Algotopic

S4 FLEXORS

relatively minor role in Janda's crossed syndromes

S4 EXTENSORS

relatively minor role in Janda's crossed syndromes

Muscle categorization - FLEXOR or EXTENSOR - corresponds to the action performed during bilateral contraction and upright posture.

Underlining is used to indicate the main spinal segment(s) of innervation for each muscle.

Underlining does not convey any comparative information between the muscles listed for each spinal segment.

References:

1. Dalley, Arthur, et al. Moore's Clinically Oriented Anatomy. Ninth edition. Wolters Kluwer, 2023.

2. Donnelly, Joseph. Travell, Simons & Simons' Myofascial Pain and Dysfunction: The Trigger Point Manual. Wolters Kluwer, 2018.