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1.  Lower Extremity Biomechanical Relationships with Different Speeds in Traditional, Minimalist, and Barefoot Footwear 
Minimalist running footwear has grown increasingly popular. Prior studies that have compared lower extremity biomechanics in minimalist running to traditional running conditions are largely limited to a single running velocity. This study compares the effects of running at various speeds on foot strike pattern, stride length, knee angles and ankle angles in traditional, barefoot, and minimalist running conditions. Twenty-six recreational runners (19-46 years of age) ran on a treadmill at a range of speeds (2.5-4.0 m·sec-1). Subjects ran with four different footwear conditions: personal, standard, and minimalist shoes and barefoot. 3D coordinates from video data were collected. The relationships between speed, knee and ankle angles at foot strike and toe-off, relative step length, and footwear conditions were evaluated by ANCOVA, with speed as the co-variate. Distribution of non-rearfoot strike was compared across shod conditions with paired t-tests. Non-rearfoot strike distribution was not significantly affected by speed, but was different between shod conditions (p < 0.05). Footwear condition and speed significantly affected ankle angle at touchdown, independent of one another (F [3,71] = 10.28, p < 0.001), with barefoot and minimalist running exhibiting greater plantarflexion at foot strike. When controlling for foot strike style, barefoot and minimalist runners exhibited greater plantarflexion than other conditions (p < 0.05). Ankle angle at lift-off and relative step length exhibited a significant interaction between speed and shod condition. Knee angles had a significant relationship with speed, but not with footwear. There is a clear influence of footwear, but not speed, on foot strike pattern. Additionally, speed and footwear predict ankle angles (greater plantarflexion at foot strike) and may have implications for minimalist runners and their risk of injury. Long-term studies utilizing various speeds and habituation times are needed.
Key pointsFoot strike style does not change with speed, but does change with shod condition, with minimalist shoes exhibiting an intermediate distribution of forefoot strikes between barefoot and traditional shoes.Plantarflexion at touchdown does change with speed and with shoe type, with barefoot and minimalist shoes exhibiting a greater plantarflexion angle than traditional running shoes.Knee angles change with speed in all shod conditions, but knee flexion at touchdown is not different between shod conditions.Relative step length changes with speed and shod condition, but there is an interaction between these variables such that step length increases more quickly in traditional shoes as speed increases.
PMCID: PMC4424455  PMID: 25983575
Running; biomechanics; gait analysis; motion analysis/kinesiology; minimalist; shoe wear
2.  Effect of Acute Alterations in Foot Strike Patterns during Running on Sagittal Plane Lower Limb Kinematics and Kinetics 
The purpose of this study was to determine the effect of foot strike patterns and converted foot strike patterns on lower limb kinematics and kinetics at the hip, knee, and ankle during a shod condition. Subjects were videotaped with a high speed camera while running a 5km at self-selected pace on a treadmill to determine natural foot strike pattern on day one. Preferred forefoot group (PFFG, n = 10) and preferred rear foot group (PRFG, n = 11) subjects were identified through slow motion video playback (n = 21, age = 22.8±2.2 years, mass = 73.1±14.5 kg, height 1.75 ± 0.10 m). On day two, subjects performed five overground run trials in both their natural and unnatural strike patterns while motion and force data were collected. Data were collected over two days so that foot strike videos could be analyzed for group placement purposes. Several 2 (Foot Strike Pattern –forefoot strike [FFS], rearfoot strike [RFS]) x 2 (Group – PFFG, PRFG) mixed model ANOVAs (p < 0.05) were run on speed, active peak vertical ground reaction force (VGRF), peak early stance and mid stance sagittal ankle moments, sagittal plane hip and knee moments, ankle dorsiflexion ROM, and sagittal plane hip and knee ROM. There were no significant interactions or between group differences for any of the measured variables. Within subject effects demonstrated that the RFS condition had significantly lower (VGRF) (RFS = 2.58 ± .21 BW, FFS = 2.71 ± 0.23 BW), dorsiflexion moment (RFS = -2.6 1± 0.61 Nm·kg-1, FFS = -3.09 ± 0.32 Nm·kg-1), and dorsiflexion range of motion (RFS = 17.63 ± 3.76°, FFS = 22.10 ± 5.08°). There was also a significantly higher peak plantarflexion moment (RFS = 0.23 ± 0.11 Nm·kg-1, FFS = 0.01 ± 0.01 Nm·kg-1), peak knee moment (RFS = 2.61 ± 0.54 Nm·kg-1, FFS = 2.39 ± 0.61 Nm·kg-1), knee ROM (RFS = 31.72 ± 2.79°, FFS = 29.58 ± 2.97°), and hip ROM (RFS = 42.72 ± 4.03°, FFS = 41.38 ± 3.32°) as compared with the FFS condition. This research suggests that acute changes in foot strike patterns during shod running can create alterations in certain lower limb kinematic and kinetic measures that are not dependent on the preferred foot strike pattern of the individual. This research also challenges the contention that the impact transient spike in the vertical ground reaction force curve is only present during a rear foot strike type of running gait.
Key pointsFootstrike pattern changes should be individually considered and implemented based on individual histories/abilitiesForefoot strike patterns increase external dorsiflexion momentsRearfoot strike patterns increase external knee flexion momentsRecreational shod runners are able to mimic habitual mechanics of different foot strike patterns
PMCID: PMC4306776  PMID: 25729311
Forefoot; rearfoot; joint moments; range of motion
3.  Effect of children's shoes on gait: a systematic review and meta-analysis 
Background
The effect of footwear on the gait of children is poorly understood. This systematic review synthesises the evidence of the biomechanical effects of shoes on children during walking and running.
Methods
Study inclusion criteria were: barefoot and shod conditions; healthy children aged ≤ 16 years; sample size of n > 1. Novelty footwear was excluded. Studies were located by online database-searching, hand-searching and contact with experts. Two authors selected studies and assessed study methodology using the Quality Index. Meta-analysis of continuous variables for homogeneous studies was undertaken using the inverse variance approach. Significance level was set at P < 0.05. Heterogeneity was measured by I2. Where I2 > 25%, a random-effects model analysis was used and where I2 < 25%, a fixed-effects model was used.
Results
Eleven studies were included. Sample size ranged from 4-898. Median Quality Index was 20/32 (range 11-27). Five studies randomised shoe order, six studies standardised footwear. Shod walking increased: velocity, step length, step time, base of support, double-support time, stance time, time to toe-off, sagittal tibia-rearfoot range of motion (ROM), sagittal tibia-foot ROM, ankle max-plantarflexion, Ankle ROM, foot lift to max-plantarflexion, 'subtalar' rotation ROM, knee sagittal ROM and tibialis anterior activity. Shod walking decreased: cadence, single-support time, ankle max-dorsiflexion, ankle at foot-lift, hallux ROM, arch length change, foot torsion, forefoot supination, forefoot width and midfoot ROM in all planes. Shod running decreased: long axis maximum tibial-acceleration, shock-wave transmission as a ratio of maximum tibial-acceleration, ankle plantarflexion at foot strike, knee angular velocity and tibial swing velocity. No variables increased during shod running.
Conclusions
Shoes affect the gait of children. With shoes, children walk faster by taking longer steps with greater ankle and knee motion and increased tibialis anterior activity. Shoes reduce foot motion and increase the support phases of the gait cycle. During running, shoes reduce swing phase leg speed, attenuate some shock and encourage a rearfoot strike pattern. The long-term effect of these changes on growth and development are currently unknown. The impact of footwear on gait should be considered when assessing the paediatric patient and evaluating the effect of shoe or in-shoe interventions.
doi:10.1186/1757-1146-4-3
PMCID: PMC3031211  PMID: 21244647
4.  Athletic Footwear, Leg Stiffness, and Running Kinematics 
Journal of Athletic Training  2006;41(4):387-392.
Context: The leg acts as a linear spring during running and hopping and adapts to the stiffness of the surface, maintaining constant total stiffness of the leg-surface system. Introducing a substance (eg, footwear) may affect the stiffness of the leg in response to changes in surface stiffness.
Objective: To determine if the type of athletic footwear affects the regulation of leg stiffness in dynamic activities.
Design: Repeated-measures design.
Setting: Motion analysis laboratory.
Patients or Other Participants: Nine healthy adults (age = 28 ± 6.8 years, mass = 71.6 ± 12.9 kg) free from lower extremity injuries.
Intervention(s): Subjects hopped at 2.2 Hz on a forceplate under 3 footwear conditions (barefoot, low-cost footwear, high-cost footwear). Subjects ran on a treadmill at 2 speeds (2.23 m/s, 3.58 m/s) under the same footwear conditions.
Main Outcome Measure(s): Limb stiffness was calculated from forceplate data. Kinematic data (knee and ankle angles at initial contact and peak joint excursion after contact) were collected during running. We calculated 1-way repeated-measures (stiffness) and 2-way (speed by footwear) repeated-measures analyses of variance (running kinematics) to test the dependent variables.
Results: A significant increase in leg stiffness from the barefoot to the “cushioned” shoe condition was noted during hopping. When running shod, runners landed in more dorsiflexion but had less ankle motion than when running barefoot. No differences were seen between the types of shoes. The primary kinematic difference was identified as running speed increased: runners landed in more knee flexion. At the ankle, barefoot runners increased ankle motion to a significantly greater extent than did shod runners as speed increased.
Conclusions: Footwear influences the maintenance of stiffness in the lower extremity during hopping and joint excursion at the ankle in running. Differences in cushioning properties of the shoes tested did not appear to be significant.
PMCID: PMC1748411  PMID: 17273463
shoes; gait; hopping task
5.  Acute Differences in Foot Strike and Spatiotemporal Variables for Shod, Barefoot or Minimalist Male Runners 
This study compared stride length, stride frequency, contact time, flight time and foot-strike patterns (FSP) when running barefoot, and in minimalist and conventional running shoes. Habitually shod male athletes (n = 14; age 25 ± 6 yr; competitive running experience 8 ± 3 yr) completed a randomised order of 6 by 4-min treadmill runs at velocities (V1 and V2) equivalent to 70 and 85% of best 5-km race time, in the three conditions. Synchronous recording of 3-D joint kinematics and ground reaction force data examined spatiotemporal variables and FSP. Most participants adopted a mid-foot strike pattern, regardless of condition. Heel-toe latency was less at V2 than V1 (-6 ± 20 vs. -1 ± 13 ms, p < 0.05), which indicated a velocity related shift towards a more FFS pattern. Stride duration and flight time, when shod and in minimalist footwear, were greater than barefoot (713 ± 48 and 701 ± 49 vs. 679 ± 56 ms, p < 0.001; and 502 ± 45 and 503 ± 41 vs. 488 ±4 9 ms, p < 0.05, respectively). Contact time was significantly longer when running shod than barefoot or in minimalist footwear (211±30 vs. 191 ± 29 ms and 198 ± 33 ms, p < 0.001). When running barefoot, stride frequency was significantly higher (p < 0.001) than in conventional and minimalist footwear (89 ± 7 vs. 85 ± 6 and 86 ± 6 strides·min-1). In conclusion, differences in spatiotemporal variables occurred within a single running session, irrespective of barefoot running experience, and, without a detectable change in FSP.
Key pointsDifferences in spatiotemporal variables occurred within a single running session, without a change in foot strike pattern.Stride duration and flight time were greater when shod and in minimalist footwear than when barefoot.Stride frequency when barefoot was higher than when shod or in minimalist footwear.Contact time when shod was longer than when barefoot or in minimalist footwear.Spatiotemporal variables when running in minimalist footwear more closely resemble shod than barefoot running.
PMCID: PMC3990880  PMID: 24790480
Flight time; contact time; foot-strike pattern
6.  A Kinematic Method for Footstrike Pattern Detection in Barefoot and Shod Runners 
Gait & posture  2011;35(2):298-300.
Footstrike patterns during running can be classified discretely into a rearfoot strike, midfoot strike and forefoot strike by visual observation. However, the footstrike pattern can also be classified on a continuum, ranging from 0–100% (extreme rearfoot to extreme forefoot) using the strike index, a measure requiring force plate data. When force data are not available, an alternative method to quantify the strike pattern must be used. The purpose of this paper was to quantify the continuum of foot strike patterns using an easily attainable kinematic measure, and compare it to the strike index measure. Force and kinematic data from twenty subjects were collected as they ran across an embedded force plate. Strike index and the footstrike angle were identified for the four running conditions of rearfoot strike, midfoot strike and forefoot strike, as well as barefoot. The footstrike angle was calculated as the angle of the foot with respect to the ground in the sagittal plane. Results indicated that the footstrike angle was significantly correlated with strike index. The linear regression model suggested that strike index can be accurately estimated, in both barefoot and shod conditions, in the absence of force data.
doi:10.1016/j.gaitpost.2011.09.104
PMCID: PMC3278526  PMID: 22075193
7.  Variation in Foot Strike Patterns among Habitually Barefoot and Shod Runners in Kenya 
PLoS ONE  2015;10(7):e0131354.
Runners are often categorized as forefoot, midfoot or rearfoot strikers, but how much and why do individuals vary in foot strike patterns when running on level terrain? This study used general linear mixed-effects models to explore both intra- and inter-individual variations in foot strike pattern among 48 Kalenjin-speaking participants from Kenya who varied in age, sex, body mass, height, running history, and habitual use of footwear. High speed video was used to measure lower extremity kinematics at ground contact in the sagittal plane while participants ran down 13 meter-long tracks with three variables independently controlled: speed, track stiffness, and step frequency. 72% of the habitually barefoot and 32% of the habitually shod participants used multiple strike types, with significantly higher levels of foot strike variation among individuals who ran less frequently and who used lower step frequencies. There was no effect of sex, age, height or weight on foot strike angle, but individuals were more likely to midfoot or forefoot strike when they ran on a stiff surface, had a high preferred stride frequency, were habitually barefoot, and had more experience running. It is hypothesized that strike type variation during running, including a more frequent use of forefoot and midfoot strikes, used to be greater before the introduction of cushioned shoes and paved surfaces.
doi:10.1371/journal.pone.0131354
PMCID: PMC4495985  PMID: 26154285
8.  EFFECTS OF WEARING ATHLETIC SHOES, FIVE‐TOED SHOES, AND STANDING BAREFOOT ON BALANCE PERFORMANCE IN YOUNG ADULTS 
Background/Purpose
Almost all research using participants wearing barefoot‐style shoes study elite runners or have participants with a history of barefoot style shoe training run on a treadmill when shod or barefoot. Wearing barefoot‐style shoes is suggested as a method of transition between shod and barefoot running. Static and dynamic balance exercises also are recommended. However, little information is available on the effects five‐toed barefoot style shoes have on static balance. The purpose of this study was to examine balance of subjects barefoot, wearing Vibram FiveFingers™ barefoot‐style shoes, and regular athletic shoes with eyes closed when using the Biodex Balance System‐SD™.
Study Design
This was a repeated measures study.
Methods
Forty nine participants aged 18‐30 years without lower extremity injury or experience wearing barefoot‐style shoes were tested for static balance on the Biodex Stability System™ with their eyes closed while wearing Vibram FiveFingers™, athletic shoes, or barefoot. Three trials of 10 seconds for each footwear type were completed. Repeated measures analysis of variance with Bonferroni's correction was used to analyze the degrees of sway in the anterior‐posterior and medial lateral directions. An overall stability index was also calculated by the Biodex.
Results
For anterior‐posterior and overall indices, differences were found between all conditions. Participants wearing athletic shoes demonstrated the smallest anterior‐posterior stability index (least sway) and spent the most time in the innermost concentric circular zone. Medial‐lateral indices were not different for any condition.
Conclusions
Wearing Vibram FiveFingers™ provided better overall and anterior‐posterior static balance than going barefoot. While differences between Vibram FiveFingers™ and barefoot are significant, results may reflect statistical significance rather than any clinical difference in young, uninjured individuals.
Clinical relevance
It would appear that Vibram FiveFingers™ mimic going barefoot and may be a bridge for exercising in preparation for barefoot exercise.
Level of Evidence
3B
PMCID: PMC4325290  PMID: 25709865
static balance; Biodex; postural control; postural index; Vibram FiveFingers
9.  Lower Limb Joint Kinetics During Moderately Sloped Running 
Journal of Athletic Training  2010;45(1):16-21.
Abstract
Context:
Knowledge of the kinetic changes that occur during sloped running is important in understanding the adaptive gait-control mechanisms at work and can provide additional information about the poorly understood relationship between injury and changes in kinetic forces in the lower extremity. A study of these potential kinetic changes merits consideration, because training and return-to-activity programs are potentially modifiable factors for tissue stress and injury risk.
Objective:
To contribute further to the understanding of hill running by quantifying the 3-dimensional alterations in joint kinetics during moderately sloped decline, level, and incline running in a group of healthy runners.
Design:
Crossover study.
Setting:
Three-dimensional motion analysis laboratory.
Patients or Other Participants:
Nineteen healthy young runners/joggers (age  =  25.3 ± 2.5 years).
Intervention(s):
Participants ran at 3.13 m/s on a treadmill under the following 3 different running-surface slope conditions: 4° decline, level, and 4° incline.
Main Outcome Measure(s):
Lower extremity joint moments and powers and the 3 components of the ground reaction force.
Results:
Moderate changes in running-surface slope had a minimal effect on ankle, knee, and hip joint kinetics when velocity was held constant. Only changes in knee power absorption (increased with decline-slope running) and hip power (increased generation on incline-slope running and increased absorption on decline-slope running in early stance) were noted. We observed an increase only in the impact peak of the vertical ground reaction force component during decline-slope running, whereas the nonvertical components displayed no differences.
Conclusions:
Running style modifications associated with running on moderate slopes did not manifest as changes in 3-dimensional joint moments or in the active peaks of the ground reaction force. Our data indicate that running on level and moderately inclined slopes appears to be a safe component of training regimens and return-to-run protocols after injury.
doi:10.4085/1062-6050-45.1.16
PMCID: PMC2808749  PMID: 20064043
biomechanics; decline running; incline running; joint moments; joint power
10.  Changes in talocrural and subtalar joint kinematics of barefoot versus shod forefoot landing 
Background
Synergetic talocrural and subtalar joint movements allow adaptation to different footwear and/or surface conditions. Therefore, knowledge of kinematic differences between barefoot and shod conditions is valuable for the study of adaptations to footwear conditions. The objective of this study was to assess the kinematic differences in the talocrural and subtalar joints during barefoot and shod landing.
Methods
Seven healthy participants (4 males and 3 females) participated in a landing trial under barefoot and shod conditions. Fluoroscopic images and forceplate data were collected simultaneously to calculate the talocrural and subtalar joint kinematics and the vertical ground reaction force.
Results
Upon toe contact, the plantarflexion angle of the talocrural joint during the barefoot condition was significantly larger than that during the shod condition (barefoot, 20.5 ± 7.1°, shod, 17.9 ± 8.3°, p =0.03). From toe contact to heel contact, the angular changes at the talocrural and subtalar joint were not significantly different between the barefoot and shod conditions; however, the changes in the subtalar eversion angles in the barefoot condition, from heel contact to 150 ms after toe contact, were significantly larger than those in the shod condition.
Conclusions
These results suggest that footwear was able to reduce the eversion angle of the subtalar joint after heel contact during landing; the effect of wearing footwear was quite limited. Therefore, induced rearfoot kinematic alterations to prevent or manage injuries by neutral-type footwear are likely to be impractical.
doi:10.1186/s13047-014-0042-9
PMCID: PMC4197340  PMID: 25320641
Kinematics; Tibia; Talus; Calcaneus; Shoes
11.  Joint kinematics and kinetics of overground accelerated running versus running on an accelerated treadmill 
Literature shows that running on an accelerated motorized treadmill is mechanically different from accelerated running overground. Overground, the subject has to enlarge the net anterior–posterior force impulse proportional to acceleration in order to overcome linear whole body inertia, whereas on a treadmill, this force impulse remains zero, regardless of belt acceleration. Therefore, it can be expected that changes in kinematics and joint kinetics of the human body also are proportional to acceleration overground, whereas no changes according to belt acceleration are expected on a treadmill. This study documents kinematics and joint kinetics of accelerated running overground and running on an accelerated motorized treadmill belt for 10 young healthy subjects. When accelerating overground, ground reaction forces are characterized by less braking and more propulsion, generating a more forward-oriented ground reaction force vector and a more forwardly inclined body compared with steady-state running. This change in body orientation as such is partly responsible for the changed force direction. Besides this, more pronounced hip and knee flexion at initial contact, a larger hip extension velocity, smaller knee flexion velocity and smaller initial plantarflexion velocity are associated with less braking. A larger knee extension and plantarflexion velocity result in larger propulsion. Altogether, during stance, joint moments are not significantly influenced by acceleration overground. Therefore, we suggest that the overall behaviour of the musculoskeletal system (in terms of kinematics and joint moments) during acceleration at a certain speed remains essentially identical to steady-state running at the same speed, yet acting in a different orientation. However, because acceleration implies extra mechanical work to increase the running speed, muscular effort done (in terms of power output) must be larger. This is confirmed by larger joint power generation at the level of the hip and lower power absorption at the knee as the result of subtle differences in joint velocity. On a treadmill, ground reaction forces are not influenced by acceleration and, compared with overground, virtually no kinesiological adaptations to an accelerating belt are observed. Consequently, adaptations to acceleration during running differ from treadmill to overground and should be studied in the condition of interest.
doi:10.1098/rsif.2013.0222
PMCID: PMC3673159  PMID: 23676896
acceleration; running; overground; treadmill; joint kinetics; unsteady-state gait
12.  Comparison of Minimalist Footwear Strategies for Simulating Barefoot Running: A Randomized Crossover Study 
PLoS ONE  2015;10(5):e0125880.
Possible benefits of barefoot running have been widely discussed in recent years. Uncertainty exists about which footwear strategy adequately simulates barefoot running kinematics. The objective of this study was to investigate the effects of athletic footwear with different minimalist strategies on running kinematics. Thirty-five distance runners (22 males, 13 females, 27.9 ± 6.2 years, 179.2 ± 8.4 cm, 73.4 ± 12.1 kg, 24.9 ± 10.9 km.week-1) performed a treadmill protocol at three running velocities (2.22, 2.78 and 3.33 m.s-1) using four footwear conditions: barefoot, uncushioned minimalist shoes, cushioned minimalist shoes, and standard running shoes. 3D kinematic analysis was performed to determine ankle and knee angles at initial foot-ground contact, rate of rear-foot strikes, stride frequency and step length. Ankle angle at foot strike, step length and stride frequency were significantly influenced by footwear conditions (p<0.001) at all running velocities. Posthoc pairwise comparisons showed significant differences (p<0.001) between running barefoot and all shod situations as well as between the uncushioned minimalistic shoe and both cushioned shoe conditions. The rate of rear-foot strikes was lowest during barefoot running (58.6% at 3.33 m.s-1), followed by running with uncushioned minimalist shoes (62.9%), cushioned minimalist (88.6%) and standard shoes (94.3%). Aside from showing the influence of shod conditions on running kinematics, this study helps to elucidate differences between footwear marked as minimalist shoes and their ability to mimic barefoot running adequately. These findings have implications on the use of footwear applied in future research debating the topic of barefoot or minimalist shoe running.
doi:10.1371/journal.pone.0125880
PMCID: PMC4444250  PMID: 26011042
13.  Variation in Foot Strike Patterns during Running among Habitually Barefoot Populations 
PLoS ONE  2013;8(1):e52548.
Endurance running may have a long evolutionary history in the hominin clade but it was not until very recently that humans ran wearing shoes. Research on modern habitually unshod runners has suggested that they utilize a different biomechanical strategy than runners who wear shoes, namely that barefoot runners typically use a forefoot strike in order to avoid generating the high impact forces that would be experienced if they were to strike the ground with their heels first. This finding suggests that our habitually unshod ancestors may have run in a similar way. However, this research was conducted on a single population and we know little about variation in running form among habitually barefoot people, including the effects of running speed, which has been shown to affect strike patterns in shod runners. Here, we present the results of our investigation into the selection of running foot strike patterns among another modern habitually unshod group, the Daasanach of northern Kenya. Data were collected from 38 consenting adults as they ran along a trackway with a plantar pressure pad placed midway along its length. Subjects ran at self-selected endurance running and sprinting speeds. Our data support the hypothesis that a forefoot strike reduces the magnitude of impact loading, but the majority of subjects instead used a rearfoot strike at endurance running speeds. Their percentages of midfoot and forefoot strikes increased significantly with speed. These results indicate that not all habitually barefoot people prefer running with a forefoot strike, and suggest that other factors such as running speed, training level, substrate mechanical properties, running distance, and running frequency, influence the selection of foot strike patterns.
doi:10.1371/journal.pone.0052548
PMCID: PMC3541372  PMID: 23326341
14.  Kinematic, kinetic and electromyographic response to customized foot orthoses in patients with tibialis posterior tenosynovitis, pes plano valgus and rheumatoid arthritis 
Rheumatology (Oxford, England)  2013;53(1):123-130.
Objective. To describe the effect of customized foot orthoses (FOs) on the kinematic, kinetic and EMG features in patients with RA, tibialis posterior (TP) tenosynovitis and associated pes plano valgus.
Methods. Patients with RA and US-confirmed tenosynovitis of TP underwent gait analysis, including three-dimensional (3D) kinematics, kinetics, intramuscular EMG of TP and surface EMG of tibialis anterior, peroneus longus, soleus and medial gastrocnemius. Findings were compared between barefoot and shod with customized FO conditions.
Results. Ten patients with RA with a median (range) disease duration of 3 (1–18) years were recruited. Moderate levels of foot pain and foot-related impairment and disability were present with moderately active disease states. Altered timing of the soleus (P = 0.05) and medial gastrocnemius (P = 0.02) and increased magnitude of tibialis anterior (P = 0.03) were noted when barefoot was compared with shod with FO. Trends were noted for reduced TP activity in the contact period (P = 0.09), but this did not achieve statistical significance. Differences in foot motion characteristics were recorded for peak rearfoot eversion (P = 0.01), peak rearfoot plantarflexion (P < 0.001) and peak forefoot abduction (P = 0.02) in the shod with FOs compared with barefoot conditions. No differences in kinetic variables were recorded.
Conclusion. This study has demonstrated, for the first time, alterations in muscle activation profiles and foot motion characteristics in patients with RA, pes plano valgus and US-confirmed TP tenosynovitis in response to customized FOs. Complex adaptations were evident in this cohort and further work is required to determine whether these functional alterations lead to improvements in patient symptoms.
doi:10.1093/rheumatology/ket337
PMCID: PMC3862974  PMID: 24097135
rheumatoid arthritis; foot orthoses; electromyography; kinematics; tibialis posterior
15.  The effect of external ankle support on the kinematics and kinetics of the lower limb during a side step cutting task in netballers 
Background
Excessive knee valgus moments are considered to be a risk factor for non-contact injuries in female athletes. Knee injuries are highly prevalent in netballers and are significant in terms of cost and disability. The aim of the study was to identify if changes in external ankle support mechanisms effect the range of motion and loading patterns at the ankle and knee joint during a sidestep cutting manoeuvre in high performance netball players.
Methods
Netballers with no previously diagnosed ankle or knee injury (n = 10) were recruited from NSW Institute of Sport netball programme. Kinematic and kinetic data were collected simultaneously using a 3-D Motion Analysis System and a force platform to measure ground reaction forces. Players performed repeated side step cutting manoeuvres whilst wearing a standard netball shoe, the same shoe with a lace-up brace and a high-top shoe.
Results
The brace condition significantly reduced ankle joint ROM in the sagittal plane by 8.9° ± 2.4 when compared to the standard netball shoe (p = 0.013). No other significant changes were seen between conditions for either kinematic or kinetic data. All shoe conditions did however produce knee valgus moments throughout the cutting cycle that were greater than those considered excessive in the previous literature (0.59 Nm/kg-Bwt).
Conclusions
The results show that an external ankle support brace can be used to reduce the ROM at the ankle in the sagittal plane without affecting the loading of the joints of the lower limb. Internal varus moments generated at the knee during the task were however greater than values reported in the literature to classify excessive knee joint moments, regardless of the condition. All netballers exhibited lower extremity patterns and alignments previously associated with increased peak external valgus moments including; increasing hip abduction, peak hip flexion and internal rotation during early contact and high laterally directed ground reaction forces. Increased external valgus knee loads have been strongly linked to the development of non-contact injuries at the knee in female athletes and could highlight a potential mechanism for the development non-contact knee injuries in netballers performing side step cutting tasks.
doi:10.1186/2052-1847-6-42
PMCID: PMC4297419  PMID: 25598984
Netball; Sidestep cutting; Biomechanics; External ankle support; Knee joint loading; Internal valgus moment
16.  Comparison of ankle and subtalar joint complex range of motion during barefoot walking and walking in Masai Barefoot Technology sandals 
Background
Masai Barefoot Technology (MBT, Switzerland) produce footwear which they claim simulate walking barefoot on soft undulating ground. This paper reports an investigation into the effect of MBT sandals on the motion of the ankle and subtalar joint complex during walking.
Methods
Range of motion data was collected in the sagittal, frontal and transverse plane from the ankle and subtalar joint complex from 32 asymptomatic subjects using the CODA MPX30 motion analysis system during both barefoot walking and walking in the MBT sandal. Shod and un-shod data were compared using the Wilcoxon signed ranks test.
Results
A significantly greater range of motion in the frontal and sagittal planes was recorded when walking in the MBT sandal (p = 0.031, and p = 0.015 respectively). In the transverse plane, no significant difference was found (p = 0.470).
Conclusions
MBT sandals increase the range of motion of the ankle and subtalar joint complex in the frontal and sagittal planes. MBT footwear could therefore have a role to play in the management of musculoskeletal disorders where an increase in frontal and sagittal plane range of motion is desirable.
doi:10.1186/1757-1146-4-1
PMCID: PMC3024926  PMID: 21194494
17.  Effects of Step Rate Manipulation on Joint Mechanics during Running 
Purpose
The objective of this study was to characterize the biomechanical effects of step rate modification during running on the hip, knee and ankle joints, so as to evaluate a potential strategy to reduce lower extremity loading and risk for injury.
Methods
Three-dimensional kinematics and kinetics were recorded from 45 healthy recreational runners during treadmill running at constant speed under various step rate conditions (preferred, ± 5% and ± 10%). We tested our primary hypothesis that a reduction in energy absorption by the lower extremity joints during the loading response would occur, primarily at the knee, when step rate was increased.
Results
Less mechanical energy was absorbed at the knee (p<0.01) during the +5% and +10% step rate conditions, while the hip (p<0.01) absorbed less energy during the +10% condition only. All joints displayed substantially (p<0.01) more energy absorption when preferred step rate was reduced by 10. Step length (p<0.01), center of mass vertical excursion (p<0.01), breaking impulse (p<0.01) and peak knee flexion angle (p<0.01) were observed to decrease with increasing step rate. When step rate was increased 10% above preferred, peak hip adduction angle (p<0.01), as well as peak hip adduction (p<0.01) and internal rotation (p<0.01) moments, were found to decrease.
Conclusion
We conclude that subtle increases in step rate can substantially reduce the loading to the hip and knee joints during running and may prove beneficial in the prevention and treatment of common running-related injuries.
doi:10.1249/MSS.0b013e3181ebedf4
PMCID: PMC3022995  PMID: 20581720
energy absorption; knee; stride length; injury prevention; rehabilitation
18.  A functional electrical stimulation system improves knee control in crouch gait 
Background
Crouch gait is a major sagittal plane deviation in children diagnosed with cerebral palsy (CP). It is defined as a combination of excessive ankle dorsiflexion and knee and hip flexion throughout the stance phase. To the best of our knowledge, functional electrical stimulation (FES) has not been used to decrease the severity of crouch gait in CP subjects and assist in achieving lower limb extension.
Purpose
To evaluate the short- and long-term effects of FES to the quadriceps muscles in preventing crouch gait and achieving ankle plantar flexion, knee and hip extension at the stance phase.
Methods
An 18-year-old boy diagnosed with CP diplegia [Gross Motor Function Classification System (GMFCS) level II] was evaluated. The NESS L300® Plus neuroprosthesis system provided electrical stimulation of the quadriceps muscle. A three-dimensional gait analysis was performed using an eight-camera system measuring gait kinematics and spatiotemporal parameters while the subject walked shod only, with ground reaction ankle foot orthotics (GRAFOs) and using an FES device.
Results
Walking with the FES device showed an increase in the patient’s knee extension at midstance and increased knee maximal extension at the stance phase. In addition, the patient was able to ascend and descend stairs with a “step-through” pattern immediately after adjusting the FES device.
Conclusions
This report suggests that FES to the quadriceps muscles may affect knee extension at stance and decrease crouch gait, depending on the adequate passive range of motion of the hip, knee extension, and plantar flexion. Further studies are needed in order to validate these results.
doi:10.1007/s11832-015-0651-2
PMCID: PMC4417739  PMID: 25786388
Cerebral palsy; Crouch gait; Functional electrical stimulation
19.  A comparison of gait biomechanics of flip-flops, sandals, barefoot and shoes 
Background
Flip-flops and sandals are popular choices of footwear due to their convenience. However, the effects of these types of footwear on lower extremity biomechanics are still poorly understood. Therefore, the objective of this study was to investigate differences in ground reaction force (GRF), center of pressure (COP) and lower extremity joint kinematic and kinetic variables during level-walking in flip-flops, sandals and barefoot compared to running shoes.
Methods
Ten healthy males performed five walking trials in the four footwear conditions at 1.3 m/s. Three-dimensional GRF and kinematic data were simultaneously collected.
Results
A smaller loading rate of the 1st peak vertical GRF and peak propulsive GRF and greater peak dorsiflexion moment in early stance were found in shoes compared to barefoot, flip-flops and sandals. Barefoot walking yielded greater mediolateral COP displacement, flatter foot contact angle, increased ankle plantarflexion contact angle, and smaller knee flexion contact angle and range of motion compared to all other footwear.
Conclusions
The results from this study indicate that barefoot, flip-flops and sandals produced different peak GRF variables and ankle moment compared to shoes while all footwear yield different COP and ankle and knee kinematics compared to barefoot. The findings may be helpful to researchers and clinicians in understanding lower extremity mechanics of open-toe footwear.
doi:10.1186/1757-1146-6-45
PMCID: PMC3907140  PMID: 24196492
Flip-flops; Sandals; Barefoot; Open-toe footwear; Kinematics; Kinetics; Gait; Footwear
20.  Effect of medial arch-heel support in inserts on reducing ankle eversion: a biomechanics study 
Background
Excessive pronation (or eversion) at ankle joint in heel-toe running correlated with lower extremity overuse injuries. Orthotics and inserts are often prescribed to limit the pronation range to tackle the problem. Previous studies revealed that the effect is product-specific. This study investigated the effect of medial arch-heel support in inserts on reducing ankle eversion in standing, walking and running.
Methods
Thirteen pronators and 13 normal subjects participated in standing, walking and running trials in each of the following conditions: (1) barefoot, and shod condition with insert with (2) no, (3) low, (4) medium, and (5) high medial arch-heel support. Motions were captured and processed by an eight-camera motion capture system. Maximum ankle eversion was calculated by incorporating the raw coordinates of 15 anatomical positions to a self-compiled Matlab program with kinematics equations. Analysis of variance with repeated measures with post-hoc Tukey pairwise comparisons was performed on the data among the five walking conditions and the five running conditions separately.
Results
Results showed that the inserts with medial arch-heel support were effective in dynamics trials but not static trials. In walking, they successfully reduced the maximum eversion by 2.1 degrees in normal subjects and by 2.5–3.0 degrees in pronators. In running, the insert with low medial arch support significantly reduced maximum eversion angle by 3.6 and 3.1 degrees in normal subjects and pronators respectively.
Conclusion
Medial arch-heel support in inserts is effective in reducing ankle eversion in walking and running, but not in standing. In walking, there is a trend to bring the over-pronated feet of the pronators back to the normal eversion range. In running, it shows an effect to restore normal eversion range in 84% of the pronators.
doi:10.1186/1749-799X-3-7
PMCID: PMC2266906  PMID: 18289375
21.  Joint torques and powers are reduced during ambulation for both limbs in patients with unilateral claudication 
Journal of vascular surgery  2009;51(1):80-88.
Objectives
Symptomatic peripheral arterial disease (PAD) results in significant gait impairment. In an attempt to fully delineate and quantify these gait alterations, we analyzed joint kinematics, torques (rotational forces) and powers (rotational forces times angular velocity) in PAD patients with unilateral claudication for both the affected and non-affected legs.
Methods
Twelve patients with unilateral PAD (age: 61.69±10.53 years, ABI: Affected Limb 0.59 ± 0.25; Non-Affected Limb 0.93 ± 0.12) and ten healthy controls (age: 67.23 ± 12.67 years, ABI>1.0 all subjects) walked over a force platform to acquire gait kinetics, while joint kinematics were recorded simultaneously. Data were collected for the affected and non-affected limbs during pain free (PAD-PF) and pain induced (PAD-P) trials. Kinetics and kinematics were combined to quantify torques and powers during the stance period from the hip, knee, and ankle joints.
Results
The affected limb demonstrated significantly (p<0.05) reduced ankle plantar flexion torque compared to control during late stance in both PAD-PF and PAD-P trials. There were significant reductions in ankle plantar flexion power generation during late stance for both the affected (P<.05) and non-affected limbs (P<.05) compared to control during PAD-PF and PAD-P trials. No significant differences were noted in torques comparing the non-affected limb in PAD-PF and PAD-P conditions to control for knee and hip joints throughout the stance phase. Significant reductions were found in knee power absorption in early stance and knee power generation during mid stance for both limbs of the PAD patients as compared to control (P<.05).
Conclusions
PAD patients with unilateral claudication demonstrate significant gait impairments in both limbs that are present even before they experience any claudication symptoms. Overall, our data demonstrate significantly reduced ankle plantar flexion torque and power during late stance with reduced knee power during early and mid stance for the affected limb. Further studies are needed to determine if these findings dependent on the location and the severity of lower extremity ischemia and whether the changes in the non-affected limb are the result of underlying PAD or compensatory changes from the affected limb dysfunction.
doi:10.1016/j.jvs.2009.07.117
PMCID: PMC4465243  PMID: 19837536
biomechanics; ischemia; peripheral arterial disease; locomotion; gait
22.  Investigating the Effects of Knee Flexion during the Eccentric Heel-Drop Exercise 
This study aimed to characterise the biomechanics of the widely practiced eccentric heel-drop exercises used in the management of Achilles tendinosis. Specifically, the aim was to quantify changes in lower limb kinematics, muscle lengths and Achilles tendon force, when performing the exercise with a flexed knee instead of an extended knee. A musculoskeletal modelling approach was used to quantify any differences between these versions of the eccentric heel drop exercises used to treat Achilles tendinosis. 19 healthy volunteers provided a group from which optical motion, forceplate and plantar pressure data were recorded while performing both the extended and flexed knee eccentric heel-drop exercises over a wooden step when barefoot or wearing running shoes. This data was used as inputs into a scaled musculoskeletal model of the lower limb. Range of ankle motion was unaffected by knee flexion. However, knee flexion was found to significantly affect lower limb kinematics, inter-segmental loads and triceps muscle lengths. Peak Achilles load was not influenced despite significantly reduced peak ankle plantarflexion moments (p < 0.001). The combination of reduced triceps lengths and greater ankle dorsiflexion, coupled with reduced ankle plantarflexion moments were used to provide a basis for previously unexplained observations regarding the effect of knee flexion on the relative loading of the triceps muscles during the eccentric heel drop exercises. This finding questions the role of the flexed knee heel drop exercise when specifically treating Achilles tendinosis.
Key pointsA more dorsiflexed ankle and a flexing knee are characteristics of performing the flexed knee heel-drop eccentric exercise.Peak ankle plantarflexion moments were reduced with knee flexion, but did not reduce peak Achilles tendon force.Kinematic changes at the knee and ankle affected the triceps muscle length and resulted in a reduction in the amount of Achilles tendon work performed.A version of the heel-drop exercise which reduces the muscle length change will also reduce the amount of tendon stretch, reducing the clinical efficacy of the exercise.
PMCID: PMC4424477  PMID: 25983597
Achilles; tendinosis; tendinopathy; rehabilitation
23.  Gait impairment in cervical spondylotic myelopathy: comparison with age- and gender-matched healthy controls 
European Spine Journal  2012;21(12):2456-2466.
Introduction
Gait impairment is a primary symptom of cervical spondylotic myelopathy (CSM); however, little is known about specific kinetic and kinematic gait parameters. The objectives of the study were: (1) to compare gait patterns of people with untreated CSM to those of age- and gender-matched healthy controls; (2) to examine the effect of gait speed on kinematic and kinetic parameters.
Materials and methods
Sixteen patients with CSM were recruited consecutively from a neurosurgery clinic, and 16 healthy controls, matched to age (±5 years) and gender, were recruited for comparison. Patients and controls underwent three-dimensional gait analysis using a Vicon® motion analysis system, at self-selected speed over a 10-m track. Controls were also assessed at the speed of their CSM match.
Results
At self-selected speed, the CSM group walked significantly more slowly, with shorter stride lengths and longer double support duration. They showed significant decreases in several kinematic and kinetic parameters, including sagittal range of motion at the hip and knee, ankle plantarflexion, anteroposterior ground reaction force (GRF) at toe-off, power absorption at the knee in loading response and terminal stance, and power generation at the ankle. At matched speed, the CSM group showed significant decreases in knee flexion during swing, total sagittal knee range of motion, peak ankle plantarflexion and anteroposterior GRF.
Conclusion and implications
The findings suggested that people with CSM have significant gait abnormalities that have not been previously reported. In particular, there are key differences in the motor strategies used in the terminal stance phase of gait that cannot be explained by speed alone.
doi:10.1007/s00586-012-2433-6
PMCID: PMC3508234  PMID: 22825630
Cervical myelopathy; Gait; Gait analysis; Biomechanics
24.  Joint Laxity Is Related to Lower Extremity Energetics during a Drop Jump Landing 
Purpose
To examine the relationships between anterior knee laxity (AKL), genu recurvatum (GR), and general joint laxity (GJL) with sagittal plane energetics in males and females during a drop jump task.
Methods
A total of 68 females and 50 males were measured for AKL, GR, and GJL and were instrumented to obtain neuromuscular and biomechanical data on their dominant limb during the initial landing phase of a 45-cm drop jump. Multiple linear regressions determined the extent to which the three joint laxity variables combined to predict hip, knee, and ankle work absorption and stiffness. Associations between joint laxity and joint kinematics, joint kinetics, and muscle activation amplitudes were also investigated to further interpret significant relationships.
Results
Higher AKL and GJL and lower GR combined to predict greater knee work absorption (R2 = 0.210, P = 0.002) and stiffness (R2 = 0.127, P = 0.033) and lower ankle stiffness (R2 = 0.115, P = 0.048) in females. These associations were modulated through greater peak knee extensor moments and flexion angles, lower hamstring activation, and lower ankle extensor moments. In males, joint laxity had little impact on knee energetics, but a significant association was observed between greater GJL and decreased ankle stiffness (R2 = 0.209, P = 0.012), a product of both greater peak ankle flexion and decreased ankle extensor moment.
Conclusions
Females with greater AKL and GJL and lower GR demonstrated a landing strategy that increased work absorption and stiffness about the knee, whereas females with greater GR demonstrated a landing style that reduced knee work absorption and stiffness. The findings suggest that AKL, GR, and GJL may represent distinct risk factors and support the need to consider more comprehensive laxity profiles as they relate to knee joint function and anterior cruciate ligament injury risk.
doi:10.1249/MSS.0b013e3181bbeaa6
PMCID: PMC2936657  PMID: 19952845
JOINT WORK ABSORPTION; JOINT STIFFNESS; KNEE BIOMECHANICS; SEX DIFFERENCES; ACL INJURY RISK FACTORS
25.  Lower extremity joint kinetics and lumbar curvature during squat and stoop lifting 
Background
In this study, kinematics and kinetics of the lower extremity joint and the lumbar lordosis during two different symmetrical lifting techniques(squat and stoop) were examined using the three-dimensional motion analysis.
Methods
Twenty-six young male volunteers were selected for the subjects in this study. While they lifted boxes weighing 5, 10 and 15 kg by both squat and stoop lifting techniques, their motions were captured and analyzed using the 3D motion analysis system which was synchronized with two forceplates and the electromyographic system. Joint kinematics was determined by the forty-three reflective markers which were attached on the anatomical locations based on the VICON Plug-in-Gait marker placement protocol. Joint kinetics was analyzed by using the inverse dynamics. Paired t-test and Kruskal-Wallis test was used to compare the differences of variables between two techniques, and among three different weights. Correlation coefficient was calculated to explain the role of lower limb joint motion in relation to the lumbar lordosis.
Results
There were not significant differences in maximum lumbar joint moments between two techniques. The hip and ankle contributed the most part of the support moment during squat lifting, and the knee flexion moment played an important role in stoop lifting. The hip, ankle and lumbar joints generated power and only the knee joint absorbed power in the squat lifting. The knee and ankle joints absorbed power, the hip and lumbar joints generated power in the stoop lifting. The bi-articular antagonist muscles' co-contraction around the knee joint during the squat lifting and the eccentric co-contraction of the gastrocnemius and the biceps femoris were found important for maintaining the straight leg during the stoop lifting. At the time of lordotic curvature appearance in the squat lifting, there were significant correlations in all three lower extremity joint moments with the lumbar joint. Differently, only the hip moment had significant correlation with the lumbar joint in the stoop lifting.
Conclusion
In conclusion, the knee extension which is prominent kinematics during the squat lifting was produced by the contributions of the kinetic factors from the hip and ankle joints(extensor moment and power generation) and the lumbar extension which is prominent kinematics during the stoop lifting could be produced by the contributions of the knee joint kinetic factors(flexor moment, power absorption, bi-articular muscle function).
doi:10.1186/1471-2474-10-15
PMCID: PMC2651112  PMID: 19183507

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