COMPARISON OF ELECTRICAL ACTIVITY OF SELECTED TRUNK AND THIGH MUSCLES IN FORWARD AND BACKWARD BENDING WITH DIFFERENT LOADS IN PEOPLE WITH AND WITHOUT CHRONIC LOW BACK PAIN

Studies have shown that carrying and holding objects requires the coordination of lower limb and trunk muscles, and is considered as a risk factor in causing low back pain. The aim of this study was to evaluate the level of activity of selected trunk and thigh muscles in forward and backward bending with different loads in people with and without chronic low back pain (CLBP).

In a semi experimental study, 31 subjects in two groups, 15 people with CLBP and 16 healthy people participated voluntarily. Subjects performed forward and backward bending in 4 positions without applying external load with 2, 5, and 10% of body mass during 6 seconds (2 seconds standing, 2 seconds bending forward and 2 seconds back). The electrical activity of eight muscles was recorded using an EMG device.

The results showed that the external load significantly affects the level of muscle activity. Also, there was a significant difference between the two groups as level of activity was higher in CLBP group. Also, the amount of load had a significant effect on the level of activity of different muscles in the groups, as the effect of 5% body mass load on the level of activity of rectus abdominis, internal oblique and multifidus was higher in CLBP group. Also, the effect of a load of 10% body mass on the level of activity of external oblique, thoracic erector spinae, lumbar erector spinae, and biceps femoris were higher in CLBP group. In addition, the effect of a load of 10% body mass on the level of activity of the gluteus maximus was higher in the healthy group.

In order to prevent muscle fatigue and ultimately to prevent the development or spread of pain, it is recommended to strengthen the muscles that had the highest level of activity when the external load increased.