Sensory contributions to stabilization of trunk posture in the sagittal plane

Abstract

Trunk stabilization is required to control posture and movement during daily activities. Various sensory modalities, such as muscle spindles, Golgi tendon organs and the vestibular system, might contribute to trunk stabilization and our aim was to assess the contribution of these modalities to trunk stabilization. In 35 healthy subjects, upper-body sway was evoked by continuous unpredictable, force-controlled perturbations to the trunk in the anterior direction. Subjects were instructed to either 'maximally resist the perturbation' or to 'relax but remain upright' with eyes closed. Frequency response functions (FRFs) of admittance, the amount of movement per unit of force applied, and reflexes, the modulation of trunk extensor activity per unit of trunk displacement, were obtained. To these FRFs, we fitted physiological models, to estimate intrinsic trunk stiffness and damping, as well as feedback gains and delays. The different model versions were compared to assess which feedback loops contribute to trunk stabilization. Intrinsic stiffness and damping and muscle spindle (short-delay) feedback alone were sufficient to accurately describe trunk stabilization, but only with unrealistically low reflex delays. Addition of muscle spindle acceleration feedback or inhibitory Golgi tendon organ feedback yielded realistic delays and improved the model fit, with a significantly better model fit with acceleration feedback. Addition of vestibular feedback did not improve the model fit. In conclusion, muscle spindle feedback and intrinsic mechanical properties are sufficient to describe trunk stabilization in the sagittal plane under small mechanical perturbations, provided that muscle spindles encode acceleration in addition to velocity and position information.

Neck postural stabilization, motion comfort, and impact simulation

“…19.12) as well as the EMG up to 4 Hz (van Drunen, Maaswinkel, van der Helm, van Dieën, & Happee, 2014). Using a larger data set, it was found that including muscle acceleration feedback enhanced the fit, in particular, for the EMG (van Dieën, van Drunen, & Happee, 2017).…”

“…Thorax pushing machine to test lumbar stabilizaƟon with the pelvis clamped (van Dieën, van Drunen, & Happee, 2017; 6DOF moƟon plaƞorm tests of lumbar and neck stabilizaƟon with the pelvis clamped (van Drunen, Koumans, van der Helm, van Dieën, & Happee, 2015; 6DOF moƟon plaƞorm tests of neck stabilizaƟon with rigid seat and 5 point harness belt, and with cushioned lateral arm support in case of lateral loading (Forbes, 2014;Forbes, de Bruijn, Schouten, van der Helm, & Happee, 2013) Linear de Jager, 1996;van der Horst, 2002) was adopted. The model was extended with postural control (Fig.…”

Identification of intrinsic and reflexive contributions to trunk stabilization in patients with low back pain: a case–control study

“…A linear neuromuscular control model was constructed to translate the FRFs into physiological elements representing intrinsic and reflexive contributions [8,10]. Model parameters were estimated by optimizing the fit of the model transfer functions to the transfer functions estimated as described above, using simulated annealing.…”

“…For more detailed information on the perturbation characteristics, data recording, data processing, system identification and parametric identification, see van Drunen et al [8] and van Dieën et al [10].…”

“…We have recently developed a method to assess intrinsic and reflexive contributions to trunk stabilization, which aims to circumvent the limitations described above [8][9][10]. The method was shown to have good reliability in healthy subjects and LBP patients [9].…”