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The impact of age-related increase in passive muscle stiffness on simulated upper limb reaching

Murtola, Tiina; Richards, Christopher


Tiina Murtola

Christopher Richards


Ageing changes the musculoskeletal and neural systems, potentially affecting a person's ability to perform daily living activities. One of these changes is increased passive stiffness of muscles, but its contribution to performance is difficult to separate experimentally from other ageing effects such as loss of muscle strength or cognitive function. A computational upper limb model was used to study the effects of increasing passive muscle stiffness on reaching performance across the model's workspace (all points reachable with a given model geometry). The simulations indicated that increased muscle stiffness alone caused deterioration of reaching accuracy, starting from the edges of the workspace. Re-tuning the model's control parameters to match the ageing muscle properties does not fully reverse ageing effects but can improve accuracy in selected regions of the workspace. The results suggest that age-related muscle stiffening, isolated from other ageing effects, impairs reaching performance. The model also exhibited oscillatory instability in a few simulations when the controller was tuned to the presence of passive muscle stiffness. This instability is not observed in humans, implying the presence of natural stabilizing strategies, thus pointing to the adaptive capacity of neural control systems as a potential area of future investigation in age-related muscle stiffening.


Murtola, T., & Richards, C. (2023). The impact of age-related increase in passive muscle stiffness on simulated upper limb reaching. Royal Society Open Science, 10, Article 221453.

Journal Article Type Article
Acceptance Date Jan 18, 2023
Online Publication Date Feb 8, 2023
Publication Date Feb 8, 2023
Deposit Date Feb 8, 2023
Publicly Available Date Feb 8, 2023
Publisher The Royal Society
Peer Reviewed Peer Reviewed
Volume 10
Article Number 221453
Keywords Subject Category: Organismal and evolutionary biology Subject Areas: computer modelling and simulation/physiology/ biomechanics Keywords: ageing; manual aiming movements; passive stiffness; Hill-type muscle model


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