Difference of the thickness and activation of trunk muscles during static stoop lift at different loads between...

Patients suffering from low back pain (LBP) have been reported to alter muscle contraction strategies.

To compare activity and thickness of the trunk muscles (external oblique (EO), internal oblique (IO), transversus abdominis (TrA), and lumbar multifidus (LM)) during static stoop lift at different lifting loads between the subjects with and without LBP.

Twenty eight subjects with LBP and twenty eight healthy subjects were recruited. The stoop lifting was performed in three conditions in 0%, 10%, and 20% of body weight.

The activity of EO (F= 9.513) and IO (F= 7.781) was significantly increased with increasing lifting loads in subjects with LBP (p< 0.05) but not significantly in subjects without LBP. The activity of the LM (F= 124.980) was significantly increased in response to lifting loads in both groups (p< 0.05). The percent change of TrA (F= 8.797) and LM (F= 48.170) muscles thickness was significantly increased with increasing lifting loads in both groups (p< 0.05). The percent change of TrA (F= 3.780) and LM (F= 16.314) muscles thickness in subjects without LBP was greater than those in subjects with LBP at all three lifting loads (p< 0.05).

The results of this study suggest that more activation of EO in subjects with LBP may contribute to increase the compressive force on the lumbar spine during stoop lift. Also, less activation of TrA and LM in subjects with LBP may contribute to decrease the lumbar stabilization during stoop lift.