Effect of age on the variability and stability of gait: A cross-sectional treadmill study in healthy individuals between 20 and 69 years of age
Introduction
Falls during walking are a major health issue in older adults. Elderly individuals exhibit more conservative gait patterns characterized by slower preferred walking speeds (PWS) and reduced step lengths [1], which are indications of greater cautiousness [2]. Musculoskeletal weakness is strongly associated with falls [3]. The decline of cognitive function is correlated with fall risk [4] and is specifically associated with reduced walking speed [5].
Many different methods have been proposed to describe gait characteristics in the older population to determine the causes of falls. Besides basic spatiotemporal gait features that are modified in older, healthy adults compared to their younger counterparts [1], it is also important to assess the variability of the gait pattern, which is caused by the decreased ability to optimally control gait from one stride to the next [6]. In this context, the root mean square (RMS) of trunk acceleration is often used as a measure of gait variability [7]. Optimal dynamic balance results in smooth trunk acceleration during walking; therefore, a low RMS value is considered evidence of a healthy gait. Another popular method is the estimation of local dynamic stability (LDS), which is derived from chaos theory (maximal Lyapunov exponent [8]). This method takes the nonlinear features of human movement into account more effectively than classical variability estimates (RMS, standard deviation, coefficient of variation). It is assumed that motor control ensures a dynamically stable gait (high LDS) if the divergence remains low between trajectories in a reconstructed state space that reflects gait dynamics. The usefulness of gait LDS to assess gait stability and falling risk has been shown in theoretical [9], experimental [10], and clinical [11] studies [12].
Although the abovementioned parameters have already been proposed to characterize gait in elderly individuals [2], [13], [14], there is insufficient information regarding the changes in these parameters with age. Most studies have compared older adults to matched young controls. However, some aspects of cognitive capabilities decline as early as the second or third decades of life [15]. Similarly, significant strength loss in the lower extremities begins between ages 40 and 50 [16]. Because musculoskeletal and cognitive status are key factors in the etiology of falls in the elderly, gait features in middle-aged adults (40–60 years) demand further investigation [7]. In other words, it is unclear whether the idiosyncrasy of gait in elderly individuals is the result of musculoskeletal/neurological degenerative processes that occur with advanced age, or whether it is the result of a slower evolution throughout the life course.
The objective of the present cross-sectional study, therefore, was to document the effect of age on gait features in 100 healthy individuals aged 20–69. In addition to basic spatiotemporal measures (PWS, step length), gait variability (RMS) and gait stability (LDS) were analyzed while each participant walked on a treadmill. More generally, we sought to assess the extent to which the typical gait characteristics observed in older adults were already present in middle-aged individuals.
Section snippets
Subjects
The study included 100 healthy subjects (50 males, 50 females) without neurological or orthopedic conditions. There were 10 males and 10 females for each decade between the ages of 20 and 69. Their anthropometric features are presented in Table 1. All participants were accustomed to treadmill walking. A subset (95/100) of the subjects was analyzed in a parallel study about LDS reliability [17]. The study was approved by the regional medical ethics committee (Commission Cantonale Valaisanne
Results
When differences among age categories were considered (Table 1), no significant effects were observed in the anthropometric characteristics (body weight and height). Similarly, spatiotemporal parameters (PWS, WR) were equal among groups; that is, the variance explained by group membership was 0%. Given the 95% CIs, which were below 18%, it is very unlikely that a substantial age effect exists at the population level. The same conclusion can be drawn regarding gait variability (acceleration
Discussion
The rationale behind the design of the present study was that (1) there is a strong relationship between musculoskeletal/cognitive deficits and fall risk in older adults, (2) the decline in muscle strength and some aspects of cognitive performance has been reported in middle-aged adults, and (3) there is a lack of studies analyzing the gait of middle-aged individuals. Thus, using trunk accelerometry, we conducted a cross-sectional analysis of 100 individuals of various ages (Table 1) while they
Conclusion
The present study showed that the documented difference between young and elderly individuals [13], [14], [29] is likely the result of an accelerating increase in gait instability that begins earlier in life-possibly as early as the fourth decade (Fig. 2). In contrast, we did not observe significant changes with age in other parameters (speed, SL, and gait variability). Interestingly, a large-scale epidemiological study showed that the frequency of falls in middle-aged adults (46–65 years) was
Conflicts of interest statement
There are no known conflicts of interest.
Acknowledgments
The authors would like to thank Olivier Dériaz for his valuable support. The study was supported by the Swiss accident insurance company SUVA, which is an independent, non-profit company under public law, and by the clinique romande de réadaptation. IRR (Institute for Research in Rehabilitation) is supported by the State of Valais and the City of Sion. Study sponsors had no role in the collection, analysis and interpretation of data; in the writing of the manuscript; and in the decision to
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