skdh.gait_old.HarmonicRatioV

class skdh.gait_old.HarmonicRatioV

Symmetry measure of the 2 steps that occur during each stride. It attempts to capture this relationship by looking at the frequency components for steps and strides and creating a ratio using these values. Higher values indicate better symmetry between the steps occuring during an individual stride.

Methods

predict(fs, leg_length, gait, gait_aux)

Predict the gait event-level endpoint

Notes

The Harmonic ratio is computed from the first 20 harmonics extracted from a fourier series. For the vertical direction, the HR is defined as

\[HR = \frac{\sum_{n=1}^{10}F(2nf_{stride})}{\sum_{n=1}^{10}F((2n-1)f_{stride})}\]

where \(F\) is the power spectral density and \(f_{stride}\) is the stride frequency. Since this is computed on a per-stride basis, the stride frequency is estimated as the inverse of stride time for the individual stride.

References

[1]

J. L. Roche, K. A. Lowry, J. M. Vanswearingen, J. S. Brach, and M. S. Redfern, “Harmonic Ratios: A quantification of step to step symmetry,” J Biomech, vol. 46, no. 4, pp. 828–831, Feb. 2013, doi: 10.1016/j.jbiomech.2012.12.008.

[2]

C. Buckley et al., “Gait Asymmetry Post-Stroke: Determining Valid and Reliable Methods Using a Single Accelerometer Located on the Trunk,” Sensors, vol. 20, no. 1, Art. no. 1, Jan. 2020, doi: 10.3390/s20010037.