The ultimate goal of gait analysis is to understand the complex relationships between an individual’s capabilities/impairments and the person’s gait pattern, so as to enhance performance while preventing injury (2).

Our gait cycle is unique to humans, forming the building block for all motion from walking to running.

The complexity of gait physiology has been made more evident as technology advances, allowing providers to examine minute abnormalities in detail to fine-tune performance.

Gait analysis is also used to understand the effects of both internal and external biomechanical factors. Modern gait analysis techniques can be used to evaluate for subtle muscle weaknesses and flexibility deficits while also evaluating the effects of shoes and orthoses on the gait pattern.

Gait can be analyzed in multiple different ways, but with advancing technology, providers have become more and more reliant on the use of video and computer analysis software. Advances in technology have allowed for the identification of minute discrepancies, yielding an improved ability to help patients.

Gait analysis techniques are actively used in rehabilitation protocols, most notably after stroke, in amputee care, in pediatric rehabilitation for children with cerebral palsy, and for the fine-tuning of elite athletes (4).

The basic unit of walking and running is the gait cycle, or stride. Perry (9) described various temporal and functional variables within the gait cycle, which has become a standard reference to describe gait.

Walking gait cycle timing is primarily divided into double support and single support phases.

When focusing on each leg’s activity, the cycle is divided into the stance and swing periods, which begin at initial and final contact of the foot, respectively.

When focusing on functional aspects of gait, the walking gait cycle can be divided into three functional tasks: weight acceptance, single limb support, and limb advancement, with the first two occurring during stance and the third occurring primarily during swing. The tasks are further subdivided into eight phases: weight acceptance comprises initial contact and loading response; single-limb support comprises midstance, terminal stance, and preswing; and limb advancement comprises initial swing, midswing, and terminal swing.

Temporal-spatial gait parameters consist of the following: stride time refers to the time from initial contact of one foot to initial contact of the same foot; step time refers to the time from initial contact of one foot to initial contact of the opposite foot; and stride length and step length refer to the distances traversed during the respective times. Gait velocity is the ratio between stride length and stride time. Cadence of gait refers to the stride (or step) frequency (i.e., the number of strides [or steps] per unit of time).

Temporal-spatial parameters can be effectively measured during either walking or running with pressure mats (cellular mats measuring foot pressure), force platforms (dynamometers sensing ground reaction forces in time), and motion analysis (system of stereophotogrammetric cameras for three-dimensional reconstruction of body motion, including foot contact timing). Temporal, but not spatial, parameters can be measured with foot switches (on/off devices detecting foot contact timing).

Temporal-spatial features of walking and running differ substantially. During walking, at least one foot is always on the ground, whereas during the majority of running, neither foot is in contact with the ground. Although walking has two double-support phases, running has two phases of double float during the swing period. The percentages of time in stance and swing are reversed in walking and running: about 60% and 40%, respectively, for walking and about 40% and 60%, respectively, for running (7,9). During normal walking at an average walking speed, each double-limb support time comprises approximately 10% of the gait cycle, whereas single-limb support comprises about 40%. Typical values (5) of temporal gait parameters in healthy young adults, walking comfortably on a level surface, are summarized in Table 22.1. At slower walking speeds, double-limb support times are greater. Conversely, with increasing walking speeds, double-limb support time intervals decrease. Walking becomes running when there is no longer an interval of time in which both feet are in contact with the ground.

The kinematics (motion) of an individual while walking or running can be effectively assessed by modeling the individual’s body as a multibody system. A multibody system is composed of links (body segments) and joints between the links. The kinematics of the system is completely known when orientation and position of each of its segments are known. Joint angles are obtained from the kinematics of both joint distal and proximal segments. Joint angular velocities are obtained from the joint angles and refer to the rapidity of variation of such angles. Joint accelerations are similarly obtained from joint velocities.

Each segment possesses a center of mass (CoM). A whole-body CoM can also be defined as the point at the center of the body mass distribution. As segments move, the whole-body CoM moves. Its position in time is important for both balance and energy-related issues (2).

With quantitative three-dimensional gait analysis, joint angles throughout the gait cycle are described with respect to flexion/extension, abduction/adduction, and internal/external rotation (6). CoM position in time is expressed in vertical, anterior-posterior, and mediolateral time histories.

Both joint and CoM kinematics are obtained from the instantaneous three-dimensional position of markers attached on the individual’s body segments.

Joint kinematics patterns during running differ somewhat from the patterns during walking. Hip flexion/extension and abduction/adduction ranges are wider in running (about 60 and 15 degrees, respectively) than in walking (about 40 and 10 degrees, respectively) (7,9). Hip and knee full extension is reached only during walking. Maximum knee flexion is higher in running (about 90 degrees) than walking (about 60 degrees). Ankle joint angle ranges are greater in running (about 50 degrees) than in walking (about 30 degrees).