Balance interpedal asymmetry in older adults

Description

In this worsheet are presented data on interpedal balance asymmetries in healthy older individuals from an evaluation based on the Equidyn protocol. Background: Previous evidence of increased between-leg muscular strength asymmetry in older adults suggests the possibility of interlateral asymmetries of balance control in older individuals. In the current investigation, we evaluated interlateral asymmetries in older adults when performing quiet and dynamic balance tasks. Methods: Fifty-two physically active and healthy older adults within the age range of 60 to 80 years were recruited. Participants performed balance tasks including quiet stance and cyclic sway of the free leg in the anteroposterior or mediolateral directions, with standardized amplitude and rhythm of leg movements. Trunk acceleration in the anteroposterior and mediolateral directions was measured using a smartphone attached to the upper trunk for evaluating balance stability. Results: Analysis revealed predominance of symmetric balance when comparing the right versus left or preferred versus nonpreferred legs, regardless of whether they were performing quiet stance or dynamic balance tasks. Further examination of the data showed high between-leg correlation coefficients across all tasks. Conclusion: Our findings indicate a low degree of lateralization in balance control among older adults. As balance requires the coordination of the entire body, we suggest that both cerebral hemispheres are involved in regulating unipedal balance when supported on either leg.

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Equipment and evaluation Interpedal asymmetry of body balance was assessed in barefoot unipedal stance, supported on either leg, using three tasks: quiet stance, and leg sway in the anteroposterior (AP) or mediolateral (ML) directions. Single leg quiet stance has been shown to be a challenging balance task sensitive to aging-related declines. For the dynamic balance tasks, participants were required to maintain unipedal stance while performing rhythmic sway movements in the AP or ML direction with the opposite free leg. To ensure similar movement amplitudes across trials and participants, these tasks were performed by alternately lightly touching proximal and distal markers, 20 cm apart on the ground, with the tip of the big toe throughout the trial duration. Leg movements were paced at a frequency of 1 Hz using a metronome. Performance was evaluated based on three consecutive trials for each task by leg, with each trial lasting 15 s. The task sequence remained constant for all participants: quiet stance, AP leg sway, and ML leg sway. The supporting leg was alternated during the evaluation protocol, starting with the right leg and then the left leg in each task. Between-trial rest intervals lasted 30 s, and 60-s intervals were provided between different tasks. Participants were familiarized with the tasks and procedures immediately before the probing trials. The complete assessment, including instructions and familiarization, took approximately 20 minutes. During the evaluation, trials with light support on the swaying leg were considered valid. Trials resulting in heavy body support on the sway leg due to body disequilibrium or failure in following the due rhythm in the dynamic tasks were canceled and immediately repeated. The entire evaluation protocol was conducted by using the Equidyn smartphone application. A smartphone (Xiaomi Mi9 Lite, version 10, Android system) with the Equidyn application was securely attached in the vertical orientation to the posterior side of the participant's trunk using an elastic belt. The smartphone was centered at the height of the thoracic spine (T10-T12), with the xiphoid process serving as the anterior anatomical reference. This positioning of the smartphone aimed to avoid recording acceleration associated with hip movements during leg sway in the dynamic tasks. The Equidyn application provided voice instructions indicating the task to be performed and the leg to be used in the ensuing trial, 1-Hz beeps to pace the leg sway rhythm in dynamic tasks, and three-dimensional measurement and recording of trunk sway acceleration for individual trials. Smartphone-based trunk accelerometry has been demonstrated to be an aging-sensitive measurement for assessing body balance in healthy adults, with results comparable to measurements obtained through force platforms and kinematics.

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