Pec Deck / Butterfly Machine

How to adjust

Set the seat height so the handles/pads sit at mid-chest level, with your upper arms parallel to the floor and elbows at shoulder height when seated.
Adjust the starting position of the forearm pads for your arm length, if the machine allows it.
Select the weight using the pin on the weight stack.

Sit with your back flat against the pad, placing your forearms/elbows on the pads or gripping the handles.
Exhale, bring the arms together in front of the chest along an arc.
Inhale, open the arms back under control, stopping before the weight stack touches down and before the arms travel behind the plane of the shoulders.
At the end of the set, let the arms travel back with the weight until the stack settles fully before releasing the handles or lifting your forearms off the pads and getting off the seat.

Adjust the seat so the handles/pads sit at mid-chest with the upper arms parallel to the floor before selecting weight, to avoid shoulder impingement.
Do not let the arms travel behind the plane of the shoulders at the deepest stretch.
If you run out of strength mid-set, keep the elbow angle fixed and let the arms open back with the weight until the stack settles fully before letting go — releasing mid-rep lets the machine yank the shoulders backward.
Control the arms opening back; do not let the weight stack crash down.