Verbal Encouragement Provokes Significant Increases in Maximal Volitional Dynamic Postural Sway

Abstract

Limits of Stability protocols are typically target-oriented, leaving volitional aspects of control unobservable. A novel unconstrained protocol, volitional Limits of Stability (vLOS), shows high test-retest-reliability. We tested if verbal encouragement impacts this protocol. Forty healthy young adults (age 20.1 ± .9 years) performed three trials of vLoS with instructions that were agnostic to strategy or vigor, except trial three included verbal encouragement. Total sway area was used to metric the maximum volitional dynamic sway during each 1-min trial. One-way, repeated-measures ANOVA revealed significant differences (F_(2,117) = 41.56, p < 0.0001, ${\mathrm{\eta }}_p^2$ = 0.52) due to encouragement. Specifically, follow-up paired t-tests showed no difference in sway area between the first two trials (p = 0.61), while trial three was much larger than trials one and two (p < 0.0001). Significant, large increases in sway area with verbal encouragement indicate that top-down mechanisms should be considered in theories of postural control. As well, clinical utilization of novel vLOS should be careful with word selection and delivery of protocol instructions.

HIGHLIGHTS

• Limits of Stability balance tests typically include a goal directed instruction and metrics.

• Dynamic postural sway should be tested in a task affording participant volitional control.

• A novel volitional Limits of Stability protocol has been developed.

• Maximal dynamic postural sway responds to motivating instructions.

• Psychological factors of postural sway control deserve further investigation.

Keywords:

• Limits of stability
• posturography
• balance
• encouragement
• motivation

AUTHORS’ CONTRIBUTIONS

JH conceived and designed the experiment, analyzed the data, prepared figures and/or tables, and wrote the first draft of the manuscript. TL wrote sections of the manuscript, prepared figures and/or tables, and reviewed drafts of the paper. ED took part in designing the study, performed the experiments, and reviewed drafts of the paper. BD took part in designing the study, performed the experiments, and reviewed drafts of the paper. BK took part in designing the study, performed the experiments, and reviewed drafts of the paper. DG took part in designing the study, analyzed the data, prepared figures and/or tables, and reviewed drafts of the paper. All authors have read and approved the final version of the manuscript, and agree with the order of presentation of the authors.

DISCLOSURE STATEMENT

DJG is eligible for royalties from a patent (OMB 0651-0032) related to the technology used in this study. In addition, he has an equity stake (stock options) in Balance Tracking Systems, Inc. This financial conflict of interest is mitigated by a management plan put in place by his academic institution to ensure the integrity of his research. The authors report no other conflicts of interest in this work.

DATA AVAILABILITY STATEMENT

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Additional information

Funding

The authors have no funding sources to declare that are relevant to the content of this article.