"torso muscles" refers to the group of muscles located in your upper body, including your chest, back, and abdomen. These muscles help you with movements like bending, twisting, and maintaining good posture. Full definition
If you feel stiffness of the leg, waist or torso muscles while doing this, then perform this posture very slowly with slow and deep breathing. (yogicwayoflife.com)
How do I get her into a safe seated position without causing any further harm to her already weak torso muscles?! (mamaot.com)
The McGill's Torso Muscular Endurance Test Battery assesses the endurance of three torso muscle groups and is comprised of the following tests: (acefitness.org)