An Electromyographic Analysis Of Three Abdominal Core Muscles

Abstract

Clinical observations suggest a growing interest among fitness trainers to incorporate Pilates exercises into workout routines, instead of abdominal crunches, as a way of developing core strength. One particular exercise, the plank, is often included in these workouts as a way to target core muscles such as the rectus abdominis and external oblique muscles. PURPOSE: To monitor the muscle activation during the plank exercise compared to an abdominal crunch exercise, with both performed to exhaustion, in activating abdominal and external oblique muscles. METHODS: Ten trained, college-age males (mean age = 20.8 yrs) volunteered to perform abdominal crunches and the plank exercise to exhaustion, in separate trials while the electrical activity of the upper rectus abdominis (URA), lower rectus abdominis (LRA) and external oblique (EO) were monitored via electromyography (EMG). The muscle electrical activity was measured using a Biopac™ bipolar electrode EMG system in which data were normalized as a percent of a maximum isometric abdominal curl against resistance. The order of trials was randomized and performed with 48 hours between trials. Data were analyzed using a 2 X 3 linear model ANOVA with a Scheffe post hoc test. RESULTS: The results showed that the crunch (URA = 10.66 ± 4.46%; LRA = 11.87 ± 4.30%; EO = 13.79 ± 3.06%) elicited a significantly higher (P<0.05) level of muscle activity than the plank (URA = 8.54 ± 2.23%; LRA = 8.75 ± 3.19%; EO = 10.29 ± 2.25%) in all three muscle groups tested. CONCLUSIONS: These results suggest that the crunch stimulates a larger percent of maximum electrical activity than the plank exercise in the three areas of the abdominal muscles tested, when completed to exhaustion. This further suggests that the crunch may be a more effective way to elicit greater muscle stimulation than the plank exercise for better potential core strength gains.