To truly understand pathologies or injuries in human locomotion, we must first understand the methods in which our patient or athlete needs to move. Gait (walking or running) is typically considered the method by which movement from point A to B occurs. Gait evaluation helps to understand specific asymmetries related to the way we move. Gait measurement can be done using kinetic (force) and kinematic (spatial/temporal) information. A standard gait evaluation requires at the very least one complete gait cycle, which comprises of a foot strike with observed leg, a contralateral foot strike with the other leg, followed by another foot strike with the observed leg. Of course, the more foot strikes analyzed the better to accomodate a consistent pool of natural foot strikes due their inherent variability.
Human gait can be defined as a series of alternating movements of the lower extremities in a rhythmic motion that results in forward progression of the body with minimal energy expenditure. In order to determine issues with gait, clinicians and researchers will often use a gait analysis to assess and treat individuals with various conditions, pathologies or injuries affecting their ability to walk or run. An understanding of the gait cycle and the various phases of the gait cycle is required to assure a positive outcome for the patients or athletes.
Looking at the gait cycle from a temporal perspective, it can be broken down into two distinct global phases: the stance phase and the swing phase.
There are also important support phases known as:
Single support phase is also known as the swing phase where only one limb in in contact with the ground. In normal gait, this phase comprises between 60-72% of the stance phase.
Initial double support phase is the sub-phase between heel contact of the phase to contralateral foot-off. This phase makes up approximately 14-20% of the stance phase.
Terminal double support phase is the sub-phase from contralateral foot-on to the toe-off. This phase makes up approximately 14-20% of the stance phase. Total double support phase is defined as the sum of the initial and terminal double support phase. This makes up approximately 28-40% of the stance phase.
Typically, gait problems/pathologies will appear during the stance phase of gait when the foot is loaded, which will ultimately impact the swing phase as well. In order to gain a better understanding of how the foot functions, the stance phase can be further broken down to more refined sub-phases to enable a more in depth look. These phases are called:
The contact phase is the first heel contact of the lead leg and end at “toe-off” of the contralateral leg. The contact phase makes up 14-20% of the stance phase.
The foot-flat phase or “loading response” phase has an important function since body weight is transferred to the lead leg at this point and thus must absorb this weight while maintaining forward momentum. This phase is defined by the first heel contact of the lead leg to the first contact of the first metatarsal head of the lead leg. The foot-flat phase makes up 16-22% of the stance phase.
The mid-stance phase is the point where the support limb moves from shock absorption to more of a stability function. This phase is defined from the toe-off point of the contralateral leg to the first point the heel comes off the ground of the lead leg. The mid-stance phase makes up 29-37% of the stance phase.
The final phase of stance is called the propulsive phase. During the propulsive phase, the foot typically supinates to allow for a more rigid mid-foot, so it can act more like a lever (Winlass mechanism) to help propel the body forward. The propulsive phase of gait is sometime broken down even further into an active propulsive and passive propulsive phase. The reason for this division is to isolate the component of the propulsive phase while still in single support, and the passive component of the propulsive phase when in double support. The total propulsive phase is the point the heel comes off for the lead leg to toe-off of the lead leg. This phase makes up 45-55% of the stance phase.
The active propulsive phase is the heel off point from the lead leg to the first contact point for the contralateral leg. This active propulsive phase makes up 31-35% of the propulsive phase.
The passive propulsive phase is the heel contact of the contralateral to toe-off of the lead leg. The passive propulsive phase makes up 14-20% of the propulsive phase.
Looking at gait from a spatial perspective allows us to measure gait asymmetries related to distance between steps and strides lengths. Some typical spatial gait parameters are: step length, stride length, step width and foot angle.
Other timing variables can be calculated from this information, step time, stride velocity and step length to leg length ratio. This can be calculated from the leg length of the patient.
There are many reasons why gait analysis is important in both clinical and research environments.
There are a variety of gait systems and software that can be used to capture spatial/temporal information of patients or athletes during gait.
Motion analysis is one methodology that can accurately capture this information; however, it can take time setting up a patient with the markers necessary for data acquisition and cannot capture continuous kinetic information unless multiple force plates are synchronized.
Force and pressure mapping systems are equipped with thousands of array sensors, arranged into a continuous walkway to enable data collection of multiple sequential foot strikes. These tools require very little set-up, allowing for quick and uninhibited evaluation of a patient or athletes’ gait, which is key in a busy gait clinic. Gait data from one simple data collection can provide spatial (step length, Stride length etc.), temporal (step time, stride time, Stride velocity etc.) and kinetic (vertical force, pressure distribution, center of force) information for a complete analysis. The data from these systems can be compared to normative gait data or asymmetries between the feet can be quantified from a spatial, temporal or kinetic point of view. This information can provide important insights towards the type of pathology or injury of the patient/athlete. It can also provide quantitative feedback regarding how the patient or athlete is progressing in their rehabilitation.
To learn more about the benefits of gait analysis with objective technology, check out this webinar: Introduction to Gait Analysis with Technology.
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