At matched loads, aging does not alter ankle, muscle, or tendon stiffness
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 asignificant 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.
README: Aging ankle, muscle, tendon stiffness
https://doi.org/10.5061/dryad.k98sf7mfx
Description of the data and file structure
The data includes all the estimates of ankle, muscle, and tendon stiffness for all participants, as well as their plantarflexion torque and muscle activations (medial gastrocnemius MG, lateral gastrocnemius LG, soleus, and tibialis anterior TA.
There is also the subject information (age group, sex, max torque, fall risk, and CHAMPS score). Fall risk and CHAMPS were not collected for young adults, and thus the values are NaN. Young adults (YA) are between 18-35 years old while older adults (OA) are older than 60 years.