musculoskeletal system disorders. Additionally, we explore the utilization of PDEV as platforms for engineering drug carriers, aiming to delve deeper into the significance and potential contributions of PDEV in the realm of the musculoskeletal system.

Principles of musculoskeletal sport injuries for epidemiologists: a review.

BACKGROUND: Musculoskeletal injuries are a common occurrence in sport. The goal of sport injury epidemiology is to study these injuries at a population level to inform their prevention and treatment. MAIN BODY: This review provides an overview of musculoskeletal sport injuries and the musculoskeletal system from a biological and epidemiologic perspective, including injury mechanism, categorizations and types of sport injuries, healing, and subsequent injuries. It is meant to provide a concise introductory substantive background of musculoskeletal sport injuries for epidemiologists who may not have formal training in the underlying anatomy and pathophysiology. CONCLUSION: An understanding of sport injuries is important for researchers in sport injury epidemiology when determining how to best define and assess their research questions and measures.

Advancing skeletal health and disease research with single-cell RNA sequencing.

Orthopedic conditions have emerged as global health concerns, impacting approximately 1.7 billion individuals worldwide. However, the limited understanding of the underlying pathological processes at the cellular and molecular level has hindered the development of comprehensive treatment options for these disorders. The advent of single-cell RNA sequencing (scRNA-seq) technology has revolutionized biomedical research by enabling detailed examination of cellular and molecular diversity. Nevertheless, investigating mechanisms at the single-cell level in highly mineralized skeletal tissue poses technical challenges. In this comprehensive review, we present a streamlined approach to obtaining high-quality single cells from skeletal tissue and provide an overview of existing scRNA-seq technologies employed in skeletal studies along with practical bioinformatic analysis pipelines. By utilizing these methodologies, crucial insights into the developmental dynamics, maintenance of homeostasis, and pathological processes involved in spine, joint, bone, muscle, and tendon disorders have been uncovered. Specifically focusing on the joint diseases of degenerative disc disease, osteoarthritis, and rheumatoid arthritis using scRNA-seq has provided novel insights and a more nuanced comprehension. These findings have paved the way for discovering novel therapeutic targets that offer potential benefits to patients suffering from diverse skeletal disorders.

Utilising redundancy in musculoskeletal systems for adaptive stiffness and muscle failure compensation: a model-free inverse statics approach.

Vertebrates possess a biomechanical structure with redundant muscles, enabling adaptability in uncertain and complex environments. Harnessing this inspiration, musculoskeletal systems offer advantages like variable stiffness and resilience to actuator failure and fatigue. Despite their potential, the complex structure presents modelling challenges that are difficult to explicitly formulate and control. This difficulty arises from the need for comprehensive knowledge of the musculoskeletal system, including details such as muscle arrangement, and fully accessible muscle and joint states. Whilst existing model-free methods do not need explicit formulations, they also underutilise the benefits of muscle redundancy. Consequently, they necessitate retraining in the event of muscle failure and require manual tuning of parameters to control joint stiffness limiting their applications under unknown payloads. Presented here is a model-free local inverse statics controller for musculoskeletal systems, employing a feedforward neural network trained on motor babbling data. Experiments with a musculoskeletal leg model showcase the controller's adaptability to complex structures, including mono and bi-articulate muscles. The controller can compensate for changes such as weight variations, muscle failures, and environmental interactions, retaining reasonable accuracy without the need for any additional retraining.

Voice Quality of Life and Musculoskeletal Symptoms of Pregnant Women.

INTRODUCTION: Quality of life in terms of voice and musculoskeletal symptoms can be affected, especially at the end of pregnancy when major physical changes occur. OBJECTIVE: To analyze the results of vocal self-assessment and musculoskeletal symptoms of pregnant women in the second and third trimester. METHODS: Forty-nine pregnant women in the second and third trimester aged between 18 and 40years were examined using the Nordic Musculoskeletal Questionnaire and the Voice-Related Quality of Life Questionnaire. The data were statistically analyzed using the R environment (R Core Team, 2019) with parametric (Student's t, chi-square, and Wald) and nonparametric (Mann-Whitney and Wilcoxon) tests, taking into account a nominal significance level of 5%. RESULTS: Voice-related quality of life: mean total score and socio-emotional domain significantly within the normal values; physical domain significantly below the normal value; larger number of pregnant women significantly below the normal value in the physical domain. Nordic Musculoskeletal Questionnaire: most of the examined aspects showed a significant negative response; there was a positive significance for the presence of pain and tingling in the lower back; pregnant women with musculoskeletal complaints and impairments showed a significant decrease in the three domains of voice-related quality of life, mainly in the physical domain. CONCLUSION: Pregnant women showed a deterioration in the physical domain of voice-related quality of life and the presence of pain and tingling in the lower back. Pregnant women who had discomfort and musculoskeletal impairments also showed a deterioration in voice-related quality of life, mainly in the physical domain.

Development and National Validation of a Musculoskeletal Emergency Medicine Assessment Tool.

Introduction Musculoskeletal (MSK) complaints and injuries are the fourth most common primary diagnosis in the emergency department in the United States (US). Despite the prevalence and economic impact on the US healthcare system, new emergency medicine (EM) residency graduates report feeling unprepared to treat MSK complaints. Currently, there are no reported means to assess MSK knowledge in EM resident physicians. The purpose of this study is to develop a validated and peer-reviewed multiple-choice assessment tool focused on MSK knowledge relevant to EM to allow us to better assess the knowledge of resident physicians. Methods A group of EM/Sports Medicine subject-matter experts (SMEs) created an initial list of the most important MSK topics in EM to generate a relevant question bank. The questions were validated by a different group of SMEs using a three-round modified Delphi method to obtain consensus on the importance of each question. Based on these results, the assessment was formed. Results From a list of 99 MSK topics, SMEs developed a final list of 37 MSK topics relevant to EM. Following round one, free-marginal kappa was 0.58, 95% CI [0.50, 0.66], with a moderate overall agreement of 71.95%. Following round two, the calculated free-marginal kappa increased to 0.88, 95% CI [0.83, 0.92], with an overall agreement of 91.79%. Using a five-point Likert scale, a threshold of an average score less than four was used to exclude questions in round three of validation and to create a final 50-question assessment tool. Conclusion Our proposed exam, titled Musculoskeletal Emergency Medicine Assessment Tool (MEAT), was successfully validated by experts in our field. It evaluates clinically important topics and offers a tool for assessing MSK knowledge in EM resident physicians. Future studies are needed to determine the feasibility of administering the tool and to establish a baseline score among different populations within the practicing field of EM.

Outcomes of ultrasound-guided injections of Bennett lesions of the shoulder.

PURPOSE: To describe our technique and short term follow up of ultrasound-guided injections of symptomatic Bennett lesions. METHODS: We performed 13 ultrasound-guided injections in 10 baseball players from August 2014 to August 2021. The cohort was comprised of 10 males, with a mean age of 25 years and 1 month (age range: 17 years, 10 months-33 years, 1 month). Of the 10 patients, 6 were major league baseball players (including 5 pitchers and a second baseman), 3 were minor league baseball pitchers; and 1 pitched in high school. Symptoms in our patients included posterior shoulder pain at rest, pain with pitching (including in the acceleration phase and with follow-through), glenoid internal reduction deficit, and decreased pitching velocity. The procedure was performed in a similar fashion as a standard posterior approach glenohumeral injection, though with the linear transducer positioned slightly more medially. The needle was inserted from a lateral to medial approach, in plane with the transducer and aimed to the superficial surface of the Bennett lesion, onto which anesthetic and steroid was injected, avoiding injection into the glenohumeral joint. RESULTS: All patients had MRIs that showed Bennett lesions and all but one of the sonograms demonstrated the Bennett lesion. In 8/12 (67%) injections, the patient reported varying degrees of immediate symptom relief. In 4/12 injections, patients were unable to assess for immediate postprocedural change in symptomatology and for one patient post-procedural symptomatology was not documented. No complications occurred. Analytics of the average 4-seam fastball velocity was available for 2 of the major league players who had in-season injections, with minimal change in postprocedural velocity in the year after their ultrasound procedure; for one of the pitchers, his fastball velocity slightly increased in the month after the procedure while the other pitcher had his injection towards the end of the season and he threw no fastballs in his final games of the season. Two of the other professional pitchers went on to surgical intervention and neither returned to pitch professionally. CONCLUSION: Injection of symptomatic Bennett lesions is a safe procedure and can provide symptomatic relief that may be temporary, though equivocally useful clinically.

Determining a musculoskeletal system's pre-stretched state using continuum-mechanical forward modelling and joint range optimization.

The subject-specific range of motion (RoM) of a musculoskeletal joint system is balanced by pre-tension levels of individual muscles, which affects their contraction capability. Such an inherent pre-tension or pre-stretch of muscles is not measureable with in vivo experiments. Using a 3D continuum mechanical forward simulation approach for motion analysis of the musculoskeletal system of the forearm with 3 flexor and 2 extensor muscles, we developed an optimization process to determine the muscle fibre pre-stretches for an initial arm position, which is given human dataset. We used RoM values of a healthy person to balance the motion in extension and flexion. The performed sensitivity study shows that the fibre pre-stretches of the m. brachialis, m. biceps brachii and m. triceps brachii with 91 % dominate the objective flexion ratio, while m. brachiradialis and m. anconeus amount 7.8 % and 1.2 % . Within the multi-dimensional space of the surrogate model, 3D sub-spaces of primary variables, namely the dominant muscles and the global objective, flexion ratio, exhibit a path of optimal solutions. Within this optimal path, the muscle fibre pre-stretch of two flexors demonstrate a negative correlation, while, in contrast, the primary extensor, m. triceps brachii correlates positively to each of the flexors. Comparing the global optimum with four other designs along the optimal path, we saw large deviations, e.g., up to 15 ∘ in motion and up to 40% in muscle force. This underlines the importance of accurate determination of fibre pre-stretch in muscles, especially, their role in pathological muscular disorders and surgical applications such as free muscle or tendon transfer.

The Relationship between Urinary Incontinence, Osteoarthritis, and Musculoskeletal System Disorders.

Background/Objectives: Urinary incontinence diminishes quality of life, and its severity can be worsened by mobility impairments. This study explored the link between urinary incontinence, osteoarthritis, and back musculoskeletal system disorders, considering pain, mobility issues, and daily activity difficulties. Methods: This cross-sectional study included respondents aged ≥ 15 years from the 2008 Turkish Health Studies Survey (n = 13,976). We assessed self-reported urinary incontinence, daily activity, mobility impairment, pain, osteoarthritis, and musculoskeletal disorders to explore their association with urinary incontinence. Gender-specific logistic regression models included chronic conditions related to urinary incontinence. Results: The prevalence of urinary incontinence was higher in the participants with osteoarthritis and back musculoskeletal system problems. Among the patients with osteoarthritis, the prevalence was 25.84% in the mobility-impaired group and 10.03% in the non-impaired group. Similarly, 33.02% of those with activities of daily living (ADL) difficulties and 12.93% of those without difficulties had incontinence. The frequency of urinary incontinence increased with pain severity. According to the multivariable logistic regression analyses, the adjusted odds ratio (95% confidence interval) of urinary incontinence for osteoarthritis was 1.58 (95% CI 1.23-2.02, p < 0.01) for females and 2.38 (95% CI 1.62-3.49, p < 0.01) for males. Conclusions: Urinary incontinence was more common in females, increased with age, and was found to be associated with osteoarthritis and back musculoskeletal system disorders. Among the patients with osteoarthritis and back musculoskeletal system disorders, those with mobility impairment and daily activity difficulties had a higher prevalence of urinary incontinence. The patients with more severe pain had a higher frequency of urinary incontinence.

Estimation of the forces exerted on the limb long bones of a white rhinoceros (Ceratotherium simum) using musculoskeletal modelling and simulation.

Heavy animals incur large forces on their limb bones, due to the transmission of body weight and ground reaction forces, and the contractions of the various muscles of the limbs. This is particularly true for rhinoceroses, the heaviest extant animals capable of galloping. Several studies have examined their musculoskeletal system and the forces their bones incur, but no detailed quantification has ever been attempted. Such quantification could help understand better the link between form and function in giant land animals. Here we constructed three-dimensional musculoskeletal models of the forelimb and hindlimb of Ceratotherium simum, the heaviest extant rhino species, and used static optimisation (inverse) simulations to estimate the forces applied on the bones when standing at rest, including magnitudes and directions. Overall, unsurprisingly, the most active muscles were antigravity muscles, which generate moments opposing body weight (thereby incurring the ground reaction force), and thus keep the joints extended, avoiding joint collapse via flexion. Some muscles have an antigravity action around several joints, and thus were found to be highly active, likely specialised in body weight support (ulnaris lateralis; digital flexors). The humerus was subjected to the greatest amount of forces in terms of total magnitude; forces on the humerus furthermore came from a great variety of directions. The radius was mainly subject to high-magnitude compressive joint reaction forces, but to little muscular tension, whereas the opposite pattern was observed for the ulna. The femur had a pattern similar to that of the humerus, and the tibia's pattern was intermediate, being subject to great compression in its caudal side but to great tension in its cranial side (i.e. bending). The fibula was subject to by far the lowest force magnitude. Overall, the forces estimated were consistent with the documented morphofunctional adaptations of C. simum's long bones, which have larger insertion areas for several muscles and a greater robusticity overall than those of lighter rhinos, likely reflecting the intense forces we estimated here. Our estimates of muscle and bone (joint) loading regimes for this giant tetrapod improve the understanding of the links between form and function in supportive tissues and could be extended to other aspects of bone morphology, such as microanatomy.

Desmoid Fibromatosis Fused With a Lipoma in the Upper Arm.

Lipoma, the most common mesenchymal tumor, often appears as a slow-growing mass in the musculoskeletal system (MSK). While generally non-invasive, their location can cause symptoms. Desmoid fibromatosis (DF), a rare and locally aggressive neoplasm, poses challenges in MSK system diagnosis and management due to its infiltrative nature. Despite lacking metastatic potential, DF has a high recurrence rate, classifying it as "intermediate, locally aggressive" in the WHO classification. Collaborative efforts among orthopedic surgeons, radiologists, and pathologists are crucial for accurate diagnosis and treatment planning for all tumors of the MSK system. This case report presents the first documented example of a DF within a lipoma, highlighting the challenges of diagnosing and treating musculoskeletal tumors.

Impacts of ß-1, 3-N-acetylglucosaminyltransferases (B3GNTs) in human diseases.

Glycosylation modification of proteins is a common post-translational modification that exists in various organisms and has rich biological functions. It is usually catalyzed by multiple glycosyltransferases located in the Golgi apparatus. ß-1,3-N-acetylglucosaminyltransferases (B3GNTs) are members of the glycosyltransferases and have been found to be involved in the occurrence and development of a variety of diseases including autoimmunity diseases, cancers, neurodevelopment, musculoskeletal system, and metabolic diseases. The functions of B3GNTs represent the glycosylation of proteins is a crucial and frequently life-threatening step in progression of most diseases. In this review, we give an overview about the roles of B3GNTs in tumor, nervous system, musculoskeletal and metabolic diseases, describing the recent results about B3GNTs, in order to provide a research direction and exploration value for the prevention, diagnosis and treatment of these diseases.

Pictorial review: challenges in distinguishing bilateral metaphyseal marrow abnormalities on magnetic resonance imaging.

The paediatric metaphysis is afflicted by a wide range of pathological processes as it is the most metabolically active and well-vascularised part of the developing skeleton. This review focuses on metaphyseal marrow signal change detected with magnetic resonance imaging, which is most often occult on radiographs. When bilateral, these imaging appearances frequently present a diagnostic quandary. This review assists the radiologist to confidently dismiss physiological signal change and confidently work through the differential diagnosis. This is achieved by illustrating a practical method of classifying signal change into four categories: physiological red marrow, red marrow reconversion, marrow infiltration, and oedema-like marrow signal intensity. In doing so, various pathological entities are reviewed along with imaging pearls and next-step investigations.

Ergonomic risks and problems of the musculoskeletal system for physiotherapists: comparison of employees in the fields of pediatric and adult care.

Objectives. The aim of this study is to compare the ergonomic risk levels, musculoskeletal complaints and quality of life of physiotherapists (PTs) according to their field of work. Methods. A total of 107 volunteer PTs participated in the study, whose information was recorded. Ergonomic risk levels were determined using rapid entire body assessment (REBA). Complaints about the musculoskeletal system of PTs were evaluated with the Cornell musculoskeletal discomfort questionnaire (CMDQ) and quality of life was evaluated by the Nottingham health profile. Results. PTs who worked with pediatric patients (Grouppediatric; n = 47) were younger (p<0.001). PTs who worked with adult patients (Groupadult; n = 60) had a higher daily number of patients (p<0.001). The REBA score did not make a difference between the groups (p = 0.379). The difference was found in the upper back region of the CMDQ (p<0.05). There was no difference between groups for quality of life (p>0.05). Conclusions. Grouppediatric may be working in ergonomically demanding positions, although there is no statistical difference. The injury sites of the musculoskeletal system can differ. However, the reflection of musculoskeletal system problems on quality of life does not show any difference between the groups of PTs.

Explorative study using ultrasound time-harmonic elastography for stiffness-based quantification of skeletal muscle function.

Time-harmonic elastography (THE) is an emerging ultrasound imaging technique that allows full-field mapping of the stiffness of deep biological tissues. THE's unique ability to rapidly capture stiffness in multiple tissues has never been applied for imaging skeletal muscle. Therefore, we addressed the lack of data on temporal changes in skeletal muscle stiffness while simultaneously covering stiffness of different muscles. Acquiring repeated THE scans every five seconds we quantified shear-wave speed (SWS) as a marker of stiffness of the long head (LHB) and short head (SHB) of biceps brachii and of the brachialis muscle (B) in ten healthy volunteers. SWS was continuously acquired during a 3-min isometric preloading phase, a 3-min loading phase with different weights (4, 8, and 12 kg), and a 9-min postloading phase. In addition, we analyzed temporal SWS standard deviation (SD) as a marker of muscle contraction regulation. Our results (median [min, max]) showed both SWS at preloading (LHB: 1.04 [0.94, 1.12] m/s, SHB: 0.86 [0.78, 0.94] m/s, B: 0.96 [0.87, 1.09] m/s, p < 0.001) and the increase in SWS with loading weight to be muscle-specific (LHB: 0.010 [0.002, 0.019] m/s/kg, SHB: 0.022 [0.017, 0.042] m/s/kg, B: 0.039 [0.019, 0.062] m/s/kg, p < 0.001). Additionally, SWS during loading increased continuously over time by 0.022 [0.004, 0.051] m/s/min (p < 0.01). Using an exponential decay model, we found an average relaxation time of 27 seconds during postloading. Analogously, SWS SD at preloading was also muscle-specific (LHB: 0.018 [0.011, 0.029] m/s, SHB: 0.021 [0.015, 0.027] m/s, B: 0.024 [0.018, 0.037] m/s, p < 0.05) and increased by 0.005 [0.003, 0.008] m/s/kg (p < 0.01) with loading. SWS SD did not change over loading time and decreased immediately in the postloading phase. Taken together, THE of skeletal muscle is a promising imaging technique for in vivo quantification of stiffness and stiffness changes in multiple muscle groups within seconds. Both the magnitude of stiffness changes and their temporal variation during isometric exercise may reflect the functional status of skeletal muscle and provide additional information to the morphological measures obtained by conventional imaging modalities.