Various methods of classifying foot structure have been presented in the literature, including, but not limited to, the Foot Posture Index [18, 19] and longitudinal arch angle [20, 21]. Classification of foot type attempts to distinguish between the static postures of a hyper-pronated, supinated, or neutrally aligned foot (Fig. 3.2). Though static foot structure has been postulated to contribute to pathology, results in the literature are conflicting [17, 22–24]. A hyper-pronated, low-arched foot is thought to contribute to excessive torsional forces about the tibia and strain on lower extremity musculature, as increased eccentric demands are required to control excessive motion. Conversely, a supinated or high-arched foot is thought to contribute to excessive stress on the bony architecture due the decreased ability to adequately absorb and dampen ground reaction forces [25].

Observational gait analysis is the most widely utilized and least expensive form of running analysis. It is a gross analysis where the examiner will directly observe a runner with the naked eye in real-time. Attention is placed on the movements associated within each phase of the running cycle and is monitored in each of the three cardinal planes of motion. Anatomical markers may be placed on specific bony landmarks to assist with observation of body segments, and is especially beneficial when looking at more subtle movements, such as rotation in the transverse plane.

Due to the high limb velocities associated with running, it is difficult to examine specific amounts of motion or the simultaneous coordination of multiple joint segments of the lower kinetic chain [39]. Therefore, each joint or anatomical region is individually observed and examined in accordance with period of the running phase. Usually, observation of the loading phase of stance follows a “bottom up” approach, identifying the lower extremity’s ability to pronate first at the foot and ankle, followed by progression up the lower kinetic chain. Conversely, when evaluating the later phase of stance, which focuses on the ability of the lower extremity to supinate, an observer can utilize a “top down” methodology [15].

The use of a video capture device will help enhance the accuracy of observational analysis. It will further allow a more quantitative description of gait parameters in relation to joint kinematics, however lacks the ability to measure associated forces acting upon the body. Motion capture is helpful to observe the movements and positions of multiple joint segments simultaneously, and assist with identifying other characteristics of gait including cadence, step length, stride length, and running speed [15]. To maintain a level of consistency and accuracy with measuring joint angles and positions within and between assessments, the marking of certain bilateral anatomical landmarks is advised (Fig. 3.3). A typical marker setup may include the anterior superior iliac spine (ASIS), posterior superior iliac spine (PSIS), greater trochanter, lateral femoral condyle, tibial tubercle, knee joint line, bisection of the posterior calcaneus, and second ray. Tight fitting clothing with increased exposure of the skin is also helpful when assessing true human movement.

The simplest form of motion capture is using a standard video camera (30–60 frames/s) that can view the runner from anterior, posterior, or lateral views. Though there has been evidence for the effectiveness of two-dimension motion analysis [40], especially in regards to observing frontal plane joint projections [41], there are inherent limitations of its use with gait analysis. Transverse plane and combined tri-planer motions are harder to interpret and often less accurate. Due to the subtlety of transverse plane motion, which is out of plane in relation to the view of the motion capture device, true representations of rotational movements are more difficult to appreciate. However, the information gathered can still be useful and may assist a medical professional in directing future management of the healthy or injured runner.

More advanced forms of motion analysis systems have been developed that enable a clinician to readily capture three-dimensional measurements [42]. Though often more expensive, they are feasible for clinical use and provide more accurate representations of movement. With the use of reflective markers, computers assist in the capturing and processing of information regarding motion of limb segments, joint velocities, and joint angles [15].

Multiple high-speed motion capture systems and intricate computer software are also utilized for analyzing running in three-dimensions. Three-dimensional analysis is ideal, and has been found to be accurate in assessing running kinematics [43]. Kinematic data can further be utilized in conjunction with force plate data and electromyography (EMG). However, due to the costliness and longer setup times of such instrumentation, these measures are often utilized for laboratory, experimental gait analysis purposes. The use of force plates will provide information pertaining to how ground reaction forces in the vertical, horizontal, and transverse planes are imposed onto the body during the stance phase of running. This can be done with force plates mounted in the floor. Often, a laboratory setting makes the simulation of a normal running stride difficult and potentially unattainable due to limited space and the location of the force plate relative to the runner’s normal stride [44, 45]. Due to the high stride to stride variance in ground reaction force measurements of both over ground and treadmill running, sufficient steps are preferred and best gathered via an instrumented treadmill [46]. Whether with level ground observation or via instrumented treadmill, measures of vertical loads, horizontal shear, vector patterns, joint torques, and center of pressure are helpful in the prevention and management of bony stress injuries [15]. EMG data is captured either by surface or fine wire electrodes, and can help in the analysis of a runner’s neuromuscular control and patterns of muscle timing.

Sagittal plane joint position and motion at the trunk, hip, knee, and ankle must be closely examined to identify possible risk factors that may predispose a running athlete to injuries. This can best be accomplished through inspecting an athlete from the lateral view. Joint positions during loading are highly related to kinetic and kinematic data that may place a runner at risk for injuries such as stress fractures. Reports show that 600,000–1,920,000 runners per year will sustain a stress fracture [1]. Due to this high volume of injuries, attempts to understand the mechanisms of these injuries have been the goal of recent research, with repeated impact loading being deemed the primary root cause [6]. Ground reaction forces, the forces exerted by the ground on a body [47], have been commonly measured as a way to approximate the external load acting on body structures during running.

To fully understand the effects of forces acting on the body, certain terminology should be defined. Loading rate is defined as the speed at which forces are applied to the body and can be identified using accelerometers or by the initial slope of the ground reaction force curve as the foot makes contact with the support surface. The steeper this slope of early stance on the ground reaction force curve, the more rapid the force application onto the body (Fig. 3.4). Vertical average loading rate, vertical impact peak, and vertical instantaneous loading rate seems to be higher in those who sustained overuse running related injuries [48].