Sensitivity of trunk variability and stability measures to balance impairments induced by galvanic vestibular stimulation during gait

Abstract

For targeted prevention of falls, it is necessary to identify individuals with balance impairments. To test the sensitivity of measures of variability, local stability and orbital stability of trunk kinematics to balance impairments during gait, we used galvanic vestibular stimulation (GVS) to impair balance in 12 young adults while walking on a treadmill at different speeds. Inertial sensors were used to measure trunk accelerations, from which variability in the medio-lateral direction and local and orbital stability were calculated. The short-term Lyapunov exponent and variability reflected the destabilizing effect of GVS, while the long-term Lyapunov exponent and Floquet multipliers suggested increased stability. Therefore, we concluded that only short-term Lyapunov exponents and variability can be used to asses stability of gait. In addition, to investigate the feasibility of using these measures in screening for fall risk, the presence or absence of GVS was predicted with variability and the short-term Lyapunov exponent. Predictions were good at all walking speeds, but best at preferred walking speed, with a correct classification in 83.3% of the cases.

Assessing the stability of human locomotion: a review of current measures

“…In a more recent study, Chang et al [95] reported that walking over an unstable support surface increases values of l S , but not of l L . Similarly, Sloot et al [39] and Van Schooten et al [34] reported that destabilizing subjects by means of galvanic vestibular stimulation led to increased values of l S , but not of l L . Finally, McAndrew et al [75] reported that gait destabilization by means of support surface perturbations or visual scene perturbations was reflected in l S , but probably not in l L .…”

“…The great advantage of this measure is that it may be calculated from any source of kinematic data, regardless of the reference frame in which the data are recorded [59,69]. This allows for using small and cheap (wireless) inertial sensors [34,39,76].…”

Kinematic measures for assessing gait stability in elderly individuals: a systematic review

“…In contrast, however, Hobbelen & Wisse [112] suggested that FMs might have severe disadvantages as a measure for fall avoidance in bipedal robots. Furthermore, evidence from both modelling [113,114] and experimental human studies [108,115] suggest that FMmax might not necessarily be related to fall risk. The use of FMmax in the assessment of fall risk, therefore, remains controversial.…”

Toward ambulatory balance assessment: Estimating variability and stability from short bouts of gait

“…In addition, the number of embedding dimensions used in this study, i.e. nine, was higher than in many other studies [8,12,16,20] but is still within the range of five to twelve used in the literature [8,10,[12][13][14]16,18,20,24,30]. This broad range of embedding dimensions might be due to the use of different types of data, such as electromyography, joint angles, angular velocity or linear accelerations, and the embedding of one single signal or more; and might call for standardization of state space reconstruction in gait research.…”