16th June 2015

Orthotic Heel Wedges do not alter Hindfoot Kinematics and Achilles Tendon Force

during Level and Inclined Walking in Healthy Individuals

Robert A Weinert-Aplin,1,2 Anthony M J Bull,2 Alison H McGregor1

1 Department of Surgery and Cancer, Imperial College London, London, U.K.; 2 Department

of Bioengineering, Imperial College London, London, U.K.

Funding: This study was funded by an EPSRC Case award, with financial contributions from

Vicon Motion Systems for the running costs of the project.

Conflicts of interest statement: None

Correspondence Address:

Robert Weinert-Aplin, Department of Bioengineering, Royal School of Mines, South Kensington Campus, Imperial College London, London, SW7 2AZ, United Kingdom

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Abstract

Conservative treatments such as in-shoe orthotic heel wedges to treat musculoskeletal

pathologies are not new. However, the mechanical basis by which such orthoses act have not

been elucidated. Quantifying the mechanical changes that occur when wearing heel wedges

may help to explain the mixed evidence supporting their use in management of Achilles

tendonitis.

A musculoskeletal modelling approach was used to quantify changes in lower limb

mechanics when walking due to the introduction of 12mm orthotic heel wedges. A control

group of 19 healthy volunteers walked on a level and inclined walkway while optical motion,

forceplate and plantar pressure data were recorded as model inputs.

Heel wedges induced a posterior shift of centre of pressure that resulted in increased ankle

dorsi-flexion moments and reduced plantar-flexion moments. Consequently, this resulted in

increased peak ankle dorsi-flexor muscle forces during early stance and reduced Tibialis

Posterior and toe flexor muscles forces during late stance. Heel wedges did not reduce triceps

surae muscle forces during any walking condition.

These results add to the body of clinical evidence that does notagainst the use of support heel

wedges hypothesised to reduce Achilles tendon loading, as a means to treat Achilles

tendonitis according to the hypothesis that heel wedges reduce Achilles tendon load during

walking . our and the findings provide an explanation as to why this may be the casetheory is

not appropriate.

Keywords: tendonitis, tendinitis, musculoskeletal, modelling, conservative treatment

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Introduction

The Achilles tendon is functionally important as it is the main driver of ankle motion

during locomotion. Consequently it is a highly loaded tendon, with reported loads of up to 5

times body weight (BW) during level walking1 and 8.2BW- 12.5BW during running.2,3 With

such high cyclic loads being experienced by the Achilles, it is unsurprising that the Achilles

is a common site of overuse injury,4 with 5-18% of all lower extremity injuries involving the

Achilles tendon.5 As a result of this high injury prevalence, there have been a number of

reviews into Achilles injuries.6-11

Risk factors for Achilles injuries include: magnitude of Achilles tendon load,

inappropriate equipment such as inflexible shoes, low heel tabs on running

shoesinappropriate footwear12, training errors7 and abnormal kinematics.6 Abnormal

kinematics are generally considered to be related to over-pronation of the subtalar joint

hindfoot causing asymmetric loading across the Achilles tendon.7 While there is some

evidence to show differences in strain across the tendon cross-section13 and along the length,14

over-pronation alone has not been linked to injury risk in running.5,15-17 It has also been shown

that differences exist between Medial Gastrocnemius and Soleus contractile behaviour during

walking,18,19 running20 and cycling,21 suggesting that differential strains across the tendon may

exist naturally during these activities.

Treatments for tendinopathies have varied substantially over the years, but have

always been aimed at reducing or eliminating pain in the tendon. Conservative treatments

which directly address the Achilles tendon include: have included: Rest Ice Compression

Elevation, eccentric strengthening exercises,22-25 insoles and splints24,26 and ultrasound.27 Of

the treatments that influence mechanical alignment of the hindfoot, insoles and splints are the

only option24,26, but have been shown

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The use of insoles or orthotics to correct abnormal hindfoot motion and correct for

biomechanical mal-alignments to reduce pain and aid in return to sport has been shown to be

possiblefollowing Achilles tendinopathy.17 However, the direct link between correcting

hindfoot motion and tendon healing has not been established, but this treatment is still

recommended.9

Currently it is believed that incorporating heel wedges aids in reducing tendon strain

during activities to avoid excess tendon loading and reduce pain during running.26,28,29

Investigations regarding heel wedges which plantarflex the ankle by raising the heel equally

on the medial and lateral sides, insoles and other orthotics have had variable success

regarding reduction of pain and ability to return to sport.6,20,26,28,30-33 However, as orthotics

require no invasive procedures and injury management can be at home and on-going, they are

particularly appealing. ThisA similar approach has been used in osteoarthritis, where knee

adduction moment has been the target of a variety of orthotics that aimed to alter the

mechanical loading of the knee by altering the frontal plane alignment of the hindfoot, with

several studies showing positive effects of using foot orthotics on knee adduction moment34

and tibio-femoral load.35 However, while studies investigating such orthotics have been

focussed on influencing out of plane moments at the knee, their investigations of orthotics

focussed on relieving Achilles tendon strain through plantarflexion of the ankle effect on the

ankle is often not reportedare less common. With wedges being able to alter loading at the

knee, it is not unreasonable to hypothesise that a similar approach could alter the loading at

the ankle, and indeed, this is the basis by which heel wedges are thought to operate during

walking when managing Achilles tendon pain in Achilles Tendonitis patients.36 Therefore, the

hypothesis of this study was that heel wedges which raise the heel are able to reduce Achilles

tendon force during level and inclined walking.

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The aim of this study was to quantify the effect of heel wedges on lower limb

mechanics, specifically ankle joint angles, moments and muscle forces; and relate these to

common injuries such as Achilles tendonitis. This is conducted during level and inclined

walking in order to understand their effect beyond the constrained context of level walking.

Methods

The subject participant group consisted of nineteen healthy individuals, with no

history of ankle injuries and no lower limb injury in the last 12 months and no clinical

symptoms of Achilles Tendinopathies (8 male [mean (SD); age: 28 (3); height: 1.76 m (0.10);

mass: 73.4 kg (12.0)] and 11 females [age: 29 (6); height: 1.63 m (0.05); mass: 58.7 kg

(10.2)]. Individuals were excluded if they had ever been diagnosed with Achilles

Tendinopathy or had any previous musculoskeletal or neuromuscular condition of the lower

limb. Ethical approval was obtained by a university institutional review board in accordance

with the Declaration of Helsinki and all participants were given an information sheet and

provided a signed consent form upon arrival.

A pair of commercially available orthotic heel wedges were used by all subjects

participants (Elevator Proheel™, Talar Made Orthotics Ltd, Springwood House, Foxwood

Way, Chesterfield, Derbyshire, England) (Figure 1). The wedges are made from medium

density ethylene vinyl acetate (EVA) foam and are designed to mould to the rearfoot and

elevate the heel, with the aim of being used as a tendonitis treatment. Wedges were available

for UK shoe sizes 2-5; 6-9 and 9.5-12.5 and all wedges had a 12mm rise from the front edge

of the wedge to approximately where the centre of the heel would be. Subjects Participants

were fitted with wedges corresponding to their running shoe size. All participants wore

standard running shoes that they felt comfortable in. Shoes were checked visually for

excessive wear under the sole and participants confirmed that they had used their running

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shoes previously before participating in the study. A wedge height of 12mm was chosen as it

represents a height that is recommended for Achilles tendonitis patients.36

The mechanical effect of heel wedges on a variety of walking conditions necessitated

the need for an inclined walkway which could securely accommodate a forceplate either on a

level or inclined surface, shown in (Figure 2). The setup allowed the subjects participants to

approach the 10° incline on a level surface for several steps, before ascending the 2m inclined

section where foot strike was recorded followed by a few steps of level walking at the top of

the incline. Subjects Participants were then asked to turn around and walk down the incline to

provide the data for the downhill walking condition. For both inclined and declined walking,

all subjects participants required three steps to cover the 2m inclined section, with the middle

step being used for subsequent analysis. Participants were given as long as they needed to

familiarise themselves with each condition. This was assessed by participants themselves as

they walked freely around the laboratory and up and down the level and inclined walkway

untiltill they felt comfortable. The amount of time taken by each individual was not

measured, but was on the order of a few minutes.

Subjects Participants were given time to familiarise themselves with the equipment

and testing protocol before data collection began. 3D Ooptical motion (Vicon Motion

Systems, Oxford, UK), plantar pressure (Novel GmbH, Munich, Germany) and forceplate

(Kistler, Winterthur, Switzerland) data were collected for all conditions and used as inputs to

the musculoskeletal model (described below). Optical motion and plantar pressure data were

recorded at 100Hz and forceplate data was were recorded at 1000Hz. Data were recorded

continuously while the subjects participants walked over the level or inclined walkway with a

minimum of 5 clean strikes of the forceplate when walking in running shoes (“shod

walking”) or in running shoes with the orthotic heel wedges (“wedged walking”). Both the

walking condition order (shod or wedged walking) and walking incline (level, uphill or

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downhill) were randomised. Subjects Participants were given time to become used to the heel

wedges when going between shod and wedged walking conditions on each incline and were

able to walk freely along the level or inclined walkway without targeting the forceplate.

The musculoskeletal model used here has been described elsewhere previously;37 in

summary, it is a unilateral model of the lower limb, scaled to subject participant height and

weight by optical markers placed on the pelvis and lower limb (Figure 3), with the Achilles

insertion, the first metatarsal head and base, the fifth metatarsal head and base and the tip of

the second phalanx digitised as virtual landmarks relative to the marker clusters on the foot

and hallux. Error: Reference source not foundThis Error: Reference source not foundThe

measured optical motion data was were used to calculate joint angles and inter-segmental

moments using Euler angle decompositions and Newton-Euler equations at the

metatarsophalangeal (MTP), ankle, knee and hip joints respectively and a static optimisation

routine used to estimate and muscle forces for the 13 muscles crossing the ankle joint and

Achilles tendon force is taken as the sum of the triceps surae muscle forces. The knee and hip

were modelled with 3 rotational degrees of freedom and the ankle modelled as a saddle with

2 degrees of freedom and the MTP as a hinge with 1 rotational degree of freedom. Inter-

segmental moment data are presented in the local segment coordinate frame in which they

were calculated. Centre of pressure (CoP) data is are presented as dimensionless values

normalised to foot length, defined as the RMS distance from the calcaneus to the second

metatarsal head.

Statistical analyses were performed in Matlab using the Statistical Analysis Toolbox

(Version 2010b, The Mathworks Inc.). All data was checked for normality using a

Kolmogorov-Smirnov test. As the effect of orthotic heel wedges on lower limb mechanics

was the parameter of interest, statistical comparisons between shod and wedged walking for

each incline individually was performed using paired t-tests, with the level of significance set

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at 0.05. P-values under 0.1 are presented as trend changes and values above 0.1 are not

presented. Statistical comparisons for all hip, knee, ankle and MTP kinematics and inter-

segmental moments were performed at heel-strike (HS), defined by a forceplate force

exceeding 40N, weight-acceptance (WA), push-off (PO) and toe-off (TO), with the latter

three time-points defined according to changes in knee flexion angle.38 Inter-segmental

moments were normalised to body weight (BW) and height (ht).39 Peak muscle forces were

compared across all of stance phase, and in the case of the inv/evertor muscles, peak forces

were compared during early (<50 %) and late (≥ 50 %) stance.

Results

For the full gait analysis results, the reader is directed to the supplementary material.

The results presented here are those directly related to the calculation of the ankle muscle

forces. Changes in overall gait dynamics due to heel wedges were only observed during

inclined walking as an increase in stance time (Table 1). During inclined walking, delays of

1-2 % stance to the first ground reaction force (GRF) peak when walking with heel wedges

was observed (P = .014 and P = .015 for uphill and downhill respectively). During uphill

walking an increase in stance time of 20ms was observed (P = .025) along with delays of 1 –

2 % stance to both GRF peaks (P = .014 and P = .028 respectively). Also reductions in the

magnitude of the first GRF peak (1 % BW, P = .027) and rate of force development (ROFD)

(6% reduction, P = .026) were observed during wedged uphill walking. Compared to shod

walking, the most anterior centre of pressure (CoP) position was found to be less anterior

during uphill and downhill wedged walking by 3% (P = .002) and 4% (P = .014) foot length

respectively.

At all time points considered no changes in peak frontal plane kinematics were

observed during level or inclined wedged walking, but changes in sagittal plane ankle

kinematics were observed during inclined walking (Figure 4). Flexion-extension angles at the

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ankle and MTP joints were largely unaffected due to heel wedges during level walking, with

only the MTP range of motion (ROM) decreasing significantly (17.7±5.4° vs. 15.4±3.5°, P =

.048). During inclined walking, the only cChanges in lower limb kinematicsankle angle were

confined to the ankle during early stance, with a more plantar-flexed ankle at HS (-1.4±5.5°

vs. -4.5±7.2°, P = .024 and -9.0±4.3° vs. -10.9±5.3°, P = .015 uphill and downhill

respectively) and WA (-1.0±5.5° vs. -5.2±9.4°, P = .034, -18.6±4.8° vs. -21.4±5.3°, P = .003

uphill and downhill respectively) during wedged walking. Sagittal plane ankle angles were

unaffected by heel wedges during level walking. During downhill walking, there was greater

knee flexion at WA (-28.1±5.8° vs. 30.0±5.5°, P = .020). Compared to the shod condition,

ankle ROM was observed to decrease during uphill wedged walking (35.1±5.7° vs.

32.1±4.6°, P = .035), but increase during downhill wedged walking (21.9±5.4° vs. 25.9±6.3°,

P < .001).

Knee, aAnkle and MTP joint moments were significantly affected by the presence of

heel wedges at each incline (Figure 5). Changes at the ankle during level walking were less

apparent compared to uphill or downhill walking, with delays to peak ankle dorsi-flexion and

plantar-flexion moments by 2% stance and 1% stance respectively only. However, a large

increase in knee push-off moment was observed (0.10 vs. -0.00 N m∙BW -1∙ht-1, P = .016)

during level wedged walking.

During uphill walking, peak ankle dorsi-flexion moment increased (0.01 vs. 0.06 N

m∙BW-1∙ht-1, P = .005), peak plantar flexion moment decreased (-0.85 vs. -0.79 N m∙BW-1∙ht-1,

P = .002) and peak inversion moment decreased (0.09 vs. 0.06 N m∙BW -1∙ht-1, P < .001). A

decrease in MTP flexion moment was also observed (-0.10 vs. -0.09 N m∙BW-1∙ht-1, P < .001).

At the knee, the first adduction peak moment was increased during wedged walking (0.16 vs.

0.20 N m∙BW-1∙ht-1, P < .001), while knee extensor moment at PO decreased (0.16 vs. 0.09 N

m∙BW-1∙ht-1, P < .001).

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Similar changes in ankle moments were observed during downhill walking, with an

increase in dorsiflexion moment (0.09 vs 0.14 N m∙BW-1∙ht-1, P < .001), a decrease in plantar-

flexion moment (-0.62 vs. -0.57 N m∙BW-1∙ht-1, P = .002) and a decrease in inversion moment

(0.09 vs. 0.07 N m∙BW-1∙ht-1, P = .030). Knee extensor moment was increased at WA (-0.64

vs. -0.71 N m∙BW-1∙ht-1), PO (-0.27 vs. -0.33 N m∙BW-1∙ht-1) and at TO (-0.39 vs. -0.47 N

m∙BW-1∙ht-1) during wedged walking (P < .001 for all three time-points).

The most consistent change in muscle force estimates due to heel wedges were in the

ankle dorsi-flexors (12–26 % BW increases in peak Tibialis Anterior force) and toe extensors

(range of 4–6 % BW increase for Extensor Digitorum/Hallucis Longus forces) muscle forces

during the first half of stance across all walking conditions (Figure 6 and Table 2). A second

consistent observation was the decrease in peak Tibialis Posterior and toe flexor forces during

level and inclined wedged walking, although this was only statistically significant during

inclined walking (mean decreases of 12-14 % BW for Tibialis Posterior and 9–11 % BW the

toe flexor muscles respectively). Critically, there was no statistically significant reduction in

peak Achilles force for any walking incline due to heel wedges (range of 5–14 % BW

decrease). The only significant changes in triceps surae loading during uphill walking were

decreases in the medial parts of the triceps surae (12 % BW and 6 % BW for medial Soleus

and medial Gastrocnemius respectively). During downhill walking, only the medial portion

of Soleus showed a significant decrease in peak force (9 % BW). Overall ankle joint reaction

force was reduced by 29 % BW during downhill wedged walking.

Discussion

The aim of this study was to quantify the effect of heel wedges on lower limb

mechanics, specifically ankle joint angles, moments and muscle forces; and relate these to

common injuries such as Achilles tendonitis. The main clinical driver behind assessing the

effect of orthotics on ankle loading during inclined walking was to determine how effective

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heel wedges are at reducing tendon load not only on during level walking, but also on

inclined surfaces, where Achilles tendon loads are known to be increased. Given the mixed

evidence surrounding the use of heel wedges to manage Achilles tendonitis, a broader

characterisation of lower limb mechanics due to orthotic heel wedges would provide some

insight into how the body may adapt to walking with such an intervention, allowing for

improvements regarding injury management.

A number of kinematic and kinetic changes were consistently observed across

walking conditions and these will be discussed further. However, the key finding of the study

was that 12mm orthotic heel wedges did not result in a reduction in peak triceps surae or

overall Achilles tendon forces, as was expected from current theories on the mechanism of

treating Achilles tendonitis with heel wedges.

No changes in ground reaction forces or ankle inversion kinematics were observed for

any wedged walking condition. While inferring subtalar kinematics through angles derived

from markers on the shoe has its limitations, information regarding out of plane changes in

kinematics can still be gained. However, as the cohort tested here consisted of healthy

individuals, hindfoot motion may not have required any correction, and as such the lack of

difference in hindfoot kinematics here should not automatically be extrapolated to a patient

population. This has similar implications for the kinetics, as kinetic changes are in response

to the kinematic and CoP changes that occur. If patient groups reported similar CoP and

kinematics changes, then it is likely that the kinetic results obtained here will have direct

relevance to the mechanical response of the lower limb to orthotic wedges in a patient

population. It should be noted that the observations here are valid only for this type of heel

wedge and wedges aiming to shift CoP in the frontal plane may act differently.

Changes in CoP were consistently shifted posteriorly across walking conditions. The

more posterior CoP at push-off coupled with relatively unaltered knee kinematics resulted in

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greater knee flexion moments (Figure 5), between weight-acceptance and push-off. This

increased demand on the knee joint likely has clinical implications for the quadriceps

muscles, as they are the main extensors of the knee, both in terms of fatigue of the muscles as

well as possible changes in knee joint loading. The posteriorly shifted CoP coupled This had

two distinct effects on lower limb loading. During early stance, a posterior shift in CoP would

place the GRF more posterior to the ankle joint centre, resulting in a greater dorsiflexion

moment and dorsiflexor muscle forces. During late stance at push-off, a posteriorly shift in

CoP places the GRF closer to the ankle joint centre, resulting in smaller plantar flexion

moments.with greater ankle plantarflexion from heel-strike until push-off would also have

resulted in greater dorsiflexion moments during weight-acceptance and smaller plantarflexion

moments at push-off. However, as was previously mentioned, this did not result in a

reduction in peak triceps surae or overall Achilles tendon forces. Instead, a redistribution of

the triceps surae loads was observed (Figure 6), where the medial triceps surae muscle loads

reduced and lateral triceps surae loading increased, while the peak forces of the less efficient,

secondary ankle plantar -flexor muscles of Tibialis Posterior and the toe flexor muscles were

consistently reduced during wedged walking. The redistribution of triceps surae loading from

the medial to lateral side has relevance in the rehabilitation of calf strains and tears, where

strains and tears are more common in the medial head of Gastrocnemius and where heel

wedges are also a prescribed treatment.40

The sensitivity of these secondary ankle plantar- flexor muscles to changes in inter-

segmental moments is of particular interest, both clinically and computationally. From a

computational perspective, the use of a static optimisation approach to derive muscle forces

inherently makes less efficient muscles more sensitive to changes in inter-segmental

moments compared to more efficient muscles. Tibialis Posterior and the toe flexors are

significantly less powerful and efficient ankle plantar- flexors compared to the triceps surae

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muscles, and as such these are the muscles that one would expect to respond to changes in

ankle moment. However, from a clinical perspective, it is not known if the body responds in

such a way to changes in demand at individual joints, possibly due to practical constraints of

determining deep muscle electromyography (EMG) data. If this observation is indeed found

to be true, it may provide some explanation as to why Achilles tendonitis patients respond so

variably to orthotics. Therefore, it is recommended that future research into the use of

orthotics to treat Achilles tendonitis focuses on the mechanical response specific orthotics

induce in the body at both individual muscle and whole joint levels with a view to proposing

methods to improve the conservative management of Achilles tendonitis.

A practical limitation of the study is that due to the inclined section being fixed to 2m,

it should be noted that some subjects participants may not have reached a steady-state of

inclined walking, despite using the middle of the three steps on the inclined surface.

However, the current setup does represent a change in walking incline which would be

commonly experienced in daily life. A second limitation of this study relates to the

lackabsence of direct measures or estimates of tendon strain, which would have

complimented the changes in muscle and tendon force observed. While estimating tendon

strain here would require combining a finite element tendon model with the musculoskeletal

model implemented here, which is beyond the scope of this study, such an approach may

have provided a greater depth of understanding into the mechanical changes that are induced

by orthotic heel wedges. relates to the lack of surface EMG data, specifically of the triceps

surae; as corroborating EMG data would have provide some measure of confidence in the

modelling approach used here. A final limitation of the study is related to the sensitivity of

musculoskeletal models to muscle morphology and geometry inputs. While a limitation of

any model that does not have MRI datasets of their subject participant cohort, the use of

scaled cadaveric muscle data in estimating muscle loads during various activities is a

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common approach,41-44 particularly when comparing intra-subject gait patterns such as in this

study.

This study characterised the effect of orthotic heel wedges on lower limb

biomechanics in the context of level, uphill and downhill walking, with the intention of trying

to quantify any mechanical differences that may arise due to heel wedges and help explain

the current mixed evidence surrounding heel wedges as a treatment for Achilles tendonitis.

Heel wedges were unable to significantly alter hindfoot kinematics, but did result in changes

in inter-segmental moments at all joints of the lower limb. However, heel wedges were

unable to reduce Achilles tendon loading across level, uphill and downhill walking conditions

in healthy individuals. Instead, secondary ankle plantarflexor muscles consistently showed

substantial reductions in loading. These results add to the body of largely clinical evidence

(pain, functional improvement etc.) that indicates that heel wedges are not an appropriate

treatment for Achilles tendonitis and has provided evidence as to why this is the case.

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References

1. Stauffer RN, Chao EY, Brewster RC. Force and motion analysis of the normal, diseased, and

prosthetic ankle joint. Clin Orthop Relat R. 1977(127):189-196.

2. Komi PV. Relevance of in vivo force measurements to human biomechanics. Journal of

Biomechanics. 1990;23 Suppl 1:23-34.

3. Scott SH, Winter DA. Internal forces of chronic running injury sites. Medicine & Science in

Sports & Exercise. Jun 1990;22(3):357-369.

4. Maffulli N, Wong J, Almekinders LC. Types and epidemiology of tendinopathy. Clinical

Journal of Sport Medicine. Oct 2003;22(4):675-692.

5. Donoghue OA, Harrison AJ, Laxton P, et al. Lower limb kinematics of subjects with chronic

achilles tendon injury during running. Research in Sports Medicine. 2008;16(1):23-38.

6. Reinking M. Tendinopathy in athletes. Phys Ther Sport. Feb 2012;13(1):3-10.

7. Kader D, Saxena A, Movin T, et al. Achilles tendinopathy: some aspects of basic science and

clinical management. Brit J Sport Med. Aug 2002;36(4):239-249.

8. Paavola M, Kannus P, Jarvinen TA, et al. Achilles tendinopathy. J Bone Joint Surg Am. Nov

2002;84-A(11):2062-2076.

9. Cook JL, Khan KM, Purdam C. Achilles tendinopathy. Manual Therapy. Aug 2002;7(3):121-

130.

10. Schepsis AA, Jones H, Haas AL. Achilles tendon disorders in athletes. The American Journal of

Sports Medicine. Mar-Apr 2002;30(2):287-305.

11. McCrory JL, Martin DF, Lowery RB, et al. Etiologic factors associated with Achilles tendinitis

in runners. Med Sci Sport Exer. Oct 1999;31(10):1374-1381.

12. McCrory JL, Martin DF, Lowery RB, et al. Etiologic factors associated with Achilles tendinitis

in runners. Med Sci Sports Exerc. Oct 1999;31(10):1374-1381.

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13. Lersch C, Grotsch A, Segesser B, et al. Influence of calcaneus angle and muscle forces on

strain distribution in the human Achilles tendon. Clin Biomech (Bristol, Avon). Nov

2012;27(9):955-961.

14. Farris DJ, Trewartha G, McGuigan MP, et al. Differential strain patterns of the human Achilles

tendon determined in vivo with freehand three-dimensional ultrasound imaging. Journal of

Experimental Biology. Feb 15 2013;216:594-600.

15. Chuter VH, Janse de Jonge XAK. Proximal and distal contributions to lower extremity injury:

A review of the literature. Gait & Posture. 2012;36(1).

16. Kaufman KR, Brodine SK, Shaffer RA, et al. The effect of foot structure and range of motion

on musculoskeletal overuse injuries. Am J Sport Med. Sep-Oct 1999;27(5):585-593.

17. Van Ginckel A, Thijs Y, Hesar NG, et al. Intrinsic gait-related risk factors for Achilles

tendinopathy in novice runners: a prospective study. Gait & Posture. Apr 2009;29(3):387-

391.

18. Cronin NJ, Avela J, Finni T, et al. Differences in contractile behaviour between the soleus and

medial gastrocnemius muscles during human walking. Journal of Experimental Biology. Mar

1 2013;216:909-914.

19. Farris DJ, Sawicki GS. Human medial gastrocnemius force-velocity behavior shifts with

locomotion speed and gait. Proceedings of the National Academy of Sciences U S A. Jan 17

2012;109(3):977-982.

20. Wyndow N, Cowan SM, Wrigley TV, et al. Triceps surae activation is altered in male runners

with Achilles tendinopathy. Journal of Electromyography and Kinesiology. Feb

2013;23(1):166-172.

21. Sanderson DJ, Martin PE, Honeyman G, et al. Gastrocnemius and soleus muscle length,

velocity, and EMG responses to changes in pedalling cadence. Journal of Electromyography

and Kinesiology. Dec 2006;16(6):642-649.

16

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365

366

367

368

369

370

371

372

373

374

375

376

377

378

379

380

381

382

383

384

385

386

22. Sayana MK, Maffulli N. Eccentric calf muscle training in non-athletic patients with Achilles

tendinopathy. Journal of Science and Medicine in Sport. Feb 2007;10(1):52-58.

23. Maffulli N, Walley G, Sayana MK, et al. Eccentric calf muscle training in athletic patients with

Achilles tendinopathy. Disability and Rehabilitation. 2008;30(20-22):1677-1684.

24. Roos EM, Engstrom M, Lagerquist A, et al. Clinical improvement after 6 weeks of eccentric

exercise in patients with mid-portion Achilles tendinopathy - a randomized trial with 1-year

follow-up. Scandinavian Journal of Medicine & Science in Sports. Oct 2004;14(5):286-295.

25. Rees JD, Lichtwark GA, Wolman RL, et al. The mechanism for efficacy of eccentric loading in

Achilles tendon injury; an in vivo study in humans. Rheumatology (Oxford). Oct

2008;47(10):1493-1497.

26. Mayer F, Hirschmuller A, Muller S, et al. Effects of short-term treatment strategies over 4

weeks in Achilles tendinopathy. Brit J Sport Med. Jul 2007;41(7).

27. Enwemeka CS. The effects of therapeutic ultrasound on tendon healing. A biomechanical

study. Am J Phys Med Rehab. Dec 1989;68(6):283-287.

28. Clement DB, Taunton JE, Smart GW. Achilles tendinitis and peritendinitis: etiology and

treatment. Am J Sport Med. May-Jun 1984;12(3):179-184.

29. Farris DJ, Buckeridge E, Trewartha G, et al. The effects of orthotic heel lifts on achilles tendon

force and strain during running. J Appl Biomech. Nov 2012;28(5):511-519.

30. Magnussen RA, Dunn WR, Thomson AB. Nonoperative treatment of midportion Achilles

tendinopathy: a systematic review. Clinical Journal of Sport Medicine. Jan 2009;19(1):54-64.

31. Gross ML, Davlin LB, Evanski PM. Effectiveness of orthotic shoe inserts in the long-distance

runner. Am J Sport Med. Jul-Aug 1991;19(4):409-412.

32. Stackhouse CL, Davis IM, Hamill J. Orthotic intervention in forefoot and rearfoot strike

running patterns. Clin Biomech. Jan 2004;19(1):64-70.

33. Ferber R, Benson B. Changes in multi-segment foot biomechanics with a heat-mouldable

semi-custom foot orthotic device. Journal of Foot & Ankle Research. 2011;4(1):18.

17

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399

400

401

402

403

404

405

406

407

408

409

410

411

412

34. Erhart JC, Mundermann A, Elspas B, et al. Changes in knee adduction moment, pain, and

functionality with a variable-stiffness walking shoe after 6 months. J Orthopaed Res. Jul

2010;28(7):873-879.

35. Kutzner I, Damm P, Heinlein B, et al. The effect of laterally wedged shoes on the loading of

the medial knee compartment-in vivo measurements with instrumented knee implants. J

Orthopaed Res. 2011;29(12):1910-1915.

36. Carcia CR, Martin RL, Houck J, et al. Achilles pain, stiffness, and muscle power deficits:

achilles tendinitis. J Orthop Sports Phys Ther. Sep 2010;40(9):A1-26.

37. Weinert-Aplin RA, Bull AMJ, McGregor AH. Investigating The Effects of Knee Flexion During

The Eccentric Heel-drop Exercise. Journal of Sports Science and Medicine. 2015;14(2):459-

465.

38. Shamaei K, Sawicki GS, Dollar AM. Estimation of quasi-stiffness of the human knee in the

stance phase of walking. PLoS One. 2013;8(3).

39. Moisio KC, Sumner DR, Shott S, et al. Normalization of joint moments during gait: a

comparison of two techniques. Journal of Biomechanics. 4// 2003;36(4):599-603.

40. Bryan Dixon J. Gastrocnemius vs. soleus strain: how to differentiate and deal with calf

muscle injuries. Curr Rev Musculoskelet Med. Jun 2009;2(2):74-77.

41. Erdemir A, McLean S, Herzog W, et al. Model-based estimation of muscle forces exerted

during movements. Clin Biomech. Feb 2007;22(2):131-154.

42. Modenese L, Phillips AT, Bull AM. An open source lower limb model: Hip joint validation.

Journal of Biomechanics. Aug 11 2011;44(12):2185-2193.

43. Lundberg HJ, Foucher KC, Andriacchi TP, et al. Direct comparison of measured and calculated

total knee replacement force envelopes during walking in the presence of normal and

abnormal gait patterns. Journal of Biomechanics. 2012;45(6):990-996.

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44. Delp SL, Anderson FC, Arnold AS, et al. OpenSim: open-source software to create and

analyze dynamic simulations of movement. IEEE Trans Biomed Eng. Nov 2007;54(11):1940-

1950.

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Figure 1: Image of the 12mm orthotic heel wedge used by all subjectsparticipants

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Figure 2: Sketch of the inclined walkway setup

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Figure 3: Posterior (left) and lateral (right) views of the optical marker setup. Note: Grey circles indicate reflective marker positions

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Figure 4: Mean shod (black lines) and wedged (grey lines) joint ankle joint angles (A-C) and moments (D-F)kinematics when walking uphill (left column), on level ground (middle column) and downhill (right column) for the knee (A-C), ankle (D-F) and MTP (G-I) joints. Note: Solid lines represent flexion/extension angles and dashed lines represent inv/eversion ankle angles and moments (or ab/adduction for the knee). * denotes a statistically significant difference

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D

GD

H I

FE

*†

*

*†

*†

†

†

*†*

*

A B C*

†

*†

*

*

*

*

Figure 5: Mean shod (black lines) and wedged (grey lines) joint moments when walking uphill (left column), on level ground (middle column) and downhill (right column) for the knee (A-C), ankle (D-F) and MTP (G-I) joints. Note: Solid lines represent flexion/extension moments and dashed lines represent inv/eversion ankle moments (or ab/adduction for the knee).* and † denote statistically significant differences in magnitude and time to peak respectively.

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A

D

G

J K L

IH

E F

CB

**

*

Figure 65: Mean shod (solid lines) and wedged (dashed lines) muscle forces when walking uphill (left column), on level ground (middle column) and downhill (right column) for the Achilles (A-C), triceps surae (D-F), inv/evertor (G-I) and toe (J-L) muscles. Note: Abbreviations are: GastMed/GastLat – Medial/Lateral heads of the Gastrocnemius, SolMed/SolLat – Medial and lateral portions of Soleus, PeroB/L and PeroT – Peroneus Brevis/Longus and Tertius, TibAnt/TibPost, Tibialis Anterior and Tibialis Posterior, EDL/EHL – Extensor Digitorum/Hallucis Longus, FDL/FHL – Flexor Digitorum/Hallucis Longus. * denotes statistically significant change in peak force (only shown for the triceps surae muscles for clarity).

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Table 1: Comparison of forceplate and spatio-temporal gait characteristics across all inclines, mean (SD).

Uphill Level DownhillShod Wedged Shod Wedged Shod Wedged

Stance time [s] 0.72 (0.08)

0.73 (0.10)

0.69 (0.08)

0.70(0.07)

0.63 (0.09)

0.65* (0.08)

Velocity [m/s] 1.20 (0.24)

1.18 (0.24)

1.24 (0.20)

1.21(0.20)

1.20 (0.24)

1.17 (0.24)

First GRFPeak [BW]

1.08 (0.10)

1.07* (0.09)

1.12 (0.08)

1.12(0.08)

1.25 (0.13)

1.25 (0.14)

Time to 1st peak [% stance]

26(3)

28*(2)

26(4)

27(3)

25(4)

26*(4)

Second GRF Peak [BW]

1.17 (0.10)

1.18 (0.13)

1.13 (0.08)

1.12(0.09)

0.95 (0.11)

0.95 (0.11)

Time to 2nd peak [% stance]

79(3)

80*(2)

79(2) 80 (2) 79

(7)79(7)

ROFD[BWs-1]

6.22 (1.78)

5.83* (1.36)

7.45 (2.50)

6.78(1.48)

9.80(3.63)

9.17(3.81)

Most Posterior CoP

[normalised]

0.03 (0.07)

0.01 (0.09)

0.01 (0.07)

-0.01 (0.08)

0.03 (0.09)

0.01 (0.08)

Most Anterior CoP

[normalised]

0.68 (0.08)

0.65* (0.08)

0.66 (0.07)

0.63 (0.07)

0.66 (0.07)

0.62* (0.07)

CoP travel per step

[normalised]

0.64 (0.10)

0.63 (0.10)

0.65 (0.09)

0.64 (0.10)

0.63 (0.11)

0.61 (0.10)

Note: ROFD denotes the rate of force development and is derived from heel-strike to the first ground reaction force peak. * denotes P < .05 between shod and wedged conditions

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Table 2: Comparison of peak muscle and ankle joint reaction forces during shod and wedged walking across all inclines. Note: For full muscle names, see Figure 6 notes; Data presented as mean (SD).

Uphill Level DownhillPeak Force

[BW] Muscle Shod Wedged p-value Shod Wedged p-value Shod Wedged p-value

TricepsSurae

SolMed 1.30 (0.26) 1.18 (0.34) 0.047 1.16 (0.27) 1.03 (0.29) - 0.96 (0.23) 0.87 (0.23) 0.040

SolLat 0.77 (0.35) 0.88 (0.41) - 0.55 (0.33) 0.59 (0.34) - 0.53 (0.23) 0.60 (0.26) -

GastMed 0.72 (0.15) 0.67 (0.18) 0.040 0.66 (0.16) 0.59 (0.16) - 0.53 (0.12) 0.49 (0.12) -

GastLat 0.24 (0.08) 0.25 (0.08) - 0.20 (0.07) 0.20 (0.06) - 0.17 (0.04) 0.18 (0.05) -

Achilles 2.98 (0.69) 2.92 (0.81) - 2.47 (0.61) 2.33 (0.59) - 2.15 (0.48) 2.10 (0.54) -

Invertor/ Evertors

(1st half of stance)

PeroB/L 0.10 (0.11) 0.30 (0.30) 0.002 0.29 (0.27) 0.61 (0.45) 0.027 0.38 (0.30) 0.67 (0.51) 0.003

PeroT 0.02 (0.03) 0.07 (0.06) 0.002 0.09 (0.06) 0.15 (0.09) 0.035 0.09 (0.07) 0.15 (0.10) <0.001

TibAnt 0.26 (0.11) 0.38 (0.24) 0.058 0.53 (0.22) 0.79 (0.37) 0.030 0.56 (0.25) 0.75 (0.36) 0.002

TibPost 0.33 (0.15) 0.20 (0.14) <0.001 0.31 (0.13) 0.20 (0.16) 0.029 0.37 (0.21) 0.26 (0.22) 0.003

Invertor/ Evertors

(2nd half of stance

PeroB/L 0.09 (0.10) 0.17 (0.19) - 0.06 (0.10) 0.11 (0.13) - 0.06 (0.08) 0.10 (0.10) 0.083

PeroT 0.01 (0.00) 0.01 (0.01) 0.057 0.00 (0.01) 0.01 (0.01) - 0.01 (0.08) 0.01 (0.01) 0.076

TibAnt 0.31 (0.14) 0.21 (0.16) 0.012 0.33 (0.15) 0.26 (0.16) - 0.26 (0.10) 0.18 (0.10) 0.006

TibPost 0.50 (0.21) 0.36 (0.23) 0.020 0.53 (0.23) 0.41 (0.26) 0.095 0.41 (0.16) 0.29 (0.17) 0.005

Toes

EDL 0.02 (0.03) 0.06 (0.06) 0.002 0.09 (0.06) 0.15 (0.09) 0.036 0.09 (0.07) 0.15 (0.09) <0.001

EHL 0.02 (0.02) 0.06 (0.05) 0.002 0.08 (0.05) 0.14 (0.08) 0.032 0.09 (0.06) 0.14 (0.08) <0.001

FDL 0.04 (0.02) 0.03 (0.02) 0.023 0.04 (0.02) 0.03 (0.02) 0.058 0.04 (0.02) 0.03 (0.02) 0.003

FHL 0.39 (0.17) 0.29 (0.16) 0.015 0.42 (0.18) 0.31 (0.18) 0.064 0.34 (0.14) 0.25 (0.15) 0.002

Ankle JRF 5.17 (0.86) 4.88 (1.12) - 4.69 (0.83) 4.28 (0.85) - 3.82 (0.64) 3.53 (0.70) 0.037

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