Balance is the most fundamental and universal movement for all humans. It is required for all functional movements including standing up, walking, running and jumping. Assessing balance has broad application across different conditions and people from sports to seniors and everything in between. Traditionally, balance has been assessed using rudimentary, unreliable, processes such as the Balance Error Scoring System (BESS) or the Timed Up & Go (TUG) Test. At Sparta Science, we collect objective and reliable balance data using high fidelity force plates. Through a combination of machine learning models and biomechanical analyses, we surface metrics that help individuals make more informed decisions about improving movement health. Let’s take a closer look at balance metrics that have unique application and help to show how complex, yet important, balance data is.
Balance can be simply understood as an individual’s ability to maintain their center of mass over their center of pressure. While this may sound simple, it is actually the extremely complex coordination of different systems that allow us to balance. The basic ability of humans to stand upright on two feet (let alone on one) is a complicated and unstable condition. As gravity acts constantly on the human body challenging balance, different systems of the human body coordinate to counteract these forces and maintain balance. Our nervous system, musculoskeletal system, vestibular system, and ocular (vision) system all work in a coordinated effort to simply allow us to stand upright or walk without falling over.
The ability to simply stand upright and balance involves the complex coordination of a variety of systems.
Sway: How well do you balance?
Generally considered the ability to stabilize, the total sway that occurs during a double leg or single leg stand still period represents a gross measure of overall balance and stability – the movement of a center of mass in a standing position. In the literature poor Sway, or stability, has been related to previous and future musculoskeletal injuries including ankle sprains, low back pain, and injuries due to falling. Literature also points to Sway being related to some “performance” capabilities such as strength and agility. Sway is representative of an individual’s global balance and proprioception and when measured unilaterally can provide a lens in which to assess inter-limb asymmetry and gait function.
MRV: How responsive or complex is your balance?
Multivariate Multi Scale Entropy, also referred to as Movement Response Variability (MRV) can most easily be thought of as a measure of variability or complexity of balance. While Sway gives us a quantitative measure of global balance and proprioception, Movement Response Variability, or MRV, is more of a measure of the quality of an individual’s balance strategy. MRV evaluates the consistency and pattern of balancing in all three directions (x, y, z), with a higher value being representative of a more complex strategy and therefore a more responsive system. MRV is sensitive enough to assess neurological function and disorders, including symptoms of TBI, Parkinson’s, and aging.
While these two qualities are conceptually related, our research shows they evaluate two independent movement qualities and can be used to identify different subsets of individuals with potentially different needs and risks.