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Session: Neuromuscular – lower extremities 1
Session starts: Friday 25 January, 10:30
Presentation starts: 10:30
Room: Lecture room 536

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Ingrid Schut (TU Delft)
Jantsje Pasma (TU Delft)
Alfred Schouten (TU Delft)
Herman van der Kooij (TU Delft)

Abstract:
Human balance is a complex interplay of several underlying mechanisms. To unravel these underlying mechanisms system identification techniques are applied in combination with dedicated perturbations, like support surface translations. However, it remains unclear what the minimal recording time and the optimal perturbation amplitude are. In this study we investigated the effect of these settings on the identification of the neuromuscular controller (NMC). 12 healthy subjects were asked to stand as normal as possible on a treadmill while small continuous belt translations were applied in the form of a periodic multisine signal. The perturbation amplitude varied over seven conditions, where 6 segments of the multisine signal were applied for each amplitude, resulting in a trial lengths of 120 sec. For one of the amplitudes 24 segments were applied. The frequency response functions (FRF) of the NMC as well as the nonlinear distortions were estimated based on the recorded external perturbation torque, body sway and ankle torque. For low amplitudes the FRF could not reliably be estimated due to a low signal-to-noise ratio (SNR). For high amplitudes the relative contribution of the non-linear contributions increased. Increasing the number of repetitions resulted in a lower variability of the FRF. The perturbation amplitude of the support surface translations must be high enough to evoke a sufficient reaction of the human body and also low enough to allow for the use of linear system identification techniques. The number of repetitions of the perturbation signal must be high enough to reduce the amount of noise in the estimation of the NMC. The results of this study showed the optimal range of perturbation amplitudes is around 10 cm (peak-to-peak) and at least 6 repetitions long.