The Effects of Bench Height on Electromyography Changes of Trunk Muscles in Student While Sitting

The aim of this study was to investigate the effects of desk and bench with same height on electromyographic muscles activity of lumbar erector spine and multifidus muscles in male subjects. The subjects of this study include 24 healthy students without any deformity and history of surgery in spine. The subjects were selected randomly from guidance schools. The subjects were divided in two groups according to their heights, control group (14.1+0.3years; 172.8+4.8cm,:66.7+9.4kg,; BMI: 19.8+3.8) and experimental group (13.8+0.9years;155.6+5.4cm; 47.9+9.8cm; BMI: 23.3+3.3).The high of desk and bench were appropriate for abnormal group according to the "scale portion" and principles of ergonomy. The height of desk and bench were higher for abnormal groups and so they were inappropriate. The collection of data was done through surface electromyography. The Root mean square (RMS)) values were collected in sitting position. Paired T-test analyses were applied to carry out pretest- posttest to comparing of muscle activity in either group (P<0.05). The result of the study indicated that there was no significant difference in the RMS measured values for Lumbar erector spine and multifidus muscles in pre and post test in the control group, but there was a significant difference in RMS values measured for lumbar erector spine and multifidus muscles in pretest – post test in experimental group (P<0.05). This study revealed that the high desks and benches cause the increase in muscle activity and muscle fatigue in lumbar erector spine and multifidus muscles in students during sitting in the classroom. Therefore it is important to pay attention to anthropometric characteristics of students for school furniture design