Strengthening the rotator cuff muscles is important for injury prevention and rehabilitation. Since muscle fascicle length improves motor performance and is suggested to reduce the risk of injury for the hamstring, it may be an important variable to promote multidirectional changes in the function and macroscopic structure for the shoulder. Recent literature reviews overwhelmingly suggest that eccentric exercises improve fascicle length and functional measures for the lower limb. However, there is a research gap for the shoulder. Since ultrasound imaging is the most commonly used imaging technique to quantify muscle structure, but has yielded heterogeneous results in different studies, there is another issue and a research gap for the imaging method. Based on the research gaps, the purpose of this study was to evaluate the effects of standardized eccentric strength training on the function and structure of the external rotator cuff muscles using an isokinetic dynamometer and MRI. Therefore, a preliminary pre-post intervention study was conducted and 16 physically active men were recruited in October 2021. For the right shoulder, an eccentric isokinetic training was performed twice a week for almost six weeks. The primary outcome measures (external rotators) were active and passive range of motion, eccentric and concentric torque at 30, 60, and 180°/s isokinetic speed, and fascicle length and fascicle volume for the supraspinatus and infraspinatus muscles. The findings show a training effect for the absolute mean values of eccentric strength (+24%, p = .008). The torque-angle relationship increased, especially in the final phase of range of motion, although a 4% (p = .002) decrease in passive range of motion was found in the stretch test. Positive changes in muscle structure were shown for the supraspinatus muscle fascicle length (+16%, p = .003) and fascicle volume (+19%, p = .002). Based on the study results, we can conclude that eccentric isokinetic training has a significant positive effect on the shoulder. To our knowledge, this is the first eccentric training study using both isokinetic dynamometer and muscle diffusion tensor imaging to access functional and structural changes in the human shoulder rotator cuff muscles. The methods were shown to be applicable for interventional studies. Based on these results, populations such as high-performance handball players with highly trained shoulders should be included in future studies.

A novel exoskeleton robotic system was developed to assist stair climbing. This active demonstrator consists of a motor with a cable system, various sensors, and a control system with a power supply. The objective of this preliminary study is a biomechanical evaluation of the novel system to determine its effectiveness in use. For this purpose, three test persons were biomechanically investigated, who performed stair ascents and descents with and without the exoskeleton. Kinematics, kinetics, and muscle activity of the knee extensors were measured. The measured data were biomechanically simulated in order to evaluate the characteristics of joint angles, moments, and reaction forces. The results show that the new exoskeleton assists both the ascent and the descent according to the measured surface electromyography (sEMG) signals, as the knee extensors are relieved by an average of 19.3%. In addition, differences in the interaction between the test persons and the system were found. This could be due to a slightly different operation of the assisting force or to the different influence of the system on the kinematics of the users.

Strengthening the rotator cuff muscles is important for injury prevention and rehabilitation. However, there is considerable evidence that range of motion and fascicle length are risk factors for injury. Since muscle fascicle length improves motor performance and reduces the risk of injury, it may be an important variable to promote multidirectional changes in the function and macroscopic structure of the target muscle. As a well-established intervention strategy, passive stretching seems best for improving the flexibility in terms of range of motion. But stretching and range of motion seem to have little effect on fascicle length changes and injury risk. However, recent reviews suggest that eccentric exercises improve functional and structural measures for the lower limbs. Since a research gap exists for the shoulder joint it has to be clarified if eccentric training for the external rotator cuff muscles produces similar functional and structural changes for a non-specific shoulder trained healthy population. The purpose of this study was to evaluate the effects of highly standardized eccentric isokinetic resistance training on the function and structure of the dominant shoulder external rotator cuff muscles. In addition, the feasibility of a new method of measuring flexibility and muscle diffusion tensor imaging to quantify three-dimensional changes in muscle fibers was tested. Therefore, 16 physically active men were recruited in October 2021. The right shoulder eccentric strength was trained twice a week for six weeks at 30°/s using an isokinetic dynamometer. The eccentric training protocol consisted of five sets and ten repetitions with subjective maximal effort. The primary outcome measures were for the external rotator cuff muscles eccentric and concentric mean and peak torque at 30, 60 and 180°/s, flexibility in terms of active and passive stretching, fascicle length and fascicle volume for the supraspinatus and infraspinatus muscles. The findings showed a training effect for eccentric strength (+24%). For the external rotator cuff muscles, the torque-angle relationship increased, especially in the final phase of range of motion, even though a 4% decrease was seen after the passive stretch test. Positive changes in muscle structure were shown for fascicle length (+16%) and fascicle volume (+19%). Secondary outcome measures for the internal rotator cuff muscles did not show significant changes from baseline to post-test. Based on the study results, we can conclude that eccentric isokinetic training has a significant effect on the function and macroscopic structure of the external rotator cuff muscles in a non-specifically trained, healthy male population. To our knowledge, this is the first eccentric training study using both isokinetic dynamometer and muscle diffusion tensor imaging to access functional and structural changes in the human shoulder rotator cuff muscles. The methods were shown to be feasible for interventional studies. Based on these results, populations such as high-performance handball players with highly trained shoulders should be included in future studies.

The ability of muscle to generate force depends on its architecture and health condition. MR-based diffusion tensor imaging of muscle (mDTI) is an innovative approach for showing the fiber arrangement for the whole muscle volume. For accurate calculations of fiber metrics, muscle segmentation prior to tractography is regarded as necessary. Since segmentation is known to be operator dependent, it is important to understand how segmentation affects tractography. The aim of this study was to compare the results of deterministic fiber tracking based on muscle models generated by two independent operators. In addition, this study compares the results with a segmentation-free approach. Fifteen subjects underwent mDTI of the right shoulder. The results showed that mDTI can be successfully applied to complex joints such as the human shoulder. Furthermore, operator segmentation did not influence the results of fiber tracking and fascicle length (FL), fiber volume (FV), fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD) showed excellent intraclass correlation estimates (≥ 0.975). As an exploratory approach, the segmentation-free fiber tracking showed significant differences in terms of mean fascicle length. Based on these findings, we conclude that tractography is not sensitive to small deviations in muscle segmentation. Furthermore, it implies that mDTI and automatic segmentation approaches or even a segmentation-free analysis can be considered for evaluation of muscle architecture.

Javelin throwers cannot safely throw with a long approach run often per training session. Therefore, implements of different shapes and masses are thrown from short run-ups to emulate the demands of achieving high throwing distances. This study examined the effects of different implements, thrown from various approaches, on the kinematics and kinetics of the throwing arm. The throwing motions of 6 athletes, each throwing 6 different implements were recorded using 12 infrared cameras. Kinematics and kinetics of the shoulder and elbow joints were calculated and statistically compared. The results show that lighter implement throws achieved higher release speeds, while heavier implements required greater work to be done on them. We identified significant differences for the shoulder external rotation angle (P < .001), the shoulder internal rotation (P = .040), and elbow extension (P = .003) angular velocities and the torques of the shoulder internal rotation (P = .006), horizontal flexion (P = .004), and the elbow varus (P = .008). It can be concluded that throws with balls of different masses have different angular velocities and joint torques, and therefore can be used to train speed and strength aspects of the javelin throw while using lower run-up speeds.

Problem: Serious knee injuries are gaining epidemiological importance. Especially in childhood, a very significant increase in knee ligament injuries, in particular ACL ruptures, can be observed. In Saxony alone, more than 70 ruptures of the anterior cruciate ligament occur each year as a result of accidents during physical education (PE). Six months after surgery, the students are normally classified as fully fit for sports and are allowed to participate in PE without restrictions. However, the number of reinjuries is very high which limits the quality of life of those affected in the long term and places a heavy financial burden on insurance companies. Methods: Therefore the status quo in the rehabilitation of schoolchildren after ACL rupture was assessed using a multilevel test battery and taking into account known risk factors such as gender, motor competence and BMI. Results: The results show that there are large interindividual differences in the funktional outcomes as well as a large discrepancy between rehabilitation status and return to physical education. Discussion: In order to effectively manage the process of rehabilitation and return to school sports, individual information is necessary in the multimodal setting. To this end, all those involved should be sensitized and trained. Key Words: Knee Injury, Return-to-Sport, Biomechanics of Sports, Prevention, School Sports