Why forefoot striking in minimal shoes might positively change the course of running injuries

Acute effects of negative heel shoes on perceived pain and knee biomechanical characteristics of runners with patellofemoral pain

BACKGROUND

To determine the effects of negative heel shoes on perceived pain and knee biomechanical characteristics of runners with patellofemoral pain (PFP) during running.

METHODS

Sixteen runners with PFP ran in negative (-11 mm drops) and positive (5 mm drops) heel shoes while visual analog scale (VAS) scores, retroreflective markers, and ground reaction force were acquired by applying a 10-cm VAS, infrared motion capture system, and a three-dimensional force plate. Knee moment, patellofemoral joint stress (PFJS), and other biomechanical parameters during the stance phase were calculated based on inverse dynamics and a biomechanical model of the patellofemoral joint.

RESULTS

The foot inclination angle, peak PFJS during the stance phase, patellofemoral joint reaction force, knee extension moment, and quadriceps force at the time of peak PFJS of runners with PFP in negative heel shoes were lower than that in positive heel shoes, no significant difference was found in VAS scores, knee flexion angle, patellofemoral contact area, and quadriceps moment arm at the time of peak PFJS.

CONCLUSIONS

Compared to positive heel shoes, running in negative heel shoes decreases peak PFJS in runners with PFP, which may decrease patellofemoral joint loading, thus reducing the possibility of further development of PFP.

TRAIL REGISTRATION

Sports Science Experiment Ethics Committee of Beijing Sport University. 2023095H, April 18, 2023 (prospectively registered).

Biomechanical Tradeoffs in Foot Function From Variations in Shoe Design

There is debate and confusion over how to evaluate the biomechanical effects of running shoe design. Here, we use an evolutionary perspective to analyze how key design features of running shoes alter the evolved biomechanics of the foot, creating a range of tradeoffs in force production and transmission that may affect performance and vulnerability to injury.

Morphological and viscoelastic properties of the Achilles tendon in the forefoot, rearfoot strike runners, and non-runners in vivo

The purpose of this study was to investigate the differences in the morphological and viscoelastic properties of the Achilles tendon (AT) among different groups (rearfoot strikers vs. forefoot strikers vs. non-runners). Thirty healthy men were recruited, including habitual forefoot strike runners (n = 10), rearfoot strike runners (n = 10), and individuals with no running habits (n = 10). The AT morphological properties (cross-sectional area and length) were captured by using an ultrasound device. The real-time ultrasound video of displacement changes at the medial head of the gastrocnemius and the AT junction during maximal voluntary isometric contraction and the plantar flexion moment of the ankle was obtained simultaneously by connecting the ultrasound device and isokinetic dynamometer via an external synchronisation box. The results indicated that male runners who habitually forefoot strike exhibited significantly lower AT hysteresis than male non-runners (p < 0.05). Furthermore, a greater peak AT force during maximal voluntary contraction was observed in forefoot strike male runners compared to that in male individuals with no running habits (p < 0.05). However, foot strike patterns were not related to AT properties in recreational male runners (p > 0.05). The lower AT hysteresis in male FFS runners implied that long-term forefoot strike patterns could enhance male-specific AT's ability to store and release elastic energy efficiently during running, resulting in a more effective stretch-shortening cycle. The greater peak AT force in male FFS runners indicated a stronger Achilles tendon.

Electromyographic Activity of the Pelvic Floor Muscles and Internal Oblique Muscles in Women during Running with Traditional and Minimalist Shoes: A Cross-Over Clinical Trial

The study aimed to investigate the effects of footwear on the electromyographic (EMG) activity of pelvic floor muscles (PFMs) and internal oblique (IO) muscles during running at different speeds. The study also aimed to explore the correlation between EMG activity of PFMs and IO muscles and participants' morphological characteristics. Ten nulliparous female runners were included in the study. The participants ran for 90 s at speeds of 9, 11, and 13 km/h wearing both traditional and minimalist shoes. EMG outcomes were presented as a percentage of maximum voluntary contraction (%MVC). Comparative analysis was conducted using the Wilcoxon rank test. Correlational analysis was performed using the Rho-Spearman correlation coefficient. The %MVC for the IO muscles was significantly lower when using minimalist shoes compared to traditional shoes (p = 0.04). No statistically significant differences were found for the PFMs (p > 0.05). The study also observed large correlations between age and %MVC of the PFMs and IO muscles (rho = -0.64; p = 0.04). Minimalist shoes decreased the activity of IO muscles in female runners. However, no significant differences in EMG activity of PFMs were found when comparing traditional and minimalist footwear. The long-term effects of minimalist footwear on EMG activity of PFMs and IO muscles, as well as their relationship to morphological characteristics, require further investigation.

Time course of muscle activation, energetics and mechanics of running in minimalist and traditional cushioned shoes during level running

The study aimed to compare the ankle muscles activation, biomechanics and energetics of running in male runners during submaximal level run using minimalist (MinRS) and traditional cushioned (TrdRS) running shoes. During 45-min running in MinRS and TrdRS, the ankle muscles pre- and co-activation, biomechanics, and energetics of running of 16 male endurance runners (25.5 ± 3.5 yr) were assessed using surface electromyography (tibialis anterior and gastrocnemius lateralis), instrumented treadmill and indirect calorimetry, respectively. The net energy cost of running (C_r) was similar for both conditions (P = 0.25) with a significant increase over time (P < 0.0001). Step frequency (P < 0.001), and total mechanical work (P = 0.001) were significantly higher in MinRS than in TrdRS with no evolution over time (P = 0.28 and P = 0.85, respectively). The ankle muscles pre- and co-activation during the contact phase did not differ between the two shoe conditions (P ≥ 0.33) or over time (P ≥ 0.15). In conclusion, during 45-min running, Cr and muscle pre- and co-activation were not significantly different between MinRS and TrdRS with significantly higher step frequency and total mechanical work noted in the former than in the latter. Moreover, C_r significantly increased during the 45-min trial in both shoe conditions along with no significant change over time in muscle activation and biomechanical variables.

Isolated effects of footwear structure and cushioning on running mechanics in habitual mid/forefoot runners

The true differences between barefoot and shod running are difficult to directly compare because of the concomitant change to a mid/forefoot footfall pattern that typically occurs during barefoot running. The purpose of this study was to compare isolated effects of footwear structure and cushioning on running mechanics in habitual mid/forefoot runners running shod (SHOD), barefoot (BF), and barefoot on a foam surface (BF+FOAM). Ten habitually shod mid/forefoot runners were recruited (male = 8, female = 2). Repeated measures ANOVA (α = 0.05) revealed differences between conditions for only vertical peak active force, contact time, negative and total ankle joint work, and peak dorsiflexion angle. Post hoc tests revealed that BF+FOAM resulted in smaller vertical active peak magnitude and instantaneous vertical loading rate than SHOD. SHOD resulted in lower total ankle joint work than BF and BF+FOAM. BF+FOAM resulted in lower negative ankle joint work than either BF or SHOD. Contact time was shorter with BF than BF+FOAM or SHOD. Peak dorsiflexion angle was smaller in SHOD than BF. No other differences in sagittal joint kinematics, kinetics, or ground reaction forces were observed. These overall similarities in running mechanics between SHOD and BF+FOAM question the effects of footwear structure on habituated mid/forefoot running described previously.

Effects of movement direction and limb dominance on ankle muscular force in sidestep cutting

Sidestep cutting is a critical movement in sports. However, biomechanical research on sidestep cutting has not hitherto reached a consensus. In order to investigate the effects of limb dominance and movement direction on ankle and subtalar joints during sidestep cutting, twelve physically active male participants were recruited in the present study. Trajectory and ground reaction force data were collected by the motion capture system and force platform. Kinematics, kinetics, and muscle forces information were obtained by running OpenSim. Two-way repeated measures ANOVA was performed with movement direction and limb dominance as independent variables. We found that movement direction had a significant effect on ankle dorsiflexion angle. In contrast, the factor of limb dominance had no effect on ankle and subtalar joints angles. For ankle joint moment, the plantarflexion moment was greater by performing a 45° sidestep cutting or using the dominant limb, while the subtalar joint moment was not affected by these two variables. In terms of muscle forces, the soleus of the dominant limb generated greater plantarflexion muscle force on the sagittal plane, while the non-dominant limb tended to contract more strongly (peroneus longus and peroneus brevis) on the frontal plane to stabilize the subtalar joint. Meanwhile, a smaller sidestep cutting angle made participants generate greater plantarflexion muscle forces (soleus and gastrocnemius). In conclusion, our findings indicated that participants should take limb dominance and movement direction into consideration for enhancing athletic performance and reducing the risk of injury during sidestep cutting.

The influence of surface and speed on biomechanical external loads obtained from wearable devices in rearfoot strike runners

External load variables such as peak tibial acceleration (PTA), peak vertical ground reaction forces (GRF) and its instantaneous vertical loading rate (IVLR) may contribute to running injuries although evidence is conflicting given the influence of training load and tissue health on injuries. These variables are influenced by footwear, speed, surface and foot strike pattern during running. The purpose of this study was to assess the influence of four surfaces and two running speeds on external load variables in rearfoot strike (RFS) runners. Twelve RFS runners (confirmed with sagittal foot contact angle) completed a 2-min running bout on a treadmill and 50-m running bouts over the three surfaces (pavement, rubber track and grass) in standardised shoes at their preferred speed and 20% faster. PTA and vertical GRFs were collected using inertial measurement units and in-shoe force insoles. No interaction or surface effects were observed (p > 0.017). The faster speed produced greater axial PTA (+19.2%; p < 0.001), resultant PTA (+20.7%; p < 0.001), peak vertical GRF (+6.6%; p = 0.002) and IVLR (+16.5%; p < 0.001). These findings suggest that surface type does not influence PTA, peak vertical GRF and IVLR but that running faster increases the magnitude of these external loads regardless of surface type in RFS runners.

Homo sapiens May Incorporate Daily Acute Cycles of “Conditioning–Deconditioning” to Maintain Musculoskeletal Integrity: Need to Integrate with Biological Clocks and Circadian Rhythm Mediators

Human evolution required adaptation to the boundary conditions of Earth, including 1 g gravity. The bipedal mobility of Homo sapiens in that gravitational field causes ground reaction force (GRF) loading of their lower extremities, influencing the integrity of the tissues of those extremities. However, humans usually experience such loading during the day and then a period of relative unloading at night. Many studies have indicated that loading of tissues and cells of the musculoskeletal (MSK) system can inhibit their responses to biological mediators such as cytokines and growth factors. Such findings raise the possibility that humans use such cycles of acute conditioning and deconditioning of the cells and tissues of the MSK system to elaborate critical mediators and responsiveness in parallel with these cycles, particularly involving GRF loading. However, humans also experience circadian rhythms with the levels of a number of mediators influenced by day/night cycles, as well as various levels of biological clocks. Thus, if responsiveness to MSK-generated mediators also occurs during the unloaded part of the daily cycle, that response must be integrated with circadian variations as well. Furthermore, it is also possible that responsiveness to circadian rhythm mediators may be regulated by MSK tissue loading. This review will examine evidence for the above scenario and postulate how interactions could be both regulated and studied, and how extension of the acute cycles biased towards deconditioning could lead to loss of tissue integrity.

Are models of plantar heel pain suitable for competitive runners? A narrative review

Background

Plantar heel pain (PHP), or plantar fasciopathy, is a common condition in active and sedentary populations, contributing to short- and long-term reductions in quality of life. The condition's aetiology and pathophysiology are the subjects of a significant body of research. However, much of this research has been conducted with sedentary participants, and comparatively little research exists in a population of highly-trained athletes focused on performance outcomes. Models for PHP and proposed mechanisms, such as high body mass index or systemic disease, are mostly absent from an athletic population. Even less is known about the origins of pain in PHP. Pain is believed to be a complex multifactorial process and may be experienced differently by sedentary and highly active populations, particularly endurance athletes. Consequently, conservative through to surgical treatment for athletes is informed by literature for a different population, potentially hindering treatment outcomes.

Aims

The aim of this review, therefore, is to summarise what is known about PHP in athletic populations and propose potential directions for future research.

Methods

Embase, PubMed, and Scopus using MeSH search terms for PHP and competitive sport and common synonyms.

Discussion

Two explanatory models for PHP were found. These primarily propose mechanical factors for PHP. It remains unclear how gait, body composition, and psychological factors may differ in an athletic population with and without PHP. Therefore, research in these three areas is needed to inform clinical and training interventions for this population.

What differentiates rearfoot strike runners with low and high vertical load rates?

BACKGROUND

Runners with a rearfoot strike pattern typically show high vertical ground reaction force loading rates (LRs), that are associated with injuries, compared with forefoot strikers. However, some runners with a rearfoot strike pattern run in a way that reduces LRs. Our purpose was to identify differences in running mechanics between rearfoot strike runners with high and low vertical LRs.

METHODS

42 healthy runners, 21 with high (≥ 80.5 BW/s) and 21 with low (≤ 46.3 BW/s) LRs, were included in the current study. Lower extremity kinematic and kinetic data were then collected while participants ran along a 30 m runway. Running mechanics were calculated, including sagittal plane knee stiffness during early stance, the components of knee stiffness (Δ knee flexion and flexion moment), sagittal joint angles at initial contact, as well as cadence. The two LR groups were compared for differences in outcome variables using independent t-tests or Mann Whitney U tests.

FINDINGS

Knee stiffness was significantly lower in the low LR group (p < 0.01, d = 0.87), due to higher knee flexion excursion (p < 0.01, d = 1.38). At initial contact, the low LR group showed lower hip and knee flexion, but greater ankle and foot dorsiflexion (p = 0.01-0.04, d = 0.64-0.93). No differences were found in cadence.

INTERPRETATION

These results provide potential targets, related to gait kinematics and kinetics, for gait retraining aimed at reducing LRs in rearfoot strike runners.

Reversing the Mismatch With Forefoot Striking to Reduce Running Injuries

Recent studies have suggested that 95% of modern runners land with a rearfoot strike (RFS) pattern. However, we hypothesize that running with an RFS pattern is indicative of an evolutionary mismatch that can lead to musculoskeletal injury. This perspective is predicated on the notion that our ancestors evolved to run barefoot and primarily with a forefoot strike (FFS) pattern. We contend that structures of the foot and ankle are optimized for forefoot striking which likely led to this pattern in our barefoot state. We propose that the evolutionary mismatch today has been driven by modern footwear that has altered our footstrike pattern. In this paper, we review the differences in foot and ankle function during both a RFS and FFS running pattern. This is followed by a discussion of the interaction of footstrike and footwear on running mechanics. We present evidence supporting the benefits of forefoot striking with respect to common running injuries such as anterior compartment syndrome and patellofemoral pain syndrome. We review the importance of a gradual shift to FFS running to reduce transition-related injuries. In sum, we will make an evidence-based argument for the use of minimal footwear with a FFS pattern to optimize foot strength and function, minimize ground reaction force impacts and reduce injury risk.

A machine learning approach to identify risk factors for running-related injuries: study protocol for a prospective longitudinal cohort trial

BACKGROUND

Running is a very popular sport among both recreational and competitive athletes. However, participating in running is associated with a comparably high risk of sustaining an exercise-related injury. Due to the often multifactorial and individual reasons for running injuries, a shift in thinking is required to account for the dynamic process of the various risk factors. Therefore, a machine learning approach will be used to comprehensively analyze biomechanical, biological, and loading parameters in order to identify risk factors and to detect risk patterns in runners.

METHODS

The prospective longitudinal cohort study will include competitive adult athletes, running at least 20 km per week and being free of injuries three months before the start of the study. At baseline and the end of the study period, subjective questionnaires (demographics, injury history, sports participation, menstruation, medication, psychology), biomechanical measures (e.g., stride length, cadence, kinematics, kinetics, tibial shock, and tibial acceleration) and a medical examination (BMI, laboratory: blood count, creatinine, calcium, phosphate, parathyroid hormone, vitamin D, osteocalcin, bone-specific alkaline phosphatase, DPD cross-links) will be performed. During the study period (one season), continuous data collection will be performed for biomechanical parameters, injuries, internal and external load. Statistical analysis of the data is performed using machine learning (ML) methods. For this purpose, the correlation of the collected data to possible injuries is automatically learned by an ML model and from this, a ranking of the risk factors can be determined with the help of sensitivity analysis methods.

DISCUSSION

To achieve a comprehensive risk reduction of injuries in runners, a multifactorial and individual approach and analysis is necessary. Recently, the use of ML processes for the analysis of risk factors in sports was discussed and positive results have been published. This study will be the first prospective longitudinal cohort study in runners to investigate the association of biomechanical, bone health, and loading parameters as well as injuries via ML models. The results may help to predict the risk of sustaining an injury and give way for new analysis methods that may also be transferred to other sports.

TRIAL REGISTRATION

DRKS00026904 (German Clinical Trial Register DKRS), date of registration 18.10.2021.

Effects of Foot-Core Training on Foot-Ankle Kinematics and Running Kinetics in Runners: Secondary Outcomes From a Randomized Controlled Trial

This study investigated the effectiveness of an 8-week foot-core exercise training program on foot-ankle kinematics during running and also on running kinetics (impact loads), with particular interest in biomechanical outcomes considered risk factors for running-related injuries in recreational runners. A single-blind, randomized, controlled trial was conducted with 87 recreational runners randomly allocated to either the control (CG) or intervention (IG) group and assessed at baseline and after 8 weeks. The IG underwent foot-core training 3 times/week, while the CG followed a placebo lower-limb stretching protocol. The participants ran on a force-instrumented treadmill at a self-selected speed while foot-segment motion was captured simultaneously with kinetic measurements. After the intervention, there were statistically significant changed in foot biomechanics, such as: IG participants strike the ground with a more inverted calcaneus and a less dorsiflexed midfoot than those in the CG; at midstance, ran with a less plantarflexed and more adducted forefoot and a more abducted hallux; and at push-off, ran with a less dorsiflexed midfoot and a less adducted and more dorsiflexed hallux. The IG runners also had significantly decreased medial longitudinal arch excursion (p = 0.024) and increased rearfoot inversion (p = 0.037). The 8-week foot-core exercise program had no effect on impact (p = 0.129) and breaking forces (p = 0.934) or on vertical loading rate (p = 0.537), but it was positively effective in changing foot-ankle kinematic patterns.”

Automatic Classification of Barefoot and Shod Populations Based on the Foot Metrics and Plantar Pressure Patterns

The human being’s locomotion under the barefoot condition enables normal foot function and lower limb biomechanical performance from a biological evolution perspective. No study has demonstrated the specific differences between habitually barefoot and shod cohorts based on foot morphology and dynamic plantar pressure during walking and running. The present study aimed to assess and classify foot metrics and dynamic plantar pressure patterns of barefoot and shod people via machine learning algorithms. One hundred and forty-six age-matched barefoot (n = 78) and shod (n = 68) participants were recruited for this study. Gaussian Naïve Bayes were selected to identify foot morphology differences between unshod and shod cohorts. The support vector machine (SVM) classifiers based on the principal component analysis (PCA) feature extraction and recursive feature elimination (RFE) feature selection methods were utilized to separate and classify the barefoot and shod populations via walking and running plantar pressure parameters. Peak pressure in the M1-M5 regions during running was significantly higher for the shod participants, increasing 34.8, 37.3, 29.2, 31.7, and 40.1%, respectively. The test accuracy of the Gaussian Naïve Bayes model achieved an accuracy of 93%. The mean 10-fold cross-validation scores were 0.98 and 0.96 for the RFE- and PCA-based SVM models, and both feature extract-based and feature select-based SVM models achieved an accuracy of 95%. The foot shape, especially the forefoot region, was shown to be a valuable classifier of shod and unshod groups. Dynamic pressure patterns during running contribute most to the identification of the two cohorts, especially the forefoot region.

Estimation of Fine-Grained Foot Strike Patterns with Wearable Smartwatch Devices

People who exercise may benefit or be injured depending on their foot striking (FS) style. In this study, we propose an intelligent system that can recognize subtle differences in FS patterns while walking and running using measurements from a wearable smartwatch device. Although such patterns could be directly measured utilizing pressure distribution of feet while striking on the ground, we instead focused on analyzing hand movements by assuming that striking patterns consequently affect temporal movements of the whole body. The advantage of the proposed approach is that FS patterns can be estimated in a portable and less invasive manner. To this end, first, we developed a wearable system for measuring inertial movements of hands and then conducted an experiment where participants were asked to walk and run while wearing a smartwatch. Second, we trained and tested the captured multivariate time series signals in supervised learning settings. The experimental results obtained demonstrated high and robust classification performances (weighted-average F1 score > 90%) when recent deep neural network models, such as 1D-CNN and GRUs, were employed. We conclude this study with a discussion of potential future work and applications that increase benefits while walking and running properly using the proposed approach.

Adolescent Running Biomechanics - Implications for Injury Prevention and Rehabilitation

Global participation in running continues to increase, especially amongst adolescents. Consequently, the number of running-related injuries (RRI) in adolescents is rising. Emerging evidence now suggests that overuse type injuries involving growing bone (e.g., bone stress injuries) and soft tissues (e.g., tendinopathies) predominate in adolescents that participate in running-related sports. Associations between running biomechanics and overuse injuries have been widely studied in adults, however, relatively little research has comparatively targeted running biomechanics in adolescents. Moreover, available literature on injury prevention and rehabilitation for adolescent runners is limited, and there is a tendency to generalize adult literature to adolescent populations despite pertinent considerations regarding growth-related changes unique to these athletes. This perspective article provides commentary and expert opinion surrounding the state of knowledge and future directions for research in adolescent running biomechanics, injury prevention and supplemental training.

Can the "Appropriate" Footwear Prevent Injury in Leisure-Time Running? Evidence Versus Beliefs

Leisure-time running is one of the most popular forms of physical activity around the world. It can be practiced almost everywhere and requires mainly a pair of "appropriate" running shoes. However, the term appropriate is ambiguous, and the properties of running footwear have always generated hot debates among clinicians, coaches, and athletes, whatever the level of practice. As the main interface between the runner's foot and the ground, the shoe potentially plays an important role in managing repetitive external mechanical loads applied to the musculoskeletal system and, thus, in injury prevention. Consequently, over the last decades, running shoes have been prescribed based on matching shoe features to foot morphology. This strategy aligns with the popular belief that footwear is one of the main extrinsic factors influencing running-related injury risk. Despite a seemingly sound strategy for shoe prescription and constant progress in running-footwear technology, the injury rate remains high. Therefore, our aim in this narrative literature review is to clarify whether the prescription of appropriate footwear to prevent injury in running is evidence based, the result of logical fallacy, or just a myth. The literature presented in this review is based on a nonsystematic search of the MEDLINE database and focuses on work investigating the effect of shoe features on injury risk in runners. In addition, key elements for a proper understanding of the literature on running footwear and injury risk are addressed. In this literature review, we outline (1) the main risk factors and the mechanisms underlying the occurrence of running-related injury, (2) important methodologic considerations for generating high-level evidence, (3) the evidence regarding the influence of running-shoe features on injury risk, (4) future directions for research, and (5) final general recommendations.

Ankle-Knee Initial Contact Angle and Latency to Maximum Angle are Affected by Prolonged Run

The initial contact and midstance angles may influence injury risk. Previous literature has not assessed these angles under the influence of new footwear for a non-exhaustive prolonged run or the relationship between the angles. To assess lower extremity kinematic changes and the relationship between kinematic parameters at initial contact and midstance with prolonged running under the influence of different types of footwear. Twelve experienced, recreational runners (6 male; 6 female; 24.8 ± 8.4 years; 70.5 ± 9.3 kg; 174.1 ± 9.7 cm) ran for 31 minutes at a self-selected pace for three testing sessions wearing maximalist, habitual, and minimalist shoes. Sixteen anatomical retroreflective markers and seven tracking clusters were placed on the participants' lower extremities. Kinematic data were collected every five minutes beginning at minute one. Initial contact angle (IC), maximum angle (MAX) during midstance, and latency (Tmax) between IC and MAX were calculated for the ankle and knee joints in the frontal and sagittal planes. No significant differences were observed between footwear. Rearfoot inversion (F3,33 = 9.72, p < .001) and knee flexion (F6,66 = 5.34, p < .001) at IC increased over time. No significant differences were detected for MAX over time. Tmax for dorsiflexion (F6,66 = 10.26, p < .001), rearfoot eversion, (F6,66 = 7.84, p < .001) and knee flexion (F6,66 = 11.76, p < .001) increased over time. Maximum eversion during midstance is related to the angle at initial contact, and regardless of footwear type, IC and Tmax increased over the duration of the run. No differences in the ankle and knee sagittal or frontal plane kinematics between minimalist, habitual, and maximalist footwear were observed During a self-paced run.

There is a difference in functional ankle stability between different types of footwear in male athletes: A cross-sectional study

CONTEXT

Lateral ankle sprains (LAS) are among the most common injuries in sports, with a poor long - term prognosis due to high chronicity and recurrence rates. Chronic ankle instability (CAI) results up to 40% of people that endured a first - time LAS.

OBJECTIVE

The aim of this study was to compare ankle stability between groups characterised by the use of different types of footwear during their sport activities.

DESIGN

Cross-sectional study.

SETTING

Firm training surface, local sport clubs.

PARTICIPANTS

Fifty - one male subjects were recruited, distributed in four groups based on the type of footwear they use during their sport activities.

MAIN OUTCOME MEASURES

All subjects performed four clinical ankle stability tests, and completed the Dutch version of the Cumberland Ankle Instability Tool (CAIT) and Profile of Mood States (POMS). All clinical ankle stability tests were performed barefoot.

RESULTS

Subjects performing their sport activities barefoot scored better than subjects performing their sport with shoes at the multiple hop test (p=.002 to .047) and executed the figure-of-8 hop test significantly faster than subjects with submalleolar ankle support (AS) (p=.019). Subjects with submalleolar AS and studs showed significantly better results than subjects with supramalleolar AS on the CAIT- score (p=.024, p=.030) and the side- hop test (p=.050, p=.045). They also scored significantly better than subjects with submalleolar AS for the side - hop test (p=.032), foot - lift test (p=.019) and figure-of 8 hop test (p=.011).

CONCLUSION

Barefoot sports performing subjects appear to have better ankle stability compared to subjects performing their sports with shoe support. Subjects performing sports with high AS appear to have worst ankle stability.

LEVEL OF EVIDENCE

Level III, Cross-sectional study.

A comparison of attachment methods of skin mounted inertial measurement units on tibial accelerations

Peak tibial accelerations during running are of interest because of their correlation with vertical ground reaction force load rates and association with running injury. Previous work has demonstrated systematically lower accelerations measured with a bone- compared to skin-mounted accelerometer. However, no studies have assessed the effects of more or less secure attachment methods for skin mounted sensors. Our purpose was to compare two methods of attaching a skin mounted sensor on mean tibial accelerations, stride-to-stride variability, and correlations with vertical load rates. 18 injury-free runners were recruited as participants. An inertial measurement unit, containing a tri-axial accelerometer, was used to record tibial accelerations while participants ran at a self-selected speed on an instrumented treadmill to collect ground reaction forces. The two attachment methods for securing the sensor to the skin were a manufacturer-provided strap (strap condition) and a combination of tape and elastic wraps (wrap condition). Mean vertical accelerations were significantly lower in the wrap condition (p = 0.02, d = 0.57). No differences were detected in resultant accelerations, vertical loading rates, or stride-to-stride variability. Correlations between tibial accelerations and vertical loading rates were strong (r = 0.79-0.91) and similar between conditions. These results provide two key findings of evidence. Evidenced by systematically lower vertical accelerations, a more secure attachment method may be necessary for capturing the most representative measure of tibial accelerations during running. However, a less secure method (i.e. the strap) is sufficient for capturing tibial accelerations as a surrogate for impact loading forces.

Rearfoot, Midfoot, and Forefoot Motion in Naturally Forefoot and Rearfoot Strike Runners during Treadmill Running

Different location and incidence of lower extremity injuries have been reported in rearfoot strike (RFS) and forefoot strike (FFS) recreational runners. These might be related to functional differences between the two footstrike patterns affecting foot kinematics and thus the incidence of running injuries. The aim of this study was to investigate and compare the kinematic patterns of foot joints between naturally RFS and FFS runners. A validated multi-segment foot model was used to measure 24 foot kinematic variables in long-distance recreational runners while running on a treadmill. These variables included the three-dimensional relative motion between rearfoot, midfoot, and forefoot segments. The footstrike pattern was identified using kinematic data and slow-motion videos. Functional analysis of variance was used to compare the time series of these variables between RFS (n = 49) and FFS (n = 25) runners. In FFS runners, the metatarsal bones were less tilted with respect to the ground, and the metatarsus was less adducted with respect to the calcaneus during stance. In early stance, the calcaneus was more dorsiflexed with respect to the shank and returned to a more plantarflexed position at push-off. FFS runners showed a more adducted calcaneus with respect to the shank and a less inverted midfoot to the calcaneus. The present study has showed that the footstrike angle characterizes foot kinematics in running. These data may help shed more light on the relationship between foot function and running-related injuries.

Barefoot Running: Between Fashion and Real Way to Prevent Joint Osteo Lesions?

Background and objectives

Running has gone from a vital necessity for the man to a playful sport. Different rheumatic and orthopedic pathologies have appeared, in front of which the shoe industry has reacted by creating reinforced shoes that are supposed to overcome the induced lesions. Several years later, the trend toward reinforcement has gone toward minimalism, which is the absence of reinforcement, that is, a more natural race.

Method

We observed variations of kinetics and kinematics in young, unprofessional, healthy runners during a shoe race and a shoeless race, which is the form of maximum minimalism. We then correlated minimalism variations with the variables of the race and the joint angles.

Results

We observed significant difference (P < 0.01) in the cycle rate, the cycle length, the step rate, and the angle of attack between running with and without shoes. A small variation of the minimalism index is associated with an increase in knee angle (r²> 0.5). Conversely, a large variation in the minimalism index is related to a decrease in the knee angle (r²> 0.5). The minimalism index has no impact on the angulation of the ankle and hip (r²< 0.3).

Conclusion

Slow transition will bring gains in terms of decreasing the length of the stride, which limits the load on the shin. Greater flexibility can be achieved by decreasing the flexion angle of the knee, which decreases the demand for quadriceps muscles and the risk of knee injury with a greater risk of injury at the tibial level.

What is the foot strike pattern distribution in children and adolescents during running? A cross-sectional study

BACKGROUND

There is a lack of studies describing foot strike patterns in children and adolescents. This raises the question on what the natural foot strike pattern with less extrinsic influence should be and whether or not it is valid to make assumptions on adults based on the knowledge from children.

OBJECTIVES

To investigate the distribution of foot strike patterns in children and adolescents during running, and the association of participants' characteristics with the foot strike patterns.

METHODS

This is a cross-sectional study. Videos were acquired with a high-speed camera and running speed was measured with a stopwatch. Bayesian analyses were performed to allow foot strike pattern inferences from the sample to the population distribution and a supervised machine learning procedure was implemented to develop an algorithm based on logistic mixed models aimed at classifying the participants in rearfoot, midfoot, or forefoot strike patterns.

RESULTS

We have included 415 children and adolescents. The distribution of foot strike patterns was predominantly rearfoot for shod and barefoot assessments. Running condition (barefoot versus shod), speed, and footwear (with versus without heel elevation) seemed to influence the foot strike pattern. Those running shod were more likely to present rearfoot pattern compared to barefoot. The classification accuracy of the final algorithm ranged from 80% to 88%.

CONCLUSIONS

The rearfoot pattern was predominant in our sample. Future well-designed prospective studies are needed to understand the influence of foot strike patterns on the incidence and prevalence of running-related injuries in children and adolescents during running, and in adult runners.

Effects of 12-week cadence retraining on impact peak, load rates and lower extremity biomechanics in running

Background

Excessive impact peak forces and vertical load rates are associated with running injuries and have been targeted in gait retraining studies. This study aimed to determine the effects of 12-week cadence retraining on impact peak, vertical load rates and lower extremity biomechanics during running.

Methods

Twenty-four healthy male recreational runners were randomised into either a 12-week cadence retraining group (n = 12), which included those who ran with a 7.5% increase in preferred cadence, or a control group (n = 12), which included those who ran without any changes in cadence. Kinematics and ground reaction forces were recorded simultaneously to quantify impact force variables and lower extremity kinematics and kinetics.

Results

Significantly decreased impact peak (1.86 ± 0.30 BW vs. 1.67 ± 0.27 BW, P = 0.003), vertical average load rates (91.59 ± 18.91 BW/s vs. 77.31 ± 15.12 BW/s, P = 0.001) and vertical instantaneous load rates (108.8 ± 24.5 BW/s vs. 92.8 ± 18.5 BW/s, P = 0.001) were observed in the cadence retraining group, while no significant differences were observed in the control group. Foot angles (18.27° ± 5.59° vs. 13.74° ± 2.82°, P = 0.003) and vertical velocities of the centre of gravity (CoG) (0.706 ± 0.115 m/s vs. 0.652 ± 0.091 m/s, P = 0.002) significantly decreased in the cadence retraining group at initial contact, but not in the control group. In addition, vertical excursions of the CoG (0.077 ± 0.01 m vs. 0.069 ± 0.008 m, P = 0.002) and peak knee flexion angles (38.6° ± 5.0° vs. 36.5° ± 5.5°, P < 0.001) significantly decreased whilst lower extremity stiffness significantly increased (34.34 ± 7.08 kN/m vs. 38.61 ± 6.51 kN/m, P = 0.048) in the cadence retraining group. However, no significant differences were observed for those variables in the control group.

Conclusion

Twelve-week cadence retraining significantly increased the cadence of the cadence retraining group by 5.7%. This increased cadence effectively reduced impact peak and vertical average/instantaneous load rates. Given the close relationship between impact force variables and running injuries, increasing the cadence as a retraining method may potentially reduce the risk of impact-related running injuries.

Changes in the Plantar Flexion Torque of the Ankle and in the Morphological Characteristics and Mechanical Properties of the Achilles Tendon after 12-Week Gait Retraining

Purpose: Although the Achilles tendon (AT) is the largest and strongest tendon, it remains one of the most vulnerable tendons among elite and recreational runners. The present study aims to explore the effects of 12-week gait retraining (GR) on the plantar flexion torque of the ankle and the morphological and mechanical properties of the AT. Methods: Thirty-four healthy male recreational runners (habitual rearfoot strikers) who never tried to run in minimal shoes were recruited, and the intervention was completed (20 in the GR group vs. 14 in the control (CON) group). The participants in the GR group were asked to run in minimal shoes (INOV-8 BARE-XF 210) provided by the investigators with forefoot strike patterns during the progressive 12-week GR. Meanwhile, the participants in the CON group were instructed to run in their own running shoes, which they were familiar with, with original foot strike patterns and intensities. The morphological properties of the AT, namely, length and cross-sectional area (CSA), were obtained by using an ultrasound device. A dynamometer was utilized simultaneously to measure and calculate the plantar flexion torque of the ankle, the rate of torque development, the peak force of the AT, and the stress and strain of the AT. Results: After 12-week GR, the following results were obtained: (1) A significant time effect in the peak ankle plantarflexion torque was observed (p = 0.005), showing a 27.5% increase in the GR group; (2) A significant group effect in the CSA was observed (p = 0.027), specifically, the increase in CSA was significantly larger in the GR group than the CON group; (3) A significant time effect in the peak AT force was observed (p = 0.005), showing a 27.5% increase in the GR group. Conclusion: The effect of 12 weeks of GR is an increase in AT CSA, plantar flexor muscle strength of the ankle, and peak AT force during a maximal voluntary isometric contraction test. These changes in AT morphology and function could be positive for tendon health and could prevent future AT injury.

Effects of the weight of shoes on calf muscle simulation

The current study investigated the effects of shoes of different weights on calf individual muscle contributions during a running cycle. Twenty male runners ran on a force platform with shoes of four different weights (175 g, 255 g, 335 g, and 415 g). The study evaluated runners’ lower extremity muscle forces under the four shoe weight conditions using a musculoskeletal modeling system. The system generates equality and inequality constraint equations to simulate muscle forces. The individual muscle contributions in each calf were determined using these muscle forces. Data were compared using one-way repeated-measure ANOVA. The results revealed significant differences in the contributions of the gastrocnemius lateralis. Post hoc comparisons revealed that running in the 175 g shoes resulted in a larger contribution of the gastrocnemius lateralis than running in the 415 g shoes during the braking phase. Therefore, wearing lightweight shoes while running may promote fatigue in the gastrocnemius muscle during the braking phase. The calf muscle activation results may indicate that an adaptation period is warranted when changing from heavy to lightweight shoes.

A real-time feedback method to reduce loading rate during running: Effect of combining direct and indirect feedback

Impact loading plays a key role in the pathophysiology of running-related injuries. Providing real-time feedback may be an effective strategy to reduce impact loading; however, it is currently unclear what an effective training method to help runners achieve a habitual low loading rate is. We subjected 20 healthy non-runners to a structured sequence of direct and indirect biofeedback designed to facilitate broader exploration of neuro-mechanical workspace for potential movement solutions (indirect feedback on cadence and foot-strike angle) and to refine and converge upon an optimal sub-set of that space to match the task goal (direct feedback on loading rate). While indirect biofeedback on foot-strike angle yielded a lower impact load than providing direct biofeedback on loading rate, compared to indirect biofeedback on foot-strike angle, providing direct feedback on loading rate statistically increased (+58%, p = 0.007) the range of goal-relevant solutions participants used to lower their impact loading. Results showed that structured feedback was effective in increasing the range of input parameters that match the task goal, hence expanding the size of goal-relevant solutions, which may benefit running performance under changing environmental constraints.

Foot Angle and Loading Rate during Running Demonstrate a Nonlinear Relationship

Vertical loading rates are typically found to be lower in forefoot compared to rearfoot strikers, promoting the idea that forefoot striking is desirable and may reduce running injury risk. However, prior work using linear models has shown that foot inclination angle (FIA) at initial contact is a poor predictor of vertical loading rate, suggesting a more complex association exists.

PURPOSE

To determine if a nonlinear model superiorly describes the relationship between FIA and average vertical loading rate (AVLR). Secondary analyses assessed the influence of sex and sport on the association between FIA and AVLR.

METHODS

Whole body kinematics and vertical ground reaction forces were collected for 170 healthy National Collegiate Athletic Association Division I athletes (97 males; 81 cross-country runners) during treadmill running at 2.68, 3.35, and 4.47 m·s. Foot inclination angle and AVLR were calculated for 15 strides and averaged across strides for each limb. Polynomial mixed effects models assessed linear and nonlinear trends in the relationship between FIA and AVLR across the entire sample and accounting for sex and sport participation.

RESULTS

Average vertical loading rate was lowest at the extremes of FIA (i.e., -15°, 20°), whereas greater AVLR were observed between 5° and 10°. The cubic model resulted in a significantly better fit than the linear model (P < 0.001). Average vertical loading rate was also more variable among FIA associated with rearfoot and midfoot strike than forefoot strike. Adding sex to the model did not influence model fit; though, controlling for sport minimally improved model fit.

CONCLUSIONS

The relationship between FIA and AVLR is best represented by a cubic model. Consequently, FIA should be treated as a continuous variable. Reducing FIA into categories may misrepresent the relationship between FIA and other gait variables.

Footwear and footstrike change loading patterns in running

Loading rates have been linked to running injuries, revealing persistent impact features that change direction among three-dimensional axes in different footwear and footstrike patterns. Extracting peak loads from ground reaction forces, however, can neglect the time-varying loading patterns experienced by the runner in each footfall. Following footwear and footstrike manipulations during laboratory-based overground running, we examined three-dimensional loading rate-time features in each direction (X, Y, Z) using principal component analysis. Twenty participants (9 M, 11 F, age: 25.3 ± 3.6 y) were analysed during 14 running trials in each of two footwear (cushioned and minimalist) and three footstrike conditions (forefoot, midfoot, rearfoot). Two principal components (PC) captured the primary loading rate-time features (PC1: 42.5% and PC2: 22.8% explained variance) and revealed interaction among axes, footwear, and footstrike conditions (PC1: F _{(2.1, 40.1)} = 5.6, p = 0.007, η ² = 0.23; PC2: F _{(2.0, 38.4)} = 62.3, p < 0.001, η ² = 0.77). Rearfoot running in cushioned footwear attenuated impact loads in the vertical direction, and forefoot running in minimalist footwear attenuated impact loads in the anterior-posterior and medial-lateral directions relative to forefoot running in cushioned shoes. Loading patterns depend on footwear and footstrike interactions, which require shoes that match the runner's footstrike pattern.

Transition to forefoot strike reduces load rates more effectively than altered cadence

BACKGROUND

Excessive vertical impacts at landing are associated with common running injuries. Two primary gait-retraining interventions aimed at reducing impact forces are transition to forefoot strike and increasing cadence. The objective of this study was to compare the short- and long-term effects of 2 gait-retraining interventions aimed at reducing landing impacts.

METHODS

A total of 39 healthy recreational runners using a rearfoot strike and a cadence of ≤170 steps/min were randomized into cadence (CAD) or forefoot strike (FFS) groups. All participants performed 4 weeks of strengthening followed by 8 sessions of gait-retraining using auditory feedback. Vertical average load rates (VALR) and vertical instantaneous load rates (VILR) were calculated from the vertical ground reaction force curve. Both cadence and foot strike angle were measured using 3D motion analysis and an instrumented treadmill at baseline and at 1 week, 1 month, and 6 months post retraining.

RESULTS

ANOVA revealed that the FFS group had significant reductions in VALR (49.7%) and VILR (41.7%), and changes were maintained long term. Foot strike angle in the FFS group changed from 14.2° dorsiflexion at baseline to 3.4° plantarflexion, with changes maintained long term. The CAD group exhibited significant reduction only in VALR (16%) and only at 6 months. Both groups had significant and similar increases in cadence at all follow-ups (CAD, +7.2% to 173 steps/min; and FFS, +6.1% to 172 steps/min).

CONCLUSION

Forefoot strike gait-retraining resulted in significantly greater reductions in VALR and similar increases in cadence compared to cadence gait-retraining in the short and long term. Cadence gait-retraining resulted in small reductions in VALR at only the 6-month follow-up.

Twelve-Week Gait Retraining Reduced Patellofemoral Joint Stress during Running in Male Recreational Runners

Purpose

To explore the changes in knee sagittal angle and moment and patellofemoral joint (PFJ) force and stress before and after 12-week gait retraining.

Methods

A total of 30 healthy male recreational runners were randomized into a control group (n = 15) who ran in their original strike pattern using minimalist shoes or experimental group (n = 15) who ran in a forefoot strike pattern using minimalist shoes during the 12-week gait retraining. The kinematic and kinetic data of the dominant leg of the participants during the 12 km/h running were collected by 3D motion capture systems and 3D force platforms. Besides, the biomechanical property of the PFJ was calculated on the basis of the joint force model and the regression equation of the contact area.

Results

After the 12-week gait retraining, 78% of the rearfoot strikers turned into forefoot strikers. Peak knee extension moment and peak PFJ stress decreased by 13.8% and 13.3% without altering the running speed, respectively. Meanwhile, no changes in maximum knee flexion angle/extension moment and PFJ force/stress were observed for the control group.

Conclusion

The 12-week gait retraining effectively reduced the PFJ stress, thereby providing a potential means of reducing the risk of patellofemoral pain syndrome while running.

Multi-Segmental Motion in Foot during Counter-Movement Jump with Toe Manipulation

Human toes are crucial for vertical jumping performance. The purpose of this study is to investigate the acute effect of hallux abduction manipulation on foot inter-segment kinematic alterations and plantar loading redistribution during the countermovement jump (CMJ). Thirteen participants were recruited to join in this experiment, for the collection of the foot inter-segment kinematics and plantar pressure data. During the take-off phase, the contact area presented a significant increase while the pressure-time integral decreased in the second metatarsal (M2), whilst the third metatarsal (M3) and fourth metatarsal (M4) decreased significantly in pressure-time integral with Toe-Manipulation (TM). During the landing phase, maximum force and peak pressure were smaller in the big toe (BT) after hallux abduction manipulation. HXFFA (hallux-forefoot angle) showed a greater pronation after manipulation in the frontal plane (0%–26% and 50%–100%) with p = 0.002 and p < 0.001. In the transverse plane, the smaller adductions were found during 62%–82% in take-off and 62%–91% in landing (p = 0.003 and p < 0.001). There was a redistributed plantar loading during the landing phase from the medial to lateral forefoot. However, a reduced hallux range of motion in the TM session was exhibited, compared to Non-Toe-Manipulation (NTM).

A biomechanical assessment of the acute hallux abduction manipulation intervention

BACKGROUND

Naturally aligned toes, particularly hallux, have reported with gripping functions during locomotion, thus expanding the forefoot loading area.

RESEARCH QUESTION

The purpose of this study was aimed to investigate the influence of hallux abduction manipulation on the foot plantar pressure distribution and inter-segment kinematic alterations.

METHODS

Thirteen subjects participated in this toe manipulation study. A Footscan® pressure plate and Vicon motion capture system were utilized for the measurement of plantar pressure distribution and lower extremity and foot inter-segment kinematics during walking and running. Paired-sample t-test from statistical parametric mapping 1d was used to check the kinematic significance.

RESULTS

Peak pressure in third metatarsal (M3) increased significantly during walking under manipulation. Contact area increased in second metatarsal (M2) with manipulation during running. Peak pressure and pressure-time integral illustrated significant increases in M3, and the maximum force and impulse in fourth metatarsal (M4) increased significantly. Arch height index increased while walking with toe manipulation. The foot progression angle in the frontal plane showed significant decrease in mid-swing phase during walking and significant increase in mid-stance phase during running. The hallux relative to forefoot angles presented higher axial rotation in the frontal plane.

SIGNIFICANCE

Findings form this study showed centrally and laterally redistributed foot loadings and increased forefoot inter-segment flexibility with manipulation, which may be used as baseline to evaluate toe-manipulation interventions in foot disorders, specifically hallux valgus deformity.

Ankle Joint Dynamic Stiffness in Long-Distance Runners: Effect of Foot Strike and Shoes Features

Foot strike mode and footwear features are known to affect ankle joint kinematics and loading patterns, but how those factors are related to the ankle dynamic properties is less clear. In our study, two distinct samples of experienced long-distance runners: habitual rearfoot strikers (n = 10) and habitual forefoot strikers (n = 10), were analysed while running at constant speed on an instrumented treadmill in three footwear conditions. The joint dynamic stiffness was analysed for three subphases of the moment–angle plot: early rising, late rising and descending. Habitual rearfoot strikers displayed a statistically (p < 0.05) higher ankle dynamic stiffness in all combinations of shoes and subphases, except in early stance in supportive shoes. In minimal-supportive shoes, both groups had the lowest dynamic stiffness values for early and late rising (initial contact through mid-stance), whilst the highest stiffness values were at late rising in minimal shoes for both rearfoot and forefoot strikers (0.21 ± 0.04, 0.24 ± 0.06 (Nm/kg/°∙100), respectively). In conclusion, habitual forefoot strikers may have access to a wider physiological range of the muscle torque and joint angle. This increased potential may allow forefoot strikers to adapt to different footwear by regulating ankle dynamic stiffness depending upon the motor task.

Reducing vertical ground reaction forces: The relative importance of three gait retraining cues

BACKGROUND

Previous studies in our department demonstrated that gait retraining as part of a conservative treatment program for service members with exercise-related leg pain can lead to persistent changes in vertical ground reaction forces while running in shoes and boots. It is not known which gait retraining cue has the largest effect and whether a combination of cues is advantageous.

METHODS

During a single gait retraining session, 12 male heel striking patients were given three cues in isolation: Cue 1. Change to a ball-of-foot strike; Cue 2. Increase cadence to 180 steps per minute; Cue 3. Stand up taller; and finally, all three cues combined. Runs were performed on an instrumented treadmill at 10 km/h, 1% incline and in running shoes. The three cues were randomly introduced. Measurements, taken during 30-second episodes, were stride length, cadence, and six force variables: maximum force (N) and maximum pressure (N/cm²) on the heel, mid-foot and fore-foot.

FINDINGS

Each cue, i.e., each change in running technique, caused a different pattern of changes among the six force variables, mostly reductions. In isolation, cue 1 produced the largest reduction of force and pressure on the heel, resulting percentages 45.8 and 67.2 respectively (p = 0.00, p = 0.00). Overall, the combination of cues 1 + 2 + 3 ranked first in reducing forces for four of the six force variables.

INTERPRETATION

Three commonly used gait retraining cues, when applied in isolation, all resulted in a reduction of most vertical ground reaction forces. The combination of the three cues is advantageous.

Do habitual foot-strike patterns in running influence functional Achilles tendon properties during gait?

The capacity of foot-strike running patterns to influence the functional properties of the Achilles tendon is controversial. This study used transmission-mode ultrasound to investigate the influence of habitual running foot-strike pattern on Achilles tendon properties during barefoot walking and running. Fifteen runners with rearfoot (RFS) and 10 with a forefoot (FFS) foot-strike running pattern had ultrasound transmission velocity measured in the right Achilles tendon during barefoot walking (≈1.1 ms^-1) and running (≈2.0 ms^-1). Temporospatial gait parameters, ankle kinematics and vertical ground reaction force were simultaneously recorded. Statistical comparisons between foot-strike patterns were made using repeated measure ANOVAs. FFS was characterised by a significantly shorter stance duration (-4%), greater ankle dorsiflexion (+2°), and higher peak vertical ground reaction force (+20% bodyweight) than RFS running (P < .05). Both groups adopted a RFS pattern during walking, with only the relative timing of peak dorsiflexion (3%), ground reaction force (1-2%) and peak vertical force loading rates (22-23%) differing between groups (P < .05). Peak ultrasound transmission velocity in the Achilles tendon was significantly higher in FFS during walking (≈100 ms^-1) and running (≈130 ms^-1) than RFS (P < .05). Functional Achilles tendon properties differ with habitual footfall patterns in recreational runners.

Prediction on the plantar fascia strain offload upon Fascia taping and Low-Dye taping during running

Background

Taping is commonly prescribed to treat plantar fasciitis for runners by virtue of its alleged ability to offload the plantar fascia and facilitate positive injury prognosis. Our study aimed to investigate how different taping methods could change the loading on the plantar fascia during running using computational simulations.

Methods

A finite element foot model was modified from a previous version to fit the study's purpose. The model featured twenty bones, bulk soft tissue, foot muscles, ligaments/tendons, and a solid part representing the plantar fascia. A runner performed several running trials under one untaped condition and two taped conditions—Low-Dye taping and Fascia taping, which were implemented by a physiotherapist using the Kinesio tapes. The captured motion data were processed to drive a scaled musculoskeletal model and calculate segmental kinematics, foot muscle force, and joint reaction force. These variables were then input as the boundary/loading conditions for finite element analyses of running. The principal tensile strain on the plantar fascia, subtalar eversion, and navicular height during the stance phase were averaged across five trials of each condition and compared using Friedman's test.

Results

Maximal subtalar eversion did not differ among conditions (p = 0.449). Fascia taping significantly reduced maximal strains on the fascia band (p = 0.034, Kendall's W = 0.64–0.76) and increased the navicular height (p = 0.013, Kendall's W = 0.84) compared with nontaping. There were no significant differences in all outcome variables between Low-Dye taping and nontaping (p = 0.173–0.618).

Conclusion

From a mechanical point of view, our study provided quantitative evidence to support the application of taping treatments for overstrained plantar fascia. The untensed fascia band by Fascia taping could be a potential indicator of pain relief for the runners. However, a prospective study targeting the patient population would be needed to address the point.

The Translational Potential of this Article

The study quantified the loading status of the plantar fascia during running and provided mechanical evidence to support the usage of taping as a mean to reduce fascial strain, thus possibly controlling injury risks for the runners. The results of the study also highlighted the importance of selecting specific taping methods based on individuals' needs.

The effect of running on foot muscles and bones: A systematic review

Despite the widespread evidence of running as a health-preserving exercise, little is known concerning its effect on the foot musculature and bones. While running may influence anatomical foot adaptation, it remains unclear to what extent these adaptations occur. The aim of this paper is to provide a systematic review of the studies that investigated the effects of running and the adaptations that occur in foot muscles and bones. The search was performed following the PRISMA guidelines. Relevant keywords were used for the search through PubMed/MEDLINE, Scopus and SPORTDiscus. The methodological quality of intervention studies was assessed using the Downs and Black checklist. For cross-sectional studies, the Newcastle-Ottawa scale was used. Sixteen studies were found meeting the inclusion criteria. In general, the included studies were deemed to be of moderate methodological quality. Although results of relevant literature are limited and somewhat contradictory, the outcome suggests that running may increase foot muscle volume, muscle cross-sectional area and bone density, but this seems to depend on training volume and experience. Future studies conducted in this area should aim for a standard way of reporting foot muscle/bone characteristics. Also, herein, suggestions for future research are provided.

Ground reaction force metrics are not strongly correlated with tibial bone load when running across speeds and slopes: Implications for science, sport and wearable tech

INTRODUCTION

Tibial stress fractures are a common overuse injury resulting from the accumulation of bone microdamage due to repeated loading. Researchers and wearable device developers have sought to understand or predict stress fracture risks, and other injury risks, by monitoring the ground reaction force (GRF, the force between the foot and ground), or GRF correlates (e.g., tibial shock) captured via wearable sensors. Increases in GRF metrics are typically assumed to reflect increases in loading on internal biological structures (e.g., bones). The purpose of this study was to evaluate this assumption for running by testing if increases in GRF metrics were strongly correlated with increases in tibial compression force over a range of speeds and slopes.

METHODS

Ten healthy individuals performed running trials while we collected GRFs and kinematics. We assessed if commonly-used vertical GRF metrics (impact peak, loading rate, active peak, impulse) were strongly correlated with tibial load metrics (peak force, impulse).

RESULTS

On average, increases in GRF metrics were not strongly correlated with increases in tibial load metrics. For instance, correlating GRF impact peak and loading rate with peak tibial load resulted in r = -0.29±0.37 and r = -0.20±0.35 (inter-subject mean and standard deviation), respectively. We observed high inter-subject variability in correlations, though most coefficients were negligible, weak or moderate. Seventy-six of the 80 subject-specific correlation coefficients computed indicated that higher GRF metrics were not strongly correlated with higher tibial forces.

CONCLUSIONS

These results demonstrate that commonly-used GRF metrics can mislead our understanding of loading on internal structures, such as the tibia. Increases in GRF metrics should not be assumed to be an indicator of increases in tibial bone load or overuse injury risk during running. This has important implications for sports, wearable devices, and research on running-related injuries, affecting >50 scientific publications per year from 2015-2017.

Analyzing the effect of an arch support functional insole on walking and jogging in young, healthy females

BACKGROUND AND OBJECTIVE

The aim of this study was to explore the effectiveness of arch support functional insoles to prevent metatarsalgia.

METHOD

Twenty-five healthy females participated in the study. A Vicon motion capture system was used to collect kinematics data of the lower limb. An AMTI force plate was used to record the vertical ground reaction force (GRF), and the Novel Pedar-X System was used to measure foot pressure while subjects wore normal insoles or functional insoles with an arch support during walking and jogging.

RESULTS

With the arch support functional insoles, the first metatarsal (FM) region's contact area was increased and the peak pressure and time-pressure integral of the FM and second and third metatarsal (SATM) were areas decreased. This suggests a lower risk of longitude stress injuries in these areas. The ankle dorsiflexion angle of jogging with the 'arch support functional insoles' (RF) and walking with the 'arch support functional insoles' (WF) were significantly increased at initial contact and the knee and hip flexion angle of RF and WF were reduced. The peak hip extension angle of WF and RF also declined. The vertical loading rate of RF was lower, which would be beneficial in reducing the risk of lower limb injuries during jogging.

CONCLUSIONS

The results demonstrate that arch support functional insoles can be used effectively to prevent and decrease pain and promote a suitable weight-bearing pattern in the foot for promoting the health of young females.

Do Strike Patterns or Shoe Conditions have a Predominant Influence on Foot Loading?

This study aimed to explore the effects of strike patterns and shoe conditions on foot loading during running. Twelve male runners were required to run under shoe (SR) and barefoot conditions (BR) with forefoot (FFS) and rearfoot strike patterns (RFS). Kistler force plates and the Medilogic insole plantar pressure system were used to collect kinetic data. SR with RFS significantly reduced the maximum loading rate, whereas SR with FFS significantly increased the maximum push-off force compared to BR. Plantar pressure variables were more influenced by the strike patterns (15 out of 18 variables) than shoe conditions (7 out of 18 variables). The peak pressure of midfoot and heel regions was significantly increased in RFS, but appeared in a later time compared to FFS. The influence of strike patterns on running, particularly on plantar pressure characteristics, was more significant than that of shoe conditions. Heel-toe running caused a significant impact force on the heel, whereas wearing cushioned shoes significantly reduced the maximum loading rate. FFS running can prevent the impact caused by RFS. However, peak plantar pressure was centered at the forefoot for a long period, thereby inducing a potential risk of injury in the metatarsus/phalanx.

Minimalist shoes running intervention can alter the plantar loading distribution and deformation of hallux valgus: A pilot study

BACKGROUND

Hallux valgus (HV) is one common deformity of the human foot. Metatarsal pain, gait deviation and foot function disorder may occur when HV is severe.

RESEARCH QUESTION

It was hypothesized that a 12-week minimalist shoes running intervention among mild and moderate hallux valgus males may alter foot morphology and plantar pressure distribution during walking and running.

METHODS

The foot morphology and plantar pressure data, in this study, were collected from eleven participants using the Easy-Foot-Scan (EFS) and Novel EMED force plate.

RESULTS

Compared to pre-intervention sessions, the hallux abductus angle and forefoot width decreased significantly with increased metatarsal waist girth in the post-intervention session. The peak pressure, maximum force and force time integral in the first metatarsal reduced significantly due to the distribution of plantar pressure to the central foot regions.

SIGNIFICANCE

The findings suggest that minimalist shoes may deform forefoot morphology and neutralize loading concentration for mild and moderate hallux valgus.

Differential effects of speed on two-dimensional foot strike pattern during barefoot and shod running in recreationally active men

The majority of barefoot running studies have not considered speed as an influential factor on foot strike pattern. The aim of this study was to investigate differences in foot strike pattern and spatiotemporal characteristics between barefoot and shod overground running at varying speeds. We first determined maximal running speed (Vm) over 50 m in 15 recreationally active men who self-reported as habitual rearfoot strikers. Participants then completed shod and barefoot running trials at different speeds equivalent to approximately 90%, 80%, 70% and 60% of Vm. Sagittal plane two-dimensional (2D) foot-ground contact angle, ankle plantar-dorsi flexion angle, contact time, flight time, step length and step rate variables for each trial were recorded. A significant interaction effect of running speed and footwear condition (p < 0.05) on foot-ground contact angle, ankle plantar-dorsi flexion angle and contact time was observed. There was a main effect of running speed (p < 0.01) on flight time, step length and step rate. There was a main effect of footwear condition on step length (p < 0.01). Participants were more inclined to plantarflex the ankle and contact the ground with the forefoot at higher percentages of Vm, especially when running barefoot.

Biomechanical Performance of Habitually Barefoot and Shod Runners during Barefoot Jogging and Running

The purpose of this study was to evaluate the biomechanical performances, running stability of habitually barefoot (BR) and shod runners (SR) during barefoot jogging and running. Ten healthy male subjects, 5 habitually shod runners and 5 habitually barefoot runners, from two different ethnics participated in this study. Subjects performed jogging (2m/s) and running (4m/s) along a 10-m runway. Three-dimensional lower-limb kinematics, ground reaction force, center of pressure (COP) and contact time (CT), were collected during testing. During jogging and running, all participants adopted rear-foot strike pattern, SR had larger VALR. SR showed significantly larger lower-limb range of motion (ROM) in sagittal plane, significantly larger hip abduction and opposite knee ROM in frontal plane, as well as significantly larger ankle internal rotation in horizontal plane. All participants’ CT showed decreased trend with running speed up; and SR was significantly longer than BR; BR and SR in COP showed different trajectories, especially forefoot and rearfoot areas. Habitually barefoot and shod runner from different ethnics still exist significant differences in lower-extremity ROM; and different foot morphological of participants is an important influential factor for these variations.

Short- and long-term effects of altered point of ground reaction force application on human running energetics

The current study investigates an acute and a gradual transition of the point of force application (PFA) from the rearfoot towards the fore of the foot during running, on the rate of metabolic energy consumption. The participants were randomly assigned in two experimental and one control groups: a short-term intervention group (STI, N=17; two training sessions), a long-term intervention group (LTI, N=10; 14-week gradual transition) and a control group (CG, N=11). Data were collected at two running velocities (2.5 and 3.0 m/s). The cost coefficient (i.e. energy required for a unit of vertical ground reaction force, J/N) decreased (p&lt;0.001) after both interventions due to a more anterior PFA during running (STI:12%, LTI:11%), but led to a higher (p&lt;0.001) rate of force generation (STI:17%, LTI:15.2%). Dynamic stability of running showed a significant (p&lt;0.001) decrease in the STI (2.1%), but no differences (p=0.673) in the LTI. The rate of metabolic energy consumption increased in the STI (p=0.038), but remained unchanged in the LTI (p=0.660). The control group had no changes. These results demonstrate that the cost coefficient was successfully decreased following an alteration in the running technique towards a more anterior PFA. However, the energy consumption remained unchanged because of a simultaneous increase in rate of force generation due to a decreased contact time per step. The increased instability found during the short-term intervention and its neutralization after the long-term intervention indicates a role of motor control errors in the economy of running after acute alterations in habitual running execution.