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1.  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
2.  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
3.  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
4.  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
5.  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
6.  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
7.  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
8.  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
9.  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
10.  Effect of Orthotics and Footwear on Static Rearfoot Kinematics 
This study examined the effect of foot orthotics and footwear on static rearfoot kinematics. Thirty-four subjects (5 males, 29 females) from physical therapy clinics and the college community gave informed consent to participate. Subject age was 42 (18) years; subject height was 1.7 (0.1) meters; subject body mass was 72.6 (12.1) kg. Markers were placed on specific sites of the lower leg and calcaneus to determine the rearfoot angle. Rearfoot angle was measured with a goniometer and digitized with video-based software (Ariel Performance Analysis System). A calcaneal mold was utilized to determine the position of the calcaneus in the shod conditions. Static rearfoot angles were measured in the following conditions: barefoot (B), barefoot with the calcaneal mold (BM), barefoot with the calcaneal mold plus the orthotic (BMO), shod with the calcaneal mold (SM), and shod with the calcaneal mold plus the orthotic (SMO). An independent t-test analyzed differences between each condition as measured with the APAS and goniometer. A one-way analysis of variance (ANOVA) was utilized to determine statistically significant differences among the 5 foot conditions (p ≤ 0.05). Independent t-tests revealed no significant differences (p > 0.05) between the APAS and goniometer measurements within each condition. One-way ANOVA showed a significant difference (p ≤ 0.01) among the five conditions as measured by APAS. Post-hoc analysis determined that the difference between BM and SM; and the BM and SMO conditions were significantly different (p ≤ 0.01). It was observed that the orthotic slightly decreased the amount of calcaneal eversion in the standing position. The shoes worn in the study, though neutral in construction, did significantly alter rearfoot kinematics in comparison to BM.
Key PointsPrevious literature concerning the effect of orthotics on lower extremity alignment is inconclusive.This study concurs with the work of others as to the effectiveness of orthotics on the reduction of calcaneal eversion.Even though the kinematic differences were small, subjects still reported a positive effect on their level of comfort with the orthotics as compared to not wearing the orthotic.
PMCID: PMC3842148  PMID: 24353465
Foot orthoses; calcaneal eversion; rearfoot motion; shoe construction
11.  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
12.  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
13.  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
14.  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
15.  Kinematic Changes During a Marathon for Fast and Slow Runners 
The purpose of this study was to describe kinematic changes that occur during an actual marathon. We hypothesized that (1) certain running kinematic measures would change between kilometres 8 and 40 (miles 5 and 25) of a marathon and (2) fast runners would demonstrate smaller changes than slow runners. Subjects (n = 179) were selected according to finish time (Range = 2:20:47 to 5:30:10). Two high-speed cameras were used to measure sagittal-plane kinematics at kilometres 8 and 40 of the marathon. The dependent variables were stride length, contact time, peak knee flexion during support and swing, and peak hip flexion and extension during swing. Two-tailed paired t-tests were used to compare dependent variables between kilometres 8 and 40 for all subjects, and regression analyses were used to determine whether faster runners exhibited smaller changes (between miles 5 and 25) than slower runners. For all runners, every dependent variable changed significantly between kilometres 8 and 40 (p < 0.001). Stride length increased 1.3%, contact time increased 13.1%, peak knee flexion during support decreased 3.2%, and peak hip extension, knee flexion, and hip flexion during swing decreased 27.9%, increased 4.3%, and increased 7.4%, respectively (p < 0.001). Among these significant changes, all runners generally changed the same from kilometres 8 and 40 except that fast runners decreased peak knee flexion during support less than the slow runners (p < 0.002). We believe that these changes, for all runners (fast and slow), were due to fatigue. The fact that fast runners maintained knee flexion during support more consistently might be due to their condition on the race day. Strengthening of knee extensor muscles may facilitate increased knee flexion during support throughout a marathon.
Key points
Runners changed kinematics significantly from kilometres 8 to 40 (increased stride length, contact time, peak hip flexion during swing, and peak knee flexion during swing, and decreased running speed, stride frequency, peak knee flexion during support and peak hip extension during swing).
Fast runners demonstrated more peak knee flexion during support throughout a marathon.
Runners generally changed kinematics similarly (between kilometres 8 and 40) except that fast runners exhibited a more consistent peak knee flexion during support than slow runners.
Resistance training that would increase both muscular strength and endurance of knee extensors may increase peak knee flexion during support and help maintain it similar to the fast runners throughout a marathon.
PMCID: PMC3737836  PMID: 24137065
Fatigue; endurance; run; biomechanics; race
16.  Comparison of Lower Extremity Kinematic Curves During Overground and Treadmill Running 
Journal of Applied Biomechanics  2010;26(4):407-414.
Researchers conduct gait analyses utilizing both overground and treadmill modes of running. Previous studies comparing these modes analyzed discrete variables. Recently, techniques involving quantitative pattern analysis have assessed kinematic curve similarity in gait. Therefore, the purpose of this study was to compare hip, knee and rearfoot 3-D kinematics between overground and treadmill running using quantitative kinematic curve analysis. Twenty runners ran at 3.35 m/s ± 5% during treadmill and overground conditions while right lower extremity kinematics were recorded. Kinematics of the hip, knee and rearfoot at footstrike and peak were compared using intraclass correlation coefficients. Kinematic curves during stance phase were compared using the trend symmetry method within each subject. The overall average trend symmetry was high, 0.94 (1.0 is perfect symmetry) between running modes. The transverse plane and knee frontal plane exhibited lower similarity (0.86–0.90). Other than a 4.5 degree reduction in rearfoot dorsiflexion at footstrike during treadmill running, all differences were ≤1.5 degrees. 17/18 discrete variables exhibited modest correlations (>0.6) and 8/18 exhibited strong correlations (>0.8). In conclusion, overground and treadmill running kinematic curves were generally similar when averaged across subjects. Although some subjects exhibited differences in transverse plane curves, overall, treadmill running was representative of overground running for most subjects.
PMCID: PMC3266869  PMID: 21245500
biomechanics; gait; waveform comparison
17.  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
18.  Biomechanical analysis of rollator walking 
Background
The rollator is a very popular walking aid. However, knowledge about how a rollator affects the walking patterns is limited. Thus, the purpose of the study was to investigate the biomechanical effects of walking with and without a rollator on the walking pattern in healthy subjects.
Methods
The walking pattern during walking with and without rollator was analyzed using a three-dimensional inverse dynamics method. Sagittal joint dynamics and kinematics of the ankle, knee and hip were calculated. In addition, hip joint dynamics and kinematics in the frontal plane were calculated. Seven healthy women participated in the study.
Results
The hip was more flexed while the knee and ankle joints were less flexed/dorsiflexed during rollator walking. The ROM of the ankle and knee joints was reduced during rollator-walking. Rollator-walking caused a reduction in the knee extensor moment by 50% when compared to normal walking. The ankle plantarflexor and hip abductor moments were smaller when walking with a rollator. In contrast, the angular impulse of the hip extensors was significantly increased during rollator-walking.
Conclusion
Walking with a rollator unloaded the ankle and especially the knee extensors, increased the hip flexion and thus the contribution of hip extensors to produce movement. Thus, rollator walking did not result in an overall unloading of the muscles and joints of the lower extremities. However, the long-term effect of rollator walking is unknown and further investigation in this field is needed.
doi:10.1186/1475-925X-5-2
PMCID: PMC1334195  PMID: 16398933
19.  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
20.  The Relation Between Mild Leg-Length Inequality and Able-Bodied Gait Asymmetry 
The causes of able-bodied gait asymmetries are unclear. Mild (< 3 cm) leg-length inequality (LLI) may be one cause of these asymmetries; however, this idea has not been thoroughly investigated. The purpose of this study was to investigate the nature of the relationship between LLI and able-bodied gait asymmetries. We hypothesized that subjects (n = 26) with relatively large LLI, quantified radiographically, would display less symmetrical gait than subjects with relatively small LLI. Gait asymmetries for joint kinematics and joint kinetics were determined using standard gait analysis procedures. Symmetry coefficients were used to quantify bilateral gait symmetry for sagittal-plane hip, knee, and ankle joint angles, moments, and powers. A Pearson product-moment correlation coefficient (r) was used to evaluate the relationship between LLI and the aforementioned symmetry coefficients. Also, these symmetry coefficients were compared between subjects with relatively small LLI (LLI < 1 cm; n = 19) and relatively large LLI (LLI ≥ 1 cm; n = 7). Statistically significant relationships were observed between LLI and the symmetry coefficient for knee joint moment (r = -0.48) and power (r = -0.51), and ankle joint moment (r = -0.41) and power (r = -0.42). Similarly, subjects with relatively large LLI exhibited significantly lower symmetry coefficients for knee joint moment (p = 0.40) and power (p = 0.35), and ankle joint moment (p = 0.40) and power (p = 0.22) than subjects with relatively small LLI. Degree of bilateral symmetry for knee and ankle joint kinetics appears to be related to LLI in able- bodied gait. This finding supports the idea that LLI is one cause of able-bodied gait asymmetries. Other factors, however, are also likely to contribute to these gait asymmetries; these may include other morphological asymmetries as well as asymmetrical neuromuscular input to the lower limb muscles.
Key pointsModerate negative relationships were observed between mild limb-length inequality and gait symmetry for knee and ankle moment and power.Subjects with relatively large mild limb-length inequality (between 1.0 and 2.3 cm) exhibited significantly less symmetrical gait for knee and ankle joint moment and power than subjects with relatively small mild limb-length inequality (< 1 cm).These results indicate that the degree of symmetry for knee and ankle joint kinetics appears to be related to mild limb-length inequality in able-bodied gait.These results further our understanding of normal human walking and provide important background information for future studies on gait pathology associated with mild limb-length inequality.
PMCID: PMC3761822  PMID: 24149783
Leg length; gait; asymmetry; kinematics; kinetics
21.  Contribution of Knee Flexor and Extensor Strength on Sex-Specific Energy Absorption and Torsional Joint Stiffness During Drop Jumping 
Journal of Athletic Training  2010;45(5):445-452.
Abstract
Context:
Lower extremity injury often occurs during abrupt deceleration when attempting to change the body's direction. Although sex-specific biomechanics have been implicated in the greater risk of acute knee injury in women than in men, it is unknown if sex differences in thigh strength affect sex-specific energy absorption and torsional joint stiffness patterns.
Objective:
To determine sex differences in energy absorption patterns and joint stiffnesses of the lower extremity during a drop jump and to determine if these sex differences were predicted by knee extensor and flexor strength.
Design:
Cross-sectional study.
Setting:
Laboratory environment.
Patients or Other Participants:
Recreationally active, college-aged students (41 women: age  =  22.1 ± 2.9 years, height  =  1.63 ± 0.07 m, mass  =  59.3 ± 8.0 kg; 40 men: age  =  22.4 ± 2.8 years, height  =  1.77 ± 0.1 m, mass  =  80.9 ± 14.1 kg).
Intervention(s):
Participants performed knee flexor and extensor maximal voluntary isometric contractions followed by double-leg drop-jump landings.
Main Outcome Measure(s):
Lower extremity joint energetics (J × N−1 × m−1) and torsional joint stiffnesses (Nm × N−1 × m−1 × degrees−1) were calculated for the hip, knee, and ankle during the initial landing phase. Body weight was measured in newtons and height was measured in meters. Sex comparisons were made and sex-specific regressions determined if thigh muscle strength (Nm/kg) predicted sagittal-plane landing energetics and stiffnesses.
Results:
Women absorbed 69% more knee energy and had 36% less hip torsional stiffness than men. In women, greater knee extensor strength predicted greater knee energy absorption (R2  =  0.11, P  =  .04), and greater knee flexor strength predicted greater hip torsional stiffness (R2  =  0.12, P  =  .03).
Conclusions:
Sex-specific biomechanics during the deceleration phase of a drop jump revealed that women used a strategy to attempt to decrease system stiffness. Additionally, only female strength values were predictive of landing energetics and stiffnesses. These findings collectively demonstrated that the task may have been more difficult for women, resulting in a different movement strategy among those with different levels of thigh strength to safely complete the task. Future researchers should look at other predictive factors of observed sex differences.
doi:10.4085/1062-6050-45.5.445
PMCID: PMC2938314  PMID: 20831388
work; energetics; lower extremity biomechanics
22.  KNEE INSTABILITY AFTER ACUTE ACL RUPTURE AFFECTS MOVEMENT PATTERNS DURING THE MID-STANCE PHASE OF GAIT 
SUMMARY
Purpose
The purpose of this study was to identify gait asymmetries during the mid-stance phase of gait among subjects with knee instability (non-copers) after acute anterior cruciate ligament (ACL) rupture.
Methods
Twenty-one non-copers with acute, isolated, unilateral ACL injury ambulated at their intentional walking speed as kinetic, kinematic, and EMG data were collected bilaterally. Lower extremity movement patterns and muscle activity were analyzed during the mid-stance and weight acceptance phases of stance.
Results
During mid-stance subjects exhibited lower sagittal plane knee excursions and peak knee extension angles, and higher muscle co-contraction on the injured limb compared to the uninjured limb. There was also a lower knee flexion moment at peak knee extension, a trend for the knee contribution to the total support moment to be lower, and a higher ankle contribution to the total support moment on the injured limb in comparison to the uninjured limb. Differences in the magnitude of muscle activity included higher hamstring activity and lower soleus activity on the injured limb compared to the uninjured limb. Changes in quadriceps, soleus, and hamstring muscle activity on the injured limb were identified during weight acceptance that had not previously been reported.
Conclusions
Subjects with knee stability after ACL rupture consistently stabilize their knee with a stiffening strategy involving less knee motion and higher muscle contraction. The variable combination of muscle adaptations that produce joint stiffness, and the ability of both the ankle and hip to compensation for lower knee control, indicate the non-coper neuromuscular system may be more malleable than previously believed.
doi:10.1002/jor.20440
PMCID: PMC2859715  PMID: 17557321
Gait; Knee; ACL; Neuromuscular
23.  Gait kinematic analysis in patients with a mild form of central cord syndrome 
Background
Central cord syndrome (CCS) is considered the most common incomplete spinal cord injury (SCI). Independent ambulation was achieved in 87-97% in young patients with CCS but no gait analysis studies have been reported before in such pathology. The aim of this study was to analyze the gait characteristics of subjects with CCS and to compare the findings with a healthy age, sex and anthropomorphically matched control group (CG), walking both at a self-selected speed and at the same speed.
Methods
Twelve CCS patients and a CG of twenty subjects were analyzed. Kinematic data were obtained using a three-dimensional motion analysis system with two scanner units. The CG were asked to walk at two different speeds, at a self-selected speed and at a slower one, similar to the mean gait speed previously registered in the CCS patient group. Temporal, spatial variables and kinematic variables (maximum and minimum lower limb joint angles throughout the gait cycle in each plane, along with the gait cycle instants of occurrence and the joint range of motion - ROM) were compared between the two groups walking at similar speeds.
Results
The kinematic parameters were compared when both groups walked at a similar speed, given that there was a significant difference in the self-selected speeds (p < 0.05). Hip abduction and knee flexion at initial contact, as well as minimal knee flexion at stance, were larger in the CCS group (p < 0.05). However, the range of knee and ankle motion in the sagittal plane was greater in the CG group (p < 0.05). The maximal ankle plantar-flexion values in stance phase and at toe off were larger in the CG (p < 0.05).
Conclusions
The gait pattern of CCS patients showed a decrease of knee and ankle sagittal ROM during level walking and an increase in hip abduction to increase base of support. The findings of this study help to improve the understanding how CCS affects gait changes in the lower limbs.
doi:10.1186/1743-0003-8-7
PMCID: PMC3040131  PMID: 21288347
24.  Crossover Cutting During Hamstring Fatigue Produces Transverse Plane Knee Control Deficits 
Journal of Athletic Training  1999;34(2):137-143.
Objective:
To assess the effects of eccentric work-induced hamstring fatigue on sagittal and transverse plane (axial) knee and ankle biodynamics and kinetics during a running crossover cut directional change (functional pivot shift).
Design and Setting:
A pretest-posttest, single-group intervention experimental design was employed. All data were collected in a biodynamics laboratory.
Subjects:
Twenty healthy athletic females were trained for 3 weeks in crossover cutting before testing.
Measurements:
Data were sampled during 3 unfatigued and 3 fatigued (20% eccentric isokinetic knee-flexor torque reduction) crossover cut trials. Three-dimensional kinematic and ground reaction-force data were sampled at 200 Hz and 1000 Hz, respectively, and joint moment estimates were calculated. Data were standardized to initial force-plate heelstrike for comparisons of mean differences between conditions using paired t tests with Bonferroni adjustments. Pearson product-moment correlations compared kinematic and eccentric hamstring-torque relationships.
Results:
During internal rotation phase 1, between heelstrike and impact absorption, mean internal rotation velocity increased by 21.2°/s ± 114°/s. During internal rotation phase II, mean peak transverse plane knee rotation during propulsion decreased by 3.1° ± 9°. During internal rotation phase II, mean peak ankle plantar flexor moment onsets occurred 12.7 ± 53 milliseconds earlier, and this activation demonstrated a moderately positive relationship with the onset of mean peak knee internal rotation during propulsion and a weak negative relationship with mean peak hamstring torque/lean body weight.
Conclusions:
The increased knee internal rotation velocity during phase I indicates transverse plane dynamic knee-control deficits during hamstring fatigue. Earlier peak ankle plantar-flexor moments and decreased internal rotation during phase II in the presence of hamstring fatigue may represent compensatory attempts at dynamic knee stabilization from the posterior lower leg musculature during the pivot shift portion of the crossover cut. The weak relationship between decreased hamstring torque/lean body weight and delayed knee internal rotation during propulsion further supports greater dependence on ankle plantar flexors for dynamic knee stabilization compensation
Images
PMCID: PMC1322902  PMID: 16558556
biomechanics; injury mechanisms; functional movement assessment
25.  EFFECTS OF A MOVEMENT TRAINING PROGRAM ON HIP AND KNEE JOINT FRONTAL PLANE RUNNING MECHANICS 
Background/Purpose:
Frontal plane running mechanics may contribute to the etiology or exacerbation of common running related injuries. Hip strengthening alone may not change frontal plane hip and knee joint running mechanics. The purpose of the current study was to evaluate whether a training program including visual, verbal, and tactile feedback affects hip and knee joint frontal plane running mechanics among females with evidence of altered weight bearing kinematics.
Methods:
The knee frontal plane projection angle of 69 apparently healthy females was determined during a single leg squat. The twenty females from this larger sample who exhibited the most acute frontal plane projection angle (medial knee position) during this activity were chosen to participate in this study (age = 20 ± 1.6 years, height = 167.9 ± 6.0 cm, mass = 63.2 ± 8.3 kg, Tegner Activity Rating mode = 7.0). Participants engaged in a 4‐week movement training program using guided practice during weight bearing exercises with visual, verbal, and tactile feedback regarding lower extremity alignment. Paired t‐tests were used to compare frontal plane knee and hip joint angles and moments before and after the training program.
Results:
After training, internal hip and knee abduction moments during running decreased by 23% (P=0.007) and 29% (P=0.033) respectively. Knee adduction and abduction excursion decreased by 2.1° (P = 0.050) and 2.7° (P=0.008) respectively, suggesting that less frontal plane movement of the knee occurred during running after training. Peak knee abduction angle decreased 1.8° after training (P=0.051) although this was not statistically significant. Contralateral peak pelvic drop, pelvic drop excursion, peak hip adduction angle, hip adduction excursion, and peak knee adduction angle were unchanged following training.
Conclusions:
A four week movement training program may reduce frontal plane hip and knee joint mechanics thought to contribute to the etiology and exacerbation of some running related injuries.
Level of Evidence:
Level 4
PMCID: PMC3537459  PMID: 23316427
female; kinematics; kinetics; neuromuscular training; rehabilitation

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