Post stroke I no longer have any rapid motor behaviors. Nothing my doctor or therapists did addressed fixing my slow speed of movement. They were responsible but did nothing.
Quantitatively assessing aging effects in rapid motor behaviours: a cross-sectional study
Journal of NeuroEngineering and Rehabilitation volume 19, Article number: 82 (2022)
Abstract
Background
An individual’s rapid motor skills allow them to perform many daily activities and are a hallmark of physical health. Although age and sex are both known to affect motor performance, standardized methods for assessing their impact on upper limb function are limited.
Methods
Here we perform a cross-sectional study of 643 healthy human participants in two interactive motor tasks developed to quantify sensorimotor abilities, Object-Hit (OH) and Object-Hit-and-Avoid (OHA). The tasks required participants to hit virtual objects with and without the presence of distractor objects. Velocities and positions of hands and objects were recorded by a robotic exoskeleton, allowing a variety of parameters to be calculated for each trial. We verified that these tasks are viable for measuring performance in healthy humans and we examined whether any of our recorded parameters were related to age or sex.
Results
Our analysis shows that both OH and OHA can assess rapid motor behaviours in healthy human participants. It also shows that while some parameters in these tasks decline with age, those most associated with the motor system do not. Three parameters show significant sex-related effects in OH, but these effects disappear in OHA.
Conclusions
This study suggests that the underlying effect of aging on rapid motor behaviours is not on the capabilities of the motor system, but on the brain’s capacity for processing inputs into motor actions. Additionally, this study provides a baseline description of healthy human performance in OH and OHA when using these tasks to investigate age-related declines in sensorimotor ability.
Background
The ability to perform rapid motor behaviours underpins our interactions with the world, e.g., driving a car, dancing with a partner, or simply reacting when bumped walking in a crowded shopping mall. In recognition of their importance to our daily lives, motor skills have been incorporated into a number of neuropsychological tests, assessing individuals for cognitive and sensorimotor impairments [1,2,3]. Unfortunately, motor abilities predictably decline with age and these declines eventually limit many individuals’ independence [4]. With the world projected to have two billion people aged 60 or over by 2050, [5], there is a powerful motivation to measure the effects of aging on the motor system.
Aging impacts individuals’ motor abilities in a number of ways, including: reducing muscle strength [6,7,8], reducing visuomotor adaptation [9, 10], worsening reach-to-grasp movements [11], declining motor imagery abilities [12], decreasing accuracy in bimanual movements [13], increasing perception of physical fatigue [14], and decreasing proprioceptive acuity [15,16,17]. There is evidence that an individual’s aging experience will be affected by their sex, with aging having different impacts on various regions in male and female brains [18,19,20]. There are also underlying sex-related differences in both sensorimotor skill [15, 21] and visuospatial abilities [22,23,24].
Confoundingly, there is also evidence that some characteristics of the sensorimotor system are resilient to age, such as the mechanical properties of the elbow [25], the ability to perform complex motor actions [26, 27], the ability to act without visual feedback [28, 29], and grip strength when fatigued [30]. This points to the difficulty in deciding how declines in motor abilities due to age will affect daily activities at the population-level, let alone for a given individual.
Therefore, there is a clear need for tests that provide a holistic view of age-related declines in motor abilities. There has been a recent proliferation of rapid motor behavioural tasks with interactive components. To date these tasks have been used to quantify impairments after stroke [31, 32], to study decision-making [33, 34], and to study planning [35], but they also hold the promise of assisting research into the effects of age and sex on sensorimotor skills. Understanding how motor behaviours change with age in these interactive settings will help to develop new neuropsychological tests and equipment to evaluate an individual’s ability to perform every day rapid motor actions.
The purpose of this study is to better understand the effects that age and sex have on an individual’s rapid motor skills. Our hypothesis is that both age and sex will affect rapid motor skills, with participants who are younger and male showing superior performance. We test this hypothesis with two interactive motor behaviour tasks, namely Object-Hit (OH) [31] and Object-Hit-and-Avoid (OHA) [32], which are performed in a robotic exoskeleton to enable the recording of upper limb and joint positions throughout trials. We verify that these tasks are appropriate for testing healthy individuals by demonstrating that participants must reach and maintain their peak steady-state rate of performance to maximize their performance during trials. We then use a large dataset of healthy control participants (n = 643, ages 18–93) who have performed these tasks to assess aging effects on motor behaviours. We perform linear regressions with 16 recorded and computed parameters to determine which are significantly impacted by age. We also tested for sex-related effects (male vs. female) on motor behaviours and on aging effects given their occurrence in the sensorimotor and aging literatures.
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