Age-dependent vestibular contributions to energy expenditure in treadmill and overground walking
Our reliance on vestibular input changes as we age; could this explain energetic differences across age in the metabolic cost of walking on a treadmill as compared to overground?
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People: Daphne Onderwater, Matto Leeuwis, Eline van der Kruk, Patrick Forbes
Topics: gait,, energergy, expenditure,, vestibular, system
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Link: External →
This project was the MSc thesis project for Daphne Onderwater to complete her studies in Biomedical Engineering at TU Delft: Repository
Humans tend to minimize the amount of energy they expend when walking. We do so by integrating sensory information to sense our environment. As we age, sensory systems tend to decline. The vestibular system is particularly affected by age, which necessitates us to rely more on other senses (like vision) to maintain our balance while standing and walking.
Most experiments on the energetic cost of walking use treadmills, as these allow much easier experiments. On a treadmill, the environment is static. This means there is less visual information to guide our balance, which may force us to rely more on (possibly declined) vestibular information. At the same time, previous work has indicated that aged (> 65 years) participants have higher energy expenditure when walking on a treadmill compared to overground (outside) walking. This difference is not observed in young participants.
In this project, we assess whether this cost difference between ages may be caused by changes in reliance on vestibular input when walking on a treadmill. We tested two groups: a young group (n=10) and an old group (n=10), both walking outdoors and indoors on a treadmill. We used a metabolic analyzer to measure participants’ energy expenditure from their exhaled oxygen and CO2 contents, and measured their movement using inertial measurement units. To test the role of the vestibular system, we used electrical vestibular stimulation. This type of stimulation uses electrodes behind the ears to induce a sensation of self-movement, as if you are standing on a moving ship. By combining this stimulation with the measured movement of the participant, we could quantify how reliant they were on vestibular signals.
Overall, we found that walking on a treadmill costs more energy than walking outdoors at the same speed. However, there was no difference in energy expenditure with age. The reliance on vestibular input was also similar across age, suggesting that any deterioration of the vestibular system did not affect overall movement outcomes.