Thomas Knellwolf – Abstract

P29      Changes in centre of pressure are encoded by muscle spindles supplying intrinsic muscle of the foot in freely standing humans

Knellwolf TP[1], Burton A[1, 2] and Macefield VG[1, 2, 3]

  1. School of Medicine, Western Sydney University, Sydney, Australia
  2. Neuroscience Research Australia, Sydney, Australia
  3. Baker Heart & Diabetes Institute, Melbourne, Australia

Muscle spindles are exquisitely sensitive length receptors located in virtually all skeletal muscles. The proprioceptive feedback they provide is important for fine motor movement, balance and locomotion (1). Presumably, the spindles of the intrinsic foot muscles would behave differently under the stress of an unstable body weight. Initially, recordings from 26 single-unit muscle spindles were obtained using the posterior tibial nerve microneurography technique (2) in seated subjects, characterizing the supplied muscle, discharge frequency and variability. With a separate group, 10 spindle recordings were obtained in an unsupported free standing position. Subjects were asked to unload and load their foot and balance with mild postural perturbations with their eyes closed.  There was a notable increase of spontaneously firing units in the free standing position (50%) compared to the seated population (27%). Interestingly, 6 of the free standing units (2 spontaneous, 4 non-spontaneous) were highly modulated by changes in centre of pressure. This was dependent on the supplied muscle and the direction of motion. Given the indication from these results that muscles spindles provide the body with information about conformations of the foot during natural body sway, it seems logical to presume that disturbances in their signaling may lead to disturbances in the control of upright stance.

  1. Macefield VG, Knellwolf TP (2018) Functional Properties of Human Muscle Spindles. J Neurophysiol
  2. Knellwolf TP, Burton A, Hammam E, Macefield VG (2018) Microneurography from the Posterior Tibial Nerve: A Novel Method of Recording Activity from the Foot in Freely Standing Humans. J Neurophysiol