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The Effect of Posterior Foot Positions on Electromyography, Joint Kinetics and Energetics During a Sit-to-Stand in Young and Older Adults

Year: 2024
Type: dissertation
Abstract: The sit-to-stand (STS) movement, defined as standing up from a chair to an upright posture, is a common task performed daily. The inability to accomplish this task may lead to dependence, institutionalization and even death in older adults. A common strategy change for the STS is positioning the feet posteriorly by increasing flexion at the knee joint. This reduces the displacement of the center of mass to the base of support while increasing the joint moment of force at the knee while decreasing it at the hip. The aims of this study were to: 1) examine the joint kinetics, joint energetics and muscle activations of a STS task between young and older adults, and 2) determine the effects of posteriorly placing the feet on joint kinetics. joint energetics and muscle activations in STS. Twenty participants were recruited for this study. The samples consisted of 10 young participants (age: 22.3±2.06 yr; mass: 70.1±11.7 kg; height: 1.71±0.06 m), and 10 older participants (age: 72.7±5.96 yr; mass: 82.2±13.84 kg; height: 1.73±0.07 m). Both groups were recreationally active, free of lower extremity injury in the past six months and had no history surgery to the lower extremity. Participants were asked to complete five STS with a natural foot position and then with their feet placed 0.10m posterior to the initial position. Three-dimensional marker coordinate data were collected synchronously with three-dimensional force data and surface electromyography (EMG) of 8 lower extremity muscles. Results indicate that older adults have statistically higher integrated EMG activity in the soleus, rectus femoris and hamstrings muscles along with a statistically higher ankle joint angular impulse. Shifting the feet back produced statistically different values for trunk flexion, time of the rising phase, lower body joint work and hip joint angular impulse. The feet back condition also significantly decreased the integrated EMG magnitude for the tibailis Anterior, vastus lateralis and the hamstring muscles. This study reveals the benefits and limitations to a feet back condition for the STS. Placing the feet back will reduce the time of the rising phase while consequently reducing the magnitude of integrated EMG of the lower body muscles and decreasing the hip joint angular impulse. However, ankle joint angular impulse was increased in older adults with a foot back position. Specific attention should be provided to the individual when applying the feet back condition.
DOI: 10.25777/6k2a-0q54
Author: Pitman, Eric A.
Language: English
Open Access status: green
OpenAlex ID: W6889642433
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