This study was performed to compare the muscle activity of lumbar stabilizers between stoop and semi-squat lifting techniques at different lifting loads. Twenty healthy subjects (9 males, 11 females) were recruited for this study. Muscle activity of external obliques (EO), internal obliques (IO) and lumbar multifidus (LM) muscle was measured by surface electromyography during stoop and semi-squat lifting at different lifting loads (10%, 20%, and 30% of the subject's body weight). A one-way repeated measure ANOVA was applied. The results showed that EMG activity of EO was significantly increased with a load of 30% of body weight compared to 10% and 20% of body weight in both lifting techniques (p<.05). Muscle activity of LM was significantly increased in 20% compared to 10% and 30% compared to 10% of subject's body weight in stoop lifting and the muscle activity of LM was significantly increased in 20% compared to 10%, 30% compared to 20%, and 30% compared to 10% of the subject's body weight in semi-squat lifting (p<.05). However, there was no significant difference in activity of IO according to lifting loads in both lifting techniques. There were no significant differences in muscle activity of EO, IO, and LM between stoop and semi-squat technique (p>.05). Therefore, the results of this study suggested that the EO can contribute to increase the lumbar stability during stoop and semi-squat lifting at 30% of body weight rather than at lower loads, and the LM seems to act as counteractor to imposed loads during stoop and semi-squat lifting with increasing loads.

Back muscles play an important role in protecting the spine. Epidemiological studies have shown that loads imposed on the human spine during daily living play a significant role in the onset of low back pain. No previous study has attempted to correlate the response of the trunk musculature with the type of external load. The purpose of this study was to use surface electromyography (EMG) to quantify the relative demands placed on the back muscles while lifting loads in one hand. Forty asymptomatic, twenty year-old subjects stood while lifting loads of 10% of body weight(BW) unilaterally. All EMG data were normalized to a percentage of the EMG voltage produced during no-load standing(%EMG). Our major analysis involved a paired t-test for repeated measures. Of particular note was the fact that the ipsilateral 10% of BW condition produced statistically less % EMG change than did the contralateral 10% of the condition.