Muscle activity of abdominal and back muscles during six starting positions in untrained individuals

Abstract

Objective: This study aimed to investigate the electromyography (EMG) activity among five abdominal and back muscles at six starting positions in untrained individuals. Material and Method: Twenty-five healthy individuals aged 20.9+3.9 years, who were inexperienced with lumbar stabilization exercise, were recruited. They were asked to perform maximum voluntary isometric contraction (MVIC), and then six starting positions in random order. EMG data of each starting position were normalized as a percentage of MVIC. Friedman two-way analysis of variance (ANOVA) and Wilcoxon signed-ranks tests were used for data analysis. Results: Significant differences in EMG activity of five abdominal and back muscles were found in all six starting positions (p < 0.001). The highest EMG activity of the transversus abdominis/internal abdominal oblique (TrA/IO) was found in crook lying, with right leg lifted (CLR), and of multifidus (MF) in four-point kneeling with straight right leg lifted horizontally (4p-SRL). Conclusion: The results suggested that CLR and sitting on a gym ball (SG) were able to facilitate TrA/IO activity with minimal activity from the rectus abdominis (RA), while CL, 4p-SRL, and SG were able to facilitate MF activity with minimal activity from erector spinae (ES).