The effect of sustained spinal load on intra-abdominal pressure and EMG characteristics of trunk muscles

Abstract

Fourteen young male students (mean age 21 years, mean weight 69-4 kg, and mean height 175-4 cm) and 12 young female students (mean age 22-2 years, mean weight 60-6 kg, and mean height 169-3 cm) held 9-07 kg and 6-8 kg, respectively, at their three-quarters horizontal reach distance in upright and stooping postures for a period of 5 min. During these periods the external torque on the lumbosacral disc, intra-abdominal pressure, and electromyographic signals from erectores spinae at T₁₂ and L₃ levels, latissimus dorsi and external obliques were recorded at 1 kHz for 2-1 s every 15 s for a period of 5 min. The EMGs were processed in magnitude and time domains to determine muscle fatigue. Through the data obtained it was seen that the intra-abdominal pressure did not follow or reflect either the spinal load or the muscle activity. Based on the arguments presented, it was concluded that the intra-abdominal pressure does not appear to have a role of relieving the spine of some of its load. Instead, it is suggested that it is a dependent variable manifesting itself when mechanisms for spinal stability are evoked to overcome large voluntary and inertial loads.

Keywords:

• Intra-abdominal Pressure
• Spinal Mechanics
• Electromyography
• Muscle Fatigue
• Spinal Loading.