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ZusammenfassungIm Rahmen kindlicher rheumatischer Erkrankungen haben die zumeist schmerzhaften Entzündungsvorgänge am muskulo-skelettalen System (z. B.: Gelenke, Muskeln, Sehnen, Gefäße) Auswirkungen auf die tägliche Mobilität der Betroffenen. Immobilität, körperliche und sportliche Inaktivität sind oft die Folge. Die geltenden Richtlinien der Nationalen Empfehlungen für Bewegung und Bewegungsförderung werden daher oftmals nicht erreicht. Bewegungsreduzierte oder -inaktive Patienten können jedoch durch verschiedene Maßnahmen in ihrem Bewegungsverhalten gefördert werden. Die Physiotherapie bietet eine erste Möglichkeit in geschütztem Rahmen und unter fachlicher Aufsicht körperlich und sportlich aktiv zu sein. Neben der Wiederherstellung und Verbesserung des physiologischen Bewegungsausmaßes liegen die Erhaltung der Selbstständigkeit und Lebensqualität im Vordergrund der physiotherapeutischen Behandlung. Dazu zählen Aktivierung, Anbahnung von physiologischen Bewegungsabläufen, Korrektur von Gelenkachsen und das Vermitteln von Körperwahrnehmung bei körperlicher Aktivität. Medizinisches Fachwissen und Verständnis sowie Wissen über die Anforderungen verschiedener Sportartenprofile ermöglicht gezielte Hilfestellungen. Durch kontinuierliche, engmaschige Begleitung und langsame Steigerung von Intensität und Umfang in der Physiotherapie können Ängste und Bedenken bezüglich dem Wiedereinstieg bzw. Einstieg in sportliche Betätigung abgebaut werden. Der jeweilige Gesundheitszustand und die Situation der Entzündungsaktivität sind maßgebend für die Therapieinterventionen. Sport gilt heute in der Physiotherapie als Therapieelement und hilft Beschwerden zu lindern, verbessert körperliche Defizite und vermittelt dabei Freude an der Bewegung. Für Alltagsaktivitäten und den Freizeitsport kann eine individuelle Sportberatung basierend auf dem bestehenden Erkrankungsstatus, dem funktionellen und sportmotorischen Leistungsniveau sowie den eigenen Interessen wirkungsvoll zu einem aktiven Lebensstil beitragen. Eine weitere Möglichkeit der angeleiteten Bewegungsförderung stellt der Schulsport dar. Individuelle, differenzierte Schulsportteilnahmebescheinigungen verbessern die Inklusion. Ein auf den Erkrankungsstatus angepasstes und vorgegebenes Trainingsprogramm kann mithilfe konkreter Vorgaben bei der Umsetzung der sportlichen Ziele unterstützen. In Zukunft soll ein digital gestütztes professionelles Monitoring die Bewegungsempfehlungen für zuhause noch weiter verbessern und helfen den Mangel an flächendeckenden Beratungsstellen für Erkrankte mit kindlichem Rheuma zu verringern.

The present review deals with the current scientific knowledge related with ski jump landing. A specific focus is given on the landing biomechanics, the methods utilized for its analysis and the injuries connected to the landing phase. Despite the demonstrated importance for the safety and the performance of ski jumpers, the landing and its preparation are rarely investigated. In this paper, after having firstly described the execution of landing and its preparation and the reason why is important to analyze it, an overview of the current status of the research related to the landing biomechanics is reported (kinetics, kinematics, electromyographic activation, aerodynamics, computer simulation). The third part describes the methods and technologies utilized in literature to analyze the landing and its preparation (video cameras, inertial sensors, force insoles, wind tunnel and computer simulation). After that, an overview of the injuries related to landing is reported. The final section proposes future research in the field of biomechanics of ski jump landing in different fields, such as computer simulations, kinematic analysis, equipment development and biomechanics of female athletes.

The single-leg squat (SLS) represents a functional movement task for determining leg function. Objective movement analysis is required to evaluate inter-limb symmetry and movement coordination. Therefore, this study aimed to investigate inter-limb symmetry of SLS kinematics and movement coordination using the modified vector coding technique. A 3D motion capture system and electromyography were used to assess SLS execution and muscle activation of hip ab- and adductors of 17 healthy, recreational athletes. Coordination patterns of hip, knee, and ankle joint movement were assessed by the modified vector coding technique. Statistical parametric mapping revealed no significant differences between both legs (p > 0.05). Inter-limb symmetry also appeared in movement coordination (p > 0.05). Additionally, the analysis of movement coordination indicates knee-dominant, in-phase coordination. However, coordination patterns were different between downward movement, change of direction, and upward movement (p < 0.001). Since perturbations during SLS execution, such as moments of imbalance, occur as anti-phase coordination patterns, the analysis of coordination patterns can be used as a new evaluation method for SLS performance. Furthermore, the modified vector coding technique might be helpful to analyze different compensation strategies during the SLS in symptomatic individuals.

In recent years, there is an increasing importance of double poling (DP) performance regarding the outcome in classic cross-country skiing (XCS) races. So far, different approaches were used to predict DP performance but there is a lack of knowledge how general strength parameters are related to DP performance parameters gathered from in field-test situations. Therefore, the aim of this study was to determine the relationship between general strength measurements of different upper-body segments and pole force measurements during a DP sprint exercise. In addition, multiple linear regressions were calculated to determine the predictive power of theses variables regarding DP sprint performance, represented as maximum velocity. Thirteen none-elite cross-country skiers performed two 60 m DP sprints at maximal speed on a tartan track using roller skis. In addition, maximum isometric and concentric strength tests were performed on a motor-driven dynamometer with four major upper-body segments (trunk flexion / extension, shoulder / elbow extension). Especially the mean pole force and the strength test parameters correlated significantly (r ≥ 0.615) in all except one comparison. However, regression analyses revealed that neither pole force parameters (R² = 0.495) nor isometric (R² = 0.456) or dynamic (R² = 0.596) strength test parameters could predict the DP performance significantly. This study showed that standardized isokinetic strength tests could be used to estimate pole force capabilities of XCS athletes. However, pole-force and strength test parameters failed to predict significantly maximal velocity during a DP sprint exercise, which might be attributed to the non-elite subject group.

Sitting with crossed legs is a commonly adopted sitting posture in everyday situations. Yet, little is known about suitable design criteria to facilitate such a position inside a vehicle. This study is aimed at determining how much space is necessary for crossing the legs while considering legroom restrictions, anthropometric measures, and individual flexibility. More specifically, 3 D-kinematics of an ankle-on-knee leg-crossing task and the easiness to move ratings of 30 participants were assessed with restrictions of the legroom (2 heights �� 3 distances) as well as without restrictions. Functional regression models revealed adaptations to a legroom restriction in the execution of movement, which occurred mainly in the knee joint and increased with more restricted legroom proportions. Therefore, the present study suggests a distance of 120% of the buttock���knee length between the dashboard and the occupant, as it requires only moderate adaptations and does not affect the perceived easiness of move. Practitioner Summary: This research investigated how much space is needed to cross the legs while sitting in a vehicle, finding that the movement execution is affected by legroom proportions, as well as individual anthropometry and flexibility. The study further presents the use of predicted motion traces to determine spatial requirements of movements. Abbreviations: BKL: buttock-knee length; H-point: hip point

Introduction: A risk factor for knee injuries is the medio-lateral displacement of the knee joint during a single-leg squat (SLS). It is to be supposed that different activation patterns of hip muscles are related to the medio-lateral displacement of the knee (1). Yet, little is known about the electromyographic (EMG) ratio between gluteus medius (GM) and the adductor muscles (ADD) at different knee flexion angles (2). Therefore, the EMG ratio between GM and ADD at different knee flexion angles was assessed during the SLS. These data should build a normative data base of healthy controls for getting in-sights on knee injury prevention. Hypotheses: The hypothesis was that according to different knee flexion angles, there is a variabil-ity of the EMG ratio between GM and ADD in healthy patients. Methods: A total of 17 healthy subjects (9 female/ 8 male, age of 25±4 years, BMI of 24±2 kg/m2) were included into the study. Exclusion criteria were Genu varum or Genu val-gum and pathologies which might affect coordination abilities of the lower extremities. Knee flexion angle was captured with a 3D motion analysis system (Vicon Motion Systems, Oxford,UK). Muscle activity of GM and ADD was measured by surface electromyography (Myon AG Schwarzener, CH). The EMG signal (10-500Hz band-pass filter, rectified, 250ms moving average) was normalized to maximum EMG am-plitude during a static maximum voluntary contraction against a handheld dynamome-ter (MicroFET2, Hoggan Scientific, UT, USA). The EMG ratio was defined as muscle activity of GM [%max] divided by muscle activity of ADD [%max]. Every participant did 12 single-leg squats on each side. Results: EMG ratio (median, interquartile range (25th - 75th quartile)) was calculated at the fol-lowing knee flexion angles (mean ± SD): EMG ratio at start position (11°±6°) = 2.5 (1.9 – 4.2), EMG ratio at 40° downward movement = 1.5 (1.1 – 2.7), EMG ratio at 60° downward movement = 1.2 (0.9 – 2.2), EMG ratio at maximum flexion angle (86°±16°) = 1.3 (0.9 – 1.9), EMG ratio at 60° upward movement = 2.0 (1.2 – 3.3), EMG ratio at 40° upward movement = 2.3 (1.5 – 4.4), EMG ratio at end position (8°±6°) = 3.2 (2.3 – 5.4). Conclusion: In the literature, the mean EMG ratios between GM and ADD at maximum knee flex-ion were ranged from 1.3 to 1.9 in healthy patients (3,4) and are comparable to our findings. The knee and hip have to be more stabilized during the upward movement by higher EMG ratios. The lower EMG ratio in the downward phase might be associated, amongst others, with the eccentrical deceleration movement. We assume that the consistently higher activation of the GM is attributed to its function as an essential hip stabilizer as well as to avoid a collapse in the knee joint in every single-leg situation. Therefore, we recommend hip abductor focused training to prevent knee injuries. Our results provide a basis for the comparison with patients and for the interpretation of medio-lateral displacements of the knee joint during a SLS.

Force plates represent the “gold standard” in measuring running kinetics to predict performance or to identify the sources of running-related injuries. As these measurements are generally limited t...

Background: Paraspinal and thigh muscles comprise the major muscle groups of the body. We investigated the composition of the psoas, erector spinae, quadriceps femoris and hamstring muscle groups and their association to each other using chemical shift encoding-based water–fat magnetic resonance imaging (MRI) in adult volunteers. Our aim was to elucidate fat distribution patterns within these muscle groups. Methods: Thirty volunteers [15 males, age: 30.5±4.9 years, body mass index (BMI): 27.6±2.8 kg/m 2 and 15 females, age: 29.9±7.0 years, BMI: 25.8±1.4 kg/m 2 ] were recruited for this study. A six-echo 3D spoiled gradient echo sequence was used for chemical shift encoding-based water–fat separation at the lumbar spine and bilateral thigh. Proton density fat fraction (PDFF), cross-sectional area (CSA) and contractile mass index (CMI) of the psoas, erector spinae, quadriceps femoris and hamstring muscle groups were determined bilaterally and averaged over both sides. Results: CSA and CMI values calculated for the erector spinae, psoas, quadriceps and hamstring muscle groups showed significant differences between men and women (P

Using inertial measurement units (IMUs) in monitoring and analysing sport movements has become popular in sports research since it avoids the laboratory limitation. However, the accuracy of modern IMU-systems (hardware combined with software) needs to be validated using gold-standard systems as baseline. In this study, we investigated the feasibility of the aktos-t IMU-system for in-field biomechanical research by comparing its outputs in various tasks (repetitive movements, gait and jumping) undertaken by 14 participants, with those of an optoelectronic system. The results showed that the accuracy of aktos-t varies according to the task performed. The accuracy of pelvis, hip and knee joints ranged between acceptable (root mean squared error (RMSE)5°) and tolerable (RMSE10°) in gait, while the upper limb joints showed inaccuracy (RMSE10°) and imprecision (coefficient of repeatability 10°) during the repetitive movement test. Jump impact appeared not to influence the IMU outcomes (

The isometric steady-state forces following lengthening are greater than those produced at the same muscle length and activation level but without prior lengthening. Although residual force enhancement (RFE) has been investigated across a range of conditions, its relevance for daily human movement is still poorly understood. We aimed to study RFE in a setup imitating daily activity, i.e., submaximal activation of the lower extremity's muscles with slightly flexed knee joints comparable to human walking. A motor-driven leg press dynamometer was used for randomly arranged purely isometric and isometric-eccentric-isometric contractions. Thirteen subjects performed multi-joint leg extensions, which were feedback-controlled at 30% of maximum voluntary vastus lateralis activation. Isometric-eccentric-isometric contractions incorporated a stretch from 30° to 50° knee flexion, while isometric contractions were performed at 50° knee flexion. Isometric contractions following stretch and purely isometric reference contractions were performed at 50° knee flexion. Kinematics, forces, and muscular activity were measured using 3D optical motion tracking, force plates, and surface EMG of 9 lower limb muscles of the right leg and joint torques were calculated by inverse dynamics. Variables of standardization (EMG, joint angles) showed no differences between contraction conditions. Eight of 13 subjects showed RFE of up to 24.8±32.5% for external forces and joint torques. Because the remaining 5 non-responders failed to produce enhanced forces during the stretch, we believe that RFE is functionally relevant for muscle function comparable to everyday human motion but only if there is enhanced force during stretch that sufficiently triggers mechanisms underlying RFE.

Introduction: The subjective single-leg squat (SLS) test can be used as a functional diagnostic agent to prevent knee injuries. [1] However, there are missing objective data about its functional rating, performance, squat depth and medio-lateral knee displacement in the frontal plane. [2] There-fore, the purpose of this pilot study was to evaluate the medio-lateral knee displacement in the frontal plane with a 3D motion capture system at different knee flexion angles during the SLS in healthy patients. Hypotheses: The hypothesis was that according to different knee flexion angles, there is a variability of medial knee displacement (= valgus positions) in healthy patients. Methods: 17 healthy and sporty subjects (9 ♀/ 8 ♂, age 25±4 years, BMI 24±2 kg/m2) participated in this study. Exclusion criteria were balance disorders, hip knee and/ or ankle complaints, sur-gery history, high deviation in lower extremity axis (i.e. Genu varum/ Genu valgus). Knee dis-placement was measured by 3D motion analysis system (Vicon Motion Systems, Oxford, UK) using a modified method of Krosshaug et al. [3] Thus, knee displacement was defined as distance between knee joint center and reference plane including the calculated hip and ankle joint center and the fixed toe marker on the second metatarsal head. A positive knee dis-placement was associated with a knee valgus, a knee varus was described as negative knee displacement. Every participant did 12 single-leg squats on each side. Results: The following knee flexion angles of all SLSs were captured (°, mean and standard deviation (±)): start position at 11 ± 6; downward phase at 40 ± 0 and 60 ± 0; maximum at 86 ± 16; up-ward phase at 60 ± 0 and 40 ± 0; end position at 8 ± 6. The medio-lateral knee displacement of all SLSs showed at the mentioned knee flexion an-gles the following values respectively (mm, median, interquartile range (25th - 75th quartile)): -12 (-19 to -5); 0 (-9 to 7); 13 (-2 to 28); 38 (8 to 61); 17 (0 to 36); 4 (-6 to 16); -15 (-22 to -7). Conclusion: According to different knee flexion angles, there is a variability of medio-lateral knee dis-placements in healthy patients. This variability should be included in the functional rating of a SLS as well as in the interpretation of different knee pathologies. Moreover, it provides an objective basis in the prediction of knee injuries.

Force plates represent the "gold standard" in measuring running kinetics to predict performance or to identify the sources of running-related injuries. As these measurements are generally limited to laboratory analyses, wireless high-quality sensors for measuring in the field are needed. This work analysed the accuracy and precision of a new wireless insole forcesensor for quantifying running-related kinetic parameters. Vertical ground reaction force (GRF) was simultaneously measured with pit-mounted force plates (1 kHz) and loadsol

Background Children suffering from juvenile idiopathic arthritis (JIA), a heterogeneous group of chronic inflammatory joint diseases, adapt to individual gait patterns to avoid loading of inflamed, swollen and painful joints. As the interpretability of previous studies is limited, this study aims to assess the functional capacity, loads and plantar pressure distribution in the gait of a homogeneous JIA group. Research question Does a symmetrical lower limb joint involvement influence the gait dynamics in JIA patients, and how are the results of three-dimensional gait analysis (3DGA) and pedobarography related? Methods Fifty JIA patients with symmetrical hip, knee and ankle joint arthritis and 27 healthy controls performed 3DGA and pedobarography at self-selected walking speeds. Kinematics and kinetics of lower limb joints were retrospectively compared in range of motion and in time-normalized waveforms. Plantar load was evaluated by measuring peak pressure, pressure-time integral and maximum force of the whole foot and ten selected foot regions. 1D-SPM analysis, parametric and non-parametric statistical significance tests and correlation coefficients were used for statistical analysis. Results JIA patients had a significantly slower walking speed with an anteriorly tilted pelvis and a reduced extension motion of all joints of the lower limb. The horizontal ground reaction forces and generated hip and ankle power during propulsion phase were small. Patients experienced reduced loading at toe regions, which correlated with limited ankle plantarflexion motion in the push-off phase. The total peak pressure was significantly increased and loads at lateral midfoot and metatarsal regions were higher in patients. Significance Symmetrical lower limb arthritis is linked to crouch-like gait and restricted gait dynamics with increased total peak pressure. The results confirm earlier results of 3DGA and provide new insights regarding waveform analysis and plantar loading in JIA patients. The used methods help to design individualized functional treatment of JIA patients.

Chemical shift encoding-based water–fat MRI derived proton density fat fraction (PDFF) of the paraspinal muscles has been emerging as a surrogate marker in subjects with sarcopenia, lower back pain, injuries and neuromuscular disorders. The present study investigates the performance of paraspinal muscle PDFF and cross-sectional area (CSA) in predicting isometric muscle strength. Twenty-six healthy subjects (57.7% women; age: 30 ± 6 years) underwent 3T axial MRI of the lumbar spine using a six-echo 3D spoiled gradient echo sequence for chemical shift encoding-based water–fat separation. Erector spinae and psoas muscles were segmented bilaterally from L2 level to L5 level to determine CSA and PDFF. Muscle flexion and extension maximum isometric torque values [Nm] at the back were measured with an isokinetic dynamometer. Significant correlations between CSA and muscle strength measurements were observed for erector spinae muscle CSA (r = 0.40; p = 0.044) and psoas muscle CSA (r = 0.61; p = 0.001) with relative flexion strength. Erector spinae muscle PDFF correlated significantly with relative muscle strength (extension: r = -0.51; p = 0.008; flexion: r = -0.54; p = 0.005). Erector spinae muscle PDFF, but not CSA, remained a statistically significant (p < 0.05) predictor of relative extensor strength in multivariate regression models (R2adj = 0.34; p = 0.002). PDFF measurements improved the prediction of paraspinal muscle strength beyond CSA. Therefore, chemical shift encoding-based water–fat MRI may be used to detect subtle changes in the paraspinal muscle composition. • We investigated the association of paraspinal muscle fat fraction based on chemical shift encoding-based water–fat MRI with isometric strength measurements in healthy subjects. • Erector spinae muscle PDFF correlated significantly with relative muscle strength. • PDFF measurements improved prediction of paraspinal muscle strength beyond CSA.

Background Progressive pseudorheumatoid arthropathy of childhood is a rare disease with an estimated prevalence of approximately 1/1,000,000. The disease manifests around the age of three to eight years and progresses with symptoms of early fatigue, muscle weakness, joint swelling and stiffness. The resulting functional limitations are often described as having a waddling gait. Walking is difficult and can be managed with multilevel compensation movements only. Aims of this study were to determine typical malpositions that arise during walking and to identify preventive strategies to reduce excessive joint damage. Methods This study presents data of three-dimensional gait analysis of nine patients with progressive pseudorheumatoid arthropathy of childhood (♀ = 2; ♂ = 7; 13.3 y; 47.0 kg; 1.39 m; BMI: 24.2 kg/m 2 ) performed with eight infrared cameras and the Plug-in-Gait Model. For comparison of spatiotemporal and kinematic parameters with age-matched healthy controls (♀ = 6; ♂ = 3; 13.4 y; 49.0 kg; 1.61 m; BMI: 18.9 kg/m 2 ), the Mann–Whitney U -test was applied with a significance level of P Findings The patients had a significantly lower height, but higher BMI. Walking speed was reduced with wide, but short steps and significant motion anomalies in the pelvis, hips, knees and ankles. Small ranges of motion in propulsion-supporting movements were typical, especially in the sagittal plane. The gait analysis revealed dominant compensatory movements in pelvic obliquity and rotation. Interpretation The deficits can be attributed to pronounced muscle weakness plus functional joint impairment and pain. Therapeutic preventive strategies therefore should consider continuous muscle power exercises, stretching programmes and restrictive weight control.

Landing and its preparation are important phases for performance and safety of ski jumpers. A correct ski positioning could influence the jump length as also the cushioning effect of the aerodynamic forces that permits the reduction of landing impacts. Consequently, the detection of ski angles during landing preparation could allow for analyzing landing techniques that result in reduced impact forces for the athletes. In this study, two athletes performed with force insoles and inertial sensors positioned on the ski during training conditions on the ski jumping hill. The results confirmed previous studies, showing that impact forces can reach more than four times body weight. In the analyzed cases, the force distribution resulted to be more concentrated on the forefoot and the main movement influencing the impact was the pitch. The combination of inertial sensors, in particular gyroscopes, plus force insoles demonstrated to be an interesting set up for ski jumping movement analysis.

The purpose of this study was to develop a preventive exercise protocol based on structural and functional changes present in shoulder joints of young throwing athletes. As a proof of concept, these changes were previously evaluated in a cross-section of high-performance junior javelin throwers. Thirteen members of the German and Bavarian junior javelin squad (mean age 17.5 ± 0.8 years) completed a systematic clinical examination, shoulder range of motion (ROM) measurement, and were scored with standardized clinical tools. 3.0 tesla magnetic resonance imaging (MRI) was conducted on both shoulders. Bilateral three-dimensional analysis of the scapulothoracic motion during multiplanar humeral elevation and isokinetic strength testing of the shoulder internal and external rotators was accomplished. Based on the findings, a preventive exercise protocol was confirmed. Dominant internal ROM was significantly decreased (dominant 48° ± 20° vs. non-dominant 57° ± 19°; P = 0.006) and dominant external ROM increased (dominant 117° ± 15° vs. non-dominant 107° ± 10°; P = 0.008). MRI revealed posterosuperior intraosseous cysts of the humeral head with a size larger than >3 mm in 69 % of the dominant shoulders and only in 15 % in the non-dominant shoulders. Motion analysis of the static scapular resting position was significantly different between dominant and non-dominant sides regarding anterior tilt (dominant > non-dominant, mean difference 4.2°, P = 0.010) and retraction (dominant > non-dominant, mean difference 2.4°, P = 0.038). Dominant scapular anterior tilt during flexion and abduction was significantly increased (−4.3°, P = 0.006; −3.4°, P = 0.046). Dominant retraction was significantly increased during abduction (−2.3°, P = 0.040). Isokinetic outcome parameters presented nonsignificant bilateral differences. Elite junior javelin throwers already present structural (humeral intraosseous cysts) and biomechanical changes (ROM deficits and asymmetric scapulothoracic motion patterns), even if they have no history of major shoulder pain or injury. A novel exercise protocol was developed in order to address the complex of alterations in a comprehensive way. Preventive diagnostics in combination with a systematic all-year preventive exercise intervention might be one option to detect and control risk factors of a symptomatic throwing shoulder at an early stage. IV.

Varus knee alignment has been identified as a risk factor for the progression of medial knee osteoarthritis (OA). This study tested the hypothesis that not only frontal plane kinematics and kinetics but also transverse plane lower extremity mechanics during gait are affected by varus malalignment of the knee.Eighteen, otherwise healthy children and adolescents with varus malalignment of the knee were studied to examine the association between static varus malalignment and functional gait parameters. Kinematic data were collected using a Vicon motion capture system (Vicon Motion Systems, Oxford, UK). Two AMTI force plates (Advanced Mechanical Technology, Inc., Watertown, MA, USA) were used to collect kinetic data.The results indicated that changes in transverse plane mechanics occur concomitantly with changes in knee malalignment in the frontal plane. A mechanical consequence of varus knee malalignment is obviously an increased endorotation of the foot (internal foot placement) and an increased internal knee rotation (tibia rotation) during stance phase. The linear correlation between the maximum external knee adduction moment in terminal stance and the internal knee rotation in terminal stance (r=0.823, p0.001) shows that this transverse plane gait mechanics is directly in conjunction with intrinsic compressive load on the medial compartment during gait.Understanding factors that influence dynamic knee joint loading in healthy, varus malaligned knees may help us to identify risk factors that lead to OA. Thus, three-dimensional gait analysis could be used for clinical prognoses regarding the onset or progression of medial knee OA.

Force and torque production of human muscles depends upon their lengths and contraction velocity. However, these factors are widely assumed to be independent of each other and the few studies that dealt with interactions of torque, angle and angular velocity are based on isolated single-joint movements. Thus, the purpose of this study was to determine force/torque-angle and force/torque-angular velocity properties for multi-joint leg extensions.Human leg extension was investigated (n = 18) on a motor-driven leg press dynamometer while measuring external reaction forces at the feet. Extensor torque in the knee joint was calculated using inverse dynamics. Isometric contractions were performed at eight joint angle configurations of the lower limb corresponding to increments of 10° at the knee from 30 to 100° of knee flexion. Concentric and eccentric contractions were performed over the same range of motion at mean angular velocities of the knee from 30 to 240° s(-1).For contractions of increasing velocity, optimum knee angle shifted from 52 ± 7 to 64 ± 4° knee flexion. Furthermore, the curvature of the concentric force/torque-angular velocity relations varied with joint angles and maximum angular velocities increased from 866 ± 79 to 1,238 ± 132° s(-1) for 90-50° knee flexion. Normalised eccentric forces/torques ranged from 0.85 ± 0.12 to 1.32 ± 0.16 of their isometric reference, only showing significant increases above isometric and an effect of angular velocity for joint angles greater than optimum knee angle.The findings reveal that force/torque production during multi-joint leg extension depends on the combined effects of angle and angular velocity. This finding should be accounted for in modelling and optimisation of human movement.

Background The purpose of this study was to evaluate clinical and magnetic resonance imaging (MRI) findings in the shoulders of high performance competitive junior javelin athletes and volleyball players. The hypothesis was that structural lesions already exist in young and asymptomatic overhead athletes. Methods Thirty-one healthy high performance junior elite athletes were included. Group 1 consisted of 15 male javelin throwers (mean age, 17.7 ± 0.8 years) and group 2 of 16 male volleyball players (16.9 ± 1.0 years). Questionnaire-based interviews, comprehensive clinical examination, and shoulder scoring systems (visual analog scale [VAS] and Constant-Murley Score) were completed. Bilateral shoulder imaging was performed using a 3.0 Tesla MRI. Results The Constant-Murley Score of group 1 was 95.5 ± 3.6 and 94.7 ± 4.6 points for group 2. Group 1 demonstrated a mean VAS of 0.9 ± 1.6 and group 2 a mean of 0.6 ± 0.8 points. Postero-superior intraosseous cysts of the humeral head were detected in 73.3% of all javelin throwers in the dominant shoulder, but only in 13.3% in the nondominant shoulder (P = .008). In the volleyball group, such cyst formation was rarely seen in 12.5% in the dominant versus 6.3% in the nondominant shoulder (P = .66). Conclusion A high percentage of junior elite athletes already demonstrate osseus signs of overloading especially in the group of javelin athletes, although none had a history of prior shoulder pathology. Therefore, junior overhead athletes might be at risk for the early development of structural lesions at the insertion of the posterior rotator cuff similar to lesions already known for adult athletes, even though they do not present clinical signs of overuse at that age.

The aim of this study was to quantify the physical demands of a simulated firefighting circuit and to establish the relationship between job performance and endurance and strength fitness measurements. On four separate days 41 professional firefighters (39 ± 9 yr, 179.6 ± 2.3 cm, 84.4 ± 9.2 kg, BMI 26.1 ± 2.8 kg/m2) performed treadmill testing, fitness testing (strength, balance and flexibility) and a simulated firefighting exercise. The firefighting exercise included ladder climbing (20 m), treadmill walking (200 m), pulling a wire rope hoist (15 times) and crawling an orientation section (50 m). Firefighting performance during the simulated exercise was evaluated by a simple time-strain-air depletion model (TSA) taking the sum of z-transformed parameters of time to finish the exercise, strain in terms of mean heart rate, and air depletion from the breathing apparatus. Multiple regression analysis based on the TSA-model served for the identification of the physiological determinants most relevant for professional firefighting. Three main factors with great influence on firefighting performance were identified (70.1% of total explained variance): VO2peak, the time firefighter exercised below their individual ventilatory threshold and mean breathing frequency. Based on the identified main factors influencing firefighting performance we recommend a periodic preventive health screening for incumbents to monitor peak VO2 and individual ventilatory threshold.

Proximal hamstring tendon ruptures are commonly associated with a significant loss of function, and operative treatment is recommended in active patients. The objective was to evaluate objective/subjective functional results and return to sports following proximal hamstring tendon repair in the mid-term follow-up. 16 repairs of proximal hamstring ruptures were performed in 15 patients (9 males, 6 females). The average age at the time of injury was 47 years (range, 21–66). All patients were clinically examined at a mean follow-up of 56 months (range, 24–112 months). Validated patient-oriented assessment scores focussing on sports activity including the Lysholm Score, Tegner Activity Score, UCLA Activity Score, adapted WOMAC Score, and the VAS were evaluated as well as the return to sports. Isokinetic strength of both legs was tested using a rotational dynamometer. The Lysholm, Tegner, UCLA Activity Score and the adapted WOMAC demonstrated predominantly a return to a preinjury activity level at follow-up. Functional measurements of the operated leg showed similar results to the uninjured leg in knee extension and flexion strength (p>0.094). In return to sports, no signficant (p>0.05) differences concerning types or frequency were noted. The surgical repair of proximal hamstring tendon ruptures leads to constantly good functional results in the mid-term follow-up, where patients demonstrate similar isokinetic results in the healthy leg.

Stretch of activated muscles leads to enhanced forces compared to isometric contractions at the same muscle length and the same level of activation. This so-called residual force enhancement (RFE) is thought to be a property of all muscles and preparations. However, observations concerning the existence, amount and duration of RFE are inconsistent, especially for voluntary activated large human muscles. Therefore, physiological relevance for daily activity is still questionable and the purpose of this study was to examine whether RFE is present in voluntary sub-maximal activated quadriceps femoris (QF). Seated in a rotational dynamometer with EMG attached to superficial parts of QF, 30 subjects performed isometric and isometric–eccentric–isometric contractions (20° stretch, ω =60°s −1 ) at 30% and 60% of maximum voluntary activation (MVA) and contraction (MVC). To account for the complexity of the multi-headed QF, a compensation model based on physiological cross-sectional area and individual EMG–torque relations was used to interpret EMG data. For both levels of intensity and both feedback control strategies, ANOVA identified significant RFE (at the same level of activation) and reduced activation (at the same level of torque). Against expectations, RFE was independent of the level of activation.

(2012). Chapter 7 - SPORTS-SCIENTIFIC SUPPORT AT THE FREIBURG OLYMPIC-TRAINING-CENTRE. Routledge Online Studies on the Olympic and Paralympic Games: Vol. 1, Science in Elite Sport, pp. 82-96.

Eccentric training (ET) has been shown to be an effective conservative treatment option for chronic patellar and Achilles tendinopathies. As part of the four-muscle-tendon-complex of the rotator cuff, the supraspinatus is involved most commonly in shoulder disorders. Histopathologic alterations of the supraspinatus tendon are comparable to findings in lower extremity tendinopathies. Hence, the question arises whether the concept of eccentric training can be successfully transferred to the upper extremity. Yet, no randomised controlled trials have been published to support this theory. This problem emerges from the fact that the supraspinatus is part of a complex functional unit. Consequently, surrounding soft tissues are frequently concomitantly affected. The inherent etiology and genesis of pathologic alterations in the supraspinatus tendon and its influence on shoulder disorders is not clear to date. However, the apparent success of ET in managing tendinopathies of the lower extremity urges further scientific work for developing evidence-based guidelines for the conservative treatment of tendinopathies in the shoulder region. Taking into account this lack of data as well as the anatomical and functional constraints, the aim of this work is to review the current state of the literature.

The purpose of this study was to investigate if force enhancement (FE) in vivo is influenced by stretch-induced changes of muscle architecture. Therefore, 18 subjects performed maximum voluntary isometric (100° knee flexion angle) and isometric-eccentric-isometric stretch contractions (80°–100° ω = 60°s−1) whereby pennation angle and fascicle length of vastus lateralis was determined using ultrasonography. We found significant (2-way repeated ANOVA; α = 0.05) enhanced torque of 5–10% after stretch as well as significant passive FE but no significant differences in muscle architecture between isometric and stretch contractions at final knee angle. Furthermore, EMG recordings during a follow-up study (n= 10) did not show significant differences in activation and mean frequency of contraction conditions. These results indicate that FE in vivo is not influenced by muscle architectural changes due to stretch.

Force enhancement is a well accepted property of skeletal muscle and has been observed at all structural levels ranging from single myofibrils to voluntarily activated m. quadriceps femoris in vivo. However, force enhancement has not been studied for multi-joint movements like human leg extension; therefore knowledge about its relevance in daily living remains limited. The purpose of this study was to determine whether there is force enhancement during maximal voluntary multi-joint leg extension. Human leg extension was studied (n=22) on a motor driven leg press dynamometer where external reaction forces under the feet as well as activity of 8 lower extremity muscles were measured. In addition, torque in the ankle and knee joints was calculated using inverse dynamics. The steady-state isometric force, joint torques, and muscle activation after active stretch (20 degrees stretch amplitude at 60 degrees/s) were compared with the corresponding values obtained during isometric reference contractions. There was consistent force enhancement during and following stretch for both forces and joint torques. Potentiation during stretch reached values between 26% and 30%, while a significant force enhancement of 10.5-12.3% and 4.3-7.4% remained 0.5-1 and 2.5-3s after stretch, respectively. During stretch, EMG signals of m. gastrocnemius medialis and lateralis were significantly increased, while following stretch all analyzed muscles showed the same activity as during the reference contractions. We conclude from these results that force enhancement exists in everyday movements and should be accounted for when analyzing or modelling human movement.

Magnetic resonance–based assessment of quadriceps muscle fat has been proposed as surrogate marker in sarcopenia, osteoarthritis, and neuromuscular disorders. We presently investigated the association of quadriceps muscle fat with isometric strength measurements in healthy males using chemical shift encoding-based water-fat magnetic resonance imaging. Intermuscular adipose tissue fraction and intramuscular proton density fat fraction correlated significantly (P < 0.05) with isometric strength (up to r = −0.83 and −0.87, respectively). Reproducibility of intermuscular adipose tissue fraction and intramuscular proton density fat fraction was 1.5% and 5.7%, respectively.

Background Patients suffering from juvenile idiopathic arthritis (JIA) frequently have affected ankle joints, which can lead to foot deformities such as pes planovalgus (JIA-PPV). Usually, JIA-PPV is diagnosed by examining the foot in non-weightbearing or in weightbearing, static condition. However, functional limitations typically appear during dynamic use in daily activities such as walking. The aim of this study was to quantify the pathophysiology of JIA-PPV in both static and dynamic condition, i.e. in upright standing and during the stance phase of walking using three-dimensional (3d) gait analysis. Methods Eleven JIA patients (age = 12y) with at least one affected ankle joint and fixed pes planovalgus (≥5°) were compared to healthy controls (CG) (n = 14, age = 11y). Kinematic and kinetic data were obtained in barefoot standing and walking condition (1.1–1.3 m/s) with an 8-camera 3d motion analysis system including two force-plates and one pressure distribution plate. All participants were prepared using reflecting markers according to the Oxford Foot and Plug-in-Gait Model. Results were compared using the Mann–Whitney-U-test and Wilcoxon signed-rank test (p

The purpose of this study is to offer standardisation of multi-articular leg extension movements for isokinetic testing, based on a two link rigid body model with equal length of thigh and shank. Such standardisation corrects interindividual variations and may enable the derivation of the force-length-velocity [F(l, v)] characteristics during multiple joint (MJ) activities.