Abstract
BackgroundInternal 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.MethodsThe 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.ResultsThe 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.ConclusionsLarger 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.
Highlights
Internal and external rotation exercises of the shoulder are frequently performed to avoid injury and pain
The resultant peak moments occurred at different angles when the exercises were performed with elastic resistance (ER) compared to when the same exercises were performed either without external load or with constant resistance (CR) achieved through the use of dumbbells [17]
No statistical analysis was performed for the range of motion (RoM) in the sternoclavicular joint centre (SCJC), but maximal RoMs were achieved during the Sho20_com exercise performed with ER and the Elb20_com exercise performed with CR, which reached up to 16.9 ± 3.5° for internal/external rotation, 22.7 ± 4.7° for adduction/abduction, and 13.3 ± 5.0° for flexion/extension
Summary
Internal and external rotation exercises of the shoulder are frequently performed to avoid injury and pain. 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. The shoulder is the most common site of During training and in the fields of injury prevention and rehabilitation, exercises addressing the internal and external rotator muscles of the shoulder are generally either performed using constant resistance (CR) (e.g. pulley, dumbbell, or barbell) or elastic resistance (ER) (e.g. elastic straps or tubes). The resultant peak moments occurred at different angles when the exercises were performed with ER compared to when the same exercises were performed either without external load or with CR achieved through the use of dumbbells [17]. Most previous studies examining kinetics or kinematics of the shoulder have investigated exercises other than internal or external rotation [17,18,19,20], and no studies have compared the three-dimensional (3D) shoulder kinetics and kinematics during internal and external rotation exercises performed with CR or with ER
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