Correlation between abdominal and scapular muscle strength in upper back pain patients with and without scapulocostal syndrome

Objectives: To determine the correlation between strength of abdominal and scapular muscles in upper back pain patients with and without scapulocostal syndrome (SCS). Methods : A cross-sectional study was conducted in 164 patients with upper back pain (85 with SCS and 79 without SCS). Participants were evaluated for strength of abdominal muscles by the double leg lowering test (DLLT) and a pressure biofeedback unit (PBU), whereas strength of scapular muscles was tested by a hand held dynamometer. Spearman’s rank correlation coefficient was used to analyze the correlation between strength of abdominal muscles and scapular muscles. Mann-Whitney U test was used to compare abdominal and scapular muscles strength between upper back pain patients with and without SCS. Results: In DLLT, moderate correlation was found between strength of abdominal muscles and upper trapezius, and left serratus anterior muscles (r = -0.503 to -0.608, p<0.001), whereas, low correlation was found between strength of abdominal muscles and right serratus anterior, and rhomboid muscles (r = -0.493 to -0.499, p<0.001). Muscles strength evaluated by PBU showed moderate correlation between strength of abdominal muscles and rhomboid, serratus anterior, and right upper trapezius muscles (r = 0.522 to 0.569, p<0.001). Meanwhile, low correlation was shown between strength of abdominal muscles and left upper trapezius muscles (r= 0.498, p<0.001). Moreover, strength of muscles in upper back pain patients with SCS was lower significantly compared to upper back pain patients without SCS. The affected muscles consisted of abdominal muscles, upper trapezius, serratus anterior, and rhomboid muscles (p<0.001). However, there was no significant differences of the strength of middle and lower trapezius muscles in both groups. Conclusion: Low to moderate correlation between strength of abdominal and scapular muscles was found. Moreover, strength of muscles in upper back pain patients with SCS was lower significantly compared to upper back pain patients without SCS. The affected muscles in upper back pain patients with SCS consisted of abdominal muscles, upper trapezius, serratus anterior, and rhomboid muscles (p<0.001).