Full length articlePulling a school trolley: A good kinematic option for children☆
Introduction
Children often use school trolleys daily as an alternative option to the traditional backpack. Although the average weight of a school trolley is greater than that of a backpack (approximately 30% or 2.4 kg more) [1], [2], the use of school trolleys allows children to avoid supporting the load on their backs and also provides an easier mode of transportation. Previous reports suggest that between 14.5 and 48.9% of children use trolleys [3], [4], [5], with the frequency of use varying by country.
On the other hand, previous studies considered the use of school trolleys to be an asymmetrical effort, and trolley use among children was related to a higher risk for scoliosis [6] and forced postures of the shoulder and spine [3]. A previous study analyzed the negative effects of pulling a trolley with a 20% of body weight (BW) load when encountering staircases and affirmed that subjects must support a peak force of nearly twice the mass of the carried load. However, the authors did not specify the possible negative effects of these forces on the musculoskeletal system of the child [7].
A single previous study analyzed the spatiotemporal gait parameters of pulling a trolley with loads of different weights and concluded that the use of a trolley produced gait changes independently of the amount of load transported (range 10–20% BW) [8]. Schmidt and Docherty [9] compared the kinematics of the trunk between two groups: one group carried a backpack, and the other group pulled a trolley. In both groups, the load to transport was approximately 11% BW. The conclusion of this study was that it is more important to adhere to an appropriate weight when carrying a backpack than to use trolleys. However, the instrument used in this study was not validated in children, and the authors did not specify the proportion of students that used the school trolley in their daily lives.
There is a need to investigate the impact of trolley use and trolley mass on walking kinematics, given the high frequency of trolley use among school-aged children and also considering that no previous studies provided an analysis of gait and posture while pulling a school trolley. Therefore, the aim of this study was to analyze the kinematics of gait while pulling a school trolley with different loads in elementary school participants.
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Participants
Fifty-three participants (25 boys and 28 girls) from an elementary school (aged 10.01 ± 1.69 years) participated in this study. The average body mass was 40.05 ± 11.09 kg, and the average height was 1.46 ± 0.09 m. All of the participants were volunteers, and their parents completed an informed consent form. The Ethics Committee of the University approved this study. The participants were healthy and did not report any history of orthopedic trauma or neurological problems. Fifty percent of the evaluated
Spatiotemporal gait parameters
Our results show that pulling the trolley with a load of 20% BW induced significant decreases in velocity (p < 0.05), stride length (p = 0.001) and single support phase (p < 0.05) and an increase of the double support phase (p = 0.001) in comparison to walking WT. No significant changes in cadence, step width or stance phase (Table 1) were obtained in any of the load conditions analyzed.
Effect of trolley weight by type of packing device user
There were non-significant interactions between trolley users and non-users (Table 2).
Trolley weight
When analyzing kinematic
Discussion
This study set out to determine the influence of pulling a school trolley on the kinematic gait parameters of children using loads that children typically transport to school: 10%, 15% and 20% BW.
Pulling the trolley with a 20% BW load produced significant changes in the investigated spatiotemporal parameters (except cadence, stance phase and step width). In spite of the significant differences obtained for some of the spatiotemporal gait parameters while pulling the trolley with a 20% BW load,
Conclusion
In conclusion, this kinematic gait analysis of children pulling a school trolley with different loads showed that the investigated spatiotemporal gait parameters were only affected by the use of the trolley with a 20% BW load. In addition, pulling a trolley only influenced the sagittal plane of the thorax and pelvis. The daily use of a backpack or a trolley did not affect the kinematic analysis. Although some of the analyzed kinematic parameters were influenced asymmetrically by the use of a
Conflict of interest statement
The authors of the present manuscript don’t have any financial and personal relationships with other people or organizations that could inappropriately influence their work or final version of the manuscript.
Acknowledgments
The authors thank all of the participants: children and parents that took part in this study. The work of Orantes-González, E was supported by the Ministry of Education, Culture and Sports of Spain (ref. FPU13/00162, EST15/00019).
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This paper is an extended manuscript of a previous pilot study published as an abstract (http://dx.doi.org/http://dx.doi.org/10.1016/j.gaitpost.2016.07.255).