Response of able-bodied persons to changes in shoe rocker radius during walking: Changes in ankle kinematics to maintain a consistent roll-over shape

doi:10.1016/j.jbiomech.2010.04.036

Journal of Biomechanics

Volume 43, Issue 12, 26 August 2010, Pages 2288-2293

https://doi.org/10.1016/j.jbiomech.2010.04.036 Get rights and content

Abstract

Recent studies have determined a seemingly consistent feature of able-bodied level ground walking, termed the roll-over shape, which is the effective rocker (cam) shape that the lower limb system conforms to between heel contact and contralateral heel contact during walking (first half of the gait cycle). The roll-over shape has been found to be largely unaffected by changes in walking speed, load carriage, and shoe heel height. However, it is unclear from previous studies whether persons are controlling their lower limb systems to maintain a consistent roll-over shape or whether this finding is a byproduct of their attempt to keep ankle kinematic patterns similar during the first half of the gait cycle. We measured the ankle–foot roll-over shapes and ankle kinematics of eleven able-bodied subjects while walking on rocker shoes of different radii. We hypothesized that the ankle flexion patterns during single support would change to maintain a similar roll-over shape. We also hypothesized that with decrease in rocker shoe radii, the difference in ankle flexion between the end and beginning of single support would decrease. Our results supported these hypotheses. Ankle kinematics were changed significantly during walking with the different rocker shoe radii (p<0.001), while ankle–foot roll-over shape radii (p=0.146) and fore–aft position (p=0.132) were not significantly affected. The results of this study have direct implications for designers of ankle–foot prostheses, orthoses, walking casts/boots, and rocker shoes. The results may also be relevant to researchers studying control of human movements.

Introduction

Many researchers have modeled the physiologic ankle–foot system in attempts to better understand its functions during able-bodied gait, aiming to improve therapies for persons with disabilities that affect the system and to improve designs of ankle–foot prostheses and orthoses. Perry (1992) described the ankle–foot system as three rockers that aid in forward progression during walking. Other models used one continuous rocker to describe walking characteristics (Morawski and Wojcieszak, 1978, Gard and Childress, 2001, Gard et al., 2004). McGeer (1990) added more realistic features to this model, including swing phase knee flexion and a trunk segment, and created both computer and physical models that could passively walk down gentle slopes. McGeer estimated that the “equivalent radius” for human walking would be about 0.3 of leg length.

Knox (1996) concluded that the effective rocker shapes of prosthetic feet are important to their function for walking. He developed a method to measure these effective shapes and compared the shapes for prosthetic and physiologic ankle–foot systems during walking. The effective rocker that the ankle–foot system conforms to from heel contact to contralateral heel contact of walking was later termed the ankle–foot roll-over shape (Hansen et al., 2004). The roll-over shape may be a useful and simple tool for design and evaluation of lower limb prostheses because it has been shown to be nearly circular and relatively unaltered by changes in walking speed (Hansen et al., 2004), added weight to the torso (Hansen and Childress, 2005), and shoe heel height (Hansen and Childress, 2004) during able-bodied walking.

Although roll-over shapes have been found to be consistent for different level walking conditions, it is possible that their consistency is a byproduct of some other control strategy for walking. For example, humans may utilize position control of the ankle in walking to maintain a similar kinematic pattern during the step cycle (the same time period used to measure the roll-over shape). If so, the roll-over shape may also remain unchanged as a byproduct of unchanged ankle kinematics. This study used a series of rocker shoes to examine the relationship between ankle kinematics and roll-over shape. The purpose of the study was to determine whether ankle kinematics and/or roll-over shape would change when using different shoe rocker radii. We hypothesized that roll-over shapes would remain unchanged with different rocker shoe radii and that with decrease in rocker shoe radii, the change in ankle flexion during single limb stance phase would decrease. The results of this study may be useful to designers of lower limb prostheses, orthoses, walking casts/boots, and rocker shoes. Additionally, the results of this study may provide insight for persons studying control of human movements.

Section snippets

Subject recruitment

We recruited eleven able-bodied subjects (six males, five females) between 24 and 35 years of age. Their demographic information is reported here as mean±standard deviation: age=28.2±3.5 years, height=175.7±10.0 cm, body mass=71.2±14.2 kg, and shoe size=8.2±2.3 (US men).

After the subjects gave written consent, approved by Northwestern University’s Institutional Review Board, we conducted ankle range of motion and strength tests. For ankle range of motion (non-weight bearing), the subjects needed

Results

Ankle kinematics changed significantly when persons walked with different rocker shoe radii (Fig. 3). The plots shown in Fig. 3 are data collected from one subject at freely selected speed, but are representative of the entire subject pool. The ankle difference during single support phase was found to be significantly affected by the rocker shoes (p<0.001), and by walking speed (p=0.013). Additionally, post-hoc pairwise comparisons indicated significant changes in ankle flexion differences

Discussion

As hypothesized, the ankle responded to changes in rocker shoe radius and walking speed to maintain a consistent ankle–foot roll-over shape. Additionally, the response to different shoes seemed to occur primarily at the ankle joint, with less dramatic changes seen in knee flexion, hip flexion, and pelvic obliquity. It is not clear why ankle–foot roll-over shape remains consistent for a variety of level walking conditions. However, results from previous studies suggest that rocker radius could

Conflict of interest statement

The authors have no financial or personal relationships with other people or organizations that could influence their work or pose conflicts of interest.

Acknowledgements

The authors would like to acknowledge the use of the VA Chicago Motion Analysis Research Laboratory. We would like to thank Rebecca Stine for her help with data collection and analysis, Stefania Fatone for her help with ankle strength and range of motion testing, Kathy Waldera for her help with making the rocker shoes, and Sara Koehler and Brian Ruhe for their help with statistics used in this study. This publication was made possible by Grant number R03-HD050428-01A2 from the NIH. Its contents

References (18)

S.A. Gard et al.
Comparison of kinematic and kinetic methods for computing the vertical motion of the body center of mass during walking
Human Movement Science
(2004)
A.H. Hansen et al.
Roll-over shapes of human locomotor systems: effects of walking speed
Clinical Biomechanics
(2004)
P.G. Adamczyk et al.
The advantages of a rolling foot in human walking
Journal of Experimental Biology
(2006)
D.C. Boone et al.
Normal range of motion of joints in male subjects
Journal of Bone and Joint Surgery
(1979)
H. Dreyfuss
The Measure of Man: Human Factors in Design
(1960)
S. Fatone et al.
Effect of ankle–foot orthosis on roll-over shape in adults with hemiplegia
Journal of Rehabilitation Research and Development
(2007)
A.P. Field
Discovering Statistics using SPSS for Windows : Advanced Techniques for the Beginner
(2000)
S.A. Gard et al.
What determines the vertical displacement of the body during normal walking?
Journal of Prosthetics and Orthotics
(2001)
Hansen, A.H., 2002. Roll-over characteristics of human walking with applications for artificial limbs. PhD Thesis,...

There are more references available in the full text version of this article.

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The interaction effects of rocker angle and apex location in rocker shoe design on foot biomechanics and Achilles tendon loading
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Some authors even reported no significant changes in pressure measures [13]. A toe-only rocker sole could diminish the metatarsophalangeal (MTP) dorsiflexion and, in most cases, reduce the ankle plantarflexion at terminal stance [14–17]. However, increased ankle plantarflexion was also demonstrated in rocker shoe wearers [18].
The influences of rocker shoes on foot biomechanics were controversial because the interaction between two design factors—rocker angle and apex location, was usually omitted. This study investigated the interaction effects of rocker angle and apex location on plantar foot pressure, metatarsophalangeal/ankle angle, and Achilles tendon force during walking. Ten participants performed walking trials under six rocker shoe conditions: 2 rocker angles (mild and severe) × 3 apex locations (distal, standard, and proximal), wherein the plantar foot pressure was measured and the movement data were processed by musculoskeletal modeling to report joint angle and Achilles tendon force. A two-way ANOVA repeated measures was used for statistics. Significant interaction effects were reported in examinations of forefoot pressure, midfoot pressure, and metatarsophalangeal dorsiflexion. The standard apex significantly reduced peak forefoot and midfoot pressures (p = 0.008–0.034, Hedges'g = 0.75–0.84), which was further decreased by a severe rocker angle (p = 0.006, Hedges'g = 0.51–0.81). Moving the apex proximally reduced Achilles tendon forces (p < 0.001, Hedges' g = 0.80) and facilitated both metatarsophalangeal dorsiflexion and ankle plantarflexion during push-off (p = 0.003–0.006, Hedges' g = 0.03–0.82). Rocker angle seemed to have fewer effects on ankle joint angle and Achilles tendon force. We concluded that apex location was likely the dominant design factor of the rocker sole in influencing foot biomechanics, yet its interactions with rocker angle should be considered. The configuration of the two features could be varied to possess different therapeutic merits and adapt to specific application purposes.
Effect of different forefoot rocker radii on lower-limb joint biomechanics in healthy individuals
2021, Gait and Posture
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Research into rocker radii is only described in roll-over shoes (Fig. 1C). It was shown that smaller radii compared to larger radii lead to both reduced peak ankle plantarflexion in loading response and reduced dorsiflexion during terminal stance [10–13]. Other research focused primarily on the effects of one rocker shoe configuration on biomechanical gait parameters and plantar pressure [3,14–18].
Previous studies showed that rocker shoes with a stiff forefoot rocker profile significantly reduce peak plantar flexion moment at the ankle (PFM) and peak ankle dorsiflexion (DF). Both parameters are related to Achilles tendon and Plantar Fascia unloading. The shape of an outsole with a forefoot rocker is described with multiple rocker design parameters. The aim of this research is, to determine the relation between different forefoot rocker radii on peak DF and peak PFM at a self-selected walking speed.
10 participants walked in standard shoes and three experimental pairs of shoes with different forefoot rocker radii. Lower extremity kinematics and kinetics were collected while walking on an instrumented treadmill at preferred walking speed and analysed with Statistical Parametric Mapping (SPM) (α = .05; post-hoc α = .05/6).
Peak value analyses showed significant decreases in peak DF, peak PFM, and peak ankle power generation for the rocker conditions. No relevant significant differences were found in spatio-temporal parameters and total work at the ankle joint. SPM showed a significant decrease (% gait cycle) in DF (40–69 %), PFM (7–15 %; 41–68 %; 69–81 %), ankle power (10–15 %; 32–51 %; 55–64 %; 64–67 %; 72–80 %) and foot-to-horizontal angle (FHA) (0–4 %; 40–62 %; 92–100 %) and an increased shank-to-vertical angle (SVA) (44–84 %) for the rocker conditions.
The results of this study suggest that rocker shoes with a proximally placed apex significantly reduce DF and PFM during the third rocker compared with control shoes. This effect is mainly explained by a change in the FHA. Smaller radii cause the largest reductions in DF and PFM, so therefore, a uniform standardisation of the forefoot rocker radius is essential.
Material properties and application of biomechanical principles provide significant motion control performance in experimental ankle foot orthosis-footwear combination
2021, Clinical Biomechanics
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We needed to minimize the interruption during rollover which is known to accompany restricted joint motion in the ankle-foot complex and which increases movement compensation, energy expenditure, muscle fatigue, and reduces gait efficiency (Ackermann and Schiehlen, 2006; Nepomuceno et al., 2017; Wutzkea et al., 2012; Vanderpool et al. 2008; Adamczyk et al. 2006; Waters et al. 1988; Ralston 1965; Waters et al., 1982; Fowler et al. 1993; Waters and Mulroy, 1999). A growing body of evidence spanning several disciplines, including biomechanics and engineering, suggests that a well-designed external sole component includeing the heel, midfoot, and forefoot can contribute to restoring rollover (Adamczyk et al. 2006; Branthwaite and Chockalingam, 2009; Hutchins et al. 2009; Wang and Hansen, 2010; Vanderpool et al. 2008; Nepomuceno et al., 2017). Informed by this evidence, we developed footwear to minimize the interruption during rollover and other movement compensations due to the constraint provided by the exAFO.
This study, the first of its kind, originated with the need for a brace (an ankle foot orthosis), to constrain ankle plantarflexion and dorsiflexion within a motion threshold of <5°. A conventional thermoplastic, solid brace failed during a quasi-static loading study, informing the investigation and development of an experimental carbon composite brace, maximizing stiffness and proximity of shank and foot cylindrical shells to provide the required degree of control.
Two experiments were conducted: a quasi-static loading study, using cadaveric limbs (n = 2), and a gait study with healthy subjects (n = 14). Conditions tested were STOP, FREE, and CONTROL. Data for all studies were collected using six motion-capture cameras (Vicon, Oxford, UK; 120 Hz) tracking bone-anchored markers (cadaveric limbs) and skin-anchored markers (subjects). In the quasi-static loading study, loading conditions were congruent with the gait study. Study 1 involved a quasi-static loading analysis using cadaveric limbs, compared motion data from a conventional thermoplastic solid brace and the experimental brace. Study 2 involved quantifying ankle plantarflexion and dorsiflexion in subjects during treadmill walking, in brace STOP, FREE, and CONTROL conditions.
The experimental brace in STOP condition consistently constrained ankle plantarflexion and dorsiflexion below the motion threshold of <5°, across all studies.
Collectively, these findings demonstrate (1) that a conventional thermoplastic, solid brace was ineffective for clinical applications that required significant motion control, and (2) that ankle motion control is most effective when considered as a relationship between the brace, the ankle-foot complex, and the external forces that affect them both.
A novel mathematical formulation for predicting symmetric passive bipedal walking motion with unbalanced masses
2016, Applied Mathematical Modelling
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It is defined in a local co-ordinate system with the y axis aligned to the ankle–knee axis. The roll-over shape has been widely used to understand the knee–ankle–foot kinematics as it is invariant to many gait parameters such as added weight, speed and shoe heel height [3–5]. The ideal roll-over shape for the prosthetic foot may be realised by aligning the prosthetic foot using number of techniques [6].
Commercial prosthetic feet weigh about 25% of their equivalent physiological counterparts. The human body is able to overcome the walking asymmetry resulting from this mass imbalance by exerting more energy. It is hypothesised that the passive walking dynamics coupled with roll-over shapes has potential to suggest energy efficient walking solutions. A two link passive walking kinematic model has been proposed to study the gait pattern with unbalanced leg masses. An optimal roll-over shape for the prosthetic foot that minimises the asymmetry in the inter-leg angle and the step period is determined. The proposed mathematical formulation provides insights into the variation of step length and inter-leg angle with respect to the position and location of the centres for mass of both prosthetic and physiological legs.
Biomechanics of the ankle-foot system during stair ambulation: Implications for design of advanced ankle-foot prostheses
2012, Journal of Biomechanics
Citation Excerpt :
In physiologic systems, the effective shape captures contributions of tissue deformation as well as joint movements at the ankle and foot to provide a net output of the ankle–foot system. The effective shape during LG has been referred to as a “roll-over shape” and is consistent when able-bodied persons walk at different speeds (Hansen and Childress, 2004), carry additional weight (Hansen and Childress, 2005), or walk with shoes of different heel heights (Hansen and Childress, 2004) or rocker radii (Wang and Hansen, 2010). These shapes also change significantly for ramp walking (Hansen et al., 2004b) in a way that suggests the need for different prosthetic alignment (e.g. dorsiflexed alignment for uphill walking).
Unilateral lower limb prosthesis users display temporal, kinematic, and kinetic asymmetries between limbs while ascending and descending stairs. These asymmetries are due, in part, to the inability of current prosthetic devices to effectively mimic normal ankle function. The purpose of this study was to provide a comprehensive set of biomechanical data for able-bodied and unilateral transtibial amputee (TTA) ankle–foot systems for level-ground (LG), stair ascent (SA), and stair descent (SD), and to characterize deviations from normal performance associated with prosthesis use. Ankle joint kinematics, kinetics, torque–angle curves, and effective shapes were calculated for twelve able-bodied individuals and twelve individuals with TTA. The data from this study demonstrated the prosthetic limb can more effectively mimic the range of motion and power output of a normal ankle–foot during LG compared to SA and SD. There were larger differences between the prosthetic and able-bodied limbs during SA and SD, most evident in the torque–angle curves and effective shapes. These data can be used by persons designing ankle–foot prostheses and provide comparative data for assessment of future ankle–foot prosthesis designs.
Effect of rocker shoe radius on oxygen consumption rate in young able-bodied persons
2011, Journal of Biomechanics
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Shoes with more uniform hardness soles such as those used in this study may actually provide an energetic benefit to able-bodied persons during walking. Wang and Hansen (2010) described gait analysis results of able-bodied persons walking with various shoes in this study and suggested that rocker shoes could be created and used clinically to “naturally immobilize” the ankle during single limb support using the person's tendency to maintain a consistent roll-over pattern. This approach may be useful in certain clinical cases where immobilization is being considered as a way to reduce pain in the foot and ankle.
We studied oxygen consumption rate of eleven young able-bodied persons walking at self-selected speed with five different pairs of shoes: one regular pair without rocker soles (REG) and four pairs with uniform hardness (35–40 shore A durometer) rocker soles of different radii (25% of leg length (LL) (R25), 40% LL (R40), 55% LL (R55), and infinite radius (FLAT)). Rocker soled shoes in the study were developed to provide similar vertical lift (three inches higher than the REG shoes condition). Oxygen consumption rate was significantly affected by the use of the different shoes (p<0.001) and pairwise comparisons indicated that persons consumed significantly less oxygen (per minute per kilogram of body mass) when walking on the R40 shoes when compared with both the FLAT (p<0.001) and REG (p=0.021) shoe conditions. Oxygen consumption was also significantly less for the R25 shoes compared with the FLAT shoes (p=0.005) and for the R55 shoes compared with FLAT shoes (p=0.027). The three-inch lift on the FLAT shoe did not cause a significant change in oxygen consumption compared to the shoe without the lift (REG).

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Response of able-bodied persons to changes in shoe rocker radius during walking: Changes in ankle kinematics to maintain a consistent roll-over shape

Abstract

Introduction

Section snippets

Subject recruitment

Results

Discussion

Conflict of interest statement

Acknowledgements

Human Movement Science

Clinical Biomechanics

The advantages of a rolling foot in human walking

Journal of Experimental Biology

Normal range of motion of joints in male subjects

Journal of Bone and Joint Surgery

The Measure of Man: Human Factors in Design

Effect of ankle–foot orthosis on roll-over shape in adults with hemiplegia

Journal of Rehabilitation Research and Development

Discovering Statistics using SPSS for Windows : Advanced Techniques for the Beginner

What determines the vertical displacement of the body during normal walking?

Journal of Prosthetics and Orthotics