Back Pec Stretch

Stand tall with your feet shoulder-width apart.

Extend your arms straight out in front of you, parallel to the ground.

Cross your arms in front of your body, with your right arm over your left arm.

Interlock your fingers and rotate your palms away from your body.

Slowly raise your arms up and away from your body, feeling a stretch in your back and chest.

Hold the stretch for 15-30 seconds, then release.

Repeat on the opposite side.

Losing tension in the core or lower back partway through the movement — because Back Pec Stretch loads multiple joints at once, a small breakdown in bracing at the hips or spine compounds through the whole chain.

Rounding the upper back or shrugging the shoulders up toward the ears at the start of the pull instead of initiating with the target muscle.

Rushing through reps using momentum rather than controlling both the lifting and lowering phase, which is especially important since there's no external load to force good tempo.

Skipping a warm-up set at lighter load/intensity — even "beginner" exercises benefit from a rehearsal set to groove the movement pattern before working sets.