As we age, our bodies undergo numerous changes, and one of the most impactful is the gradual decline in mobility. A groundbreaking new study from the Royal Veterinary College (RVC) has shed light on the specific muscle changes responsible for this deterioration, offering valuable insights for both human and veterinary medicine.
Understanding the Mechanics of Age-Related Mobility Loss
The research, published in PLOS Computational Biology, reveals why goal-directed movements in mammals become slower and less precise with age. Led by Dr. Delyle Polet and Professor Christopher Richards at the RVC’s Structure and Motion Laboratory, the study employed a computational model to isolate and investigate the effects of individual muscle properties.
The team conducted 3,920 simulations, varying five key muscle characteristics known to change with age: peak force, peak contraction speed, activation rate, deactivation rate, and stiffness. This approach allowed them to link age-related muscle changes to movement performance in a way that would be impossible through human studies alone.
Key Findings: The Complex Interplay of Muscle Properties
The simulations revealed that reduced muscle strength, contraction speed, and activation rate all independently reduce performance and are the main factors behind slower and less accurate movement. However, the study also uncovered a more nuanced relationship between muscle stiffness and deactivation.
When muscles can deactivate quickly, increased stiffness can actually improve performance by helping to propel movement, similar to how a slingshot works. However, when muscles deactivate more slowly, the same stiffness can work against the movement, effectively resisting it.
Additionally, the research challenged the common assumption that muscle co-contraction (when opposing muscles activate at the same time) in older adults is simply a compensatory deficit. Instead, the simulations revealed that co-contraction can be an optimal strategy for achieving high performance, suggesting its relationship with movement performance may be more complex than previously thought.
Implications for Human and Animal Health
These findings have significant implications for both human and animal health. In humans, age-related changes in muscle function are closely linked to an increased fall risk. Falls are one of the leading causes of injury and death in older adults, with approximately one-third of people over 65 in the UK experiencing at least one fall each year.
Beyond human health, age-related muscle decline also affects many animal species, including domestic animals such as horses and dogs, where conditions like sarcopenia (the gradual loss of muscle mass and strength with age) are recognized clinical concerns. By identifying which muscle changes have the greatest impact on movement, these findings could help inform more targeted interventions, including approaches to rehabilitation, physiotherapy, and mobility support in both human and veterinary medicine.
Future Directions and Potential Applications
The researchers are excited about the potential of their modeling approach to simulate the multi-factorial effects of ageing. Professor Richards noted, “I hope that follow-on work will contribute towards increasingly realistic models of humans and animals which we can digitally age to study the consequences on behaviour.”
This research opens up new avenues for developing targeted interventions to maintain mobility in aging populations, both human and animal. By understanding the specific muscle changes that contribute most significantly to mobility loss, researchers and clinicians can develop more effective strategies for preserving independence and quality of life as we age.
The study was funded by a Wellcome Trust Investigator Award, highlighting the importance of continued investment in research that bridges human and veterinary medicine to improve health outcomes across species.
For those interested in learning more about this research or the RVC’s work in this area, the full paper can be accessed at https://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1014023. The RVC’s Structure and Motion Laboratory continues to be at the forefront of multidisciplinary research into movement across species, with state-of-the-art facilities and a long-standing international reputation.
