Differences in cervical multifidus muscle thickness during isometric contraction of shoulder muscles: A comparison between patients with chronic neck pain and healthy controls

Objective The purposes of this study were to (1) measure the thickness of cervical multifidus muscle (CMM) in different maximal voluntary contraction percentages of isometric contraction of shoulder muscles, (2) evaluate the differences of the CMM thickness in different directions of the shoulder movement, and (3) compare the changes in the CMM thickness of participants with neck pain and also of healthy individuals. Methods Twenty healthy men (age, 27.45 ± 4.37 years; height, 177 ± 4.66 cm; weight, 72.85 ± 6.46 kg) and 20 men with chronic mechanical neck pain (age, 28.90 ± 5.53 years; height, 176 ± 5.98 cm; weight, 73.15 ± 7.82 kg) participated in the study. Both the right and left CMM thicknesses were measured using an ultrasound device while participants performed isometric contraction of shoulder muscles in 6 movement directions. Results In both groups, an increment of CMM thickness followed as the increase of isometric force (P <.01).The increase of muscle thickness of healthy participants was substantially more than the chronic mechanical neck pain participants (P =.03). Although no significant difference of CMM thickness was seen among the effects of the 6 force directions (P >.05), there was a significant difference of activity noted between the left and right sides (P =.047). Conclusion The results of the present study indicate that isometric contraction of shoulder muscles caused an increase in the CMM thickness regardless of force direction. This increase was seen in both groups of healthy participants and patients with neck pain. However, less thickness changes were observed in participants with neck pain, which may be interpreted as reduced CMM activity in such people.