EMG activity in neck and back muscles during selected static postures in adult males and females

Abstract

Surface electromyographic (EMG) amplitudes were gathered from 100 men and 100 women while maintaining the end range of nine motor tasks. Ratios of EMG amplitudes were used to characterise the activation patterns of 14 muscle groups of the back and trunk during 10 motor tasks. Procedures to identify electrode placement sites were developed to ensure reliability of all EMG recordings. Subcutaneous fat was estimated at each muscle site and a correction factor was used to account for signal attenuation due to the impedance attributable to adipose tissue thickness. Logarithmic transformations were performed to obtain a Gaussian distribution of the EMG amplitudes and muscle ratios. The transformed EMG amplitudes and transformed ratios were highly reliable between sessions across nine active motor tasks (Pearson's r and intra-class correlations ranged from 0.74 to 0.96). Significant gender differences were observed in the transformed EMG amplitudes and ratios of amplitudes in selected muscles and muscle pairs. It appears that the transformed EMG ratios represent a reliable means of assessing muscle recruitment patterns in a series of well-defined motor tasks in a large population of presumably normal adult male and female subjects. The acquisition of this large database under well-controlled conditions using defined criteria for each motor task provides a template to which individuals with injuries involving the neck and trunk musculature can be compared.