Nerve Stiffness Affects Ankle Flexibility in Older Adults

While muscle stiffness affects ankle flexibility in young people, in older adults nerve stiffness appears to be the culprit instead, according to a new study.

In a study published in the October 2020 issue of Medicine & Science in Sports & Exercise, Shibaura Institute of Technology researchers evaluated the differences between passive ankle dorsiflexion range of motion (ROM) and stiffness of the triceps surae, sciatic nerve, and deep fascia located in the posterior leg between young and older people.

For “Associations between Range of Motion and Tissue Stiffness in Young and Older People,” the researchers had 20 young and 20 older males lie in a prone position with their hip and knee fully extended. They determined passive ankle dorsiflexion ROM based on the onset of pain during passive dorsiflexion at 1˚s^-1using an isokinetic dynamometer.

Then they used ultrasound shear wave elastography to evaluate shear wave speeds of the triceps surae, the sciatic nerve, and the deep fascia in the posterior leg.

According to the data collected, the shear wave speeds of the medial and lateral gastrocnemius measured at 15˚ dorsiflexion was negatively associated with passive ROM in the young, but not older men. However, the shear wave speed of the sciatic nerve measured at 15˚ dorsiflexion was negatively associated with passive ROM only in the older men.

There was no association between passive ROM and shear wave speed of the deep fascia in the posterior leg. Stretch tolerance influenced ROM in both groups.

The researchers concluded “that the relative contribution of non-muscular tissues to joint flexibility become stronger than that of muscles with age.”

Prof. Ryota Akagi of the Shibaura Institute of Technology in Saitama, Japan, said in a statement, “Not every one of our hypotheses was supported—for example, we didn’t find an association between fascia stiffness and ROM—the key outcome here is that a difference exists in the underlying factors affecting joint flexibility between young and old people.”

The researchers hope that their findings open up discussion about the need for new flexibility training methods that are specific for older people and target nerve bundles.