The phrase "slumped shoulders" refers to the drooping or sagging posture of a person's shoulders, showing a lack of energy, confidence, or sadness. Full definition
Just like I did: by sitting my ass down with slumped shoulders day after day, year after year, enduring discomfort, distractions, numb legs and a crazy mind. (mindbodygreen.com)
Feel the belly firm and keep lifting from your chest to avoid slumping the shoulders. (mindbodygreen.com)