Lower-limb coordination and variability during gait: The effects of age and walking surface
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.
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2022, Clinical BiomechanicsCitation Excerpt :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)).
The impact of outdoor walking surfaces on lower-limb coordination and variability during gait in healthy adults
2022, Gait and PostureCitation Excerpt :In gait research, changes in lower-limb coordination and variability have been studied from the perspective of gait speed [9], asymmetrical leg loading [10], obstacle crossing [11], and to a lesser extent, walking surfaces [12]. The latter are of particular interest because they replicate the challenges of navigating real-world walking environments and can increase sensitivity in identifying age-related gait changes [12,13]. Recent work observed more in-phase and variable Knee-Hip coordination on irregular, compared to flat, surfaces, with changes in coordination being accentuated in older adults during early stance phase [12].