The study of lower trapezius muscle when performing shoulder forward lift in prone and varying pelvic tilts quadruped positions.

Electromyographic (EMG) data will be collected during manual muscle testing performed by the subject with their dominant arm, to acquire maximal voluntary isometric contraction (MVIC) of the serratus anterior (SA), upper trapezius (UT) and lower trapezius (LT) muscle. For the electrodes placement, the skin will be shaved if required and wiped with isopropyl alcohol to reduce skin impedance. For the UT, the shoulder was abducted 90°. Two electrodes were positioned parallel to the UT fibres, 1 electrode superior-medial, and 1 inferior-lateral at 2 cm apart, and at a distance one-half away from the spinous process C7 and the lateral acromion tip. For the LT, the shoulder was flexed into 90° and electrodes were angled obliquely. 1 electrode was placed superiorly and 1 inferiorly, 5cm inferior-medially from the root of the spine of scapula. For the SA, electrodes were vertically positioned at the mid-axillary of ribs 6 to 8. In manual muscle testing, the SA will be tested with the shoulder in 125° flexion. Resistance is applied above the elbow and at the inferior angle of the scapula attempting to de-rotate the scapula. The subject seats tall without back support. The UT will be tested with resistance given to shoulder abduction at 90° with simultaneous resistance to the head after the neck is first side-bent to the same side, rotated to the opposite side, and then extended. The LT will be tested in the prone position. The subject’s arm is raised diagonally overhead with shoulder in 145°abduction, in line with the LT fibres. Resistance is applied distal to the elbow. The isometric contraction will be held for 6 seconds with maximal effort against manual resistance until muscular failure. The first and last second of EMG data will be removed. Only the remaining 4 seconds are used. Each test is performed for 3 repetitions with 2 mins intervals between them. The EMG values from each muscle during the shoulder flexion exercise in prone and quadruped will be normalized as a percentage of the highest EMG value that the muscle produced during the MVIC. The EMG data from exercises will be expressed as a percentage MVIC (%MVIC). Prone: The subject is positioned in prone on a plinth. The humerus was aligned diagonally overhead with shoulder abduction of 145° using a goniometer. The angle is maintained using a metal bar. The forearm is kept in neutral. The subject placed their non-dominant hand under the forehead to stabilize the neck and thoracic spine. A cable rope, attached to a 22.5kg load on the floor, is wrapped 5cm above the radial styloid process of the dominant arm which hangs off the plinth. The maximum length of the rope is adjusted according to the distance between the floor and the final position of the arm in shoulder diagonal flexion, where the medial epicondyle is in line with the subject’s earlobe. When instructed, the subject lifts the dominant arm with elbow in extension against the resistance, to achieve maximal isometric contraction of the tested muscles. Quadruped: The participants begin in kneeling position on a plinth with both hands and knees in equal weight bearing. The hips, arms and knees were flexed at 90°. The shoulder girdles were directly above the hands. The fingers pointed forward with the hands at shoulder width apart. The shins were flat on the floor and the feet in plantarflexion. The subject will assume one of the three pelvic positions (neutral, full anterior pelvic tilt, full posterior pelvic tilt) before the shoulder of the dominant arm is diagonal flexed. A similar method for loaded resistance in the prone position will be used for each quadruped shoulder diagonal flexion exercise. All exercises were performed with maximal isometric effort for 5 seconds. The participants repeat each exercise a second time after a 15-minute rest period on the same day for test-retest reliability of the recorded EMG.