Motor Unit Recruitment of Abdominal Flexors in Two Common Exercise Positions

Core training has become a popular mode of conditioning for not only rehabilitation, but also the general and athletic populations. PURPOSE: To determine the highest motor recruitment in to commonly used exercise positions for the rectus abdominis (RA) and external oblique (EO) muscles. METHODS: Thirteen college-aged healthy subjects volunteered to participate in the study. Isometric exercises were performed for the abdominal crunch and rotating abdominal crunch. Electromyographical data was collected over three trials, with the average (P-P) root mean square compared between exercises for the right rectus abdominis and right external oblique. RESULTS: The RA had a significantly higher recruitment (p = 0.008) in the rotating crunch (0.3077 ± .204mV) than in the straight crunch (0.1139 ± .129mV) where as the EO had a significantly higher recruitment (p = 0.001) in the straight crunch (0.4531 ± 0.347 mV) than in the rotating crunch (0.2181 ± 0.165 mV). CONCLUSION: Although the straight crunch exercise is commonly used for the rectus abdominis and the rotating crunch for external obliques, this study has shown that the opposite may provide improved recruitment for the muscles tested. PRACTICAL APPLICATION: This study may provide some important information regarding commonly used exercises in the conditioning of abdominal flexors, improving certain performance outcomes.