The effect of load and exercise speed on activation pattern of middle trapezius and posterior deltoid muscles in prone fly position.

After Maximum Voluntary Isometric Contraction (MVIC) Testing, there should be a five-minute rest for each subject before proceeding. In the starting position, subjects lay prone on the treatment table with neutral shoulders resting in 90° forward flexion (to confirm with goniometer measurements). Prone Horizontal Abduction in External Rotation (PHAER) is performed by extending elbows and horizontally abducting shoulders to a horizontal position, adding external rotation of the shoulder towards the end of the movement. Subjects will undergo a dynamic warm-up of shoulder movements in all directions within their available range. Skin impedance will be reduced by shaving any hair on the skin and thorough cleaning with an alcohol swab. Proper electrode placement will be confirmed by monitoring EMG signals during specific muscle testing. First, subjects will complete 3 trials of 5 PHAER exercises (progressive load from 0.5 to 2 kg), with a 2-minute rest between exercises. Repetition velocity will be kept consistent at two seconds concentric to two seconds eccentric using a metronome. Second, subjects will complete 3 trials of 5 PHAER exercise (progressive velocity from 4 to 0.5 seconds), with a 2-minute rest between exercises. The study will be administered by the Principal Investigator and Co-Investigators approved by the ethics committee. The trial is conducted through direct participant engagement. Each participant is expected to spend 2 hours in the trial and will be remunerated with cash vouchers. The trial is conducted in the Singapore Institute of Technology and opened to the public. Each participant is involved in 1 session.