Is a Sprained Ankle Also a Brain Injury? How Neuroscience Is Helping Athletes, Astronauts, and ‘Average Joes’

Have you ever thought of a sprained ankle as a brain injury? Most people probably wouldn’t.

However, we are beginning to understand how the brain continually adapts, which we call plasticity.

Even though the damage from a sprained ankle is to the ankle, the brain may also experience some changes in how well it feels pain and movement.

One of our PhD students, Ashley Marchant showed something similar happens when we change the weight (or load) imposed on the muscles of the lower limb. The closer the load is to normal earth’s gravity, the more true our sense of movement; the less the load on the muscles, the less true our sense of movement.

This work means we need to rethink how the brain controls and responds to movement.

Solving an crucial puzzle

Historically, exercise science has sought to improve muscle function by resistance training, cardiovascular exercises and flexibility.

One of the major problems in treating and preventing sports injuries is that even when the sports medicine team determines that the athlete is ready to return, the risk of future injuries remains two to eight times higher than if they had never been injured.

This means the sports doctors missed something.

Our work at the University of Canberra and the Australian Institute of Sport has focused on sensory input to solve this puzzle. The aim has been to assess the ability to receive the sensory, or perception, aspect of movement control.

Entry nerves (sensory) they outnumber the output (motor) nerves by about ten times to one.

For more than 20 years, scientists have developed tools that allow us to determine the quality of sensory input reaching the brain, which is the basis for how well we can perceive movement. Measuring this input could be useful for everyone from astronauts to athletes to older people at risk of falls.

We can now measure how well a person absorbs information from three key input systems:

• vestibular system (inner ear balance organ)
• visual system (pupil reactions to changes in lightweight intensity)
• positional sensing system in the lower limbs (mainly from sensors located in the muscles and skin of the ankle and foot).

This information allows us to build a picture of how well a person’s brain is collecting information about movement. It also indicates which of the three systems could benefit from additional rehabilitation or training.

Lessons from space

You may have seen videos of astronauts, for example on the International Space Station, moving only using their arms, with their legs hanging behind them.

This shows how humans lose Earth’s gravity when they leave it. minimal information for the sensory system from the skin and muscles of the legs.

The brain quickly deactivates the connections it normally uses to control movement. This is fine when an astronaut is in space, but anytime they have to stand or walk on the surface of the Earth or the moon, they are more likely to fall and injure themselves.

Similar brain changes may occur in athletes due to changes in movement patterns following injury.

For example, limping after a leg injury means that the brain is receiving completely different information about movement than the movement patterns of that leg. In the case of plasticity, this may mean that the movement control pattern does not return to its optimal pre-injury state.

As mentioned earlier, injury history is the best predictor of the risk of experiencing a subsequent injury.

This suggests that after an injury, the athlete experiences some changes in the motor control processes – most likely in the brain – which prolongs out of time when the damaged tissue heals.

Measures of how well an athlete perceives movement are linked to how well they perform in different sports. So sensory awareness may also be a way to recognize sports talent early.

In older adults and in the context of fall prevention, impoverished performance on the same measures of sensory perception may predict later falls.

This may be due to reduced physical activity in some older people. This “operate it or lose it” idea may illustrate how brain connections for perception and movement control can deteriorate over time.

Precision healthcare

Recent technologies for tracking sensory abilities are part of a up-to-date trend in healthcare known as precise health.

Precision healthcare uses technology and artificial intelligence to take into account a range of factors (such as genetic background) that affect a person’s health and provide treatment designed specifically for them.

Applying a precision health approach to movement control could enable much more targeted rehabilitation for athletes, training for astronauts, and earlier fall prevention in older adults.