Arnaud Gouelle
Functional Gait Analysis: Between Apparent Simplicity and Analytical Complexity, a Reflection of the Patient’s Motor Control

Walking is, above all, about getting from one point to another without falling and, if possible, efficiently. Over time, many tests, questionnaires, and classifications have been proposed as means of assessing functional abilities and fall risk, most of them focused on the level of dependency, the need for assistive devices, walking range, or the time taken to complete a given distance—all implicitly referring to the concept of speed.

With the advent of motion capture systems dedicated to locomotion, it is not surprising that most evaluations initially focused on walking speed—considered by some as a true sixth vital sign—followed by a few other spatiotemporal parameters deemed functionally relevant. Today, the associated systems and software offer a multitude of parameters, but making the most of them requires extensive knowledge of so-called normal walking, even before assessing the impact of pathological disorders.

Behind their apparent simplicity lies the complexity of interpreting parameters that are intrinsically linked to one another and depend on numerous personal (e.g., age, sex) or environmental factors (e.g., recording protocol, calculation algorithms). For example, considering only walking speed to evaluate the results of a rehabilitation protocol makes little sense when speed depends on both cadence and step length. Tracking a child’s walking development without accounting for growth will inevitably lead to misinterpretations. Similarly, evaluating only average values means overlooking a significant portion of information about disturbances and regulations, which are visible through variability.

Functional gait analysis, once called simplified analysis, plays a key role in this approach. It mainly relies on direct measurement of ground contact (e.g., electronic walkways) or indirect measurement (e.g., inertial sensors) and allows us to understand the motor organization and regulation resulting from the person’s constraints and capabilities. Thus, beyond standardized gait examination—which remains a central element of clinical assessment—we can also consider implementing functional evaluation under more varied conditions, closer to real-life situations.