Control of trunk motion following sudden stop perturbations during cart pushing
Introduction
Pushing has been associated with the risk of low-back pain (Damkot et al., 1984, Harber et al., 1987, Hoozemans, 2001, Plouvier et al., 2008). This is remarkable since in pushing, joint moments around the lumbar spine are low (Hoozemans et al., 2004). However, these low moments probably coincide with a relatively low trunk stiffness (Stokes et al., 2000, Chiang and Potvin, 2001), which may put the spine at risk of mechanical injury when trunk perturbations occur (Cholewicki and McGill, 1996), especially given the high inertia of objects handled in industrial pushing tasks (Chaffin et al., 1999, Nussbaum et al., 2000).
When pushing a cart, perturbations of the trunk may occur because of sudden stops. One may, for example, be required to suddenly stop the cart to avoid a collision. The high inertia of the transported object may in this case impose a sudden, yet self-induced, flexion perturbation of the trunk similar to that when lifting an unexpectedly heavy object (van der Burg et al., 2000). Alternatively, sudden stops may occur due to an external event, for example when an obstacle blocks the wheels. In contrast to the self-induced stop, this may impose an external trunk extension moment due to high reaction forces at the hands. Both situations may perturb trunk movement, which could be a cause of injury.
When experiencing unpredictable continuous perturbations during pushing while walking (Lee et al., 2010) and lifting (van DieenDieën et al., 2003), participants respond by stiffening the trunk using cocontraction. The objective of the present study was to investigate how trunk motion and trunk muscle activity are controlled in relation to unexpected sudden stops during pushing. We hypothesized that both types of sudden stops (self-induced and externally induced) could lead to uncontrolled trunk motions, i.e. an increase in trunk inclination due to an external flexion moment during self-induced stops and a decrease in trunk inclination due to an external extension moment during externally induced stops. Additionally, we hypothesized that trunk inclination would be more affected when sudden stops occur during pushing at shoulder height than at hip height. As higher trunk moments and hence higher muscle activity would be present prior to the perturbation when pushing at hip height (Hoozemans et al., 2007). Furthermore, we hypothesized that trunk flexor and extensor muscles would cocontract in response to perturbations in both types of sudden stops.
Section snippets
Methods
Twelve healthy male volunteers (age 30.2 (SD 5.4) years, height 1.86 m (SD 0.06 m) and weight 79.4 kg (SD 8.1 kg)) participated in the experiment after signing an informed consent. Participants reported no history of low-back pain or other musculoskeletal disorders within the past 12 months. The ethics committee of the Faculty of Human Movement Sciences approved the experiment.
Results
The mean self-selected walking speed during all pushing tasks was 1.17 ms−1 (SD 0.15). The walking speed during the reference condition was not different from the walking speed just before the perturbations (1.16±0.13 ms−1 vs. 1.18±0.16 ms−1; F (1,11)=0.52, p=0.604).
ANOVA for repeated measures on the log transformed data showed significant effects of condition (reference and two sudden stops) on the peak values of external moment, trunk inclination and trunk muscle EMG (Table 1). Compared to the
Discussion
The present study was designed to investigate how trunk inclination and trunk muscle activity are controlled after sudden stops while pushing a cart at walking speed. In the self-induced stop, an external flexion (internal extensor) moment coincided with a decrease in trunk inclination. In contrast, the externally induced stop appeared to cause an involuntary trunk motion, a decrease in trunk inclination due to an external extension (internal flexor) moment. Smaller changes in trunk inclination
Conflict of interest
The authors declare that no financial and personal relationships with other people or organisations have inappropriately influenced the content of the work reported in this paper.
Acknowledgements
We thank Sjoerd M. Bruijn for his crazy and explosive shouting played in the experiment, Marit Balder for her assistance in data acquisition and Gert S. Faber for his assistance in data analysis.
References (18)
- et al.
Mechanical stability of the in vivo lumbar spine: implications for injury and chronic low back pain
Clin. Biomech. (Bristol, Avon)
(1996) - et al.
Cart pushing: the effects of magnitude and direction of the exerted push force, and of trunk inclination on low back loading.
International Journal of Industrial Ergonomics
(2007) - et al.
Segment inertial parameter evaluation in two anthropometric models by application of a dynamic linked segment model
J. Biomech.
(1996) - et al.
Oblique abdominal muscle activity in response to external perturbations when pushing a cart
J. Biomech.
(2010) - et al.
Lifting an unexpectedly heavy object: the effects on low-back loading and balance loss
Clin. Biomech. (Bristol, Avon)
(2000) - et al.
Evidence for a role of antagonistic cocontraction in controlling trunk stiffness during lifting
J. Biomech.
(2003) - et al.
Low-back stresses when learning to use a materials handling device
Ergonomics
(1999) - et al.
The in vivo dynamic response of the human spine to rapid lateral bend perturbation: effects of preload and step input magnitude
Spine (Phila Pa 1976)
(2001) - et al.
The relationship between work history, work environment and low-back pain in men
Spine
(1984)
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