Table 4 Results of linear mixed model investigating the relationship between muscle fat infiltrate (as a percent of muscle volume) and group (pain vs. asymptomatic), accounting for side (left or right), muscle, spinal level (C3-T1), sex, age, body mass index (BMI).

Group

Asymptomatic

-0.87 (-3.01 to 1.26)

0.418

Side (left)

Right

-0.36 (-0.46 to -0.25)

< 0.001

Muscle (levator scapulae)

SCM^c

-3.09 (-3.37 to -2.82)

< 0.001

Muscle (multifidus)^b

SCM

9.53 (9.24 to 9.81)

< 0.001

Muscle (semispinalis capitis)

SCM

-0.06 (-0.36 to 0.21)

0.667

Muscle (splenius capitis)^b

SCM

-2.27 (-2.54 to -1.99)

< 0.001

Muscle (longus colli)

SCM

2.21 (1.94 to 2.49)

< 0.001

Spinal level (C4)

C3

-1.28 (-1.46 to -1.10)

< 0.001

Spinal level (C5)

C3

-2.15 (-2.34 to -1.97)

< 0.001

Spinal level (C6)

C3

-1.71 (-1.90 to -1.53)

< 0.001

Spinal level (C7)

C3

-0.03 (-0.21 to 0.15)

0.728

Spinal level (T1)

C3

3.10 (2.92 to 3.27)

< 0.001

Sex (Female)

Male

2.00 (-0.23 to 4.23)

0.078

Age

–

0.11 (0.004 to 0.22)

0.043

BMI

–

0.44 (0.19 to 0.69)

0.001

Muscle (levator scapulae)*group(pain)

SCM/asymptomatic

0.56 (0.20 to 0.92)

0.002

Muscle (multifidus)*group(pain)

SCM/asymptomatic

3.19 (2.82 to 3.57)

< 0.001

Muscle (semispinalis capitis)*group(pain)

SCM/asymptomatic

1.52 (1.16 to 1.88)

< 0.001

Muscle (splenius capitis)*group(pain)

SCM/asymptomatic

1.80 (1.44 to 2.15)

< 0.001

Muscle (longus colli)*group(pain)

SCM/asymptomatic

1.52 (1.17 to 1.88)

< 0.001