Proceedings of The Physiological Society

University of Manchester (2010) Proc Physiol Soc 19, PC228

Poster Communications

Static postural after-effect of stepping on a rotating treadmill

C. J. Osler1, R. F. Reynolds1

1. School of Sport and Exercise Sciences, University of Birmingham, Birmingham, United Kingdom.

  • A) Experimental protocol; subjects demonstrated a change in yaw relative to feet following stepping in place on a rotating turntable. B) Mean (

The adaptive nature of the somatic sensorimotor system has been shown in the control of locomotion using a circular treadmill (Gordon et al., 1995). Following a period of stepping in place on a rotating surface, subjects turn in circles when asked to step in place on a stationary surface with eyes closed (Weber et al., 1998). It is likely a remodelling of the relationship between the trunk and feet occurs, primarily mediated by somatic information. It has been suggested that the effects on dynamic locomotion may partly be caused by a reorganisation of static posture, namely, head and trunk rotation over the feet (Hollands et al., 2007). Here, we further investigated this postural after-effect; our aim was to ascertain its magnitude and at what level of the body it occurs. The adaptation protocol consisted of stepping in the centre of a turntable rotating at 60°/sec. Participants (n=6) were required to step at a cadence of 100steps/min for 20min. Equal numbers of subjects experienced clockwise and anti-clockwise rotations. Yaw of the head and trunk relative to the feet were measured over a 60sec period pre- and post- adaptation. Subjects were instructed to stand facing their perceived straight ahead, with feet together and eyes closed. The results show subjects demonstrated a significant change in the magnitude of actual head yaw (ΔHY) and trunk yaw (ΔTY) post-adaptation (mean ± SD: ΔHY 19.7 ± 7.6°, ΔTY 14.1± 5.3°; one-sample t-tests: both p=0.001). There was no significant difference in the magnitude of the after-effect between clockwise and anti-clockwise rotations (independent-samples t-tests: ΔHY p=0.853, ΔTY p=0.742). This confirms static posture is altered as a result of stepping on the rotating turntable. When studying the level at which the post-adaptation yaw occurs, results show that ΔTY accounted for 71.5% of ΔHY. This suggests the majority of the adaptation takes place below the level of the trunk. This most likely occurs at the hips, due to a remodelled relationship between the upper body and the feet. It also appears to result in an altered perception of “straight-ahead”. This after-effect in static posture could be used to investigate how an altered head-on-feet orientation is integrated with other sensory channels for the control of posture.

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