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Designing for Upper Torso and Arm Anatomy
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
Grasp your shoulder near the glenohumeral joint with your hand curving over the top of the joint, and look at the muscles illustrated in Figure 4.23. Move your arm and shoulder to feel the muscles work on the front and back of your body. The deltoid muscle bridges between the shoulder area and the upper arm. It forms a smooth bowl-shape that originates from the edge of the acromion, the spine of the scapula, and the lateral clavicle. When designing an upper torso product, consider the size, shape, and contour of the deltoid along with the skeletal structure underneath. Large deltoid muscles often require a broader and higher sleeve cap to accommodate the muscle. A larger deltoid may also require a greater than standard upper sleeve circumference for a comfortable fit.
How does multi-set high-load resistance exercise impact neuromuscular function in normoxia and hypoxia?
Published in European Journal of Sport Science, 2023
N. Benjanuvatra, D. Bradbury, G. Landers, P. S. R. Goods, O. Girard
Surface EMG activity of the pectoralis major, anterior deltoid and the lateral and medial heads of triceps brachii muscles was recorded with surface electrodes (Cleartrace, 1700-050, Conmed., Utica, NY, USA) at an interelectrode distance of 20 mm on the participant’s dominant side. Before placing the electrodes, the overlying skin was carefully prepared (any hair was shaved, the skin lightly abraded with scourers and cleaned with alcohol wipes). Electrode placement followed recommendations from the Anatomical Guide for the Electromyographer (Perotto & Delagi, 2005). Electrodes were placed while the participant was in a standing position. For the pectoralis major muscle, the electrodes were placed over the anterior axillary fold level with the sternocostal portion of the muscle. For the anterior deltoid muscle, the electrodes were placed 6 cm below the anterior margin of the acromion. For the lateral head of triceps brachii muscle, the electrodes were placed immediately posterior to the deltoid tuberosity. For the medial head of triceps brachii muscle, the electrode were placed 6 cm proximal to the medial epicondyle of the humerus. Electrodes were fixed length-wise, over the middle of the muscle bellies. The electrodes were taped down with cotton wool swabs to minimise sweat-induced interference. The EMG reference electrode was placed over the sternal end of the clavicle, also on the subjects’ dominant side. To minimise movement artefact, wires between the electrodes and the EMG unit were secured to the skin with adhesive tape.
Upper limb biomechanics and dynamics of a core skill on floor exercise in female gymnastics
Published in Journal of Sports Sciences, 2023
Pavel Brtva, Gareth Irwin, Genevieve K.R. Williams, Roman Farana
Two force plates (Kistler, 9286 AA, Switzerland) were used to determine ground reaction force data at a sampling rate of 1200 Hz. To collect the kinematic data, a motion-capture system (Oqus, Qualisys, Sweden) consisting of 10 infrared cameras was used at a sampling rate of 240 Hz. Data from the force plate and the cameras were synchronised and collected simultaneously. Based on C-motion (Rockville, MD, USA) recommendations, 30 retroreflective markers (diameter of 9 mm) and clusters were attached to the gymnasts upper limbs and trunk. Markers were bilaterally placed on each participant at the following anatomical locations: vertebra prominens (C 7), scapula inferior angle, thoracic vertebra 10 (Th 10), the acromio-clavicular joint, centre of shoulder deltoid muscle, lateral epicondyle of the humerus, medial epicondyle of the humerus, radial-styloid, ulnar-styloid and head of the second metacarpal. Four clusters containing four markers each were also placed bilaterally on the upper arms.
A design tool to estimate maximum acceptable manual arm forces for above-shoulder work
Published in Ergonomics, 2022
Supraspinatus tendon compression, shear, and tension can also increase when the deltoid muscle, which is the primary muscle for abducting and flexing the shoulder, becomes fatigued. The supraspinatus muscle stabilises the shoulder and assists in abduction when the deltoid is fatigued. For above-shoulder work, once the deltoid fatigues, and the force it can generate is reduced, workers will shift to a shrug posture to reduce loads on the shoulder muscles (Fuller et al. 2009). With deltoid muscle fatigue, the humerus is translated in the superior direction and this increases supraspinatus compression (Dickerson, McDonald, and Chopp-Hurley 2020). Shoulder fatigue may also lead to less scapular rotation during upper arm rotation, and this may further increase impingement (McQuade, Dawson, and Smidt 1998, McQuade, Wei, and Smidt 1995). Muscle fatigue is related to the level of muscle load relative to strength (e.g. Maximum Voluntary Contraction, MVC%) and the duration of muscle load (e.g. duty cycle). Fatigue can be controlled by following recommendations from the Maximum Acceptable Effort (MAE) equation (Potvin 2012) or the ACGIH Upper Limb Localized Fatigue Threshold Limit Value (ACGIH 2016). Repetitive, hand intensive work should be designed so that these guidelines are not exceeded.