psoas major muscle
Anatomical term for the large muscle running from the lumbar vertebrae to the femur, important for hip flexion and posture.
The psoas major muscle is important for hip joint flexion.
Sitting for long periods tends to make the psoas major muscle tight.
Compound of 大 (large), 腰 (waist/lumbar), and 筋 (muscle), directly describing the muscle's location and relative size.