Lumbar paraspinal electromyographic activity during trunk extension exercises on two types of exercise machines

The objective of this study was to evaluate and compare lumbar paraspinal muscle activity during trunk extension exercises on two lumbar extension machines with different types of pelvic stabilization mechanisms. Thirteen healthy male (n = 9) and female (n = 4) volunteers aged 21-24 (22.6 +/- 1.4) were recruited in a university setting. Surface electromyographic activity was recorded bilaterally from the L3-4 paraspinal region during trunk extension exercises performed on two different exercise machines. One machine, the MedX, has a complex pelvic stabilization mechanism. The other machine, the Cybex, has a relatively simple pelvic stabilization mechanism. There was no significant difference between lumbar paraspinal electromyographic activity during trunk extension on the MedX compared to the Cybex dynamic variable resistance trunk extension machine. These results suggest that a complex pelvic stabilization mechanism does not significantly enhance the level of activation of the lumbar paraspinal muscles during lumbar extension exercises. Thus, a less expensive trunk extension machine with a less sophisticated pelvic stabilization mechanism, such as the Cybex, can be used to train the lumbar paraspinal muscles. This is important to rehabilitation clinicians because these machines are often more readily available and easier for patients to use. Further research is warranted to determine the applicability of these findings to a patient population.