Journal
JOURNAL OF BIOMECHANICS
Volume 42, Issue 2, Pages 125-130Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.jbiomech.2008.10.012
Keywords
Backpack; Stiffness; Energetics; Walking; Linear model
Categories
Funding
- Decathlon Research and Development Department
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The objectives of the experiment were (i) to characterize the mechanical properties of backpacks and (ii) to study the influence of a flexible backpack on the energetics and kinematics of walking. Twelve subjects walked at different speeds on a treadmill with each of two backpacks loaded with 25% bodyweight, with either a rigid or a flexible link between the body attachment and the suspended loads. A single degree of freedom linear model of the link between the pack and the trunk was used to calculate the stiffness and damping coefficient of the two backpacks. The oxygen consumption (VO2) and the vertical acceleration of both the backpack and trunk were measured. The vertical excursion of the pack given by the model was significantly correlated with that actually measured (R = 0.87, p < 0.001). At 3.7 and 4.5km h(-1) the flexible pack induced lower acceleration peaks (respectively - 22% and -8%: p < 0.05) and tended to reduce VO2 (p = 0.055 at 4.5 km h (1)) compared with the rigid one. At 5.2 and 6 km h (1) both the accelerative forces and VO2 increased with the flexible pack (p < 0.05) mainly because of the high vertical movement of the pack. It was concluded that a simple model can be used to predict the vertical excursion of the pack and that a flexible backpack can provide energetic benefits when its oscillations are nearly in phase with those of the trunk. However, any resonance effect can lead to a modified walking pattern and an increased metabolic cost. (C) 2008 Elsevier Ltd. All rights reserved.
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