Elsevier

Gait & Posture

Volume 85, March 2021, Pages 251-257
Gait & Posture

Lower-limb coordination and variability during gait: The effects of age and walking surface

https://doi.org/10.1016/j.gaitpost.2021.02.009Get rights and content

Highlights

  • Walking data on flat and uneven walkways were collected in older and young adults.

  • Coordination and variability were studied in the Knee-Hip and Ankle-Knee joint pairs.

  • Older adults were more coordinated during early stance on uneven surfaces.

  • Older adults were more variable during mid-swing on uneven surfaces.

  • Uneven walkways may have prompted a more cautious gait strategy in older adults.

Abstract

Background

Falls among community-dwelling older adults are often triggered by uneven walkways. Joint coordination and its variability change with age and may place older adults at risk of falling. It is unclear how irregular surfaces impact lower-limb joint coordination and if such changes are exacerbated by aging.

Research question

To what extent do lower-limb inter-joint coordination and its variability, over flat and uneven brick walkways, differ between older and young healthy adults?

Methods

A motion-capture system collected kinematic data from walking trials on flat and uneven walkways in seventeen older (72.0 ± 4.2 years) and eighteen younger (27.0 ± 4.7 years) healthy adults. Continuous relative phase analyses were performed for the Knee-Hip and Ankle-Knee joint pairs. Mean Absolute Relative Phase (MARP) quantified coordination amplitude. Deviation Phase (DP) quantified coordinative variability. Two-way mixed ANOVA’s tested for effects of age, surface, and age × surface interactions.

Results

Uneven surfaces prompted more in-phase MARP inter-joint coordination in adults during most gait phases (p ≤ 0.024). Age × surface interactions were observed during initial contact (Ankle-Knee: p = 0.021, Knee-Hip: p = 0.001) and loading response (Knee-Hip: p = 0.017), with post-hoc analyses showing coordination accentuated in older adults. Uneven surfaces induced higher DP in Knee-Hip (p = 0.017) and Ankle-Knee joint coupling (p < 0.001) during gait, largely independent of age. An age × surface interaction was observed during mid-swing (p = 0.050), with post-hoc analysis revealing increased variability in older adults.

Significance

More in-phase and variable lower-limb gait behavior was observed on uneven walkways. These differences were accentuated in older adults during early stance phase (more tightly coordinated) and mid-swing (more variable). This may reflect a cautious gait strategy on challenging walkways to maintain stability and help prevent falls.

Introduction

Falls among older adults are a major public health concern across many countries. In the United States, between 30 and 60 % of persons aged 65 and older experience a fall each year [1]. These events are linked to negative health outcomes [2] and are leading causes of traumatic brain injury and hip fractures in this population [3,4]. Among community-dwelling older adults, falls typically occur while walking and are often triggered by environmental factors [1]. Of these, uneven walkways are especially problematic in the outdoor built environment [5].

Biomechanical gait analysis can identify impairments during walking and help elucidate factors that contribute to falls. Specifically, patterns of inter-joint coordination (i.e. relationships between joints during motion) and its variability provide insight into neuromuscular control during functional movement [6,7]. For instance, a lack of coordinative variability during gait reflects an overly rigid motor system, while excessive variability is suggestive of unstable neuromuscular control [8]. Both behaviors point to a less adaptable motor system and may place an individual at risk of falls due to a lack of robust “movement options” when navigating a complex environment [9]. Similar to other gait metrics, patterns of lower limb inter-joint coordination and coordinative variability in the sagittal plane change with healthy aging [10,11], and these changes may have implications for falls in the elderly. For instance, Chiu et al. reported greater Ankle-Knee coordinative variability during stance phase in older, fall-prone adults, and correlated their findings to clinical measures indicating poor balance [9]. Hafer and Boyer observed more in-phase foot-shank coordination during mid-stance in older, compared to young, adults; findings which may reflect an age-specific attempt to maintain stability during single-leg loading [10]. These studies, however, were conducted on flat surfaces and extrapolating these findings to adults walking on uneven walkways is difficult.

The impact of walking surfaces on joint coordination are not well researched. This has been studied from the standpoint of comparing treadmill versus ground walking [12], or examining the impact of obstacle crossing on gait [13]; however, these situations may not reflect the real-life walking environment of community-dwelling adults. Marigold et al. studied gait variability on multi-surface terrain from the perspective of step parameters, reporting greater step-length and step-width variability, independent of age [14]. In contrast, others have shown age-specific adaptations on irregular surfaces, reporting greater step-width and step timing variability in older, compared to younger, adults [15,16]. While measures of step parameter variability are useful metrics, they may not reflect patterns of joint/segment coordinative variability in the lower extremity. The study of coordination and its variability will extend this literature base by providing insight into motor control during gait.

Irregular walking surfaces represent a challenge to the neuromuscular system and can increase sensitivity in identifying age-related changes during gait [17,18]. It is unclear if irregular surfaces similarly impact lower-limb coordination and variability, and if such changes are greater in older adults. Better understanding of changes in lower-limb motor control strategies during gait could have implication for falls and future fall prevention strategies. Therefore, the aims of this study were to (1) compare patterns of lower-limb inter-joint coordination and coordinative variability over flat and uneven brick walkways, and (2) assess differences between older and young healthy adults for these two surfaces. We hypothesized that (1) inter-joint coordination and variability will differ between walking surfaces, and (2) these differences will be exacerbated in older adults.

Section snippets

Participants

Forty-six older (65+ years) and younger (18–35 years) community-dwelling adults were recruited from the Hopkinton, MA area and provided informed consent prior to participating in this study. Twelve participants were excluded based on screening for neurological impairments, musculoskeletal abnormalities (e.g. joint replacement), diabetes, elevated body mass indexes (>30), and poor balance ability. Full screening procedures are described elsewhere [18]. Data from seventeen older (12 females,

Results

A post-hoc mixed ANOVA showed no main effect of age (p = 0.090) nor walking surface (p = 0.293) on mean self-selected gait speed.

Summary

This study investigated differences in lower-limb joint coordination amplitude (MARP) and variability (DP), during gait on flat and uneven walking surfaces, in young and older healthy adults. The uneven walkway prompted more in-phase Ankle-Knee coupling (i.e. more tightly coordinated) in all adults during key aspects of stance and swing phases (Fig. 3), with this response being greater in older adults during initial contact (Fig. 2). For Knee-Hip coupling, a more in-phase walking strategy on an

Conclusion

In conclusion, an uneven walking surface prompted more tightly coordinated and more variable patterns of Ankle-Knee and Knee-Hip coupling during walking in healthy adults. These changes were accentuated in older adults during early stance (i.e. more in-phase) and mid-swing phases (i.e. more variable). This response may reflect a cautious gait pattern, or a functional strategy to help mitigate the risk of falls in older adults.

Code and data associated with this investigation are available at: //github.com/PhilD001/crp_irregular_surfaces

Declaration of Competing Interest

The authors report no declarations of interest.

Acknowledgements

Patrick Ippersiel is supported by an Institut de Recherche Robert-Sauvé en Santé et en Sécurité du Travail (IRSST) doctoral scholarship and an OPPQ-REPAR project grant for clinical research (programme 4.2.1). The funding sources had no involvement in this study or preparation of this manuscript.

References (34)

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    Indeed, gait adaptations (e.g., in-phase coupling) during challenging gait cycle phases may be greater to maintain a stable walking posture and reduce the potential risk of falling due to loss of dynamic balance (Harbourne and Stergiou, 2009). Similar results have been observed in elderly people, where greater KH in-phase coupling during initial contact and loading response reported in comparison to younger adults (Ippersiel et al., 2021). From a neurophysiological perspective, the KH in-phase coordination may be explained by the reduced selective motor control of children with CP (i.e., the impaired ability to isolate muscles activation following voluntary demands of movement (Sanger et al., 2006)).

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