Full length articleCalcaneus range of motion underestimated by markers on running shoe heel
Introduction
Running studies regularly investigate rearfoot motion due to its link to running injury. For example, excessive tibial internal rotation is coupled to calcaneal movement in the frontal and transverse planes, with implications for both typical and pathological running gaits [1], [2], [3]. Investigations into rearfoot motion often use reflective markers attached to the runner’s shoe to estimate calcaneus kinematics. These methods are both noninvasive and have a short time requirement [4]; however, the use of shoe markers to estimate calcaneus kinematics assumes the motion of the shoe is identical to that of the foot [5]. Several studies have compared kinematic data collected directly from the calcaneus with that collected from shoe markers, yet there is disagreement on whether shoe markers accurately represent calcaneus motion in the frontal, sagittal, and transverse planes [6], [7], [8], [9], [10]. An investigation of calcaneus motion relative to the running shoe heel is needed to better interpret findings from the literature. In these studies, holes or “windows” were cut in the shoe heel to provide access to the foot within. The effect of this methodology on ankle kinematics has been indirectly investigated by Van Gheluwe et al. [11], who quantified changes in rearfoot frontal plane motion due to the heel counter rigidity. However, the effect of heel counter rigidity on knee kinematics is currently unknown.
Prior investigations suggest calcaneus motion is overestimated by shoe markers during running, but results focused primarily on frontal plane motion or did not control for confounding variables related to shoe design [6], [7], [8], [9], [10]. Several of these studies implemented bone pins when measuring calcaneus motion, and while the use of bone pins allows for a direct measurement of the calcaneus, study participants must often run at relatively low running speeds due to the procedure’s invasive nature, discomfort, or the required local anesthetic [6], [7], [10], [12].
The effect of such modifications on shoe deformation [13], kinematic data quality [14], and ankle kinematics [11] have been previously explored, but no studies have determined the effect of heel counter modification on lower leg kinematics during running. Excessive internal rotation of the tibia has been associated with common running injuries such as patella femoral pain syndrome and iliotibial band syndrome [15], [16], [17]. Additionally, the coupling relationship between the calcaneus, talus, and tibia suggests that changes in rearfoot motion can cause changes in more proximal segments [3]. Understanding the effect of placing holes in the heel counter of shoes on tibial kinematics may provide insight into the degree that such modifications can influence the overall function of footwear.
Therefore, the objectives of this study were to (1) use non-invasive skin markers to determine calcaneus three-dimensional ROM relative to the shoe heel during running, and (2) determine the effect of holes placed in the shoe’s heel counter on the internal rotation of the tibia across two levels of shoe support (neutral/support). It was hypothesized that markers on a neutral and support shoes would underestimate calcaneus ROM in the frontal, sagittal, and transverse planes. It was also hypothesized that there would be an effect of Support Level (Neutral/Support) on frontal plane ROM, with support shoes decreasing calcaneus ROM due to the presence of a medial midsole support [18], [19]. Lastly, it was hypothesized that holes in the shoe’s heel counter would have no effect on tibia rotation, indicating that this particular function of the shoe was not significantly affected by the required shoe modifications.
Section snippets
Participants
Kinematic data were collected on 14 healthy participants who were habitual rearfoot strikers (M/F: 9/5) and recreational runners (29 ± 17.4 (±SD) miles per week). Mean participant age was 29 ± 6 years (±SD) and mean body mass was 66.0 ± 8.5 kg (±SD). This study was performed in accordance with all applicable ethical regulations and all participants were informed of the procedures and risks of the study and provided written consent. Participants were excluded from the study if they had
Support level * marker set (Calcaneus)
There were no significant interactions between Marker Set and Support Level in the frontal, sagittal, or transverse plane (p = 0.141, p = 0.483, p = 0.409). There were significant main effects of Support Level (p = 0.021) and Marker Set (p < 0.001) on frontal plane ROM. In the frontal plane, mean calcaneus ROM was greater than shoe heel ROM by 1.5°. There was no main effect of Support Level on transverse plane ROM (p = 0.380) and sagittal plane ROM (p = 0.580). There were significant main
Discussion
The primary aim of the present study was to determine differences between shoe-mounted and skin marker 3D ROM during running. It was hypothesized that shoe markers would underestimate calcaneus ROM and the results support this hypothesis. Shoe markers significantly underestimated calcaneus ROM across all planes of motion by 1.5–5.9°. Additionally, neutral shoe ROM was greater than support shoe ROM by 0.9°, suggesting the medial post in the support shoe reduced calcaneus frontal plane ROM. The
Conclusions
The present study adds to the current literature a comparison of 3D calcaneus motion relative to neutral and support shoes, as well as an investigation of how shoe heel modifications affect tibial rotation. Given that shoe markers significantly underestimated calcaneus ROM across all planes of motion, it is concluded that shoe markers did not best represent calcaneus motion compared to skin markers and that there may be a need to differentiate between shoe and calcaneus kinematics in
Conflict of interest
The authors wish to confirm that MT and ER are currently employed at Brooks Running Company (Seattle, WA, USA). However, the results presented in this manuscript do not in any way represent a bias towards Brooks Running Company products over other brands.
Acknowledgements
Brooks Running Company (Seattle, WA, USA) funded this study and provided the footwear tested. However, the results presented in this article do not in away way represent a bias towards Brooks Running Company products over other brands.
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