title: Changes in postural and trunk muscles responses in patients with chronic nonspecific low back pain during sudden upper limb loading.
abstract: BACKGROUND
  Alterations in the neuromuscular control of the spine were found in patients with chronic low back pain (CLBP). Sudden loading of the spine is assumed to be the cause of approximately 12% of lower back injuries. However, some aspects of this problem, such as alterations in the sensory-motor control of the spine, remain questionable. This study investigated postural and neuro- motor changes in trunk muscles during sudden upper limb loading in patients with CLBP.
  
  
  METHODS
  Electromyography of the erector spinae (ES) and transverses abdominis/internal oblique (TrA/IO) and external oblique (EOA) muscles were recorded in 20 patients with CLBP and 20 asymptomatic individuals with eyes open (EO) and eyes closed (EC) conditions. Moreover, measurements of the center of pressure (COP) and vertical ground reaction force (GRF) or Fz were recorded using a force plate. Data were analyzed using paired t-test and independent t-test at the significance level of 0.05.
  
  
  RESULTS
  In patients with CLBP, decreased electrical activity of the ES muscle was observed under both the EO and EC conditions and that of the TrA/IO muscle was observed under the EO condition (p< 0.05). Other findings included a shorter peak latency of the ES muscle in the EO condition and a greater increase in the peak latency of the ES muscle following the EC condition (p< 0.05). No significant differences were observed in COP and GRF measurements between the groups.
  
  
  CONCLUSIONS
  Electrical muscle activity may indicate less stiffening or preparatory muscle activity in the trunk muscle of patients with CLBP. Altered latency of the muscle may lead to microtrauma of lumbar structures and CLBP.
authors.affiliation: PhD Candidate, Department of Physiotherapy, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran. makbari_pt@yahoo.com.
authors.forename: Mahmood
authors.initials: M
authors.lastname: Akbari
authors.affiliation: PT, PhD, Department of Physiotherapy, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran. sarrafzadeh.j@iums.ac.ir.
authors.forename: Javad
authors.initials: J
authors.lastname: Sarrafzadeh
authors.affiliation: PT, PhD, Department of Physiotherapy, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran. naderpt46@yahoo.com.
authors.forename: Nader
authors.initials: N
authors.lastname: Maroufi
authors.affiliation: PhD, Department of Biostatistics, School of Public health, Iran University of Medical Sciences, Tehran, Iran. haghani511@yahoo.com.
authors.forename: Hamid
authors.initials: H
authors.lastname: Haghani
keywords: Abdominal muscles; Electromyography; Low back pain; Posture