Objectives: the purpose of this study was to investigate the relationship between the scapular upward rotation and the electromyographic (EMG) activity of gluteus maximus (GMax) and latissimus dorsi (LD) muscles in subjects with chronic nonspecific low back pain (CNSLBP).
Methods: in an EMG laboratory, 26 subjects with a diagnosis of unilateral CNSLBP with a mean age (y) of 25.15 ± 4.11 were recruited through direct referrals. EMG activity of the GMax and LD muscles was recorded while subjects were walking on a treadmill. Scapular upward rotation was measured using bubble inclinometers at 0⁰, 45⁰, 90⁰, 135⁰, and end range abduction. Pearson's Correlation Coefficient (r) was used to correlate the outcome variables.
Results: a significant correlation between the GMax EMG activity and scapular upward rotation measured at 0-degree abduction (p= .009) was found while there was no significant correlation between the GMax activity and scapular upward rotation measured at the other four ranges (45⁰, 90⁰, 135⁰, end range abduction). Also, there was no significant correlation between the EMG activity of GMax and LD muscles (p>.05)
Conclusion: subjects with unilateral CNSLBP may have dysfunctional scapular upward rotation not related to the degree of GMax EMG activities. In addition, a correlation between increased or decreased GMax and LD muscles EMG activity could not be established.