Comparison of the electromyographic activity of the abdominal and rectus femoris muscles during traditional crunch and Rock Gym® device

Abstract

Abdominal exercises are performed with the purpose of preventing or rehabilitating low back pain, improving sports performance, and increasing strength and endurance during activities of daily living, and for aesthetic reasons. The objective of this study is to analyze and compare the electromyographic activity of the rectus abdominis (RA), external oblique abdominis (EO), and rectus femoris (RF) muscles during traditional crunch and exercise with Rock Gym® device. A convenience sample of 15 healthy men (mean ± standard deviation, age 22.47 ± 2.26 years, body fat percentage 13.44 ± 4.37%) was selected. All men regularly participated in physical activity. Electromyographic recordings were performed using simple differential surface electrodes during five repetitions of each abdominal exercise (traditional and Rock Gym® at levels RG1, RG2, RG3, and RG4) in a randomized and counterbalanced manner. Electromyographic signals were quantified by root mean square and normalized using the maximum voluntary isometric contraction. Data were analyzed using repeated measures analysis of variance (p < 0.05). Electromyographic activity of the abdominal muscles RA and EO in the crunch exercise was significantly higher (RA) or similar (EO) compared with the Rock Gym® device; however, the activity of the RF muscle in the device was significantly greater in relation to the traditional exercise. Traditional crunch produced greater or similar EMG activity in the abdominal muscles and minimized RF activity compared with the Rock Gym® device; hence, traditional crunch is preferred for training, especially for people with weak abdominal musculature and/or problems in the lower back.