EMG study of erector spinae and multifidus in two isometric back extension exercises.

Back exercises addressing deep muscles with a prime stabilising role such as multifidus are important in the rehabilitation of patients with low back pain. Electromyography of erector spinae and multifidus of 18 healthy subjects was investigated during prone arch and two isometric back extension exercises; trunk holding and leg holding. When compared with prone arch, both erector spinae and multifidus were recruited at a high level during trunk holding (76-79 per cent) and leg holding (66-68 per cent). Relative activity of erector spinae and multifidus was similar in different loading conditions and this implied they were working together as a single functional unit Further studies are needed to investigate the possibility of selective recruitment of individual lumbar muscles in back exercises.