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Background: Internal and external rotation exercises of the shoulder are frequently performed to avoid injury and pain. Knowledge about the motion and loadings of the upper extremities during these exercises is crucial for the development of optimal training recommendations. However, a comparison of the angles and corresponding moments in the upper extremities that are achieved during internal and external rotation exercises for the shoulder by using different resistance types has not yet been performed. Therefore, the aim of the study was to examine upper extremity kinetics and kinematics in 3D of the internal and external rotation exercises. Methods: The kinematics and kinetics of 12 participants while they performed 10 different exercises with a constant and with an elastic external load corresponding to 2% body mass was assessed. The motion of the upper extremities was recorded three-dimensionally with a motion capture system, using a newly developed marker set and joint coordinate systems with 28 markers. The applied external load was measured with a load cell placed in series with the external resistance, and moments were calculated using an inverse dynamics approach. Results: The range of motion and the joint loading was highly dependent on the exercises. The range of motion in the glenohumeral joint did not differ significantly between the two resistance types, whereas internal/external rotation moments were significantly higher with constant resistance than those with elastic resistance. Conclusions: Larger or lower moments can, therefore, be achieved through selection of the appropriate resistance type, while the range of motion can be altered through the selection of exercise type. Therefore, the loading motion patterns identified in this study can help to choose suitable shoulder exercises dependent on the training objective., BMC Sports Science, Medicine and Rehabilitation, 28 (10), ISSN:2052-1847

Description of the coordinate systems. Definition of the segmental coordinate system and the joint coordinate centers. (PDF 161 kb)

Figure S3. Averaged values of the knee moment in the frontal plane [Nm/Kg] as a function of the knee adduction angle [°] in the experienced cohort with the wooden bar (e) and with extra load on the barbell (e+) for all nine positions. (PDF 189 kb)

Figure S2. Averaged values of the knee moment in the sagittal plane [Nm/Kg] as a function of the knee flexion angle [°] in the experienced cohort with the wooden bar (e) and with extra load on the barbell (e+) for all nine positions. (PDF 176 kb)

Figure S1. Averaged values of the hip moment in the sagittal plane [Nm/Kg] as a function of the hip flexion angle [°] in the experienced cohort with the wooden bar (e) and with extra load on the barbell (e+) for all nine positions. (PDF 181 kb)

Table S1. Basic motion tasks. Tables S2. and S3. Fixed effects coefficients and standard error. Table S4. Random effects coefficients and standard error. (PDF 224 kb)

Background To ensure an efficient and targeted adaptation with low injury risk during strength exercises, knowledge of the participant specific internal loading conditions is essential. The goal of this study was to calculate the lower limb muscles forces during the strength exercises deadlifts, goodmornings and splits squats by means of musculoskeletal simulation. Methods 11 participants were assessed performing 10 different variations of split squats by varying the step length as well as the maximal frontal tibia angle, and 13 participants were measured performing deadlift and goodmorning exercises. Using individualised musculoskeletal models, forces of the Quadriceps (four parts), Hamstrings (four parts) and m. gluteus maximus (three parts) were computed. Results Deadlifts resulted highest loading for the Quadriceps, especially for the vasti (18–34 N/kg), but not for the rectus femoris (8–10 N/kg), which exhibited its greatest loading during split squats (13–27 N/kg) in the rear limb. Hamstrings were loaded isometrically during goodmornings but dynamically during deadlifts. For the m. gluteus maximus, the highest loading was observed during split squats in the front limb (up to 25 N/kg), while deadlifts produced increasingly, large loading over large ranges of motion in hip and knee. Conclusions Acting muscle forces vary between exercises, execution form and joint angle. For all examined muscles, deadlifts produced considerable loading over large ranges of motion, while split squats seem to be highly dependent upon exercise variation. This study provides key information to design strength-training programs with respect to loading conditions and ranges of motion of lower extremity muscles., BMC Sports Science, Medicine and Rehabilitation, 9 (1), ISSN:2052-1847

In competitive BMX racing, a fast start, that is, the shortest possible elapsed time and the highest possible instantaneous velocity at the end of the starting phase, is crucial for obtaining a favourable position in the middle portion of the race and the best possible final ranking. This study aimed first to evaluate several influencing factors for their relative importance in determining starting performance in competitive BMX racers. Also, this study describes basic leg kinematics during the first few pedal strokes of the starting phase. Subjects performed practice starts on a supercross ramp while various kinematic and kinetic parameters were obtained using a modified powermeter crank and a 3-d motion capture system. Data were analyzed with linear regression with starting performance as the output. The results show that an early turnaround during the preparation maneuver (countermovement) prior to the gat drop and a powerful first pedal stroke, with both a high torque and equivalent cadence, have the most influence on overall starting performance. End velocity is also related to attained peak cadence and the torque at peak cadence. Regarding leg kinematics, extension velocities are similar to ballistic jumps with relatively high loads. Thus, BMX racers should focus technical training on a quick and early turnaround in the preparation maneuver and strength training should be focused on developing strength and power at relatively high loads., Journal of Science and Cycling, 6 (2)

Background Back extension (BE) is a strength exercise for training the dorsal trunk and hip muscles. To optimise training recommendations that avoid overloading and possible injury, the aim of this study was to determine the loading conditions and the influence of different execution forms of BE on spine, hip and knee ranges of motion (RoMs), joint moments and muscle activity. Methods The kinematics, kinetics and muscle activity (EMG) of two execution types (BEh: dynamic hip, BEs: dynamic spine) and two versions (one-legged and two-legged) of BE were measured in 16 subjects. RoMs and external joint moments were calculated using an inverse dynamics approach and analysed with a linear mixed model. Results Although lumbar spine flexion was observed in both execution types, thoracic spine flexion predominantly occurred during BEs, whereas thoracic spine extension was observed during BEh. Larger maximal back and hip moments were observed for BEh than for BEs. The activity of the dorsal back and hip muscles, as observed using EMG, was increased for one-legged executions. Conclusion To strengthen the hips and lower back, BEh seem to be more efficient due to the higher moments, with higher or similar RoMs in the hip and lower back. One-legged BEs seem to provide an effective training for the hamstrings and hip regions without subjecting the spine to excessive loading, possibly promoting this as an effective exercise during training and rehabilitation., BMC Sports Science, Medicine and Rehabilitation, 9, ISSN:2052-1847

Seventh Annual Congres of the Swiss Society of Sports Sciences, Lausanne, 12-‐13 February 2015 : Programme and Book of Abstracts

Background. Knowledge of the musculoskeletal loading conditions during strength training is essential for performance monitoring, injury prevention, rehabilitation, and training design. However, measuring muscle forces during exercise performance as a primary determinant of training efficacy and safety has remained challenging. Methods. In this paper we review existing computational techniques to determine muscle forces in the lower limbs during strength exercises in vivo and discuss their potential for uptake into sports training and rehabilitation. Results. Muscle forces during exercise performance have almost exclusively been analysed using so-called forward dynamics simulations, inverse dynamics techniques, or alternative methods. Musculoskeletal models based on forward dynamics analyses have led to considerable new insights into muscular coordination, strength, and power during dynamic ballistic movement activities, resulting in, for example, improved techniques for optimal performance of the squat jump, while quasi-static inverse dynamics optimisation and EMG-driven modelling have helped to provide an understanding of low-speed exercises. Conclusion. The present review introduces the different computational techniques and outlines their advantages and disadvantages for the informed usage by nonexperts. With sufficient validation and widespread application, muscle force calculations during strength exercises in vivo are expected to provide biomechanically based evidence for clinicians and therapists to evaluate and improve training guidelines.