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Fig. 5 | Journal of NeuroEngineering and Rehabilitation

Fig. 5

From: Frequency-dependent force direction elucidates neural control of balance

Fig. 5

Effect of varying parameter values on the frequency-dependence of the intersection point. Each model parameter was varied with respect to the “best-fit” parameter set that closely resembled human subject data observed in [11] (\(\alpha = 10^6\), \(\beta = 0.3\), \(\sigma _r = 0.9\)). The height of the center of mass is indicated by a dashed line. The shaded region, based on human experiments, indicates the frequency band in which the mean of the intersection point height was not significantly different from the center of mass height in [11]. a The parameter \(\alpha\) determined the cost of the overall magnitude of the control effort relative to state deviation from equilibrium. When varying \(\alpha\), the other parameters were set to \(\beta = 0.3\) and \(\sigma _r = 0.9\). b The parameter \(\beta\) determined the relative cost of ankle and hip torque. When \(\beta > 1\), there was more penalty on ankle torque. When varying \(\beta\), the other parameters were set to \(\alpha = 10^6\) and \(\sigma _r = 0.9\). c The parameter \(\sigma _r\) determined the relative strength of noise in the ankle and the hip. When \(\sigma _r > 1\), ankle noise was greater than hip noise. When varying \(\sigma _r\), the other parameters were set to \(\alpha = 10^6\) and \(\beta = 0.3\). d The difference of the intersection point in the 1.2–2.6 Hz frequency range of the simulated data compared to the human subject data [11] with respect to \(\beta\). The parameter \(\sigma _r\) was kept at 0.9. e The difference of the intersection point in the 3–8 Hz frequency range of the simulated data compared to the human subject data [11] with respect to \(\sigma _r\). The parameter \(\beta\) was kept at 0.3. In both cases, the effect of varying \(\alpha\) is also shown. The error bars indicate the 95% confidence interval of the mean of difference when \(\alpha = 10^6\)

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