Measuring Balance with IMUs: How Many Do We Need?

Standing still might seem simple, but it's a complex balance act. Many health conditions can mess with this balance, making daily tasks tough. Researchers usually test balance in labs, but now there are affordable tools called inertial measurement units (IMUs) that can check balance in real life. But how many IMUs do we need to get an accurate reading?Researchers stuck 16 people with IMUs on their head, chest, back, and legs. They stood on a special platform in different stances: narrow, hip-width, and shoulder-width. Each stance was held for two minutes, three times. Using a model that breaks down body parts, researchers guessed where the body's center of mass (CoM) was moving. They then compared these guesses with the platform's readings to see how many IMUs were needed. Turns out, four IMUs did the job. Placed on the back, right thigh, and both shins, they gave strong readings in all stances. This means IMUs can estimate how the body's center of mass moves while standing still. This is great news for researchers and doctors who can now monitor patients with balance issues in real life.