Biomechanical analysis of the stance phase during barefoot and shod running

This study investigated spatio-temporal variables, ground reaction forces and sagittal and frontal plane kinematics during the stance phase of nine trained subjects running barefoot and shod at three different velocities (3.5, 4.5, 5.5 m s(-1)). Differences between conditions were detected with the general linear method (factorial model). Barefoot running is characterized by a significantly larger external loading rate than the shod condition. The flatter foot placement at touchdown is prepared in free flight, implying an actively induced adaptation strategy. In the barefoot condition, plantar pressure measurements reveal a flatter foot placement to correlate with lower peak heel pressures. Therefore, it is assumed that runners adopt this different touchdown geometry in barefoot running in an attempt to limit the local pressure underneath the heel. A significantly higher leg stiffness during the stance phase was found for the barefoot condition. The sagittal kinematic adaptations between conditions were found in the same way for all subjects and at the three running velocities. However, large individual variations were observed between the runners for the rearfoot kinematics.     

The effect of stride length on the dynamics of barefoot and shod running

A number of interventions and technique changes have been proposed to attempt to improve performance and reduce the number of running related injuries. Running shoes, barefoot running and alterations in spatio-temporal parameters (stride frequency and stride length) have been associated with significant kinematic and kinetic changes, which may have implications for performance and injury prevention. However, because footwear interventions have been shown to also affect spatio-temporal parameters, there is uncertainty regarding the origin of the kinematic and kinetic alterations. Therefore, the purpose of this study was to independently evaluate the effects of shoes and changes in stride length on lower extremity kinetics. Eleven individuals ran over-ground at stride lengths ±5 and 10% of their preferred stride length, in both the barefoot and shod condition. Three-dimensional motion capture and force plate data were captured synchronously and used to compute lower extremity joint moments. We found a significant main effect of stride length on anterior–posterior and vertical GRFs, and sagittal plane knee and ankle moments in both barefoot and shod running. When subjects ran at identical stride lengths in the barefoot and shod conditions we did not observe differences for any of the kinetic variables that were measured. These findings suggest that barefoot running triggers a decrease in stride length, which could lead to a decrease in GRFs and sagittal plane joint moments. When evaluating barefoot running as a potential option to reduce injury, it is important to consider the associated change in stride length.     

Comparison of lower limb kinetics,kinematics and muscle activation during drop jumping under shod and barefoot conditions

This study was to investigate the acute effects of wearing shoes on lower limb kinetics, kinematics and muscle activation during a drop jump. Eighteen healthy men performed a drop jump under barefoot and shod conditions. Vertical ground reaction force (GRF) was measured on a force plate during the contact phase of a drop jump, and GRF valuables were calculated for each condition. The angles of the knee and ankle joints, and the foot strike angle (the angle between the plantar surface of the foot and the ground during ground contact) as well as the electromyography of 7 muscles were measured. The shod condition showed a significant larger first peak GRF, longer time to first peak GRF from the initial ground contact and lower initial loading rate than the barefoot condition. The shod condition showed a significant larger ankle joint angle at initial ground contact, smaller knee joint angle between the second peak GRF and take-off as well as smaller foot strike angle at both initial ground contact and take-off than the barefoot condition. There were significant correlations between relative differences in ankle joint at the initial ground contact and relative differences in the initial loading rate. The muscle activity of all muscles during foot ground contact did not differ between two conditions; however, in the shod condition, muscle activation of 150 ms before foot ground contact was significantly higher in the rectus femoris, whereas it was lower in the biceps femoris and tibialis anterior muscles than the barefoot condition. These results indicate that wearing shoes alternates the GRF variables at initial ground contact, joint kinematics at the ground contact and muscle activation before foot ground contact during a drop jump, suggesting that the effects of wearing shoes on drop jump training differ from being barefoot.     

Stiffness adaptations in shod running

When mechanical parameters of running are measured, runners have to be accustomed to testing conditions. Nevertheless, habituated runners could still show slight evolutions of their patterns at the beginning of each new running bout. This study investigated runners' stiffness adjustments during shoe and barefoot running and stiffness evolutions of shoes. Twenty-two runners performed two 4-minute bouts at 3.61 m.s-1 shod and barefoot after a 4-min warm-up period. Vertical and leg stiffness decreased during the shoe condition but remained stable in the barefoot condition, p < 0.001. Moreover, an impactor test showed that shoe stiffness increased significantly during the first 4 minutes, p < 0.001. Beyond the 4th minute, shoe properties remained stable. Even if runners were accustomed to the testing condition, as running pattern remained stable during barefoot running, they adjusted their leg and vertical stiffness during shoe running. Moreover, as measurements were taken after a 4-min warm-up period, it could be assumed that shoe properties were stable. Then the stiffness adjustment observed during shoe running might be due to further habituations of the runners to the shod condition. To conclude, it makes sense to run at least 4 minutes before taking measurements in order to avoid runners' stiffness alteration due to shoe property modifications. However, runners could still adapt to the shoe.     

A comparison of the physiological exercise intensity differences between shod and barefoot submaximal deep-water running at the same cadence

The purpose of this investigation was to identify whether physiological exercise intensity differed with the use of aquatic training shoes (ATS) during deep-water running (DWR) compared to using a barefoot condition. Eight male intercollegiate (National Collegiate Athletic Association Division III [NCAA III]) varsity distance runners were videotaped from the right sagittal view while running on a treadmill (TR) and while barefoot in deep water at 60-70% of their TR VO2max for 30 minutes. Based on the stride rate of the barefoot DWR trial, a subsequent 30-minute session was completed while wearing ATS. Variables of interest were energy expenditure, oxygen consumption (VO2), heart rate, respiratory exchange ratio (RER), and rating of perceived exertion (RPE). Multivariate omnibus tests revealed statistically significant differences for energy expenditure (p < 0.011), VO2 (p < 0.001), RPE (p < 0.001), and RER (p < 0.002). The post hoc pairwise comparisons revealed significant differences between barefoot and shod DWR conditions for energy expenditure (p < 0.005) and VO2 (p < 0.002), representing a 9 and 7.6% increase in exercise intensity demand while running shod vs. barefoot. These comparisons also revealed significantly higher RPE and RER values while DWR than those found in TR. Wearing the ATS may be recommended as a method of statistically significantly increasing the exercise intensity while running in deep water as compared to not wearing a shoe. Shod compared to TR yields very small differences, which indicates that the shoes may help better match land-based running exercise intensities.     

Pattern classification of kinematic and kinetic running data to distinguish gender,shod/barefoot and injury groups with feature ranking

The identification of differences between groups is often important in biomechanics. This paper presents group classification tasks using kinetic and kinematic data from a prospective running injury study. Groups composed of gender, of shod/barefoot running and of runners who developed patellofemoral pain syndrome (PFPS) during the study, and asymptotic runners were classified.

The features computed from the biomechanical data were deliberately chosen to be generic. Therefore, they were suited for different biomechanical measurements and classification tasks without adaptation to the input signals. Feature ranking was applied to reveal the relevance of each feature to the classification task.

Data from 80 runners were analysed for gender and shod/barefoot classification, while 12 runners were investigated in the injury classification task. Gender groups could be differentiated with 84.7%, shod/barefoot running with 98.3%, and PFPS with 100% classification rate. For the latter group, one single variable could be identified that alone allowed discrimination.     

Pattern classification of kinematic and kinetic running data to distinguish gender, shod/barefoot and injury groups with feature ranking

The identification of differences between groups is often important in biomechanics. This paper presents group classification tasks using kinetic and kinematic data from a prospective running injury study. Groups composed of gender, of shod/barefoot running and of runners who developed patellofemoral pain syndrome (PFPS) during the study, and asymptotic runners were classified. The features computed from the biomechanical data were deliberately chosen to be generic. Therefore, they were suited for different biomechanical measurements and classification tasks without adaptation to the input signals. Feature ranking was applied to reveal the relevance of each feature to the classification task. Data from 80 runners were analysed for gender and shod/barefoot classification, while 12 runners were investigated in the injury classification task. Gender groups could be differentiated with 84.7%, shod/barefoot running with 98.3%, and PFPS with 100% classification rate. For the latter group, one single variable could be identified that alone allowed discrimination.     

Reproducibility of plantar pressure distribution data in barefoot running

The aim of this study was to provide detailed information on rationales, calculations, and results of common methods used to quantify reproducibility in plantar pressure variables. Recreational runners (N=95) performed multiple barefoot running trials in a laboratory setup, and pressure variables were analyzed in nine distinct subareas of the foot. Reproducibility was assessed by calculating intraclass correlation coefficients (ICC) and the root mean square error (RMSE). Intraclass correlation coefficients ranged from 0.58 to 0.99, depending on the respective variable and type of ICC. Root mean square errors ranged between 2.3 and 3.1% for relative force-time integrals, between 0.07 and 0.23 for maximum force (Fmax), and between 107 and 278 kPa for maximum pressure (Pmax), depending on the subarea of the foot. Force-time integral variables demonstrated the best within-subject reproducibility. Rear-foot data suffered from slightly increased measurement error and reduced reproducibility compared with the forefoot.     

Foot internal stress distribution during impact in barefoot running as function of the strike pattern

The aim of the present study is to examine the impact absorption mechanism of the foot for different strike patterns (rearfoot, midfoot and forefoot) using a continuum mechanics approach. A three-dimensional finite element model of the foot was employed to estimate the stress distribution in the foot at the moment of impact during barefoot running. The effects of stress attenuating factors such as the landing angle and the surface stiffness were also analyzed. We characterized rear and forefoot plantar sole behavior in an experimental test, which allowed for refined modeling of plantar pressures for the different strike patterns. Modeling results on the internal stress distributions allow predictions of the susceptibility to injury for particular anatomical structures in the foot.     

Support vector machines for detecting age-related changes in running kinematics

Age-related changes in running kinematics have been reported in the literature using classical inferential statistics. However, this approach has been hampered by the increased number of biomechanical gait variables reported and subsequently the lack of differences presented in these studies. Data mining techniques have been applied in recent biomedical studies to solve this problem using a more general approach. In the present work, we re-analyzed lower extremity running kinematic data of 17 young and 17 elderly male runners using the Support Vector Machine (SVM) classification approach. In total, 31 kinematic variables were extracted to train the classification algorithm and test the generalized performance. The results revealed different accuracy rates across three different kernel methods adopted in the classifier, with the linear kernel performing the best. A subsequent forward feature selection algorithm demonstrated that with only six features, the linear kernel SVM achieved 100% classification performance rate, showing that these features provided powerful combined information to distinguish age groups. The results of the present work demonstrate potential in applying this approach to improve knowledge about the age-related differences in running gait biomechanics and encourages the use of the SVM in other clinical contexts.     

T2 relaxation time measurements in tibiotalar cartilage after barefoot running and its relationship to ankle biomechanics

The influence of ankle kinematics and plantar pressure from mid-range barefoot running on T2 relaxation times of tibiotalar cartilage is unknown. This study aimed to quantitatively evaluate the T2 relaxation time of tibiotalar cartilage and ankle biomechanics following 5 km barefoot running. Twenty healthy runners (who had no 5 km barefoot running experience) underwent 3.0-Tesla magnetic resonance (MR) scans and assessment of running gait before and after 5 km barefoot running. Participants were divided into two groups consisting of marathon-experienced (n = 10) and novice (n = 10) with equal number of males and females in each group. Three musculoskeletal radiologists measured T2 relaxation times in 18 regions of the ankle cartilage: anterior zone, central zone, and posterior zone, or lateral, middle, and medial sections in the sagittal plane. Three-dimensional ankle kinetics, kinematics, and plantar pressure were all also assessed during barefoot running. In the novice group, the T2 relaxation time in the posterior zone of tibial cartilage (p = 0.001) and lateral section in both tibial (p = 0.02) and talar (p = 0.02) cartilage were significantly increased after barefoot running. Ankle kinematics exhibited significant changes in females. Plantar loading was shifted from the medial to lateral aspect after running. This included a significant reduction in the loading under the toes and the 1st, 2nd and 3rd metatarsals, with a significant increase under the 4th and 5th metatarsals and lateral midfoot. The results suggest that plantar pressure may directly lead to local increases in cartilage T2 signal, which was not associated with changes in ankle kinematics.     

The integration of lateral gastrocnemius muscle function and kinematics in running turkeys

Animals commonly move over a range of speeds, and encounter considerable variation in habitat structure, such as inclines. Hindlimb kinematics and muscle function in diverse groups of vertebrates are affected by these changes in behavior and habitat structure, providing a fruitful source of variation for studying the integration of kinematics and muscle function. While it has been observed in a variety of vertebrates that muscle length change can be minimal during locomotion, it is unclear how, and to what degree, in vivo muscle length change patterns are integrated with kinematics. We tested the hypothesis that the length of the turkey lateral gastrocnemius (LG), a biarticular muscle that has moments at the ankle and knee, is not solely affected by changes in joint kinematics. We recorded in vivo muscle length changes (using sonomicrometry) and hindlimb movements (using high-speed video) of wild turkeys running on various inclines, and at different speeds. We quantified the relationship between joint angle (knee and ankle separately) and muscle length in freshly euthanized specimens, and then applied an empirically derived correction for changes in pennation angle and tendon strain during locomotion to improve the accuracy of our predicted lengths. We estimated muscle length at four points during each stride and then compared these values with those measured directly. Other than during swing, the predicted changes in muscle length calculated from the changes in joint kinematics did not correspond with our measured values of LG length. Therefore, the lengths at which the LG operates in turkeys are not determined entirely by kinematics. In addition to strain in series elastic components, we hypothesize that heterogeneous strain within muscles, interactions between muscles and muscle pennation angle all contribute to the nonlinear relationship between muscle length changes and kinematics.     

Tibiotalar cartilage stress corresponds to T2 mapping: application to barefoot running in novice and marathon-experienced runners

Abstract

A 3D anatomically-based finite-element foot model was adopted for predicting von Mises stresses within tibiotalar cartilage following 5?km barefoot running. To compare this predicted stress with T2 maps, magnetic resonance scans of the right ankle and plantar pressure were obtained from ten novices and ten marathon-experienced runners before and after running. Following running, tibiotalar cartilage stress was decreased in experienced runners. This corresponded with T2 values that did not change between pre- and post-running suggesting no increase in cartilage fluid levels. In contrast, novices maintained the same level of von Mises stress and this corresponded with a significant T2 increase in tibiotalar cartilage.     

Running kinematics and shock absorption do not change after brief exhaustive running

Because of the nature of running, the forces encountered require a proper coordination of joint action of the lower extremity to dissipate the ground reaction forces and accelerations through the kinetic chain. Running-related muscle fatigue may reduce the shock absorbing capacity of the lower extremity and alter running kinematics. The purpose of this study was to determine if a bout of exhaustive running at a physiologically determined high intensity, changes running kinematics, impact accelerations, and alters shock attenuating capabilities. It was hypothesized that as a result of fatigue induced by an exhaustive run, running kinematics, impact accelerations at the head and shank, acceleration reduction, and shock attenuation would change. A within-subject, repeated-measures design was used for this study. Twelve healthy, competitive male and female distance runners participated. Subjects performed 2 testing sessions consisting of a VO2max treadmill protocol to determine the heart rate at ventilatory threshold and a fatigue-inducing running bout at the identified ventilatory threshold heart rate. Kinematic data included knee flexion, pronation, time to maximum knee flexion, and time to maximum pronation. Acceleration data included shank acceleration, head acceleration, and shock attenuation. No significant differences resulted for the kinematic or acceleration variables. Although the results of this study do not support the original hypotheses, the influence of running fatigue on kinematics and accelerations remains inconclusive. Future research is necessary to examine fatigue-induced changes in running kinematics and accelerations and to determine the threshold at which point the changes may occur.     

Leg kinematics and muscle activity during treadmill running in the cockroach, Blaberus discoidalis: II. Fast running

We have combined kinematic and electromyogram (EMG) analysis of running Blaberus discoidalis to examine how middle and hind leg kinematics vary with running speed and how the fast depressor coxa (Df) and fast extensor tibia (FETi) motor neurons affect kinematic parameters. In the range 2.5–10 Hz, B. discoidalis increases step frequency by altering the joint velocity and by reducing the time required for the transition from flexion to extension. For both Df and FETi the timing of recruitment coincides with the maximal frequency seen for the respective slow motor neurons. Df is first recruited at the beginning of coxa-femur (CF) extension. FETi is recruited in the latter half of femur-tibia (FT) extension during stance. Single muscle potentials produced by these fast motor neurons do not have pronounced effects on joint angular velocity during running. The transition from CF flexion to extension was abbreviated in those cycles with a Df potential occurring during the transition. One effect of Df activity during running may be to phase shift the beginning of joint extension so that the transition is sharpened. FETi is associated with greater FT extension at higher running speeds and may be necessary to overcome high joint torques at extended FT joint angles. Accepted: 24 May 1997     

Effects of specific versus cross-training on running performance

The cross-training (XT) hypothesis suggests that despite the principle of specificity of training, athletes may improve performance in one mode of exercise by training using another mode. To test this hypothesis we studied 30 well-trained individuals (10 men, 20 women) in a randomized longitudinal trail. Subjects were evaluated before and after 8 weeks of enhanced training (+10%/week), accomplished by adding either running (R) or swimming (XT) to baseline running, versus continued baseline running (C). Both R ( – 26.4s) and XT (– 13.2s) improved time trial (3.2 km) performance, whereas C did not (– 5.4s). There were no significant changes during treadmill running in maximum oxygen uptake (O_2peak; – 0.2, – 6.0, and + 2.7%), steady state submaximal O₂ at 2.68 m · s^–1 ( – 1.2, – 3.3 and + 0.2 ml · kg^–1 · min^–1), velocity at O_2peak (+0.05, +0.25 and +0.09 m · s^–1) or accumulated O₂ deficit (+ 11.2, – 6.1 and + 9.4%) in the R, XT or C groups, respectively. There was a significant increase in velocity associated with a blood lactate concentration of 4 mmol · l^–1 in R but not in XT or C ( + 0.32, + 0.07 and + 0.08 m · s^–1). There were significant changes in arm crank O_2peak ( + 5%) and arm crank O₂ at 4 mmol · l^–1 ( + 6.4%) in XT. There was no significant changes in arm crank O_2peak ( + 1.3 and – 7.7%) or arm crank O₂ at 4 mmol · l^–1 ( + 0.8 and + 0.4%) in R or C, respectively. The data suggest that muscularly non-similar XT may contribute to improved running performance but not to the same degree as increased specific tranining.