Effects of cervical muscle fatigue on the perception of the subjective vertical and horizontal

Guy Gosselin,Michael J Fagan

doi:10.1186/2193-1801-3-78

Abstract

IntroductionCervical functional capacity outcome measures that are simple and reliable are urgently needed in order permit accurate assessment/reassessment during treatments and rehabilitation. Induced neck muscle fatigue has been shown to alter functional capacities such as balance and kinaesthetic sense in the standing posture. The Rod and Frame Test has also shown promise as a method of assessing the effects of chronic neck pain and injury, but currently only in the sitting position. The objectives of this project were therefore 1) to validate the computerised rod and frame test in the standing posture, and 2) to measure the effects that different cervical muscle fatigue protocol would have on the assessment of the subjective visual vertical and horizontal.MethodThe validation of the standing computerised rod and frame test in the standing posture was obtained by comparing results (n = 74) between the sitting and standing positions with the Spearman’s correlation coefficient. In addition, agreement between the two methods was analysed with the Bland-Altman method.Participants (n = 56) resisted with their neck muscles approximately 35% maximum isometric voluntary contraction force for 15 minutes on a purpose built apparatus in eight different directions. Wilcoxon signed rank tests analysed changes in horizontal and vertical rod and frame test between the neutral and all different directions of contraction. The changes of recorded unsigned vertical and horizontal errors for the combined frame condition in all situations of isometric contraction were analysed with two respective one-way repeated measures analysis of variance (ANOVA).DiscussionThe Spearman’s rho and Bland-Altman plots show that the Rod and Frame Test works equally well in sitting and standing positions.After muscle contraction, there were significant increases in error in all participants for both horizontal and vertical rod and frame tests, except after flexion. These errors were predominantly present after fatigue of muscles in the coronal plane of contraction. Proprioception alone cannot explain the difference in the rod and frame results between different muscle groups. It is suggested that an evolutionary advantage of developing improved subjective verticality awareness in the same direction as the main visual field could explain these findings.

Highlights

Cervical functional capacity outcome measures that are simple and reliable are urgently needed in order permit accurate assessment/reassessment during treatments and rehabilitation
The Rod and Frame Test (RFT) or tests measuring the perception of the subjective visual vertical (SVV) and subjective visual horizontal (SVH) have been used to study the functional effects of either neck pain or whiplash (Bagust et al, 2005; Grod and Diakow, 2002; Docherty et al, 2012)
The RFT is a measure of perceptual style, and advances in technology have permitted the development of a modern version of the classic sitting rod and frame test by using a computer and video goggles described as the Computerised Road and Frame Test (C-RFT) (Bagust, 2005)

Summary

Introduction

Cervical functional capacity outcome measures that are simple and reliable are urgently needed in order permit accurate assessment/reassessment during treatments and rehabilitation. The Rod and Frame Test has shown promise as a method of assessing the effects of chronic neck pain and injury, but currently only in the sitting position The objectives of this project were 1) to validate the computerised rod and frame test in the standing posture, and 2) to measure the effects that different cervical muscle fatigue protocol would have on the assessment of the subjective visual vertical and horizontal. There is a growing body of evidence indicating that after neck injury some parameters associated with cervical functional capacities, such as altered eye movement control, kinaesthetic sensibility, or other problems associated with distorted postural control, the change in altered balance or increased errors in the perception of the visual vertical and horizontal, may not return to the pre-injury state (Roijezon et al, 2010; Yu et al, 2011; Treleaven, 2008) In such situations, few clinicians have access to the sophisticated equipment necessary to accurately assess the neck’s functional capacity. Docherty and Bagust improved the C-RFT with the use of two dots instead of a rod-line (C-RFTdot) thereby decreasing the visual cues due to screen pixilation seen on the rod during the C-RFT (Docherty and Bagust, 2010)

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