Frequency domain analysis of ground reaction force in preadolescents with and without Down syndrome

• We study frequency content of vertical GRF in children with and without DS.
• Children with DS have a similar fundamental frequency during treadmill walking.
• Children with DS have a lower frequency at 99% and 99.5% of total power.
• Walking faster with ankle load helps produce a more typical power spectrum in DS.

Children with Down syndrome (DS) display less stable and coordinated gait patterns in the time domain than their healthy peers. However, little is known about whether this group difference exists in the frequency domain. The purpose of this study was to investigate differences in vertical ground reaction force (GRF) in the frequency domain between preadolescents with and without DS. Twenty children at 7–10 years of age with and without DS participated in this study. Participants walked on an instrumented treadmill at two speeds with and without external ankle load. Vertical GRF was collected and the data was processed through a Fourier transform. Frequency content variables included fundamental frequency, power of the first five harmonics, and the frequency and number of harmonics at 95%, 99% and 99.5% of total power. Preadolescents with DS had a similar fundamental frequency as their healthy peers even though the DS group walked at slower speeds. The DS group displayed a different power spectrum of the first five harmonics and had the lower frequency and number of harmonics at 99% and 99.5% of total power. However, walking at a faster speed with external ankle load helped the DS group produce a power spectrum more similar to healthy children. Frequency content of vertical GRF provides additional assessment parameters in functional gait evaluation of children with DS. Treadmill intervention at a faster speed and with external ankle load appears to be clinically promising and needs further investigation.