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Background: Flatfoot (pes planus) is a postural deformity in which the arch of the foot collapses. Obesity increases the stresses applied to the foot directly, via increased bodyweight, and indirectly, via alterations to foot structure. Extrinsic and intrinsic foot muscles act as the main components of foot function. Foot posture index is a clinical tool used to quantify the degree to which a foot is pronated, neutral or supinated. Studies done have concluded that strengthening intrinsic muscles enhances dynamic support of MLA and foot stability. There is lack of literature on effectiveness of intrinsic exercise on flat foot in obese individuals, hence the present study is undertaken to assess and evaluate the effect of intrinsic foot muscle training on Foot Posture Index in obese individuals with pes planus. Methodology: This study was an experimental study where 30 obese patients were selected using convenient sampling. Pre and post treatment score of foot posture index was calculated. After that intrinsic foot muscle exercises and SFE were implemented on the subjects. Protocol (2times/day for 6weeks). Results: This study included 30 subjects consisting of 16 females and 14 males. Intra-group comparison of right leg and left leg foot posture index revealed that the FPI score scores were significantly reduced in obese individuals at sixth week from baseline (p

Background The intrinsic muscles of the foot are key contributors to foot function and are important to evaluate in lower limb disorders. Magnetic resonance imaging (MRI), provides a non-invasive option to measure muscle morphology and composition, which are primary determinants of muscle function. Ultra-high-field (7-T) magnetic resonance imaging provides sufficient signal to evaluate the morphology of the intrinsic foot muscles, and, when combined with chemical-shift sequences, measures of muscle composition can be obtained. Here we aim to provide a proof-of-concept method for measuring intrinsic foot muscle morphology and composition with high-field MRI. Methods One healthy female (age 39 years, mass 65 kg, height 1.73 m) underwent MRI. A T1-weighted VIBE – radio-frequency spoiled 3D steady state GRE – sequence of the whole foot was acquired on a Siemens 7T MAGNETOM scanner, as well as a 3T MAGNETOM Prisma scanner for comparison. A high-resolution fat/water separation image was also acquired using a 3D 2-point DIXON sequence at 7T. Coronal plane images from 3T and 7T scanners were compared. Using 3D Slicer software, regions of interest were manually contoured for each muscle on 7T images. Muscle volumes and percentage of muscle fat infiltration were calculated (muscle fat infiltration % = Fat/(Fat + Water) x100) for each muscle. Results Compared to the 3T images, the 7T images provided superior resolution, particularly at the forefoot, to facilitate segmentation of individual muscles. Muscle volumes ranged from 1.5 cm3 and 19.8 cm3, and percentage muscle fat infiltration ranged from 9.2–15.0%. Conclusions This proof-of-concept study demonstrates a feasible method of quantifying muscle morphology and composition for individual intrinsic foot muscles using advanced high-field MRI techniques. This method can be used in future studies to better understand intrinsic foot muscle morphology and composition in healthy individuals, as well as those with lower disorders.

Clinical Scenario: Deformation of the arch, as measured by navicular drop (ND), is linked to lower-extremity musculoskeletal injuries. The short foot exercise (SFE) has been used to strengthen the intrinsic foot muscles that support the arch. Clinical Question: Does the SFE decrease ND in healthy adults? Summary of Key Findings: Three studies that examined the use of the SFE on ND were included. A randomized control trial that compared the SFE to a towel-curl exercise and a control group found no significant differences between the 3 groups. A randomized control trial compared the SFE to the use of arch support insoles in individuals with a flexible flatfoot and found a significant improvement in the SFE group. A prospective cohort study, without a control group, reported a significant decrease in ND following a 4-week SFE intervention without a regression at an 8-week follow-up. Overall, two of the three studies reported a significant reduction in ND following an SFE. Clinical Bottom Line: There is preliminary data supporting the use of the SFE to decrease ND—particularly in individuals with a flexible flatfoot. However, issues with the study designs make it difficult to interpret the data. Strength of Recommendation: Due to limited evidence, there is grade B evidence to support the use of the SFE to decrease ND.

Foot stiffness is essential in enabling the ankle plantar flexors to generate large plantar flexion moments and propulsive power. During propulsion, the foot allows the plantar flexor external mome...

Purpose: The purpose of this study was to compare the morphology of the intrinsic foot muscle between typical foot and flat foot with the use ultrasound. Methods: Thirty-seven healthy participants were recruited in this study. Foot types were classified using the Foot posture index 6-item version. A total of 43 flat feet and 31 typical feet were examined. Using B-mode ultrasound imaging, the morphology of the abductor hallucis, oblique head of adductor hallucis, abductor digiti minimi, and flexor digitorum brevis muscles were measured. Morphology of all muscles measured was normalized by body height. The independent Student’s t-test was used to examine the differences in the thickness and the cross-sectional area (CSA) of the intrinsic foot muscle among the two groups. Results: The thickness of abductor hallucis was significantly larger in flat foot group. The thickness and CSA of abductor digiti minimi and the thickness of oblique head of adductor hallucis were significantly smaller in flat foot group. Conclusions: Our results showed hypertrophied adductor hallucis, atrophied abductor digiti minimi, and atrophied oblique head of the adductor hallucis in individuals with flat feet, suggesting a possible tendency to hypertrophy in muscles that are located in a medial position and a possible tendency to atrophy in muscles that are located in a lateral position in flat feet.

IntroductionPlantar fasciitis (PF) is the most common cause of heel pain.(1) This condition was described as a degenerative syndrome associated with pain, lack of functionality and stiffness on the plantar fascia. The aim of the present study was to compare with ultrasound imaging (USI) the thickness and cross-sectional area of the intrinsic foot muscles between individuals with and without plantar fasciitis (PF).Material and methodsA total of 64 volunteers from 18 to 55 years were recruited for the present study. The sample was divided in two groups: A group, composed of participants diagnosed by PF (n = 32) and B group, composed by healthy participants (n = 32).ResultsUSI measurements for FBH CSA (p = 0.035) was decreasing showing statistically significant differences for the PF group, while the QP CSA (p = 0.40) was increasing reporting statistically significant differences for the PF group with respect the healthy group. The rest of the IFM did not show statistically significant differences, however in FHB, FDB, QP and AHB thicknesses and FDB CSA a slightly decrease for the PF group have been observed.ConclusionsUSI measurements showed that the CSA of the FHB muscle is reduced in patients with PF while the CSA of the QP muscle is increased in patients with PF.

Chiu, LZF and Daehlin, TE. Midfoot and ankle mechanics in block and incline heel raise exercises. J Strength Cond Res XX(X): 000-000, 2021-Although the heel raise exercise is performed to strengthen the calf muscles, the combination of calf muscle and ground reaction forces elicits moments that may deform the foot's longitudinal arch. The primary purpose of this investigation was to examine whether the foot muscles contribute to supporting the longitudinal arch during heel raises. The secondary purpose was to compare foot and ankle mechanical efforts between traditional block vs. 22° incline heel raises. Six women and 6 men performed heel raises with body mass plus a barbell loaded with 40% (BM + 40%) and 60% (BM + 60%) of their body mass. Three-dimensional motion analysis and force platform data were collected. The midfoot joint was evaluated from the angle between the forefoot and rearfoot (i.e., arch angle) and net joint moment, which may elevate or reduce the arch height. Midfoot joint arch elevator moment seemed to be greater for BM + 60% than BM + 40% (p < 0.05; Cohen's d = 1.24-1.61), with minimal change in arch angle (p < 0.05; Cohen's d = 0.15-0.19). Midfoot joint arch elevator and ankle plantar flexor moments seemed to be greater in incline vs. block heel raises for both loads (p < 0.05; Cohen's d = 0.58-0.67). The increase in midfoot joint arch elevator moment with trivial change in arch angle supports the hypothesis that the foot muscles contribute to longitudinal arch support during heel raises. Performing incline heel raises may be hypothesized to be more effective to stimulate foot and calf muscle adaptations than block heel raises.

Background The purpose of this study was to investigate the relationship between plantar pressure distribution and the stiffness, thickness, and cross-sectional area of the plantar fascia (PF) and abductor hallucis (AbH), flexor hallucis brevis (FHB), and flexor digitorum brevis (FDB) muscles. Methods The present study included a total of 41 healthy females between the ages of 20 and 34 years. Plantar pressure during static standing position was measured using a pedobarography system (MatScan, Tekscan, Inc., South Boston, Massachusetts, USA). Peak pressure, mean pressure, maximum force (Max-F), contact area (Con-A), pressure time integral, and force time integral (FTI) were measured. The thickness, cross-sectional area and stiffness of the intrinsic foot muscles and PF were measured using an ACUSON S3000 Ultrasound System and a 9L4 probe (4–9 MHz) (Siemens Medical Solution, Mountain View, CA, USA). Shear Wave Velocity (SWV) of the intrinsic foot muscles and PF was measured using a customized software program (Virtual Touch Imaging and Quantification; Siemens Medical Solution). Results Con-A had a moderate correlation with the thickness and cross-sectional area of PF, AbH, FHB, and FDB. A fair to moderate correlation was found between heel Max-F and the thickness and cross-sectional area of PF, AbH, FHB, and FDB. There is no significant correlation between the SWV of the assessed tissues and plantar pressure distribution parameters. Body mass and BMI had a fair to good correlation with Mean-P, Con-A, heel Max-F, midfoot Max-F, metatarsal Max-F, FTI, thickness, and cross-sectional area of the PF and assessed muscles Significance The results suggest that abnormal force, contact area, and higher body mass may cause hypertrophy of the PF and foot intrinsic muscles.

AIM: The purpose of the present study was to compare and quantify with ultrasound imaging (USI) the extensor digitorum longus (EDL), tibialis anterior (TA) and peroneus muscles (PER) muscle thickness and cross-sectional area (CSA) between chronic non-insertional Achilles tendinopathy (AT) and healthy subjects. METHODS: a sample of 143 individuals was recruited and divided in two groups: chronic non-insertional AT group (n = 71) and a healthy group (n = 72). The thickness and CSA were assessment by USI for EDL, TA and PER muscles in both groups. RESULTS: The thickness evaluation for the TA muscle increased showing statistically significant differences (P = 0.018) as well as for the thickness of the PER muscles significant differences (P = 0.001) were observed in favor the tendinopathy group. The CSA measurements showed statistically significant differences for a decrease in EDL (P = 0.000), TA (P = 0.001) and PER muscles (P = 0.011) for the tendinopathy group with respect to the control group. CONCLUSIONS: The CSA of the EDL, TA and PER muscles is reduced in participants with chronic non-insertional AT. The thickness for TA muscle is increased as well as a decrease of PER muscles thickness is presented for the AT group with respect to the control group. Sin financiación 1.926 JCR (2019) Q2, 22/68 Rehabilitation, 44/85 Sport Sciences 0.721 SJR (2019) Q2, 874/2754 Medicine (miscellaneous), 99/284 Orthopedics and Sports Medicine, 53/207 Physical Therapy, Sports Therapy and Rehabilitation, 60/125 Sports Science No data IDR 2019 UEM

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.

Background: The aim of the present study was to investigate the morphologic features and mechanical properties of plantar fascia (PF), flexor hallucis brevis (FHB), flexor digitorum brevis (FDB), and abductor hallucis (AbH) muscles in individuals with halluks valgus (HV) and to compare the results with individuals without HV. Methods: A total of 30 participants (27 female, 3 male) between the ages of 19–58 years with HV deformity and 30 individuals without HV (27 female, 3 male) between the ages of 20–58 years were included in the study. AbH, PF, FHB, and FDB thickness, cross-sectional area and stiffness were measured with an ultrasonography device. For stiffness measurements, Shear Wave Velocity (SWV) of the assessed soft tissues was calculated using a customized software program. Results: Mean and standard deviation of SWV of PF, AbH, FHB, FDB, and thickness of PF, AbH, FHB, FDB, and cross-sectional area of AbH, FHB, FDB in individuals with HV were 7.6 ± 1.0 m/sec, 2.8 ± 0.3 m/sec, 2.6 ± 0.4 m/sec, and 3.4 ± 0.2 m/sec, 3.3 ± 0.5 mm, 11.4 ± 2.2 mm, 16.5 ± 1.9 mm, 8.9 ± 1.8 mm, 2.4 ± 0.5 cm2, 2.7 ± 0.5 cm2, 1.9 ± 0.6 cm2, respectively. Mean and standard deviation of SWV of PF, AbH, FHB, FDB and thickness of PF, AbH, FHB, FDB, and cross-sectional area of AbH, FHB, FDB in controls groups were 7.6 ± 1.2 m/sec, 2.3 ± 0.3 m/sec, 2.3 ± 0.4 m/sec, and 3.4 ± 0.4 m/sec, 3.3 ± 0.5 mm, 9.7 ± 2.1 mm, 14.5 ± 1.4 mm, 9.7 ± 1.2 mm, 2.1 ± 0.3 cm2, 2.3 ± 0.4 cm2, 2.1 ± 0.4 cm2, respectively. Individuals with HV had lower AbH and FHB thickness, cross-sectional area and SWV, however FDB thickness and cross-sectional area were higher in individuals with HV compared to that of individuals without HV (p

Background Strengthening exercises of the plantar intrinsic foot muscles (PIFMs) are often prescribed to flat-footed subjects because of the capacity of the PIFMs to support the medial longitudinal arch (MLA). However, it is unclear whether the capacity of the PIFMs to support the MLA is enough to change the foot kinematics in flat-footed subjects. To confirm this, the current study examined changes in foot kinematics in flat-footed subjects during standing and gait accompanied by changes in the activity of the PIFMs. Methods Eighteen flat-footed subjects were randomly assigned to an electrical stimulation group (ESG) or a control group (CG). In the ESG, electrical stimulation to the PIFMs was applied during standing and gait to simulate reinforcement of the PIFMs. Then, foot kinematics were measured using 3D motion analysis, and the amount of change from baseline (when no electrical stimulation was applied) was compared between the groups. Results In the gait analysis, the time at which the MLA height reached its minimum value was significantly later in the ESG, with no reduction in the MLA height at that time. Moreover, forefoot inversion angle and tibial external rotation angle were significantly increased in the ESG at that time. In the standing analysis, there were no significant differences between the groups. Conclusion The results revealed that in flat-footed subjects, the PIFMs have the capacity to support the MLA enough to change foot kinematics during gait. Strengthening these muscles may be effective in preventing or treating lower extremity overuse injuries related to flat-foot alignment.

Background/Aims: The medial longitudinal arch of the foot is supported by both active and passive systems. Focusing on the active system by strengthening the intrinsic and extrinsic foot muscles and its effect on the foot parameters in pregnant women has been underresearched. Methods: A total of 86 primigravidae (women who were pregnant for the first time) were recruited at the 18th week of gestation. The control group received routine antenatal exercises and the study group received intrinsic and extrinsic foot exercises along with the routine antenatal exercises. The outcome measures evaluated were foot parameters and foot dysfunctions, which were reassessed at the 24th and 32nd week of gestation. Results: The results suggested that there was a significant difference between the study group and control group in terms of foot width, navicular height, truncated foot length and normalised navicular height truncated, which indicated that there was a significant drop in the arch of the foot (pronation) in the control group compared to the study group (P=Conclusions: A comprehensive foot exercise programme was found to be effective in reducing the drop in arch height and also in preventing foot dysfunctions in pregnant women.

Weakness of foot muscles may contribute to a variety of loading-related injuries. Supportive footwear may contribute to intrinsic foot muscle weakness by reducing the muscles' role in locomotion (e.g., absorbing forces and controlling motion). Increased stimulus to the foot muscles can be provided through a variety of mechanisms, including minimalist footwear and directed exercise.To determine the effect of walking in minimalist footwear or performing foot strengthening exercises on foot muscle size and strength.Fifty-seven runners were randomly assigned to one of three groups-minimalist shoe walking (MSW), foot strengthening (FS) exercise, or control (C). All groups maintained their prestudy running mileage throughout the study. The MSW group walked in provided footwear, increasing weekly the number of steps per day taken in the shoes. The FS group performed a set of progressive resistance exercises at least 5 d·wk. Foot muscle strength (via custom dynamometers) and size (via ultrasound) were measured at the beginning (week 0), middle (week 4), and end (week 8) of the study. Mixed model ANOVA were run to determine if the interventions had differing effects on the groups.There were significant group-time interactions for all muscle size and strength measurements. All muscle sizes and strength increased significantly from weeks 0 to 8 in the FS and MSW groups, whereas there were no changes in the C group. Some muscles increased in size by week 4 in the FS and MSW groups.Minimalist shoe walking is as effective as foot strengthening exercises in increasing foot muscle size and strength. The convenience of changing footwear rather than performing specific exercises may result in greater compliance.

The human foot is uniquely stiff to enable forward propulsion, yet also possesses sufficient elasticity to act as an energy store, recycling mechanical energy during locomotion. Historically, this dichotomous function has been attributed to the passive contribution of the plantar aponeurosis. However, recent evidence highlights the potential for muscles to modulate the energetic function of the foot actively. Here, we test the hypothesis that the central nervous system can actively control the foot’s energetic function, via activation of the muscles within the foot’s longitudinal arch. We used a custom-built loading apparatus to deliver cyclical loads to human feet in vivo, to deform the arch in a manner similar to that observed in locomotion. We recorded foot motion and forces, alongside muscle activation and ultrasound images from flexor digitorum brevis (FDB), an intrinsic foot muscle that spans the arch. When active, the FDB muscle fascicles contracted in an isometric manner, facilitating elastic energy storage in the tendon, in addition to the energy stored within the plantar aponeurosis. We propose that the human foot is akin to an active suspension system for the human body, with mechanical and energetic properties that can be actively controlled by the central nervous system. NEW & NOTEWORTHY The human foot is renowned for its ability to recycle mechanical energy during locomotion, contributing up to 17% of the energy required to power a stride. This mechanism has long been considered passive in nature, facilitated by the elastic ligaments within the arch of the foot. In this paper, we present the first direct evidence that the intrinsic foot muscles also contribute to elastic energy storage and return within the human foot. Isometric contraction of the flexor digitorum brevis muscle tissue facilitates tendon stretch and recoil during controlled loading of the foot. The significance of these muscles has been greatly debated by evolutionary biologists seeking to understand the origins of upright posture and gait, as well as applied and clinical scientists. The data we present here show a potential function for these muscles in contributing to the energetic function of the human foot.

We recently developed an approach for recording from muscle spindles in the intrinsic muscles of the foot in freestanding humans by inserting a tungsten microelectrode into the posterior tibial nerve behind the medial malleolus of the ankle. Here we characterize the behavior of muscle spindles in the small muscles of the foot in 1) seated subjects with the leg horizontal and the foot naturally plantarflexed and 2) standing subjects. In the first study, recordings were made from 26 muscle spindle afferents located within flexor digiti minimi brevis ( n = 4), abductor digiti minimi ( n = 3), quadratus plantae ( n = 3), plantar interossei ( n = 4), flexor digitorum brevis ( n = 3), dorsal interossei ( n = 2), and lumbricals ( n = 2), with one each supplying abductor hallucis, adductor hallucis, and flexor hallucis brevis. The identity of another two muscle afferents was unknown. The majority of the units were silent at rest, only seven (27%) being spontaneously active. Because of the anatomic constraints of the foot, some spindles supplying muscles acting on the toes responded to movements of one or more digits. In the second study, 12 muscle spindle afferents were examined during standing. The ongoing discharge of eight spindle afferents covaried with changes in the center of pressure during postural sway. We conclude that the majority of spindle endings in the small muscles of the foot are silent at rest, which may allow them to encode changes in conformation of the foot when it is loaded during standing. Moreover, these muscle spindle afferents can provide useful proprioceptive information during standing and postural sway. NEW & NOTEWORTHY We have characterized the firing properties of muscle spindles in the intrinsic muscles of the human foot for the first time. The majority of the spindle endings are silent in seated subjects, and most fire tonically during standing, their discharge covarying with center of pressure during postural sway. We conclude that spindle endings in the intrinsic muscles of the foot provide useful proprioceptive information during free standing.

The plantar fascia and intrinsic foot muscles (IFM) modulate foot stiffness. However, it is unclear whether the corresponding ultrasonography findings reflect it. This study aimed to examine the effect of the plantar fascia and IFM morphologies on force attenuation during landing and reactivity when jumping in healthy adults (n = 21, age, 21–27 years). Thickness, cross-sectional area (CSA), and hardness of the plantar fascia, abductor hallucis (AbH), and flexor hallucis brevis (FHB) muscles were measured using ultrasonography. Single-leg drop landing and repetitive rebound jumping tests assessed the ground reaction force (GRF) and reactive jump index (RJI), respectively. The CSA of FHB was negatively correlated with maximum vertical GRF (r = −0.472, p = 0.031) in the single-leg drop landing test. The CSA of AbH was negatively correlated with contact time (r = −0.478, p = 0.028), and the plantar fascia thickness was positively correlated with jump height (r = 0.615, p = 0.003) and RJI (r = 0.645, p = 0.002) in the repetitive bound jump test. In multivariate regression analysis, only the plantar fascia thickness was associated with RJI (β = 0.152, 95% confidence interval: 7.219–38.743, p = 0.007). The CSA of FHB may contribute to force attenuation during landing. The thickness of the plantar fascia and CSA of AbH may facilitate jumping high with minimal contact time.

The extrinsic foot muscles are essentially for controlling the movement path but our knowledge of their behavior during prolonged running is still very limited. Therefore, this study analyzed the time-course of muscle activation using T2 mapping during 75 min of running. In this prospective study, 19 recreational active runners completed 75 min of treadmill running at a constant speed. Interleaved T2 mapping sequences were acquired and segmented at timepoints 0, 2.5, 5, 10, 15, 45, and 75 min. ANOVA for repeated measurements followed by a Tukey post hoc test and Pearson correlation between running speed and initial signal increase at 2.5 min were calculated. All muscles showed a significant signal increase between baseline and 2.5 min (e.g. medial gastrocnemius: + 15.48%; p p p = 0.0104) and soleus (r = − 0.47, p = 0.0412). The decrease of relaxation times times in the later running phases was less pronounced for faster runners (≥ 10 km/h). T2 relaxation times do not only decrease after cessation of exercise but already during prolonged running. The lesser initial increase and later decrease in faster runners may indicate training induced changes.

This study determined the strength training (ST) habits of amateur endurance runners in Spain regarding athletic level. A sixteen-item online questionnaire comprised of (i) demographic information, (ii) performance, and (iii) training contents was completed by 1179 athletes. Five group levels were determined according to the personal best times of the athletes in a 10-km trial (LG1: level group 1, 50&ndash, 55 min, LG2: level group 2, 45&ndash, 50 min, LG3: level group 3, 40&ndash, 45 min, LG4: level group 4, 35&ndash, 40 min, LG5: level group 5, 30&ndash, 35 min). Most athletes (n = 735, 62.3%) perceived ST as being a key component in their training program. Resistance training (RT) was reported as a ST type used by 63.4% of the athletes, 66.9% reported using bodyweight exercises, 46.8% reported using plyometric training, 65.6% reported using uphill runs, and 17.8% reported using resisted runs. The prevalence of runners who excluded ST from their training programs decreased as the athletic performance level increased (18.2% in lower-level athletes vs. 3.0% in higher-level), while the inclusion of RT, bodyweight exercises, plyometric training, and uphill and resisted runs was more frequent within higher-level groups. Most athletes included ST using low-to-moderate loads and high a number of repetitions/sets comprised of RT, plyometric training, resisted runs, and core, respiratory, and foot muscles training.

We aimed to compare the degree of pes planovalgus and muscle mass of the ankle joint and foot muscles between children with Down syndrome (DS) and children with typical development (TD). We also examined the association of the degree of pes planovalgus with muscle mass of the ankle joint and foot muscles in children with DS and children with TD. The subjects were 24 children with TD (control [CTR] group) and 23 children with DS (DS group). To assess pes planovalgus, the Arch Height Index (AHI) in the standing position was measured. Muscle thickness of the ankle joint and foot muscles was measured using an ultrasound imaging device. The AHI and thickness of the soleus and tibialis posterior muscles were significantly lower in the DS group than those in the CTR group. The thickness of the flexor digitorum longus muscle was significantly greater in the DS group than that in the CTR group. Stepwise regression analysis revealed that the thickness of the flexor digitorum longus muscle was a significant and independent factor of the AHI in children comprising the CTR and DS groups. The thickness of the flexor digitorum longus muscle increased with decreasing AHI. The results of this study suggest that the AHI and muscle mass of the soleus and tibialis posterior muscles decrease, while muscle mass of the flexor digitorum longus muscle increases in children with DS. The results also indicate that decreased AHI is associated with increased muscle mass of the flexor digitorum longus muscle in children.

Background: In recent years, a three-dimensional ankle exercise has been proposed as a practice for strengthening the intrinsic foot muscles, however this topic still requires further research. This study aimed to compare the activities of the intrinsic muscles in healthy participants during 3D foot&ndash, ankle exercises, namely, short foot (SF), and toe spread out (TSO). Methods: Prior to the experiment, 16 healthy adults were trained on how to perform SF, TSO, and 3D foot&ndash, ankle exercises for an hour. Once all participants passed the foot&ndash, ankle exercise performance test, we randomly measured the activity of the intrinsic foot muscles using electromyography while the patients were performing foot&ndash, ankle exercises. Results: The abductor hallucis (AbH), extensor hallucis longus (EHL), and flexor hallucis brevis (FHB) activities showed significant differences among the exercises for intrinsic foot muscle strengthening (p &lt, 0.01). Additionally, the AbH/AdH (adductor hallucis) ratio showed significant differences among the exercises for strengthening the intrinsic foot muscles (p &lt, 0.01). Conclusions: Our results showed that the 3D extension exercise is as effective as the therapeutic exercise in terms of the AbH and FHB activities, and the AbH/AdH ratio. On the contrary, the 3D flexion exercise showed superiority in terms of the EHL activity.

Background: Intrinsic foot muscles are the contributors in the medial longitudinal arch and weakness of these muscle contributes to range of foot deformities but the level of weakness is still unknown as there is no valid and reliable method available to measure the strength of these muscles. Previous efforts to quantify these muscle strengths were done like toe dynamometry, planter pressure etc. All such instruments made do not consider two major biomechanical consideration 1. Position of Metatarsophalangeal Joint and 2. Position of Ankle joint which is very important for keeping extrinsic foot muscle in disadvantage and no effort was made to isolate the intrinsic muscle during measurement Methods: The present prototype is designed to measure the forces of the planter intrinsic foot muscles for research and clinical purposes All the considerations which was not taking care of in previous design considered in the present design of our prototype. Conclusion: Our device is one stop destination for the assessment and treatment of planter intrinsic muscle where we can measure their strength and also strengthen them on the same platform by various exercises and strengthening and therapeutic devices.

© 2020 The Author(s) Background: Increased postural balance challenge is associated with more fluctuations in centre of pressure movement, indicating increased interference from the postural control system. The role of intrinsic foot muscles in balance control is relatively understudied and whether such control system interference occurs at the level of these muscles is unknown. Research Question: Do fewer fluctuations in intrinsic foot muscle excitation occur in response to increased postural balance challenge? Methods: Surface EMGs were recorded using a grid of 13 × 5 channels from the plantar surface of the foot of 17 participants, who completed three balance tasks: bipedal stance; single leg stance and bipedal tip-toe. Centre of pressure (CoP) movement was calculated from simultaneously recorded force plate signals. Fluctuations in CoP and EMGs for each task were quantified using a sample entropy based metric, Entropy Halflife (EnHL). Longer EnHL indicates fewer signal fluctuations. Results: The shortest EMG EnHL, 9.27 ± 3.34 ms (median ± interquartile range), occurred during bipedal stance and the longest during bipedal tip-toe 15.46 ± 11.16 ms, with 18.80 ± 8.00 ms recorded for single leg stance. Differences were statistically significant between bipedal stance and both bipedal tip-toe (p < 0.001) and single leg stance (p < 0.001). CoP EnHL for both anterior-posterior and medial-lateral movements also differed significantly between tasks (p < 0.001, both cases). However, anterior-posterior CoP EnHL was longest for bipedal stance 259.84±230.22 ms and shortest for bipedal tip-toe 146.25±73.35 ms. Medial-lateral CoP EnHL was also longest during bipedal stance 215.73±187.58 ms, but shortest for single leg stance 113.48±83.01 ms. Significance: Fewer fluctuations in intrinsic foot muscle excitation occur in response to increased postural balance challenge. Fluctuations in CoP movement during balance must be predominantly driven by excitation of muscles extrinsic to the foot. Intrinsic foot muscles therefore likely play a greater role in stabilisation of the foot than balance control during the postural tasks studied.

Plantar Fasciopathy (PF) is soreness or irritability experienced underneath infero-medial aspect of the heel. It is a multifactorial disorder where myofascial involvement also seems to be associated with it, in which, muscles of posterior thigh, leg and foot muscles are affected. Trigger points in these muscles may interfere with biomechanics and normal functioning of the lower limb.To find an association between trigger points of the posterior thigh, leg and foot muscles and plantar fasciopathy.A cross sectional study.100 patients with plantar fasciopathy who fulfilled inclusion criteria were included in this study. They were examined for trigger points by manual palpation in posterior thigh, leg and foot muscles. Totally 15 muscles were examined on both affected and unaffected side.Results showed that myofascial trigger points were more prevalent in medial gastrocnemius (98%, Chi-square: 110.07, p 0.05, Phi-0.74), quadratus plantae (83%, Chi-square:126.96, p 0.05, Phi- 0.79), soleus (69%, Chi-square: 28.88, p 0.05, Phi-0.38), tibialis posterior (46%, Chi-square 41.98 p0.05%, Phi-0.50), abductor hallucis (42%, Chi-square: 43.61 p0.05% Phi-0.46), flexor halluces longus (41%, Chisquare: 39.25, p 0.05, Phi-0.44) than other muscles on the affected side. Whereas, on the unaffected side, trigger points were more prevalent among peroneus longus (50%, Chi-square: 26.14, p 0.05, Phi-0.36) followed by medial gastrocnemius (26%, Chisquare: 110.07, p 0.05, Phi-0.74).Plantar fasciopathy is strongly associated with trigger points of medial gastrocnemius, quadratus plantae followed by soleus, tibialis posterior, abductor hallucis and flexor hallucis longus.

BackgroundAutism spectrum disorders (ASDs) fall under neurodevelopmental disorders and are characterized by impaired social interaction and communication, restricted interests, and repetitive behaviors. The current available treatments aim at functional rehabilitation with resultant partial improvement in few and the persistent handicap in rest of them. Manual physical therapy or manual manipulation therapy has the basis in structural rehabilitation of the patient and has been proposed to act by both peripheral and central mechanisms.Case presentationTo study improvement in different components of ASD by manual physical therapy, the therapy comprised of soft tissue therapy, in the form of myofascial release (MFR) of deep fascia of leg and foot muscles. The child with ASD, treated by manual physical therapy had global improvement in all the deficits.ConclusionsThis is probably first case of autism reported to have almost complete symptom resolution, with any single form of treatment and this form of therapy holds promise in integrative and holistic management of the patient.

The important function of the intrinsic foot muscles is the dynamic stabilization of the medial longitudinal arch (MLA). Several studies have reported that implementing short foot exercise (SFE) and electrical stimulation (ES) amid the intrinsic foot muscles may increase MLA height. Hence, the aim of this study was to compare the effects of ES versus SFE on navicular drop (ND), calcaneal pitch angle (CPA), and cross sectional area (CSA) of the abductor hallucis (AbdH) muscle. 20 healthy female subjects were randomly assigned to undergo ES (n=10) or SFE (n=10). SFE performed 30 repetitions whereas 20 min per day for ES, 3 days/week, for 4 weeks. ND, CPA, and the CSA of the AbdH muscle were assessed before and after intervention. The results showed that ES group significantly decreased in ND after training (p0.05). The CSA of the AbdH muscle in both groups was increased (ES =10.93 mm2 and SFE=7.44 mm2 ; p

We studied the effects of repeated injections of methylprednisolone and its micellar complex with block-copolymer on locomotor activity of a terrestrial snail. It was shown that methylprednisolone solution injected into the hemolymph of the animal produced a direct effect on the muscle system of the animal as soon as 1 h after administration: it slowed down snail locomotion and reduced contractile activity of the foot muscles. The micellar complex of methylprednisolone with block-copolymer prevented this effect during the first 2 days of injection and negatively affected locomotion only in 2 days after injection, the decrease in locomotion in this case was not accompanied by a decrease in contractile activity of the foot muscle.

Willwacher, S, Fischer, KM, Rohr, E, Trudeau, MB, Hamill, J, and Bruggemann, G-P. Surface stiffness and footwear affect the loading stimulus for lower extremity muscles when running. J Strength Cond Res XX(X): 000-000, 2020-Running in minimal footwear or barefoot can improve foot muscle strength. Muscles spanning the foot and ankle joints have the potential to improve performance and to reduce overuse injury risk. Surface stiffness or footwear use could modify the intensity of training stimuli acting on lower extremity joints during running. The purpose of this study was to systematically investigate external ankle, knee, and hip joint moments during shod and barefoot running while considering the stiffness of the running surface. Two footwear conditions (barefoot and neutral running shoe) and 4 surface conditions (Tartan, Tartan + Ethylene Vinyl Acetate [EVA] foam, Tartan + artificial turf, Tartan + EVA foam + artificial turf) were tested at 3.5 m·s. Repeated measures analysis of variance revealed that barefoot running in general and running barefoot on harder surfaces increased and decreased ankle (between +5 and +26%) and knee (between 0 and -11%) joint moments, respectively. Averaged over all surfaces, running barefoot was characterized by a 6.8° more plantarflexed foot strike pattern compared with running shod. Foot strike patterns were more plantarflexed on harder surfaces; the effects, however, were less than 3°. Most surface effects were stronger in barefoot compared with shod running. Surface stiffness may be used to modulate the loading intensity of lower extremity muscles (in particular extrinsic and intrinsic foot muscles) during running. These results need to be considered when coaches advise barefoot running as a method to improve the strength of extrinsic and intrinsic foot muscles or when trying to reduce knee joint loading.

Human legs operate like springs with adjustable stiffness during locomotion, improving movement economy and versatility. The potential for the foot to contribute to this spring-like mechanism has been established. However, due to previous modelling approaches assuming a rigid-foot segment, it is unknown if ankle and foot quasi-stiffness can be actively regulated, quasi-stiffness being a measure of joint deformation under an applied load. In this study, we sought to determine if midfoot quasi-stiffness was increased in a similar manner as the ankle with increasing load demands, and if these changes were mediated by increased activation of the intrinsic foot muscles. We also quantified differences in measures of ankle joint quasi-stiffness attributable to the modelling assumption of a rigid-foot segment versus a multi-segment foot. Twenty-two healthy individuals performed a single-leg hopping task at three frequencies (2.0 Hz, 2.3 Hz, and 2.6 Hz) while measuring lower limb kinematics, kinetics and muscle activation (EMG). Kinetics and kinematics were calculated at the midfoot and using two different ankle models: rigid-foot model (shank-foot) and an anatomical ankle (shank-calcaneus). Midfoot quasi-stiffness increased with hopping-frequency (p < 0.05), while contact phase intrinsic foot muscle activation decreased (p < 0.05). The assumption of a rigid-foot model overestimated ankle ROM by ∼10° and underestimated ankle quasi-stiffness by 45-60%. This study demonstrates that midfoot quasi-stiffness increases with hopping-frequency; however, the mechanism for these changes remains unclear. Furthermore, this study demonstrates the need to assess the ankle and foot independently, using appropriate models, to avoid significant inaccuracies in basic ankle kinematic and kinetic outputs, such as range of motion and joint quasi-stiffness.

Background. Tracking progression of diabetic peripheral polyneuropathy (DPN) is usually focused on sensory nerves and subjective testing methods. Recent studies have suggested that distal muscle atrophy may precede sensation loss. Methods to objectively measure distal muscle size and strength are needed to help understand how neuropathy affects muscle function. Purpose. To evaluate individual intrinsic and extrinsic foot muscle sizes and functional foot strength in participants with DPN. Methods. Thirty individuals participated in this cross-sectional study (15 DPN and 15 matched controls). Sizes of 10 separate muscles of the lower leg and foot were measured using ultrasound imaging. Functional foot strength was also quantified using custom great toe and lateral toe flexion tests along with a doming test. Muscle size and strength metrics were compared between groups using ANOVAs and paired t-tests (α=0.05). Correlations between strength and relevant muscle sizes were also evaluated. Results. The sizes of all four intrinsic foot muscles were smaller in individuals with DPN (p≤0.03), while only one (toe extensor) of the six extrinsic muscles was smaller (p<0.01). Great toe flexion (p=0.03) and lateral toe flexion (p<0.01) strengths were decreased between groups and showed moderate to strong correlations (0.43≤r≤0.80) with several corresponding intrinsic muscle sizes. The doming strength test did not show any difference between groups and was moderately correlated with one muscle size (r=0.59). Conclusion. Diabetic peripheral polyneuropathy affects intrinsic muscles before extrinsics. Ultrasound imaging of individual muscles and functional toe flexion tests can be used clinically to monitor DPN progression and foot function. Participants need to be trained in the doming test before a relationship can be established between this test and DPN foot function. Future studies should include muscle quality measurements to better understand characteristics of affected muscles.

Quadratus plantae (QP), one of the plantar intrinsic foot muscles, assist plantarflexion of the lesser toes. QP has medial and lateral muscle heads with different anatomical structures. The two heads of this muscle may have different roles in foot function. Ultrasound real-time tissue elastography (RTE) measurements have allowed quantitative assessment of deep-layer muscle elasticity. The purpose of this study was to determine the activity of the QP in flexion movements of the lateral four toes using RTE. Thirteen healthy subjects performed maximal voluntary contractions using a hand-held dynamometer with external belt fixation for each toe flexion movement. The elasticity of the muscles were measured using RTE during rest and flexion of each toe. The strain ratio of the muscle to that in an acoustic coupler was calculated as an index of muscle elasticity. Higher strain ratio values imply lower elasticity. The strain ratio of the medial head of QP for second toe flexion (0.10 ± 0.11) was significantly stiffer than at rest (0.34 ± 0.33). The strain ratios of the lateral head of QP for flexion of the second (0.32 ± 0.19), third (0.41 ± 0.37), fourth (0.33 ± 0.26), and fifth (0.45 ± 0.39) toes were significantly stiffer than at rest (1.02 ± 0.68). These results suggest that the medial head of QP has a role in assisting second-toe flexion, and the lateral head has a role in assisting flexion of all four lateral toes.

Toe flexor strength is important for preventing older adults from falling. Although intrinsic foot muscles are the main determinants of toe flexor strength, exercises for strengthening these muscles are difficult for older adults. This study therefore aimed to determine whether the use of electromyographic biofeedback helps older adults to perform intrinsic foot muscle strengthening exercises.This randomized controlled trial had two parallel arms. Participants were randomly allocated to the control group or the electromyographic biofeedback group. Control participants performed two progressive intrinsic foot muscle strengthening exercises twice a week for 6 weeks. Participants in the other group performed these exercises assisted by electromyographic biofeedback. Primary outcome measures were changes in toe flexor strength and the timed up-and-go and functional reach tests (the latter two being balance tests).Altogether, 23 older adults were randomized to the control group (n = 12) or the electromyographic biofeedback group (n = 11). After the 6-week intervention, toe flexor strength on the dominant side increased in both groups (P 0.017). However, toe flexor strength on the nondominant side increased only in the electromyographic biofeedback group (P 0.017), with a large effect size of 1.5. There were no changes in the two balance tests. Three of the control group and two of the electromyographic biofeedback group were lost to follow- up.Our results indicate that, the use of electromyographic biofeedback can enhance the effect of intrinsic foot muscle strengthening exercises on the nondominant side in older adults.UMIN000036521.

OBJECTIVES: To determine the differences in the morphology of foot soft tissues between runners using different types of running shoes. DESIGN: Cross-sectional study. METHODS: Thirty-eight recreational runners were divided into four groups based on running shoe type, namely, neutral shoes, motion control shoes, minimalistic shoes and neutral shoes with custom-made insoles. An arch height index and a relative arch deformation index were calculated for each participant. An ultrasound device was used to measure the cross-sectional area and/or the thickness of selected intrinsic foot muscles (abductor hallucis, flexor hallucis brevis and flexor digitorum brevis) and extrinsic foot muscles (flexor digitorum longus, tibialis anterior and the peroneus muscles), and the thickness of the plantar fascia, Achilles tendon and heel pad. RESULTS: Recreational runners using minimalistic shoes demonstrated stiffer foot arches than those using neutral shoes. Among the selected foot muscles, only abductor hallucis showed a significant morphological difference between shoe groups. Runners using minimalistic shoes had the thickest abductor hallucis. The minimalistic shoe runners also showed a thinner proximal plantar fascia and a thicker Achilles tendon than other runners. Insole runners had a thinner heel pad than neutral shoe runners. CONCLUSIONS: This study suggests that the morphology of foot soft tissues is associated with running shoe type in recreational runners. A sudden change in running shoe type without adjusting training volume should be undertaken with caution, since it may take time for foot soft tissues to adapt to a new shoe condition. ispartof: Journal of Science and Medicine in Sport vol:21 issue:7 pages:686-690 ispartof: location:Australia status: published

Background The plantar intrinsic foot muscles (PIFMs) contribute to support the medial longitudinal arch. But the functional role of the PIFMs during dynamic activities is not clear. The purpose of this study was to examine the change in the foot dynamics during gait accompanied with the change in the PIFMs activity to determine the functional role of the PIFMs during gait. Methods Twenty healthy male subjects were randomly assigned to the electrical stimulation group (ESG) or control group (CG). In the ESG, the electrical stimulation to the PIFMs was provided from mid-stance to pre-swing using surface electrodes to simulate reinforcement of the PIFMs. The foot dynamics during the stance phase of gait was measured using a 3D motion analysis, and the amount of change from baseline (electrical stimulation was not provided) was compared between groups using an independent sample t-test. Results In the ESG, the timing for the navicular height to reach the minimum value was significantly later, and the vertical ground reaction force (2nd peak) significantly decreased more. There were no group differences in the amount of change from baseline on gait velocity, stance phase duration, minimum navicular height and ground reaction force in other directions. Conclusion Results from this study showed that the functions of the PIFMs most likely include shock absorption and facilitation of efficient foot ground force transmission during the stance phase of gait.

[Purpose] Few studies on the transverse arch (TA) in the forefoot have been conducted. The forefoot is where pains occur most frequently and is related to walking and balance; hence, paying attention to TA is vital. However, the relationship between TA and foot muscles has not been investigated. Therefore, this study aims to investigate muscles related to TA. [Subjects and Methods] Nineteen healthy young males were included. Measurements of their feet, excluding one foot with recent foot pain (n=37), were obtained. The height of TA (TAH) was measured in two ways: during 10% and 90% loading of body weight. The cross-sectional area and thickness of five muscles were measured: flexor digitorum longus, peroneus longus and brevis, flexor hallucis brevis, flexor digitorum brevis (FDB) and abductor hallucis (ABH). All measurements were performed with an ultrasound device. [Results] FDB and ABH were correlated with TAH during 10% and 90% loading after removing the effect of body mass index and age. The greater FDB and ABH, the higher TAH. [Conclusion] As FDB becomes larger, the second, third and fourth metatarsal heads are raised more. Furthermore, the height of the first metatarsal head is lowered by a larger ABH. These mechanisms may increase TAH.

Bozer, Cuneyt (Trakya author) Donmez, Didem Parlak, Muhammed Introduction: The communicating branches between the medial (MPN) and lateral (LPN) plantar nerves aren't frequently observed in relation to the innervation of the foot muscles in previous studies. In this study, the number and localization of the communicating branch on the innervations of foot muscles were evaluated to open a new sight considering the innervations of lumbrical muscles. Material and methods: 30 formalin-fixed feet (15 right-15 left feet), with an average age of 76 from the inventory of Trakya and Mersin University Anatomy Departments in 2015 were dissected. The innervations of the lumbricals and the communicating branches were revealed and then photographed. Results: In all feet, first lumbricals were observed to be innervated by MPN, while the remaining muscles were innervated by deep branches of LPN. In four cadaveric feet, communicating branches of MPN, LPN and deep branch of LPN were appeared but, in one of them, proximal to the branches of MPN and LPN to lumbricals, a communicating branch between MPN and deep branch of LPN were observed. Discussion: Data about the innervations of the lumbricals were found to be consistent with the previous studies. Taking into account the localization of the communicating branches between the MPN and LPN, it should be considered that nerve injuries during surgical procedures such as flexor tendon transfers, island flap surgery, treatment of hallux valgus or lesser toes deformity in the foot and ankle region may unexpectedly lead to different functional failures. (C) 2018 Anatomical Society of India. Published by Elsevier, a division of RELX India, Pvt. Ltd. All rights reserved.

Maintaining balance is vitally important in everyday life. Investigating the effects of individual foot muscle morphology on balance may provide insights into neuromuscular balance control mechanisms. This study aimed to examine the correlation between the morphology of foot muscles and balance performance during single-leg standing. Twenty-eight recreational runners were recruited in this study. An ultrasound device was used to measure the thickness and cross-sectional area of three intrinsic foot muscles (abductor hallucis, flexor digitorum brevis and quadratus plantae) and peroneus muscles. Participants were required to perform 30s of single-leg standing for three trials on a force plate, which was used to record the center of pressure (COP). The standard deviation of the amplitude and ellipse area of the COP were calculated. In addition, stabilogram diffusion analysis (SDA) was performed on COP data. Pearson correlation coefficients were computed to examine the correlation between foot muscle morphology and traditional COP parameters as well as with SDA parameters. Our results showed that larger abductor hallucis correlated to smaller COP sway, while larger peroneus muscles correlated to larger COP sway during single-leg standing. Larger abductor hallucis also benefited open-loop dynamic stability, as well as supported a more efficient transfer from open-loop to closed loop control mechanisms. These results suggest that the morphology of foot muscles plays an important role in balance performance, and that strengthening the intrinsic foot muscles may be an effective way to improve balance.

Previous data indicate that a strong sensory input from orally administered TRPV1 and TRPA1 activators alleviates muscle cramps in foot muscles by reducing the α-motor neuron hyperexcitability. We investigated if TRP activators increase the cramp threshold frequency of the medial gastrocnemius. We randomly assigned 22 healthy male participants to an intervention (IG) and a control group (CG). While participants of the IG ingested a mixture of TRPV1 and TRPA1 activators, the CG received a placebo. We tested the cramp threshold frequency (CTF), the cramp intensity (EMG activity), and the perceived pain of electrically induced muscle cramps before (pre), and 15 min, 4, 8, and 24 h after either treatment. We further measured the maximal isometric force of knee extensors at pre, 4, and 24 h to assess potential side-effects on the force output. When we included all measurement time points, no group-by-time interaction was observed for the CTF. However, when only pre and 15 min values were incorporated, a significant interaction, with a slightly greater CTF increase in IG (3.1 ± 1.5) compared to the CG (2.0 ± 1.5), was observed. No significant group by time interaction was found for the cramp intensity, the perceived pain, and the maximal isometric force. Our data indicate that orally administered TRPV1 and TRPA1 activators exert a small short-term effect on the CTF, but not on the other parameters tested. Future studies need to investigate whether such small CTF increments are sufficient to prevent exercise-associated muscle cramps.

[Purpose] There are no reliable evidences that the weakening of intrinsic foot muscles causes the decrease of the medial longitudinal arch (MLA) height. The purpose of this study was to confirm whether the fatigue of intrinsic foot muscles decrease the MLA height during standing and gait using 3D motion analysis system. [Subjects and Methods] Twenty healthy male subjects participated in this study. Foot kinematics was measured using an Oxford Foot Model before and after fatigue-inducing exercises of the abductor hallucis and flexor hallucis brevis muscles. [Results] Following fatigue-inducing exercise, in both standing and gait, the MLA height did not decrease but slightly increased. In addition, the reduction of a rear foot eversion angle was noted. [Conclusion] Fatigue of the abductor hallucis and flexor hallucis brevis muscles did not cause a change associated with collapsing of the MLA during both standing and gait. This suggested that the MLA support force from these muscles would be compensated by other MLA support structures, such as extrinsic foot muscles.

The foot is a complex system with multiple degrees of freedom that play an essential role in running or sprinting. The intrinsic foot muscles (IFM) are the main local stabilizers of the foot and are part of the active and neural subsystems that constitute the foot core. These muscles lengthen eccentrically during the stance phase of running before shortening at the propulsion phase, as the arch recoils in parallel to the plantar fascia. They play a key role in supporting the medial longitudinal arch, providing flexibility, stability and shock absorption to the foot, whilst partially controlling pronation. Much of the foot rigidity in late stance has been attributed to the windlass mechanism - the dorsiflexion of the toes building tension up in the plantar aponeurosis and stiffening the foot. In addition, recent studies have shown that the IFM provide a necessary active contribution in late stance, in order to develop sufficient impedance in the metatarsal-phalangeal joints. This in turn facilitates the propulsive forces at push-off. These factors support the critical role of the foot in providing rigidity and an efficient lever at push-off. During running or sprinting, athletes need to generate and maintain the highest (linear) running velocity during a single effort in a sprinting lane. Acceleration and sprinting performance requires forces to be transmitted efficiently to the ground. It may be of particular interest to strengthen foot muscles to maintain and improve an optimal capacity to generate and absorb these forces. The current evidence supports multiple exercises to achieve higher strength in the foot, such as the "short foot exercise," doming, toes curl, towing exercises or the more dynamic hopping exercises, or even barefoot running. Their real impact on foot muscle strength remains unclear and data related to its assessment remains scarce, despite a recognized need for this, especially before and after a strengthening intervention. It would be optimal to be able to assess it. In this article, we aim to provide the track and field community with an updated review on the current modalities available for foot strength assessment and training. We present recommendations for the incorporation of foot muscles training for performance and injury prevention in track and field.

The majority of motor unit studies were performed predominantly on calf muscles, where three types of units: S, FR and FF were found. These muscles are involved in postural activity, walking, running and jumping. The properties of foot muscles that perform other functions, e.g. scratching (in animals), and are purely co-active with calf muscles, are poorly known. The aim of the present study was to investigate the contractile properties of motor units in the flexor digitorum brevis. Fifty-six motor units were studied in male Wistar rats. Several methods of fast/slow motor unit categorization, presence of sag, contraction time values, and 20 Hz index, did not allow the separation of the studied motor units into discrete clusters. Therefore, motor units were divided into two groups: fatigable and resistant to fatigue, based on the fatigue index with the border value of 0.5 (although the distribution of the index was not bimodal). The fatigable motor units were stronger and faster compared to the resistant ones. In conclusion, the distribution of motor unit contractile properties in the studied foot muscle was continuous and indicated a lack of three separate physiological types of motor units that usually occurs for the majority of hindlimb muscles. This discrepancy appears to be associated with differences in the typical forms of motor unit activity in distinct muscles.

Many species that run or leap across sparsely vegetated habitats, including horses and deer, evolved the severe reduction or complete loss of foot muscles as skeletal elements elongated and digits were lost, and yet the developmental mechanisms remain unknown. Here, we report the natural loss of foot muscles in the bipedal jerboa, Jaculus jaculus. Although adults have no muscles in their feet, newborn animals have muscles that rapidly disappear soon after birth. We were surprised to find no evidence of apoptotic or necrotic cell death during stages of peak myofiber loss, countering well-supported assumptions of developmental tissue remodeling. We instead see hallmarks of muscle atrophy, including an ordered disassembly of the sarcomere associated with upregulation of the E3 ubiquitin ligases, MuRF1 and Atrogin-1. We propose that the natural loss of muscle, which remodeled foot anatomy during evolution and development, involves cellular mechanisms that are typically associated with disease or injury., eLife digest Intrinsic muscles are a group of muscles deep inside the hands and feet. They help to control the precise movements required, for example, for a pianist to play their instrument or for certain animals to climb with remarkable agility. Some animals, such as horses and deer, have evolved in such a way that they no longer grasp objects with hands and feet. Where intrinsic muscles were once present in the hands and feet of their ancestors, these animals now have strong ligaments that prevent over-extension of the wrist and ankle joints during hard landings. Given their size, it is difficult to study horses and deer in the laboratory and understand how they lost their intrinsic muscles during evolution. Tran et al. therefore focused on a small rodent called the lesser Egyptian jerboa, which also displays long legs with strong ligaments and no intrinsic muscles. Newborn jerboas have foot muscles that look very much like the intrinsic muscles found in mice, but these muscles disappear within 4 days of birth. A mechanism called programmed cell death is often responsible for specific tissues disappearing during development, but the experiments of Tran et al. revealed that this was not the case in jerboas. Instead, their intrinsic muscles were degraded by processes triggered by genes that disassemble underused muscles. In mice and humans, fasting, nerve injuries, or immobility trigger this type of muscle degradation, but in jerboas these processes appear to be a normal part of development. This unexpected discovery shows that development and disease-like processes are linked, and that more studies of nontraditional research animals may help scientists better understand these connections.

The purpose of this study was to investigate the effect of thickness, cross-sectional area and stiffness of intrinsic foot muscles on performance in single-leg stance balance tasks in healthy sedentary young females. This study included a total of 40 healthy sedentary young females between the ages of 19 and 35 years. Single-leg stance balance assessments were carried out using Biodex Balance Systems (Biodex Medical Systems, Shirley, NY, USA). Performance in the single-leg stance balance tests was assessed using the overall stability index (OSI), mediolateral stability index (MLSI) and the anteroposterior stability index (APSI). Lower scores indicated better postural stability. Stiffness, thickness and cross-sectional area measurements of the abductor hallucis (AbH), flexor digitorum brevis (FDB) and flexor hallucis brevis (FHB) muscles were performed using an ultrasonography device. Larger AbH and FHB muscles were correlated with higher OSI, APSI, and MLSI (r = 0.31-0.46, p 0.05), whereas larger FDB muscle was correlated with higher OSI and MLSI (r = 0.28-0.38, p 0.05). Higher stiffness of the AbH and FHB muscles were correlated with lower OSI, APSI, and MLSI (r = -0.32 to 0.58, p 0.05), but stiffness of the FDB muscle was not significantly correlated with OSI, APSI, and MLSI (r = 0.03-0.22, p ˃ 0.05). These results suggest that larger AbH, FDB and FHB muscles are related to reduced performance in single-leg stance balance tests, whereas higher AbH and FHB stiffness are related to better performance in single-leg stance balance tests in healthy sedentary young females.

The foot has been considered both as an elastic mechanism that increases the efficiency of locomotion by recycling energy, as well as an energy sink that helps stabilize movement by dissipating energy through contact with the ground. We measured the activity of two intrinsic foot muscles, flexor digitorum brevis (FDB) and abductor hallucis (AH), as well as the mechanical work performed by the foot as a whole and at a modelled plantar muscle–tendon unit (MTU) to test whether these passive mechanics are actively controlled during stepping. We found that the underlying passive visco-elasticity of the foot is modulated by the muscles of the foot, facilitating both dissipation and generation of energy depending on the mechanical requirements at the centre of mass (COM). Compared to level ground stepping, the foot dissipated and generated an additional –0.2 J kg −1 and 0.10 J kg −1 (both p < 0.001) when stepping down and up a 26 cm step respectively, corresponding to 21% and 10% of the additional net work performed by the leg on the COM. Of this compensation at the foot, the plantar MTU performed 30% and 89% of the work for step-downs and step-ups, respectively. This work occurred early in stance and late in stance for stepping down respectively, when the activation levels of FDB and AH were increased between 69 and 410% compared to level steps (all p < 0.001). These findings suggest that the energetic function of the foot is actively modulated by the intrinsic foot muscles and may play a significant role in movements requiring large changes in net energy such as stepping on stairs or inclines, accelerating, decelerating and jumping.

Background The short foot (SF) exercise is a strengthening exercise for the intrinsic foot muscles that is difficult to master. Objective To examine the effect of three different electromyographic (EMG) biofeedback methods on learning the SF exercise. Methods Thirty-six healthy subjects were randomly allocated to the control group (CTG), EMG-controlled electrical stimulation group (ESG), visual EMG biofeedback group (VSG), and combination EMG-controlled electrical stimulation with visual EMG biofeedback group (CBG). The CTG practiced the SF exercise for 5 minutes using the conventional method. The other groups each used the EMG biofeedback method and the conventional method. The EMG activity of the abductor hallucis (ABH), the medial longitudinal arch (MLA) angle, and the foot length during the SF exercise were measured before and after 5 minutes of practice. Results The EMG activity of the ABH in the VSG and CBG was significantly higher than that before practice. There were no intergroup differences in MLA morphology. Conclusions These results suggest that visual EMG biofeedback is an effective method of increasing the EMG activity of the ABH during the SF exercise in a short practice time.

Objective To compare the thickness and cross-sectional area (CSA) of the Abductor Hallucis Brevis (AHB), Flexor Digitorum Brevis (FDB) and Flexor Hallucis Brevis (FHB) in subjects with and without chronic mid-portion Achilles tendinopathy (AT). Design A case-control research study. Setting A private clinic. Participants A total sample of 143 subjects was recruited for the study and divided in two groups, such as chronic mid-portion AT group (n = 71) and healthy group (n = 72). Main outcome measures Ultrasound B-Mode imaging was used to measure the thickness and CSA of the AHB, FDB and FHB in subjects with and without chronic mid-portion AT at rest. Results USI measurements of the AHB (p

Randomized controlled trials over the last two decades, although promising with favorable results, have shown varied efficacy in treatment of "plantar fasciitis" with botulinum toxin injection1. One reason may be due to conflating the variabilities of plantar heel conditions solely as plantar fasciitis. Plantar Heel Pain Syndrome can be of one or more etiologies and symptoms which refutes the mistaken tendency to categorize all plantar heel pain singularly as either plantar fasciitis or fasciosis. Recognizing that there is likely an interplay of inflammatory, degenerative, and neuropathic etiologic conditions of this often-difficult malady to treat, a novel injection paradigm of botulinum toxin is explored in the treatment of 4 distinct presentations of Plantar Heel Pain Syndrome with encouraging results. Botulinum toxin injection into two intrinsic foot muscles; Abductor Hallucis and Quadratus Plantae at their origins with electrical stimulation is presented as novel method to treat four distinct etiologies of Plantar Heel Pain Syndrome. This method of botulinum toxin injection resulted in significant prolonged improvement of patient function and pain reduction in four variations of Plantar Heel Pain Syndrome. A precise injection paradigm facilitated with direct intrinsic muscle stimulation of the Abductor Hallucis and Quadratus Plantae at their origins may prove to be effective in reducing the disabilities of Plantar Heel Pain Syndrome and its associated pain.

Background The intrinsic foot muscles are vital for maintaining normal foot function. This study was conducted to systematically review the literature on the functional capacity and morphological characteristics of the intrinsic foot muscles in subjects with Hallux Valgus (HV) deformity. Methods A search was carried out in all available electronic databases, including Pub Med, Scopus, Embase and Web of Science, for identifying any relevant studies published from 1990 to October 2018. Results Three studies had investigated intrinsic foot muscle size using ultrasound imaging; two had reported electromyography parameters and four had measured the muscle force capacity. The results of the present review suggested that the functional capacity and morphological characteristics of intrinsic foot muscles are different in subjects with HV compared to those without this deformity. Conclusion This review found scientific evidence on muscle performance impairment in the abductor hallucis and flexor hallucis brevis in subjects with HV deformity.

The present study aimed to determine the differences in thicknesses of the lower leg and foot muscles between sprinters and non-sprinters and to examine the relationship between these muscle thicknesses and sprint performance in sprinters. Twenty-six well-trained sprinters and 26 body size-matched non-sprinters participated in this study. Total 9 muscle thicknesses of bilateral lower leg and foot muscles in participants were measured using ultrasonography. Regarding the lower leg muscles, thicknesses of the tibialis anterior, gastrocnemius medial, and gastrocnemius lateral were measured. Regarding the foot muscles, thicknesses of the flexor digitorum longus, flexor hallucis longus, peroneal longus and brevis, abductor hallucis, flexor digitorum brevis, and flexor hallucis brevis were measured. Most muscle thicknesses were significantly larger in sprinters than in non-sprinters. The differences in mean thicknesses of both legs between the two groups were greater in the foot muscles, where it ranged from 10.2% to 17.1%, than in the lower leg muscles, where it ranged from -0.9% to 9.4%. Among foot muscles, the thickness of only the abductor hallucis was positively correlated with the personal best 100-m sprint time in sprinters (r = 0.419, P = 0.033), indicating that a greater abductor hallucis may be a negative factor for superior sprint performance. These findings suggest that although the foot muscles in addition to the lower leg muscles are more developed in sprinters than in non-sprinters, these muscle sizes may not contribute to achieve superior sprint performance.