Lumbar iEMG during isotonic exercise: chronic low back pain patients versus controls.

Two studies investigated the use of lumbar integrated electromyography (iEMG) during flexion-extension exercises of the lumbar spine. The first study compared the iEMG fatigue slopes of 12 pain-free controls during a standardized isotonic workout with a heavy weight and a light weight. Results indicated that the slopes of the iEMG across flexion-extension repetition was negative in both conditions, with the heavy weight producing significantly steeper fatigue slopes. In the second study, iEMG was compared from 16 chronic low back pain (CLBP) patients and 12 asymptomatic controls during isotonic exercise. Integrated EMG was recorded during 18 lumbar extension-flexion cycles (3 min) at a standard pace. Each subject exercised at a weight equal to 60% of his maximum isometric torque produced at the most extended position. Results indicated significantly less iEMG was produced by the CLBP group during both concentric and eccentric exertion. For both groups, eccentric exertion produced significantly less iEMG than concentric exertion. The groups showed significantly different iEMG fatigue slopes, with the control group showing declining iEMG by repetition, while the CLBP group showed flatter, slightly increasing iEMG. This occurred for both eccentric and concentric comparisons. A muscle deficiency model of CLBP is supported and results suggest the importance of endurance factors in addition to strength in rehabilitation efforts. Results also suggest the possibility of using this methodology for detecting insincere efforts in lumbar spine assessment.