Optical systems
To obtain reliable data and measurements, gait laboratories often use OMCS. Different techniques and technologies are available, each with their advantages and limitations; however, their common goal is to capture movement data in order to examine and study gait patterns or features. OMCS—such as Optotrak® and Vicon®—use reflective markers, infrared cameras, and licensed software to obtain an accuracy of the position of up to 0.1 mm and resolution of 0.01 mm.
These kinds of systems have several advantages: they provide a high level of accuracy; they can capture complex movement patterns; and some can even provide data in real time. Nevertheless, the high cost of the required hardware and software is a drawback, as are the need for a professional calibration and model setup. For FC tracking in general (i.e. for research in the lab), optical systems are an option but become impractical for tracking FC outside the laboratory. In order for the system to be used in the community, a wearable device is needed.
Only one group of researchers has been able to measure and use FC in real time by means of OMCS —Rezaul K. Begg and colleagues. This group used an Optotrak Certus® optoelectric movement analysis system to provide real-time feedback of foot position with respect to the walking surface. The study recruited ten healthy young and ten older adults, performing walking trials on a treadmill at self-selected speed. Infrared markers were attached to the left and right foot at the fifth metatarsal head and heel, and were tracked at 100Hz. A 10 minute baseline was obtained from each participant, and then a visual biofeedback of the FC was projected along with a target band within which participants were requested to maintain FC. The results highlighted that real-time biofeedback of foot trajectory gait parameters has potential to assist in gait rehabilitation and other biomedical and healthcare applications.
Another type of optical system, the optical proximity sensors (OPS), can detect the presence of nearby objects. The typical setup includes a light source and a sensor that detects the light. Most of the OPS are used in confined spaces to avoid other light sources, and even then they are programmed to send and receive light patterns at special frequencies. In 2010, Andy Kerr et al.
developed a new sensor and tested its validity in measuring FC through comparison with an OMCS. Although the system showed promising results, the sensors are still under development and are not commercially available. Furthermore, the OPS can only take measurements within a 4 to 30cm range. Kerr et al. worked around this problem by raising the height of the sensor on top of the shoe, introducing a methodical difference in the measurement with respect to the location of the reflective markers. The correlation between the reflective marker and the OPS were modest but statistically significant. As a proposed solution by the authors, the post-calculation of FC based on the phase of gait should allow for a more extensive processing of the signals improving the correlation.
optical systems
