Journal of Applied Biomechanics, 2015, 31, 28-34 http://dx.doi.org/10.1123/JAB.2014-0086 © 2015 Human Kinetics, Inc.
An Official Journal of ISB www.JAB-Journal.com ORIGINAL RESEARCH
The Effects of Orthotic Intervention on Multisegment Foot Kinematics and Plantar Fascia Strain in Recreational Runners J. Sinclair, J. Isherwood, and P.J. Taylor University of Central Lancashire Chronic injuries are a common complaint in recreational runners. Foot orthoses have been shown to be effective for the treatment of running injuries but their mechanical effects are still not well understood. This study aims to examine the influence of orthotic intervention on multisegment foot kinematics and plantar fascia strain during running. Fifteen male participants ran at 4.0 m∙s–1 with and without orthotics. Multisegment foot kinematics and plantar fascia strain were obtained during the stance phase and contrasted using paired t tests. Relative coronal plane range of motion of the midfoot relative to the rearfoot was significantly reduced with orthotics (1.0°) compared to without (2.2°). Similarly, relative transverse plane range of motion was significantly lower with orthotics (1.1°) compared to without (1.8°). Plantar fascia strain did not differ significantly between orthotic (7.1) and nonorthotic (7.1) conditions. This study shows that although orthotics did not serve to reduce plantar fascia strain, they are able to mediate reductions in coronal and transverse plane rotations of the midfoot. Keywords: running, orthoses, kinematics Distance running is known to be physiologically beneficial.1 However, studies analyzing the predominance of running injuries suggest that chronic injuries are a prominent complaint for both recreational and competitive runners alike.2 Over the course of one year, between 19.4%–79.3% of runners will experience an injury due to running.3 Malalignment of the foot segment has been associated with the etiology of chronic injuries.4,5 The coronal and transverse plane motion of the foot and tibia has been associated with a number of different pathologies such as tibial stress syndrome, plantar fasciitis, and anterior knee pain.6–9 A key mechanism advocated by both biomechanists and clinicians for the treatment and prevention of injuries are foot orthoses. Foot orthoses have been shown to be effective in the treatment of running injuries.10,11 However, the biomechanical mechanisms responsible for their clinical efficacy are not yet known. Foot orthoses habitually encompass some degree of medial arch support that mimics the contours of the medial longitudinal arch (MLA) and mechanically restrain nonsagittal rotations. Custom foot orthotics have been reported to reduce maximum foot eversion and ankle inversion moment during running;12 however, custom orthotics have also been shown not to influence lower extremity kinematics in runners who exhibit either forefoot or rearfoot strike patterns.13 While six weeks of custom foot orthotic therapy have demonstrated reductions in peak eversion, eversion velocity, and peak tibial internal rotation.14 A further key function of medial arch support in foot orthotics is to control MLA deformation. It has therefore been further hypothesized that foot orthoses may be able to attenuate plantar fascia strain by controlling the deflection of the MLA.15 However, Sinclair and Isherwood are with the Division of Sport Exercise and Nutritional Sciences, University of Central Lancashire, Preston, Lancashire, UK. Taylor is with the School of Psychology, University of Central Lancashire, Preston, Lancashire, UK. Address author correspondence to Sinclair at [email protected]. 28
the long held notion with regard to foot orthoses is that they serve to promote a restoration of normal foot mechanics. Nonetheless, the research investigating the effects of orthotic intervention in running have habitually used a single segment foot model,12–14 thus understanding the effects of foot orthoses on the coronal and transverse plane articulations of the foot segments, linked to the potential development of chronic injuries of the foot during running,16 have not been quantitatively examined. The effects of orthotic intervention have been examined in walking studies using multisegment foot models. Cobb et al17 observed increased rearfoot dorsiflexion during midstance when walking with an orthotic; they concluded that this may promote improved foot kinematics. Ferber and Benson18 examined the effects of semicustom orthotics on multisegment foot kinematics and plantar fascia strain during walking. They showed that plantar fascia strain was significantly reduced when walking using orthotics but they had reported significant effect on multisegment foot kinematics. There is currently a paucity of information regarding the influence of orthotic intervention on multisegment foot kinematics and plantar fascia strain during running. This study aims to examine the influence of orthotic shoe inserts on three-dimensional multisegment foot kinematics and plantar fascia strain during the stance phase of running. A study of this nature may be beneficial to runners who suffer from foot pathologies related to malalignment of the foot itself that may be treatable through orthotic intervention. The current investigation tests the hypothesis that orthotic intervention will reduce plantar fascia strain and reduce coronal and transverse plane motions of the foot segments.
Methods Participants Fifteen healthy male participants (age 25.41, SD 2.36 years; height 1.75 m, SD 0.12; mass 74.22, SD 4.45 kg) volunteered to take part
Effects of Orthotic Intervention on Foot Kinematics 29
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Figure 1 — Orthotic device used in the current investigation.
in this study. All were free from musculoskeletal pathology at the time of data collection and provided informed consent in written form. Ethical approval was obtained from a university ethical committee in accordance with the Declaration of Helsinki.
Orthotic Device Commercially available orthotics (Shock Stopper Sorbo Pro; Sorbothane, Nottinghamshire, UK) were examined in the current investigation (Figure 1). These orthotics were made from a custom foam polymer of 6 mm thickness under the calcaneus and featured medial arch support designed to control ankle motion in the coronal plane. Although the right side was selected for analysis, orthotic devices were placed inside both shoes.
Procedure Participants completed 10 trials running at 4.0 m∙s–1 ± 5% with and without orthotics. The order in which participants ran in each condition was counterbalanced. All runners were considered to be rearfoot strikers as they exhibited a clear first peak in their vertical ground reaction force-time curve. Multisegment foot kinematics were obtained at 250 Hz using an eight-camera motion analysis system (Qualisys Medical, Sweden). Participants struck an embedded force platform (Kistler 9281CA; Kistler Instruments, UK)19 sampling at 1000 Hz with their dominant foot. The stance phase of running was determined as the time over which > 20 N of force in the axial direction was applied to the force platform.20 Calibration of the motion analysis system was performed before each data collection session. Only calibrations which produced average residuals of less than 0.85 mm for each camera for a 750.5 mm wand length and points above 4000 in all cameras were accepted before data collection. The calibrated anatomical systems technique (CAST) for modeling and tracking segments was adhered to.21 Markers were placed on anatomical landmarks in accordance with the Leardini et al22 foot model protocol, allowing the anatomical frames of the calcaneus (Cal), midfoot (Mid), and forefoot (Fore) to be defined (Figure 2). Markers were positioned on the medial and lateral femoral epicondyles to allow the anatomical frame of the tibia (Tib) to be delineated and a rigid tracking cluster was also positioned on the tibia. Participants wore the same footwear throughout (Saucony Pro Grid Guide II; Saucony, USA).
Data Processing Data were digitized using Qualisys track manager and exported to Visual 3D (C-motion, Germantown, USA). Marker trajectories
Figure 2 — Marker set for multisegment foot kinematics and calculation of MLA angle (distance) between first metatarsal and medial calcaneus (1st Met = first metatarsal; Nav = navicular tuberosity; M Cal = medial calcaneus; MLA = medial longitudinal arch).
were filtered at 15 Hz using a low-pass zero-lag Butterworth filter. This frequency was selected based on residual analysis.23 Cardan angles were used to calculate three-dimensional rotations of the foot segments. Stance phase angles were computed using an XYZ Cardan sequence of rotations between the calcaneus-tibia (Cal-Tib), midfoot-calcaneus (Mid-Cal), forefoot-midfoot (For-Mid), and forefoot-calcaneus (For-Rear). MLA angle was quantified in accordance with the protocol documented by Tome et al24 as the angle created by the lines from the marker on the medial calcaneus to the navicular tuberosity and from the first metatarsal to the navicular tuberosity (Figure 1). Discrete three-dimensional kinematic measures which were extracted for statistical analysis were: (1) angle at foot strike, (2) angle at toe-off, (3) range of motion from foot strike to
30 Sinclair, Isherwood, and Taylor
toe-off during stance, (4) peak angle during stance, and (5) relative range of motion (representing the angular displacement from foot strike to peak angle). Plantar fascia strain (PFS) was quantified by calculating the distance between the first metatarsal and calcaneus markers and quantified as the relative position the markers were altered. PFS strain was calculated as the change in length during the stance phase divided by the original length.
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Statistical Analysis Descriptive statistics were calculated for both the orthotic and nonorthotic conditions. Differences in kinematic and plantar fascia parameters were examined using paired samples t tests with significance accepted at the P < .05 level.25 A Shapiro-Wilk test was used to screen the data for normality and it was confirmed that the normality assumption was not violated. Effect sizes for all statistical main effects were calculated using Cohen’s d. Statistical procedures were undertaken using SPSS v.21 (IBM Inc., USA).
Results The overall patterns of the multisegment foot and MLA waveforms were qualitatively similar between orthotic and nonorthotic conditions (Figures 3 and 4). Of the 66 experimental parameters, four exhibited significant differences. These differences were shown at the midfoot-rearfoot articulation (Table 1) and also the MLA (Table 2). At the midfoot-rearfoot there was a significant (t (14) = 8.95, P < .05, D = 5.40) increase (1.2°) in relative coronal plane motion when running without orthotics. There was also a significant (t (14) = 8.95, P < .05, D = 3.38) increase (0.7°) in transverse plane relative range of motion when running without orthotics (Table 1). No significant (P > .05) differences between orthotic and nonorthotic conditions were found at the rearfoot-tibial (Table 3), forefoot-midfoot (Table 4) and forefoot-rearfoot (Table 5) articulations. There was a significant (t (14) = 3.50, P < .05, D = 1.87) increase (3.7°) in MLA angle at foot strike when running with orthotics.
Figure 3 — Stance phase multisegment foot kinematics obtained when running with and without orthotics (black = nonorthotic; gray = orthotic): (a) sagittal, (b) coronal, and (c) transverse plane. (Rear-Tib = rearfoot-tibia; Mid-Rear = midfoot-rearfoot; For-Mid = forefoot-midfoot; For-Rear = forefootcalcaneus; DF = dorsiflexion; IN = inversion; INT = internal).
Effects of Orthotic Intervention on Foot Kinematics 31
There was also a significant (t (14) = 3.11, P < .05, D = 1.70) increase (4.0°) in peak MLA angle when running with orthotics (Table 2). No significant (P > .05) differences in PFS were observed.
Discussion
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Figure 4 — Medial longitudinal arch angles obtained when running with and without orthotics (black = nonorthotic; gray = orthotic).
This study aimed to determine whether orthotic shoe inserts influence three-dimensional multisegment foot kinematics and plantar fascia strain during the stance phase of running. This study represents the first to examine the effects of orthotic intervention on these parameters during running and may provide clinically meaningful information to runners. In support of the hypothesis, the first key observation from the current investigation was that the orthotic intervention was associated with reductions in coronal and transverse plane relative range of motion of the midfoot relative to the rearfoot. This finding opposes the walking studies of Cobb et al17 and Ferber and
Table 1 Midfoot-rearfoot kinematics with and without orthotic intervention
Sagittal plane Angle at foot strike (°) Angle at toe-off (°) Peak dorsiflexion (°) Range of motion (°) Relative range of motion (°) Coronal plane Angle at foot strike (°) Angle at toe-off (°) Peak eversion (°) Range of motion (°) Relative range of motion (°)* Transverse plane Angle at foot strike (°) Angle at toe-off (°) Peak external rotation (°) Range of motion (°) Relative range of motion (°)
Nonorthotic Mean SD
Orthotic Mean SD
0.7 –4.2 4.3 4.9 3.6
2.8 2.1 2.2 1.3 2.0
1.6 –2.9 5.2 4.5 3.7
2.3 1.5 1.1 1.4 1.8
P = .167, D = 0.79 P = .09, D = 0.99 P = .140, D = 0.85 P = .07, D = 1.07 P = .834, D = 0.11
0.1 –0.4 –2.2 0.6 2.2a
1.4 1.6 1.9 0.3 0.8
–0.4 –0.5 –1.4 0.7 1.0
1.8 2.2 2.2 0.4 0.7
P = .302, D = 0.58 P = .666, D = 0.24 P = .189, D = 0.75 P = .444, D = 0.42 P = .000002, D = 5.40
0.3 1.6 –1.2 1.4 1.8a
1.3 1.3 2.0 0.9 1.0
0.7 1.8 –0.5 1.3 1.1
1.1 1.1 1.6 0.8 0.8
P = .162, D = 0.80 P = .431, D = 0.44 P = .194 D = 0.74 P = .06, D = 1.14 P = .0001, D = 3.38
p Value, Effect Size
Note. * = significant difference. a Nonorthotic is significantly larger.
Table 2 MLA angle and PFS with and without orthotic intervention
Angle at foot strike (°) Angle at toe-off (°) Peak MLA angle (°) Range of motion (°) Relative range of motion (°) PFS
Nonorthotic Mean SD 140.1a 7.6 142.7 8.3 6.2 150.0a 2.4 1.1 9.8 3.5 7.1 5.3
Orthotic Mean SD 136.4 7.2 139.1 9.3 146.0 6.5 2.8 2.6 9.6 2.1 7.1 5.6
Note. MLA = medial longitudinal arch; PFS = plantar fascia strain. * Significant difference. a Nonorthotic is significantly larger.
p Value, Effect Size P = .015, D = 1.87* P = .320, D = 0.56 P = .020, D = 1.70* P = .782, D = 0.15 P = .332, D = 0.55 P = .732, D = 0.19
Table 3 Rearfoot-tibial kinematics with and without orthotic intervention
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Sagittal plane Angle at foot strike (°) Angle at toe-off (°) Peak dorsiflexion (°) Range of motion (°) Relative range of motion (°) Coronal plane Angle at foot strike (°) Angle at toe-off (°) Peak eversion (°) Range of motion (°) Relative range of motion (°) Transverse plane Angle at foot strike (°) Angle at toe-off (°) Peak external rotation (°) Range of motion (°) Relative range of motion (°)
Nonorthotic Mean SD
Orthotic Mean SD
8.6 –15.2 18.9 23.7 10.3
9.2 5.3 5.7 7.1 5.5
7.9 –15.3 18.7 23.3 10.8
8.9 4.8 4.4 7.0 6.2
P = .528, D = 0.35 P = .815, D = 0.13 P = .824, D = 0.44 P = .518, D = 0.36 P = .487, D = 0.38
2.3 1.0 –8.9 2.2 11.2
3.0 4.4 3.2 2.4 2.9
1.9 1.2 –8.0 1.9 9.8
3.1 4.9 3.1 1.7 2.4
P = .197, D = 0.73 P = .757, D = 0.17 P = .119, D = 0.90 P = .427, D = 0.44 P = .094, D = 1.14
–2.8 1.4 –8.4 4.3 5.7
5.6 6.7 5.2 3.3 3.0
–3.1 0.8 –8.6 4.1 5.5
5.2 6.0 4.8 2.9 2.5
P = .279, D = 0.61 P = .151, D = 0.83 P = .570, D = 0.31 P = .517, D = 0.36 P = .521, D = 0.35
p Value, Effect Size
Table 4 Forefoot-midfoot kinematics with and without orthotic intervention
Sagittal plane Angle at foot strike (°) Angle at toe-off (°) Peak dorsiflexion (°) Range of motion (°) Relative range of motion (°) Coronal plane Angle at foot strike (°) Angle at toe-off (°) Peak inversion (°) Range of motion (°) Relative range of motion (°) Transverse plane Angle at foot strike (°) Angle at toe-off (°) Peak internal rotation (°) Range of motion (°) Relative range of motion (°)
Nonorthotic Mean SD
Orthotic Mean SD
4.4 10.5 17.0 6.1 12.6
1.3 3.7 3.1 3.0 2.5
4.0 9.4 15.9 5.5 12.0
1.4 2.7 3.5 1.7 2.6
P = .392, D = 0.48 P = .235, D = 0.67 P = .078, D = 1.04 P = .259, D = 0.64 P = .125, D = 0.85
–1.1 0.3 0.8 1.4 1.9
0.7 1.0 1.2 0.8 1.0
–0.7 0.4 0.9 1.0 1.5
0.8 0.8 1.1 0.6 0.9
P = .113, D = 0.95 P = .718, D = 0.20 P = .889, D = 0.08 P = .123, D = 0.88 P = .142, D = 0.72
–0.1 0.2 1.1 0.7 1.2
0.3 1.0 1.0 0.5 0.8
0.0 0.3 1.1 0.5 1.0
0.8 1.0 1.1 0.4 0.6
P = .691, D = 0.22 P = .634, D = 0.26 P = .806, D = 0.13 P = .101, D = 0.96 P = .131, D = 0.87
p Value, Effect Size
Table 5 Forefoot-rearfoot kinematics with and without orthotic intervention
Sagittal plane Angle at foot strike (°) Angle at toe-off (°) Peak dorsiflexion (°) Range of motion (°) Relative range of motion (°) Coronal plane Angle at foot strike (°) Angle at toe-off (°) Peak eversion (°) Range of motion (°) Relative range of motion (°) Transverse plane Angle at foot strike (°) Angle at toe-off (°) Peak external rotation (°) Range of motion (°) Relative range of motion (°) 32
Nonorthotic Mean SD
Orthotic Mean SD
4.9 6.2 13.6 2.5 8.7
3.1 3.8 3.9 3 3.5
5.4 6.5 13.8 2.1 8.5
2.3 1.9 3 1.5 3.2
P = .473, D = 0.40 P = .828, D = 0.12 P = .734, D = 0.19 P = .505, D = 0.37 P = .425, D = 0.44
0.1 0.2 –2.1 0.8 2.3
1.7 2.2 2 0.3 0.7
–0.2 0 –2.1 0.8 1.9
2.2 2.5 2.3 0.4 0.8
P = .271, D = 0.62 P = .609, D = 0.28 P = .944, D = 0.04 P = .915, D = 0.06 P = .126, D = 0.88
–1.4 0.4 –2.1 1.8 0.7
1.7 1.4 1.9 0.6 0.8
–0.5 0.9 –1.2 1.5 0.7
1.2 1.1 1.4 0.6 0.7
P = .09, D = 1.00 P = .095, D = 0.98 P = .254, D = 0.66 P = .287, D = 0.59 P = .952, D = 0.03
p Value, Effect Size
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Effects of Orthotic Intervention on Foot Kinematics 33
Benson,18 who observed no significant differences in coronal and transverse plane motion as a function of orthotic intervention. It is hypothesized that this finding relates to the influence of the medial arch support, which is positioned at the midfoot region of the foot, physically restraining the coronal and transverse plane motions of the midfoot region. This observation supports the Williams et al26 hypothesis stating orthotic devices could control midfoot kinematics. Because coronal and transverse plane foot motions have been proposed as being associated with the etiology of chronic injuries,16 these results may be important to runners. However, it should be noted that the mean angular differences between conditions were small and thus further aetiological work is necessary before clinical significance can be established. This study also showed that peak MLA angle was decreased as a function of orthotic intervention. It is likely that this is attributable to the medial support provided by the orthotics serving to enhance the angulation between the calcaneus, navicular tuberosity, and first metatarsal landmarks. This observation disagrees with those of Ferber and Benson,18 who found no differences in MLA kinematics as a function of orthotic intervention. It is proposed that this divergence is attributable to the difference in locomotion velocity between studies, as the influence of orthotics is likely to be more pronounced at higher velocities. However, more importantly, the relative range of motion for MLA angle was shown not to differ between orthotic and nonorthotic conditions. This is further substantiated by the finding that PFS was similar between orthotic and nonorthotic conditions, an observation which opposes the hypothesis. Therefore, it can be concluded that although the orthotics used in the current investigation are able to influence the MLA angulation during the stance phase, they are not sufficiently robust to reduce its deflection magnitude following foot strike and thus the strain remains unchanged. There are a number of limitations that are associated with the current investigation. PFS and MLA were quantified using retroreflective markers attached to the foot segment and the location of this tissue was considered to span from the calcaneus to the first metatarsal. Although this technique has been used previously to quantify PFS and MLA18,24 and the measures presented here closely correspond with previous values, this represents a simplified technique for which there is likely to be some degree of error. It may be prudent for future analyses to consider more direct techniques such as digital fluoroscopy in conjunction with three-dimensional motion capture to provide more accurate measurements of PFS alongside multisegment foot kinematics. In conclusion, the findings from the current study show that while running with foot orthoses do not serve to influence plantar fascia strain they are associated with significant reductions in coronal and transverse plane motions of the midfoot when compared with running without orthotics. Given the proposed relationship between excessive coronal and transverse plane rotations of the foot segments and the etiology of injury, it is proposed that the potential risk of developing running injuries in relation to excessive coronal and transverse plane movements of the midfoot may be mediated through orthotic intervention.
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dysfunction and healthy controls. J Orthop Sports Phys Ther. 2006;36:635–644. PubMed doi:10.2519/jospt.2006.2293 25. Sinclair J, Taylor PJ, Hobbs SJ. Alpha level adjustments for multiple dependent variable analyses and their applicability – A review. Int J Sports Sci Eng. 2013;7(1):17–20. www.worldacademicunion.com/ journal/SSCI/SSCIvol07no01paper03.pdf 26. Williams DS, McClay Davis I, Baitch SP. Effect of inverted orthoses on lower-extremity mechanics in runners. Med Sci Sports Ex. 2003;35(12):2060–2068. PubMed
An Official Journal of ISB www.JAB-Journal.com ORIGINAL RESEARCH
The Effects of Orthotic Intervention on Multisegment Foot Kinematics and Plantar Fascia Strain in Recreational Runners J. Sinclair, J. Isherwood, and P.J. Taylor University of Central Lancashire Chronic injuries are a common complaint in recreational runners. Foot orthoses have been shown to be effective for the treatment of running injuries but their mechanical effects are still not well understood. This study aims to examine the influence of orthotic intervention on multisegment foot kinematics and plantar fascia strain during running. Fifteen male participants ran at 4.0 m∙s–1 with and without orthotics. Multisegment foot kinematics and plantar fascia strain were obtained during the stance phase and contrasted using paired t tests. Relative coronal plane range of motion of the midfoot relative to the rearfoot was significantly reduced with orthotics (1.0°) compared to without (2.2°). Similarly, relative transverse plane range of motion was significantly lower with orthotics (1.1°) compared to without (1.8°). Plantar fascia strain did not differ significantly between orthotic (7.1) and nonorthotic (7.1) conditions. This study shows that although orthotics did not serve to reduce plantar fascia strain, they are able to mediate reductions in coronal and transverse plane rotations of the midfoot. Keywords: running, orthoses, kinematics Distance running is known to be physiologically beneficial.1 However, studies analyzing the predominance of running injuries suggest that chronic injuries are a prominent complaint for both recreational and competitive runners alike.2 Over the course of one year, between 19.4%–79.3% of runners will experience an injury due to running.3 Malalignment of the foot segment has been associated with the etiology of chronic injuries.4,5 The coronal and transverse plane motion of the foot and tibia has been associated with a number of different pathologies such as tibial stress syndrome, plantar fasciitis, and anterior knee pain.6–9 A key mechanism advocated by both biomechanists and clinicians for the treatment and prevention of injuries are foot orthoses. Foot orthoses have been shown to be effective in the treatment of running injuries.10,11 However, the biomechanical mechanisms responsible for their clinical efficacy are not yet known. Foot orthoses habitually encompass some degree of medial arch support that mimics the contours of the medial longitudinal arch (MLA) and mechanically restrain nonsagittal rotations. Custom foot orthotics have been reported to reduce maximum foot eversion and ankle inversion moment during running;12 however, custom orthotics have also been shown not to influence lower extremity kinematics in runners who exhibit either forefoot or rearfoot strike patterns.13 While six weeks of custom foot orthotic therapy have demonstrated reductions in peak eversion, eversion velocity, and peak tibial internal rotation.14 A further key function of medial arch support in foot orthotics is to control MLA deformation. It has therefore been further hypothesized that foot orthoses may be able to attenuate plantar fascia strain by controlling the deflection of the MLA.15 However, Sinclair and Isherwood are with the Division of Sport Exercise and Nutritional Sciences, University of Central Lancashire, Preston, Lancashire, UK. Taylor is with the School of Psychology, University of Central Lancashire, Preston, Lancashire, UK. Address author correspondence to Sinclair at [email protected]. 28
the long held notion with regard to foot orthoses is that they serve to promote a restoration of normal foot mechanics. Nonetheless, the research investigating the effects of orthotic intervention in running have habitually used a single segment foot model,12–14 thus understanding the effects of foot orthoses on the coronal and transverse plane articulations of the foot segments, linked to the potential development of chronic injuries of the foot during running,16 have not been quantitatively examined. The effects of orthotic intervention have been examined in walking studies using multisegment foot models. Cobb et al17 observed increased rearfoot dorsiflexion during midstance when walking with an orthotic; they concluded that this may promote improved foot kinematics. Ferber and Benson18 examined the effects of semicustom orthotics on multisegment foot kinematics and plantar fascia strain during walking. They showed that plantar fascia strain was significantly reduced when walking using orthotics but they had reported significant effect on multisegment foot kinematics. There is currently a paucity of information regarding the influence of orthotic intervention on multisegment foot kinematics and plantar fascia strain during running. This study aims to examine the influence of orthotic shoe inserts on three-dimensional multisegment foot kinematics and plantar fascia strain during the stance phase of running. A study of this nature may be beneficial to runners who suffer from foot pathologies related to malalignment of the foot itself that may be treatable through orthotic intervention. The current investigation tests the hypothesis that orthotic intervention will reduce plantar fascia strain and reduce coronal and transverse plane motions of the foot segments.
Methods Participants Fifteen healthy male participants (age 25.41, SD 2.36 years; height 1.75 m, SD 0.12; mass 74.22, SD 4.45 kg) volunteered to take part
Effects of Orthotic Intervention on Foot Kinematics 29
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Figure 1 — Orthotic device used in the current investigation.
in this study. All were free from musculoskeletal pathology at the time of data collection and provided informed consent in written form. Ethical approval was obtained from a university ethical committee in accordance with the Declaration of Helsinki.
Orthotic Device Commercially available orthotics (Shock Stopper Sorbo Pro; Sorbothane, Nottinghamshire, UK) were examined in the current investigation (Figure 1). These orthotics were made from a custom foam polymer of 6 mm thickness under the calcaneus and featured medial arch support designed to control ankle motion in the coronal plane. Although the right side was selected for analysis, orthotic devices were placed inside both shoes.
Procedure Participants completed 10 trials running at 4.0 m∙s–1 ± 5% with and without orthotics. The order in which participants ran in each condition was counterbalanced. All runners were considered to be rearfoot strikers as they exhibited a clear first peak in their vertical ground reaction force-time curve. Multisegment foot kinematics were obtained at 250 Hz using an eight-camera motion analysis system (Qualisys Medical, Sweden). Participants struck an embedded force platform (Kistler 9281CA; Kistler Instruments, UK)19 sampling at 1000 Hz with their dominant foot. The stance phase of running was determined as the time over which > 20 N of force in the axial direction was applied to the force platform.20 Calibration of the motion analysis system was performed before each data collection session. Only calibrations which produced average residuals of less than 0.85 mm for each camera for a 750.5 mm wand length and points above 4000 in all cameras were accepted before data collection. The calibrated anatomical systems technique (CAST) for modeling and tracking segments was adhered to.21 Markers were placed on anatomical landmarks in accordance with the Leardini et al22 foot model protocol, allowing the anatomical frames of the calcaneus (Cal), midfoot (Mid), and forefoot (Fore) to be defined (Figure 2). Markers were positioned on the medial and lateral femoral epicondyles to allow the anatomical frame of the tibia (Tib) to be delineated and a rigid tracking cluster was also positioned on the tibia. Participants wore the same footwear throughout (Saucony Pro Grid Guide II; Saucony, USA).
Data Processing Data were digitized using Qualisys track manager and exported to Visual 3D (C-motion, Germantown, USA). Marker trajectories
Figure 2 — Marker set for multisegment foot kinematics and calculation of MLA angle (distance) between first metatarsal and medial calcaneus (1st Met = first metatarsal; Nav = navicular tuberosity; M Cal = medial calcaneus; MLA = medial longitudinal arch).
were filtered at 15 Hz using a low-pass zero-lag Butterworth filter. This frequency was selected based on residual analysis.23 Cardan angles were used to calculate three-dimensional rotations of the foot segments. Stance phase angles were computed using an XYZ Cardan sequence of rotations between the calcaneus-tibia (Cal-Tib), midfoot-calcaneus (Mid-Cal), forefoot-midfoot (For-Mid), and forefoot-calcaneus (For-Rear). MLA angle was quantified in accordance with the protocol documented by Tome et al24 as the angle created by the lines from the marker on the medial calcaneus to the navicular tuberosity and from the first metatarsal to the navicular tuberosity (Figure 1). Discrete three-dimensional kinematic measures which were extracted for statistical analysis were: (1) angle at foot strike, (2) angle at toe-off, (3) range of motion from foot strike to
30 Sinclair, Isherwood, and Taylor
toe-off during stance, (4) peak angle during stance, and (5) relative range of motion (representing the angular displacement from foot strike to peak angle). Plantar fascia strain (PFS) was quantified by calculating the distance between the first metatarsal and calcaneus markers and quantified as the relative position the markers were altered. PFS strain was calculated as the change in length during the stance phase divided by the original length.
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Statistical Analysis Descriptive statistics were calculated for both the orthotic and nonorthotic conditions. Differences in kinematic and plantar fascia parameters were examined using paired samples t tests with significance accepted at the P < .05 level.25 A Shapiro-Wilk test was used to screen the data for normality and it was confirmed that the normality assumption was not violated. Effect sizes for all statistical main effects were calculated using Cohen’s d. Statistical procedures were undertaken using SPSS v.21 (IBM Inc., USA).
Results The overall patterns of the multisegment foot and MLA waveforms were qualitatively similar between orthotic and nonorthotic conditions (Figures 3 and 4). Of the 66 experimental parameters, four exhibited significant differences. These differences were shown at the midfoot-rearfoot articulation (Table 1) and also the MLA (Table 2). At the midfoot-rearfoot there was a significant (t (14) = 8.95, P < .05, D = 5.40) increase (1.2°) in relative coronal plane motion when running without orthotics. There was also a significant (t (14) = 8.95, P < .05, D = 3.38) increase (0.7°) in transverse plane relative range of motion when running without orthotics (Table 1). No significant (P > .05) differences between orthotic and nonorthotic conditions were found at the rearfoot-tibial (Table 3), forefoot-midfoot (Table 4) and forefoot-rearfoot (Table 5) articulations. There was a significant (t (14) = 3.50, P < .05, D = 1.87) increase (3.7°) in MLA angle at foot strike when running with orthotics.
Figure 3 — Stance phase multisegment foot kinematics obtained when running with and without orthotics (black = nonorthotic; gray = orthotic): (a) sagittal, (b) coronal, and (c) transverse plane. (Rear-Tib = rearfoot-tibia; Mid-Rear = midfoot-rearfoot; For-Mid = forefoot-midfoot; For-Rear = forefootcalcaneus; DF = dorsiflexion; IN = inversion; INT = internal).
Effects of Orthotic Intervention on Foot Kinematics 31
There was also a significant (t (14) = 3.11, P < .05, D = 1.70) increase (4.0°) in peak MLA angle when running with orthotics (Table 2). No significant (P > .05) differences in PFS were observed.
Discussion
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Figure 4 — Medial longitudinal arch angles obtained when running with and without orthotics (black = nonorthotic; gray = orthotic).
This study aimed to determine whether orthotic shoe inserts influence three-dimensional multisegment foot kinematics and plantar fascia strain during the stance phase of running. This study represents the first to examine the effects of orthotic intervention on these parameters during running and may provide clinically meaningful information to runners. In support of the hypothesis, the first key observation from the current investigation was that the orthotic intervention was associated with reductions in coronal and transverse plane relative range of motion of the midfoot relative to the rearfoot. This finding opposes the walking studies of Cobb et al17 and Ferber and
Table 1 Midfoot-rearfoot kinematics with and without orthotic intervention
Sagittal plane Angle at foot strike (°) Angle at toe-off (°) Peak dorsiflexion (°) Range of motion (°) Relative range of motion (°) Coronal plane Angle at foot strike (°) Angle at toe-off (°) Peak eversion (°) Range of motion (°) Relative range of motion (°)* Transverse plane Angle at foot strike (°) Angle at toe-off (°) Peak external rotation (°) Range of motion (°) Relative range of motion (°)
Nonorthotic Mean SD
Orthotic Mean SD
0.7 –4.2 4.3 4.9 3.6
2.8 2.1 2.2 1.3 2.0
1.6 –2.9 5.2 4.5 3.7
2.3 1.5 1.1 1.4 1.8
P = .167, D = 0.79 P = .09, D = 0.99 P = .140, D = 0.85 P = .07, D = 1.07 P = .834, D = 0.11
0.1 –0.4 –2.2 0.6 2.2a
1.4 1.6 1.9 0.3 0.8
–0.4 –0.5 –1.4 0.7 1.0
1.8 2.2 2.2 0.4 0.7
P = .302, D = 0.58 P = .666, D = 0.24 P = .189, D = 0.75 P = .444, D = 0.42 P = .000002, D = 5.40
0.3 1.6 –1.2 1.4 1.8a
1.3 1.3 2.0 0.9 1.0
0.7 1.8 –0.5 1.3 1.1
1.1 1.1 1.6 0.8 0.8
P = .162, D = 0.80 P = .431, D = 0.44 P = .194 D = 0.74 P = .06, D = 1.14 P = .0001, D = 3.38
p Value, Effect Size
Note. * = significant difference. a Nonorthotic is significantly larger.
Table 2 MLA angle and PFS with and without orthotic intervention
Angle at foot strike (°) Angle at toe-off (°) Peak MLA angle (°) Range of motion (°) Relative range of motion (°) PFS
Nonorthotic Mean SD 140.1a 7.6 142.7 8.3 6.2 150.0a 2.4 1.1 9.8 3.5 7.1 5.3
Orthotic Mean SD 136.4 7.2 139.1 9.3 146.0 6.5 2.8 2.6 9.6 2.1 7.1 5.6
Note. MLA = medial longitudinal arch; PFS = plantar fascia strain. * Significant difference. a Nonorthotic is significantly larger.
p Value, Effect Size P = .015, D = 1.87* P = .320, D = 0.56 P = .020, D = 1.70* P = .782, D = 0.15 P = .332, D = 0.55 P = .732, D = 0.19
Table 3 Rearfoot-tibial kinematics with and without orthotic intervention
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Sagittal plane Angle at foot strike (°) Angle at toe-off (°) Peak dorsiflexion (°) Range of motion (°) Relative range of motion (°) Coronal plane Angle at foot strike (°) Angle at toe-off (°) Peak eversion (°) Range of motion (°) Relative range of motion (°) Transverse plane Angle at foot strike (°) Angle at toe-off (°) Peak external rotation (°) Range of motion (°) Relative range of motion (°)
Nonorthotic Mean SD
Orthotic Mean SD
8.6 –15.2 18.9 23.7 10.3
9.2 5.3 5.7 7.1 5.5
7.9 –15.3 18.7 23.3 10.8
8.9 4.8 4.4 7.0 6.2
P = .528, D = 0.35 P = .815, D = 0.13 P = .824, D = 0.44 P = .518, D = 0.36 P = .487, D = 0.38
2.3 1.0 –8.9 2.2 11.2
3.0 4.4 3.2 2.4 2.9
1.9 1.2 –8.0 1.9 9.8
3.1 4.9 3.1 1.7 2.4
P = .197, D = 0.73 P = .757, D = 0.17 P = .119, D = 0.90 P = .427, D = 0.44 P = .094, D = 1.14
–2.8 1.4 –8.4 4.3 5.7
5.6 6.7 5.2 3.3 3.0
–3.1 0.8 –8.6 4.1 5.5
5.2 6.0 4.8 2.9 2.5
P = .279, D = 0.61 P = .151, D = 0.83 P = .570, D = 0.31 P = .517, D = 0.36 P = .521, D = 0.35
p Value, Effect Size
Table 4 Forefoot-midfoot kinematics with and without orthotic intervention
Sagittal plane Angle at foot strike (°) Angle at toe-off (°) Peak dorsiflexion (°) Range of motion (°) Relative range of motion (°) Coronal plane Angle at foot strike (°) Angle at toe-off (°) Peak inversion (°) Range of motion (°) Relative range of motion (°) Transverse plane Angle at foot strike (°) Angle at toe-off (°) Peak internal rotation (°) Range of motion (°) Relative range of motion (°)
Nonorthotic Mean SD
Orthotic Mean SD
4.4 10.5 17.0 6.1 12.6
1.3 3.7 3.1 3.0 2.5
4.0 9.4 15.9 5.5 12.0
1.4 2.7 3.5 1.7 2.6
P = .392, D = 0.48 P = .235, D = 0.67 P = .078, D = 1.04 P = .259, D = 0.64 P = .125, D = 0.85
–1.1 0.3 0.8 1.4 1.9
0.7 1.0 1.2 0.8 1.0
–0.7 0.4 0.9 1.0 1.5
0.8 0.8 1.1 0.6 0.9
P = .113, D = 0.95 P = .718, D = 0.20 P = .889, D = 0.08 P = .123, D = 0.88 P = .142, D = 0.72
–0.1 0.2 1.1 0.7 1.2
0.3 1.0 1.0 0.5 0.8
0.0 0.3 1.1 0.5 1.0
0.8 1.0 1.1 0.4 0.6
P = .691, D = 0.22 P = .634, D = 0.26 P = .806, D = 0.13 P = .101, D = 0.96 P = .131, D = 0.87
p Value, Effect Size
Table 5 Forefoot-rearfoot kinematics with and without orthotic intervention
Sagittal plane Angle at foot strike (°) Angle at toe-off (°) Peak dorsiflexion (°) Range of motion (°) Relative range of motion (°) Coronal plane Angle at foot strike (°) Angle at toe-off (°) Peak eversion (°) Range of motion (°) Relative range of motion (°) Transverse plane Angle at foot strike (°) Angle at toe-off (°) Peak external rotation (°) Range of motion (°) Relative range of motion (°) 32
Nonorthotic Mean SD
Orthotic Mean SD
4.9 6.2 13.6 2.5 8.7
3.1 3.8 3.9 3 3.5
5.4 6.5 13.8 2.1 8.5
2.3 1.9 3 1.5 3.2
P = .473, D = 0.40 P = .828, D = 0.12 P = .734, D = 0.19 P = .505, D = 0.37 P = .425, D = 0.44
0.1 0.2 –2.1 0.8 2.3
1.7 2.2 2 0.3 0.7
–0.2 0 –2.1 0.8 1.9
2.2 2.5 2.3 0.4 0.8
P = .271, D = 0.62 P = .609, D = 0.28 P = .944, D = 0.04 P = .915, D = 0.06 P = .126, D = 0.88
–1.4 0.4 –2.1 1.8 0.7
1.7 1.4 1.9 0.6 0.8
–0.5 0.9 –1.2 1.5 0.7
1.2 1.1 1.4 0.6 0.7
P = .09, D = 1.00 P = .095, D = 0.98 P = .254, D = 0.66 P = .287, D = 0.59 P = .952, D = 0.03
p Value, Effect Size
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Effects of Orthotic Intervention on Foot Kinematics 33
Benson,18 who observed no significant differences in coronal and transverse plane motion as a function of orthotic intervention. It is hypothesized that this finding relates to the influence of the medial arch support, which is positioned at the midfoot region of the foot, physically restraining the coronal and transverse plane motions of the midfoot region. This observation supports the Williams et al26 hypothesis stating orthotic devices could control midfoot kinematics. Because coronal and transverse plane foot motions have been proposed as being associated with the etiology of chronic injuries,16 these results may be important to runners. However, it should be noted that the mean angular differences between conditions were small and thus further aetiological work is necessary before clinical significance can be established. This study also showed that peak MLA angle was decreased as a function of orthotic intervention. It is likely that this is attributable to the medial support provided by the orthotics serving to enhance the angulation between the calcaneus, navicular tuberosity, and first metatarsal landmarks. This observation disagrees with those of Ferber and Benson,18 who found no differences in MLA kinematics as a function of orthotic intervention. It is proposed that this divergence is attributable to the difference in locomotion velocity between studies, as the influence of orthotics is likely to be more pronounced at higher velocities. However, more importantly, the relative range of motion for MLA angle was shown not to differ between orthotic and nonorthotic conditions. This is further substantiated by the finding that PFS was similar between orthotic and nonorthotic conditions, an observation which opposes the hypothesis. Therefore, it can be concluded that although the orthotics used in the current investigation are able to influence the MLA angulation during the stance phase, they are not sufficiently robust to reduce its deflection magnitude following foot strike and thus the strain remains unchanged. There are a number of limitations that are associated with the current investigation. PFS and MLA were quantified using retroreflective markers attached to the foot segment and the location of this tissue was considered to span from the calcaneus to the first metatarsal. Although this technique has been used previously to quantify PFS and MLA18,24 and the measures presented here closely correspond with previous values, this represents a simplified technique for which there is likely to be some degree of error. It may be prudent for future analyses to consider more direct techniques such as digital fluoroscopy in conjunction with three-dimensional motion capture to provide more accurate measurements of PFS alongside multisegment foot kinematics. In conclusion, the findings from the current study show that while running with foot orthoses do not serve to influence plantar fascia strain they are associated with significant reductions in coronal and transverse plane motions of the midfoot when compared with running without orthotics. Given the proposed relationship between excessive coronal and transverse plane rotations of the foot segments and the etiology of injury, it is proposed that the potential risk of developing running injuries in relation to excessive coronal and transverse plane movements of the midfoot may be mediated through orthotic intervention.
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