Gait analysis is the systematic study of human locomotion, offering objective insights into how a person walks or runs. This process uses specialized instruments to quantify the complex mechanics of movement. The goal is to transform subjective assessments into measurable, repeatable, and quantifiable data. This objective data is paramount for understanding the underlying biomechanical factors contributing to movement patterns.
Stationary Contact-Based Measurement Tools
Gait analysis often uses equipment requiring direct physical contact with the ground to measure the forces generated during movement. Force plates are precise instruments containing sensors, typically strain gauges or piezoelectric transducers, that measure the ground reaction forces (GRF) exerted by the body. These plates record the GRF, which is the equal and opposite force the ground exerts when a person pushes down on it, following Newton’s Third Law.
Force plates measure forces in three dimensions: vertical, anterior-posterior (forward and backward shear), and medial-lateral (side-to-side shear). Analyzing the GRF data allows calculation of parameters like the center of pressure, which tracks the location of force application under the foot during the stance phase. Instrumented treadmills integrate these sensors into the walking surface, allowing continuous GRF measurement over multiple steps at controlled speeds. Pressure-sensing mats, or pressure plates, use hundreds or thousands of small sensors to create a detailed pressure map. This map shows the distribution of force across the entire foot, which is useful for analyzing foot function and identifying areas of high pressure.
Non-Contact Optical Motion Capture Systems
Non-contact optical motion capture systems provide a detailed method for capturing the body’s movement. These setups utilize multiple high-speed cameras, often operating at 100 to 200 frames per second or higher, placed around a movement area. The system tracks the three-dimensional movement of reflective markers, which are small spheres or specialized light-emitting diodes (LEDs) affixed to specific anatomical landmarks, such as joints and limb segments.
Markers are either passive, reflecting infrared light emitted by the cameras, or active, emitting their own light signal. The cameras triangulate the position of each marker in three-dimensional space by capturing it simultaneously from multiple viewpoints. Specialized software uses these coordinates to create a kinematic model of the subject, calculating parameters like joint angles, velocities, and accelerations for every body segment. Markerless motion capture is an emerging alternative that uses standard video and deep-learning algorithms to identify body segments without physical markers. This reduces setup time but may currently limit accuracy for specific joint angles compared to marker-based systems.
Portable and Wearable Sensing Devices
To analyze movement outside a specialized laboratory, researchers and clinicians rely on portable and wearable sensing devices. The most common are Inertial Measurement Units (IMUs), which are small, lightweight sensors containing a three-axis accelerometer and a three-axis gyroscope. The accelerometer measures linear acceleration, while the gyroscope measures angular velocity or rotational movement along the three spatial axes.
IMUs are often attached to the limbs or pelvis to track segment orientation and motion, offering a user-friendly way to collect data in real-world environments. Smart insoles integrate IMUs and pressure sensors directly into the shoe insert, capturing foot movement and plantar pressure distribution simultaneously. While portable and capable of collecting data over extended periods, these systems may have trade-offs in precision compared to fixed optical systems due to potential sensor drift or movement on the body.
Applications in Clinical and Athletic Settings
The objective data collected by gait analysis tools serves distinct purposes across different fields. In clinical settings, the data provides a quantitative basis for diagnosing neurological or orthopedic issues, such as stroke, cerebral palsy, or osteoarthritis. By identifying deviations in stride length, joint angles, or ground reaction forces, clinicians can design targeted rehabilitation programs and precisely track a patient’s recovery progress following surgery or injury.
For athletes, gait analysis data is used to enhance performance and mitigate injury risk. Analyzing a runner’s form with force plates and motion capture can pinpoint subtle asymmetries or inefficient movement patterns contributing to overuse injuries. Coaches use this information to optimize running mechanics, improve power generation, and ensure training interventions are tailored to the athlete’s unique biomechanics.