The stability of the spine depends on co-activation of the trunk muscles. Co-activation of these muscles is neces- sary in programs aimed at treating and preventing lumbar pain1–3). To stabilize the spine, harmonious coordination of all of the trunk muscles is crucial, rather than activation of a particular muscle3). Adjusting the co-ordination of global and local muscles maintains the stability of the spine2, 4). The trunk muscles are anatomically classified into global muscles and local muscles. The global muscles largely gen- erate strength and are involved in overall stabilization of the trunk, and the local muscles are involved in segmen- tal trunk stabilization5). The stabilization of the trunk is necessary for the stability of the spine and the pelvis when they are in a functional position, to increase stability dur- ing movement, to enhance muscle strength, and to adjust muscle movements and balance6).
The principal trunk stabilization exercises are pelvic tilt exercises, quadruped exercises, abdominal hollowing ex- ercises, and bridging exercises7). Among these, the aim of bridging exercises is to make lumbar pain patients feel more comfortable by reducing their pain and retraining their global and local muscles to ensure they are coordinated in
*Corresponding author. Ji Won Park (E-mail: mylovept@ cu.ac.kr)
©2013 The Society of Physical Therapy Science
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an appropriate manner4). Berkefors et al.8) reported that the use of a deep abdominal muscle training method enhanced the activity of the deep muscles. Akuthota and Nadler9) stressed the importance of core strengthening of the lumbar area in different positions. Exercise on an unstable surface increases the co-contraction of the muscles and the stability of the trunk10), and prompts postural adjustment and bal- ance more than exercise on a stable surface11). In addition to methods which gradually increase the intensity of trunk stabilization exercises, there are methods which increase the intensity of the resistance and the intensity of the exer- cise. Such methods heighten the degree of instability on a support surface using a treatment ball, a vestibular balance plate, or a form roller12).
Bridging exercise is a method which is often used clini- cally, and much research has been conducted using diverse methods and modifications. Recently, attention has focused on changes in the activities of the trunk muscles during bridging exercises, and many studies have attempted to identify an efficient method of enhancing the activities of the trunk muscles. The conventional bridging exercise is conducted in a supine position, and most are other exercises are modifications of this exercise. To the best of our knowl- edge, very little research of prone bridging exercises has taken place. Accordingly, this study investigated the effect of different types of bridging exercise (in prone and supine positions) on the activities of the trunk muscles.