Limit cycle oscillations in standing human posture

Abstract

Limit cycle oscillations (LCOs) are a hallmark of dynamic instability in time-delayed and nonlinear systems such as climate change models, biological oscillators, and robotics. Here we study the links between the human neuromuscular system and LCOs in standing posture. First, we demonstrate through a simple mathematical model that the observation of LCOs in posture is indicative of excessive neuromuscular time-delay. To test this hypothesis we study LCOs in the postural sway of individuals with multiple sclerosis and concussed athletes representing two different populations with chronically and acutely increased neuromuscular time-delays. Using a wavelet analysis method we demonstrate that 67% of individuals with multiple sclerosis and 44% of individuals with concussion exhibit intermittent LCOs; 8% of MS-controls, 0% of older adults, and 0% of concussion-controls displayed LCOs. Thus, LCOs are not only key to understanding postural instability but also may have important applications for the detection of neuromuscular deficiencies.

Clinical Facts Along With a Feedback Control Perspective Suggest That Increased Response Time Might Be the Cause of Parkinsonian Rest Tremor

“…Recently, arguments based on a control-system analogy were used to support the hypothesis that Parkinsonian tremor may indeed be a limit cycle oscillation [1], and established a direct logical connection between increased response time and limit-cycle behaviour of Parkinsonian tremor. Since then, similar connections between increased time delays and limit cycle oscillations in human biomechanics (although not necessarily in the context of Parkinson's disease) have also been drawn [17,18,19]. In this paper, we exploit this link between increased time delays (observed as an increase in response times) and Parkinsonian tremors to address two specific objectives (see Fig.…”

Comparison of Pixel-based Position Input and Direct Acceleration Input for Virtual Stick Balancing Tests

“…The nature and the characteristics of this feedback process is still a subject of debates. Investigation of different human balancing tasks, such as simple quiet standing [1][2][3][4][5] standing on pinned or rolling balance boards [6,7], stick balancing on the fingertip or on a Ping-Pong racket [8][9][10][11], may help in identifying and in understanding the underlying control mechanism. Experimental investigation of these balancing tasks requires motion capture system, e.g., IMU sensors fixed on the balanced object or a camera system, which records the spatial position of markers fixed on the balanced object.…”

Mathematical models for balancing tasks on a see-saw with reaction time delay

“…Many human activities can be associated with a similar feedback mechanism, one might think of simple quiet standing, gait or running where the feedback delay is the reaction time. Human balancing tasks, such as stick balancing on a fingertip or on a pingpong racket Cabrera and Milton (2002); Mehta and Schaal (2002); Milton et al (2016); Yoshikawa et al (2016), quiet standing Maurer and Peterka (2005); Suzuki et al (2012); Hwang et al (2016), standing on pinned or rolling balance boards Chagdes et al (2016); Molnar et al (2017), are therefore often analyzed via simplified mechanical and mathematical models.…”