Rike patterns and running injuries, more work is necessary before broad conclusions on foot strike recommendations can be made to modify injury risk. Foot Inclination Angle at Initial Contact The angle created by the sole of the shoe and the treadmill belt is noted as the inclination angle of the foot (relative to a global coordinate system, not the tibia) at initial contact (Fig. 3). This variable is not applicable for midfoot strike and FFS runners. A recent study by Wille and colleagues21 found inclination angle to be particularly important in estimating ground reaction forces and joint kinetics during running. Specifically, increased foot inclination angle was found to be related to higher peak knee extensor moments, increased knee energy absorbed, higher peak vertical ground reaction force, and greater braking impulse during running. Each of these variables has been implicated in injury biomechanics, suggesting that a very high foot inclination angle at initial contact may not be desirable. This may be a source for intervention in runners whoPhys Med Rehabil Clin N Am. Author manuscript; available in PMC 2016 February 01.SouzaPageexperience injuries associated with high ground reaction forces or excessive joint kinetics. There are no cutoffs at which this angle is determined to be abnormal. Rather, it is likely on a sliding scale, where lower values are generally associated with lower ground reaction forces and joint kinetics, and higher values as associated with increased forces. However, it PD325901 web should be noted that a high foot inclination angle in isolation may be a benign finding and needs to be evaluated in the context of the entire running evaluations (see Overstriding). Tibia Angle at Loading Response The vertical alignment of the lower leg during loading response can be a valuable indicator of stride mechanics. Video of the runner should be evaluated using freeze-frames at the moment of loading response (as the shoe begins to deform just after initial contact). The alignment of the lower leg relative to a vertical line in the video field of view can be evaluated easily. An extended tibia is identified when the lateral knee joint marker is posterior to the lateral malleolus marker (Fig. 4A). Conversely, a flexed tibia is identified when the lateral knee marker is anterior to the lateral malleolus (Fig. 4C), and when these 2 markers are directly vertical to one another, this would be identified as a vertical tibia (Fig. 4B). For a runner that suffers from impact-related running injuries, an extended tibia is not ideal. A vertical or flexed tibia allows the runner to dissipate impact more readily though knee flexion. Similar to foot inclination angle, the tibia angle in itself may not be meaningful in isolation. It is a variable that can be grouped in a series of stride mechanics variables to better describe the characteristics of the runners stride and biomechanical risk profile. Knee Flexion During Stance Peak knee flexion angle during stance may occur at slightly different phases in different runners. It is recommended to scroll through stance phase frames to identify maximum knee flexion. Key aspects of knee flexion during stance include the peak Pemafibrate web amount of knee flexion and the knee joint excursion during stance (difference in angle from initial contact to peak knee flexion). In general, normal peak knee flexion approaches approximately 45?at midstance (Fig. 5). Although explicit cutoffs have not been developed for this variable.Rike patterns and running injuries, more work is necessary before broad conclusions on foot strike recommendations can be made to modify injury risk. Foot Inclination Angle at Initial Contact The angle created by the sole of the shoe and the treadmill belt is noted as the inclination angle of the foot (relative to a global coordinate system, not the tibia) at initial contact (Fig. 3). This variable is not applicable for midfoot strike and FFS runners. A recent study by Wille and colleagues21 found inclination angle to be particularly important in estimating ground reaction forces and joint kinetics during running. Specifically, increased foot inclination angle was found to be related to higher peak knee extensor moments, increased knee energy absorbed, higher peak vertical ground reaction force, and greater braking impulse during running. Each of these variables has been implicated in injury biomechanics, suggesting that a very high foot inclination angle at initial contact may not be desirable. This may be a source for intervention in runners whoPhys Med Rehabil Clin N Am. Author manuscript; available in PMC 2016 February 01.SouzaPageexperience injuries associated with high ground reaction forces or excessive joint kinetics. There are no cutoffs at which this angle is determined to be abnormal. Rather, it is likely on a sliding scale, where lower values are generally associated with lower ground reaction forces and joint kinetics, and higher values as associated with increased forces. However, it should be noted that a high foot inclination angle in isolation may be a benign finding and needs to be evaluated in the context of the entire running evaluations (see Overstriding). Tibia Angle at Loading Response The vertical alignment of the lower leg during loading response can be a valuable indicator of stride mechanics. Video of the runner should be evaluated using freeze-frames at the moment of loading response (as the shoe begins to deform just after initial contact). The alignment of the lower leg relative to a vertical line in the video field of view can be evaluated easily. An extended tibia is identified when the lateral knee joint marker is posterior to the lateral malleolus marker (Fig. 4A). Conversely, a flexed tibia is identified when the lateral knee marker is anterior to the lateral malleolus (Fig. 4C), and when these 2 markers are directly vertical to one another, this would be identified as a vertical tibia (Fig. 4B). For a runner that suffers from impact-related running injuries, an extended tibia is not ideal. A vertical or flexed tibia allows the runner to dissipate impact more readily though knee flexion. Similar to foot inclination angle, the tibia angle in itself may not be meaningful in isolation. It is a variable that can be grouped in a series of stride mechanics variables to better describe the characteristics of the runners stride and biomechanical risk profile. Knee Flexion During Stance Peak knee flexion angle during stance may occur at slightly different phases in different runners. It is recommended to scroll through stance phase frames to identify maximum knee flexion. Key aspects of knee flexion during stance include the peak amount of knee flexion and the knee joint excursion during stance (difference in angle from initial contact to peak knee flexion). In general, normal peak knee flexion approaches approximately 45?at midstance (Fig. 5). Although explicit cutoffs have not been developed for this variable.
