Basic Study
Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. Feb 18, 2017; 8(2): 142-148
Published online Feb 18, 2017. doi: 10.5312/wjo.v8.i2.142
Neuromuscular trunk activation patterns in back pain patients during one-handed lifting
Juliane Mueller, Tilman Engel, Stephan Kopinski, Frank Mayer, Steffen Mueller
Juliane Mueller, Tilman Engel, Stephan Kopinski, Frank Mayer, Steffen Mueller, University Outpatient Clinic, Sports Medicine and Sports Orthopaedics, University of Potsdam, 14469 Potsdam, Germany
Author contributions: Mueller J, Mayer F and Mueller S designed the research; Mueller J, Engel T and Kopinski S assessed and analyzed the data; Mueller J, Mayer F and Mueller S interpreted the results; Mueller J and Mueller S wrote the paper; all authors revised the paper.
Supported by German Federal Institute of Sport Science and realized under the auspices of MiSpEx - the National Research Network for Medicine in Spine Exercise, No. BISp IIA1-080102A/11-14; The present study was also funded by the European Union (European Regional Development Fund), No. 80132471.
Institutional review board statement: The study was approved by the Ethics commission of the University of Potsdam.
Institutional animal care and use committee statement: No animals were analysed during this study.
Conflict-of-interest statement: There is no conflict of interest.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Juliane Mueller, Research Assistant, University Outpatient Clinic, Sports Medicine and Sports Orthopaedics, University of Potsdam, Am Neuen Palais 10 - House 12, 14469 Potsdam, Germany. thormei@uni-potsdam.de
Telephone: +49-331-9771085 Fax: +49-331-9771296
Received: August 16, 2016
Peer-review started: August 18, 2016
First decision: October 21, 2016
Revised: November 8, 2016
Accepted: November 27, 2016
Article in press: November 29, 2016
Published online: February 18, 2017
Abstract
AIM

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’s t-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/Hmatchedvs BPP using χ2.

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). χ2 analysis revealed statistically significant differences in task failure between H vs BPP (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.

CONCLUSION

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.

Keywords: Lifting, Core, Trunk, EMG, MISPEX

Core tip: The aim of this study was 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. Neuromuscular trunk compensation strategies for expected loading with different weights did not differ between BPP and H, and showed a similar muscular activation pattern with the highest activity found in the contralateral abdominal muscles (VR). Heavier loading leads to an increase (2- to 3-fold) in trunk muscle activity with comparable patterns between groups. Heavy loading (20 kg) may lead to task failure, especially in women with back pain.