A preliminary study of the measurement of overload applied to the foot support of a wheelchair and a seated postural support device

[Purpose] The mechanical strength of wheelchair and seating products is specified by standards to ensure user safety. However, some individual users are affected by severe spasticity resulting from cerebral palsy that occasionally breaks such devices. Until recently, reports of quantitative measurement of these mechanical overloads have been scarce, and the exact loads applied have been unknown. This study aimed to conduct a sampling survey prior to conducting a future full-scale study. [Subjects and Methods] Using two force plates, we measured the load on the foot support applied by three participants with cerebral palsy. The applied load was measured at a 100 Hz sampling rate, and maximum load and vertical/horizontal component forces were analyzed. [Results] The maximum load applied by participants was approximately 1.34 times their body weight. The vertical force applied on the foot support accounted for 70-80% of the total load. The horizontal force also reached about 35% at its maximum. [Conclusion] Because the horizontal load also reached 1/3 of the total load, it will be advantageous to use a three-axis force plate to measure forces in a future study with more participants.