Suspend yourself and let bodyweight carve the chest.
Keep your body a straight line from head to heels. Don't let your hips sag.
Opening your arms into a wide arc while leaning into the handles loads the chest in its most stretched position, the exact spot where flys do their best work, and the adduction back together is pure pec. The shoulders assist by controlling the arc and keeping the joint stable as the straps try to pull your arms apart faster than you would like. It earns a place as one of the few fly variations that also demands a full-body plank, so your chest gets isolation while your trunk holds the line.
Usually yes. The wide arc puts your chest at a huge mechanical disadvantage in the stretch, so most people need a more upright body angle for flys than for presses.
Open until you feel a strong stretch across the chest without your shoulders complaining or your elbows straightening. Keep the soft elbow bend fixed the whole rep.
The stretch position pulls your whole body forward and your core gives out before your chest does. Squeeze glutes hard, or walk your feet back to a more upright angle until your plank holds.
