Gait initiation: The first four steps in adults aged 20–25 years, 65–79 years, and 80–91 years
Introduction
Mobility is an important factor in maintaining independence and quality of life in older adults [1], [2]. Age-related loss of mobility is due to many factors including progressive sensory, neural, and motor declines. The ultimate outcome of these declines is an increased rate of falls: one in three adults over the age of 65 falls each year [3], [4], and this number doubles after age 80 [5]. A standard paradigm to establish age-related mobility changes is the comparison of younger and older individuals. However, when all older adults over the age of 65 are placed into a single experimental group, age-related changes in mobility that occur throughout older adulthood are not captured. Given the steep increase in falls after age 80 and the heterogeneity of the aging population, it is important to document the impact of advancing age on mobility.
Examination of multiple older age groups has demonstrated the detrimental impact of advancing age. When avoiding an unexpected obstacle, advancing age was a significant predictor of success rates and reaction times [6], consistent with the observation that more falls are observed in the oldest adults [5]. The examination of advancing age should be extended to other tasks that occur in daily life and are related to falls. For example, falls occur most often during activities of ‘ambulation’, including walking, turning, and standing [7], [8] or while walking, carrying objects, or reaching/leaning [9]. In addition, the majority of falls occur in the home for older adults [9], and the number of falls in the home increases with age [7]. Typical ambulation tasks in the home, such as setting the table or answering the phone, require just a few steps due to room size constraints. The transition from standing to walking may be especially challenging, as the body must be accelerated forward from a stationary posture, while simultaneously maintaining equilibrium with a smaller base of support due to the shorter steps [10]. The ability of the first few steps to characterize adults with compromised balance is demonstrated by the observations that elderly fallers had a smaller step length (SL) and higher SL variability than elderly non-fallers [11]. Further, populations with higher fall risk, including persons with Alzheimer's disease and Parkinson's disease, exhibit higher spatiotemporal variability during gait initiation [12], [13]. Therefore, the transition from standing to steady state gait is an ideal paradigm to examine the impact of advancing age on mobility. Existing research has focused mainly on the first step, but examination of the temporal evolution of the gait parameters as speed increases with each subsequent step may provide unique insights.
The purpose of this study is to examine the impact of advancing age in the first four steps following gait initiation. Since many diseases and disorders are associated with age, it is important to examine a healthy, active older population to ensure that observations are not confounded by disease, disorder, or inactivity. Three age groups were examined: young adults aged 20–25 years old (20–25 yo), older adults aged 65–79 years old (65–79 yo), and older adults over 80 years of age (80–91 yo). We hypothesized the following: (1) 65–79 yo will have a smaller base of support (SL and step width), slower gait speed and higher variability than 20–25 yo across all four steps, (2) 80–91 yo will have a smaller base of support, slower gait speed and higher variability than 65–79 yo across all four steps, and (3) the largest differences across age groups will be observed in the first step.
Section snippets
Methods
Forty-eight adults were categorized into three age groups: 20–25 yo (N = 19), 65–79 yo (N = 11), and 80-91yo (N = 18) (Table 1). All participants were healthy, with no neuromuscular or orthopedic disorders that would impact gait, walked without the use of an aid, and were able to climb 1.5 flights of stairs (37 steps). The latter requirement ensured a minimum threshold of strength and fitness, as stair climbing imposes strength and aerobic demands. All participants gave informed consent approved by the
Gait speed
Interaction effects (step number by age group) were observed for gait speed (F(6,896) = 4.26, p < 0.01, Fig. 1a). Post hoc analysis revealed that each age group progressively increased gait speed from steps 1–3. The gait speed in step 4 leveled off for 20–25 yo and 65–79 yo, while 80–91 yo continued to increase speed in this step. The speed at each step was slower with increasing age. The percent change in gait speed between 65–79 yo and 20–25 yo progressively decreased with each step: −20, −16, −13,
Discussion
The transition from standing to steady state gait is a challenging daily activity, providing an ideal task to examine changes as a function of advancing age. The robust age-related changes during steady state gait, slower gait speed and shorter step length (SL) (e.g. [14]), were also observed during the transition paradigm of this study. Our analysis emphasized gait speed, as it reflects health, functional status [15], and predicts survival [16]. Further, in order to predict survival, previous
Conflict of interest statement
The authors declare that there is no conflict of interest.
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