Abstract
Older adults have difficulty maintaining balance when faced with postural disturbances, a task that is influenced by the stiffness of the triceps surae and Achilles tendon. Age-related changes in Achilles tendon stiffness have been reported at matched levels of effort, but measures typically have not been made at matched loads, which is important due to age-dependent changes in strength. Moreover, there has been limited investigation into age-dependent changes in muscle stiffness. Here, we investigate how age alters muscle and tendon stiffness and their influence on ankle stiffness. We hypothesized that age-related changes in muscle and tendon contribute to reduced ankle stiffness in older adults and evaluated this hypothesis when either load or effort were matched. We used B-mode ultrasound with joint-level perturbations to quantify ankle, muscle, and tendon stiffness across a range of loads and efforts in seventeen healthy younger and older adults. At matched loads relevant to standing and the stance phase of walking, there was no significant difference in ankle, muscle, or tendon stiffness between groups (all p > 0.13). However, at matched effort, older adults exhibited a significant decrease in ankle (27%; p = 0.008), muscle (37%; p = 0.02), and tendon stiffness (22%; p = 0.03) at 30% of maximum effort. This is consistent with our finding that older adults were 36% weaker than younger adults in plantarflexion (p = 0.004). Together, these results indicate that, at the loads tested in this study, there are no age-dependent changes in the mechanical properties of muscle or tendon, only differences in strength that result in altered ankle, muscle, and tendon stiffness at matched levels of effort.
Original language | English (US) |
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Pages (from-to) | 2556-2568 |
Number of pages | 13 |
Journal | Annals of Biomedical Engineering |
Volume | 52 |
Issue number | 9 |
DOIs | |
State | Published - Sep 2024 |
Funding
Research reported in this publication was supported by the National Institute On Aging of the National Institutes of Health under Award Number F31AG069412. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Research supported by the American Society of Biomechanics' Graduate Student Grant-in-aid.
Keywords
- Achilles tendon
- Biomechanics
- Mechanics
- Older adults
- System identification
- Triceps surae
ASJC Scopus subject areas
- Biomedical Engineering