Electromyographic comparison of concentric and eccentric contraction phase in abdomical exercises

Abstract

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