Fig. 1. Measurement of total cross-sectional area for the MF, SCER, SCAP, and SPL muscles at C2–C3 (A) and C4–C5 (B). The MF and SCER muscles were measured together at the C2–C3 spinal level. MF, multifidus; SCER, semispinalis cervicis; SCAP, semispinalis capitis; SPL, splenius capitis.