title: Neuromuscular trunk activation patterns in back pain patients during one-handed lifting.
abstract: OBJECTIVE
  To analyze neuromuscular activity patterns of the trunk in healthy controls (H) and back pain patients (BPP) during one-handed lifting of light to heavy loads.
  
  
  METHODS
  After assessment of back pain (graded chronic pain scale according to von Korff) all subjects (n= 43) performed a warm-up (treadmill walking). Next, subjects were instructed to lift 3 × a 20 kg weight placed in front of them (with both hand) onto a table (height: 0.75 m). Subsequently, all subjects lifted with one hand (left-side, 3 repetitions) a weight of 1 kg (light), 10 kg (middle) and 20 kg (heavy) in random order from the ground up onto the table left of them. Trunk muscle activity was assessed with a 12-lead EMG (6 ventral/6 dorsal muscles; 4000 Hz). EMG-RMS (%) was averaged over the 3 repetitions and analyzed for the whole one-handed lifting cycle, then normalized to RMS of the two-handed lifting. Additionally, the mean (normalized) EMG-RMS of four trunk areas [right/left ventral area (VR/VL); right/left dorsal area (DR/DL)] was calculated. Data were analyzed descriptively (mean ± SD) followed by student'st-test comparing H and BPP (α = 0.05). With respect to the unequal distribution of subjects in H and BPP, a matched-group analysis was conducted. Seven healthy controls were gender- and age-matched (group Hmatched) to the 7 BPP. In addition, task failure was calculated and compared between H/HmatchedvsBPP usingχ2.
  
  
  RESULTS
  Seven subjects (3m/4f; 32 ± 7 years; 171 ± 7 cm; 65 ± 11 kg) were assigned to BPP (pain grade ≥ 2) and 36 (13m/23f; 28 ± 8 years; 174 ± 10 cm; 71 ± 12 kg) to H (pain grade ≤ 1). H and BPP did not differ significantly in anthropometrics (P> 0.05). All subjects were able to lift the light and middle loads, but 57% of BPP and 22% of H were not able to lift the heavy load (all women).χ2analysis revealed statistically significant differences in task failure between HvsBPP (P= 0.03). EMG-RMS ranged from 33% ± 10%/30% ± 9% (DL, 1 kg) to 356% ± 148%/283% ± 80% (VR, 20 kg) in H/BPP with no statistical difference between groups regardless of load (P> 0.05). However, the EMG-RMS of the VR was greatest in all lifting tasks for both groups and increased with heavier loads.
  
  
  CONCLUSIONS
  Heavier loading leads to an increase (2- to 3-fold) in trunk muscle activity with comparable patterns. Heavy loading (20 kg) leads to task failure, especially in women with back pain.
authors.affiliation: Juliane Mueller, Tilman Engel, Stephan Kopinski, Frank Mayer, Steffen Mueller, University Outpatient Clinic, Sports Medicine and Sports Orthopaedics, University of Potsdam, 14469 Potsdam, Germany.
authors.forename: Juliane
authors.initials: J
authors.lastname: Mueller
authors.affiliation: Juliane Mueller, Tilman Engel, Stephan Kopinski, Frank Mayer, Steffen Mueller, University Outpatient Clinic, Sports Medicine and Sports Orthopaedics, University of Potsdam, 14469 Potsdam, Germany.
authors.forename: Tilman
authors.initials: T
authors.lastname: Engel
authors.affiliation: Juliane Mueller, Tilman Engel, Stephan Kopinski, Frank Mayer, Steffen Mueller, University Outpatient Clinic, Sports Medicine and Sports Orthopaedics, University of Potsdam, 14469 Potsdam, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Kopinski
authors.affiliation: Juliane Mueller, Tilman Engel, Stephan Kopinski, Frank Mayer, Steffen Mueller, University Outpatient Clinic, Sports Medicine and Sports Orthopaedics, University of Potsdam, 14469 Potsdam, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Mayer
authors.affiliation: Juliane Mueller, Tilman Engel, Stephan Kopinski, Frank Mayer, Steffen Mueller, University Outpatient Clinic, Sports Medicine and Sports Orthopaedics, University of Potsdam, 14469 Potsdam, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Mueller
keywords: Core; EMG; Lifting; MISPEX; Trunk