Electromyographic comparison of concentric and eccentric contraction phase in abdomical exercises
The study was conducted to compare the Electromyographic (EMG) activity variation of contractions (concentric and eccentric) during three different abdominal exercises (sit-up) exercises on rectus abdominal (upper and lower rectus). The sit-up exercises were: straight leg sit-up, bent leg sit-up and crunches. The EMG activity during exercise was recorded on ten selected male All India Intervarsity players. Their mean age, height and weight were 20.6 yrs (SD 1.90), 167.4 cm (SD 4.92) and 62.6 kg (SD 2.45) respectively. The Student Physiograph (Biodevices) for the group experimentation and research was used for EMG activity recording with the sensitivity set at 100μv /cm, amplitude signals bandwidth of 50Hz and the paper speed at 25mm/sec. Bipolar silver chloride surface electrodes of diameter of 1.3 cm were located over the belly on upper rectus and right lower rectus of the rectus abdominis muscle and oriented along its longitudinal axis, and an interelectrode distance was maintained consistent from subject to subject.. An unshielded ground electrode was placed over the lateral malleolus. The skin over each muscle was shaved and cleansed with sprit to reduce the impedance at the skin electrode interface. Electromyographic activity (EMG) was determined by averaging frequency, duration, and amplitude. Subjects performed one repetition for each sit-up exercises from the supine lying position and data were collected during a single session. To ensure consistency in the speed and velocity of the movement, subject performed each sit-up exercise with a given rhythm along the amplified watch beat, through a constant range of movement round an angle-marked projector at a rate of 3.00 seconds each contraction phase. Paired t-test analysis was used to compare mean electromyographic activity of concentric and eccentric contraction phase of upper rectus and lower rectus during sit-up exercises. Results showed no significant differences (p ≤ 0.05) in muscle activation among the conditions.
Keywords: Electromyographic; Sit-up; Abdominal; Sports.
South African Journal for Research in Sport, Physical Education and Recreation Vol. 29 (2) 2007: pp. 59-66