Human musculoskeletal function can be modelled through simulation
Wearable sensors have been used to study human movement for a long time already. However, it is still difficult to obtain detailed information on the internal forces in the body affecting movement.
"For example, it is challenging to measure the forces affecting bones, because bones are inside the body, surrounded by muscles," says Professor Aki Mikkola of LUT University, Department of Mechanical Engineering.
Accelerometers are typically used for measurement, such as those worn on the wrist of the person being studied. Commercial sports watches unfortunately aren't good enough for measurement, at least not yet.
"A motion sensor on the wrist doesn't say much about the loading on the shoulder or the wrist; instead, we need mathematics to calculate it," says Professor Pasi Karjalainen of the University of Eastern Finland.
"When the simulation model is taught to repeat the same movement, we can eventually get 'inside' the skin and assess, for example, pressure distributions in the knee cartilage," Mikkola says.
Each object, such as a shoulder or a knee, needs to provide its own measurement data.
"We are also looking into how measurements could be performed with as few sensors as possible," Karjalainen says.
"The trick is to base measurements on computing, and extensive manual processing is no longer needed," Mikkola says.
Human walking is simulated first
To model movement, a state estimation method where a digital Kalman filter evaluates the state of the system being measured, is used.
"It is impossible to simulate reality in real time. That is why we are performing controlled simulation that is compared to real life," Mikkola explains.
"We seek to determine the minimum amount of measurement data that is needed to create sufficiently reliable loading estimates," Postdoctoral Researcher Paavo Vartiainen of the University of Eastern Finland adds.
The first thing to be simulated is human walking. If the method works, it can be expanded and tailored to other forms of movement—to sports or, for example, to the development of ergonomics.
The method will not replace competent physiotherapists but could be used by them as an additional tool in guiding clients either in person or remotely.
One area of interest to the researchers is the ergonomics of care. The project will pilot a method that is based on wearable sensors and a state estimation algorithm, which allows physiotherapists to see if there is any harmful loading during the working day, such as excessive vertebral loading caused by lifting and moving of patients.
"We have previously studied, in a laboratory setting, the impact of a tool that reduces friction on the forces at play when moving patients. Now, one of our objectives is to develop, using wearable motion sensors and pressure sensing insoles, a measurement method and analysis software that is suitable for nurses' working environment," Vartiainen says.
The study is based on engineering design research carried out by Mikkola's research group, which has been applied to cranes used in the forest industry and in excavators, among other things. This existing collaboration between LUT University and the University of Jyväskylä is now supplemented by musculoskeletal biomechanics research carried out in the HUMEA Lab at the Department of Technical Physics of the University of Eastern Finland.
According to Vartiainen, one pilot will be to examine the ergonomics of physicians rehearsing endoscopic surgery.
"During rehearsing in an arthroscopy simulator, we can determine the orientation of the physician's head and shoulders in real time by using wearable sensors. Based on the pilot cases, it is possible to develop an app that warns the surgeon of a wrong neck position or excessive loading in real time."
Provided by University of Eastern Finland