Effects of performing abdominal hollowing and abdominal bracing exercises on abdominal muscle activity during curl-up exercise

Abstract

Introduction. Effective maneuvers such as abdominal hollowing (AH) and abdominal bracing (AB) that increase trunk muscle activation before dynamic loading conditions are necessary for preventing injuries of the spine [1,2]. Although there are some studies analyzing AB and AH maneuvers in a different starting position [3,4] there were no studies found showing trunk muscle activity while performing these maneuvers during dynamic exercise such as curl-up exercise. Research aim. The aim of this study was to investigate the effects of abdominal hollowing and abdominal bracing exercises on abdominal muscle activity during curl-up exercise. Research methods and organization. This study was approved by the Bioethics Center of the Lithuanian University of Health Sciences. This study was performed in Kaunas University of Technology. Twenty young subjects, 10 males and 10 females (body mass index, 21.3  2.3) whose ages ranged from 20 to 32 (age, 25.4  2.9 years) participated in the study. None of them experienced musculoskeletal injury in the previous 12 months. The sites for electrode placement were prepared as in previous studies [5,6] Surface electrode pairs were placed on the muscles on the right side only, as left and right side EMG signal symetry has been demonstrated in core muscles during supine and prone position exercises [6]. EMG data were collected from rectus abdominis (RA), external oblique abdominis (OE) and internal oblique abdominis (OI) muscles. For normalization of the EMG data, a maximum voluntary isometric contraction (MVIC) was performed for each muscle and EMG amplitude recorded. Subjects were positioned in electromechanical dynamometer (Humac Norm; CSMI, Stoughton, MA). All participants were asked to perform trunk flexion and lateral trunk flexion to generate maximal EMG activity for each of three abdominal muscles. The EMG data of each muscle during curl-up were normalized as a percentage of[...].