Contributions of flexor hallucis longus and brevis muscles to isometric toe flexor force production.

PURPOSE: Morphological differences between the two primary great toe flexors - flexor hallucis longus (FHL) and flexor hallucis brevis (FHB) - likely drive differences in how these muscles contribute to functional toe flexor torque production. The aim of the study was to investigate FHL and FHB activation in two isometric toe flexion tasks - one called a "toe-pushing" task with the metatarsophalangeal (MTP) joints dorsiflexed and the interphalangeal (IP) joints in neutral and another called a "toe-gripping" task with the MTP joints in neutral and flexed IP joints. METHODS: Twenty participants' FHL and FHB muscles were instrumented with intramuscular electromyography electrodes. Muscle activation was normalized to a maximum voluntary contraction and compared between the two isometric toe flexor force production tasks. RESULTS: Overall, participants utilized these two toe flexors completely differently in the two tasks. In the toe-gripping task, the FHL was activated to a much greater extent than the FHB. In fact, 18 our of 20 participants activated FHL at more than 70% maximum voluntary contraction and half of participants activated FHB at less than 10%. In contrast, muscle activation during the toe-pushing task appeared more reliant on the FHB for most participants. CONCLUSIONS: Different contributions from the FHL and FHB to toe flexor force production in these two tasks are potentially driven by differences in muscle functional length among other factors. These findings help to inform the selection of rehabilitation and training exercises meant to preferentially target intrinsic or extrinsic foot musculature.

Limitación de la flexión dorsal del tobillo y del hallux en nadadores de categoría máster / Limitation of ankle dorsiflexion and hallux in master category swimmers

Objetivos: Los objetivos son observar qué variables de las estudiadas presentan diferencias al realizar comparación entre nadadores que presentan test de Lunge positivo, dolor en tríceps sural y musculatura plantar y los nadadores que no presentan dolor. Pacientes y métodos: Se trata de un estudio observacional, descriptivo, de corte transversal que se ha realizado sobre una muestra de veinte nadadores de categoría máster (12 hombres y 8 mujeres) y que presentan de forma habitual dolor en pie (musculatura plantar) y pierna (tríceps sural) durante el nado. Resultados: Los resultados han mostrado que las variables extensión de rodilla (p = 0.020), flexión dorsal de tobillo (p = 0.006) y ángulo poplíteo (p = 0.003) son las que mayores diferencias significativas tienen entre los nadadores con y sin dolor en tríceps sural y entre aquellos con test de Lunge positivo y negativo. Las variables de flexión dorsal de la primera articulación metatarsofalángica (AMTF) (p = 0.039) y plantar flexión del primer radio (p = 0.011) con las que han presentado mayor diferencia estadística entre nadadores con test de Lunge positivo y negativo. Conclusiones: Al comparar nadadores que presentan dolor en tríceps sural y musculatura plantar entre nadadores que no presentan dolor, los deportistas que sí presentan dolor, son aquellos cuyos valores de media en las variables flexión dorsal de tobillo, flexión dorsal de la primera AMF, extensión de rodilla y plantarflexión del primer radio, son menores en comparación con los que no presentan dolor, presentándose diferencias entre ambas extremidades (AU)

Objectives: The objectives are to observe which of the variables studied present differences when comparing swimmers who present a positive Lunge Test, pain in the triceps surae and plantar muscles and swimmers who do not present pain. Patients and methods: This is an observational, descriptive, cross-sectional study that has been carried out on a sample of twenty master category swimmers (12 men and 8 women) who regularly present foot pain (plantar muscles) and leg (triceps surae) during swimming. Results: The results have shown that the variables knee extension (p = 0.020), ankle dorsiflexion (p = 0.006) and popliteal angle (p = 0.003) are the ones with the greatest significant differences between swimmers with and without pain in the ankle, triceps surae and between those with positive and negative Lunge Test. The variables dorsiflexion of the first metatarsopahlangeal (MTP), joint (p = 0.039) and plantar flexion of the first ray (p = 0.011) are those that have presented the greatest statistical difference between swimmers with a positive and negative Lunge test. Conclusions: When comparing swimmers who present pain in the triceps surae and plantar muscles with swimmers who do not present pain, the athletes who do present pain are those whose average values in the variables ankle dorsiflexion, first MTP dorsiflexion, knee extension and plantar-flexion of the first ray are lower compared to those who do not present pain, with differences between both limbs (AU)

Immediate effect of neuromuscular electrical stimulation on the abductor hallucis muscle: A randomized controlled trial.

Hallux valgus (HV) is a foot deformity with deviation of the greater toe and the first metatarsal. There is little evidence on training the abductor hallucis muscle (AbdH) to treat HV because of the difficulty in implementing the necessary interventions. Although neuromuscular electrical stimulation (NMES) has been used to induce voluntary exercise, there is currently no study on NMES for AbdH. We aimed to verify the immediate effect of NMES on the AbdH muscle function. For the NMES group (n = 15), electrical stimulation was applied for 20 min. In the sham group (n = 15), the stimulating device was set but not turned on. Electromyogram, HV angle (HVA) at rest and during abduction of the big toe, and strength of the AbdH were evaluated. Analysis of covariance was used to investigate differences within groups using the baseline as the covariate. NMES significantly improved the maximal voluntary isometric contractions (%MVIC), HVA at exercise, and muscle strength (%MVIC: p = .00, HVA exercise: p = .00, AbdH strength: p = .00). HVA at rest showed no change (p = .12). Application of NMES on the AbdH muscle immediately improved its activity output, muscle strength, and HVA during exercise.

Plantar pressure sensors indicate women to have a significantly higher peak pressure on the hallux, toes, forefoot, and medial of the foot compared to men.

BACKGROUND: Sex-related differences of plantar pressure distribution during activities should be thoroughly inspected as it can help establish treatment and prevention strategies for foot and ankle problems. In-shoe measurement systems are preferable without space and activity restrictions; however, previously reported systems are still heavy and bulky and induce unnatural movement. Therefore, a slim and light plantar pressure sensor was newly developed to detect the effect of sex difference on plantar pressure during standing and walking. METHODS: One-hundred healthy adult volunteers (50 women and 50 men) were recruited. Ten plantar pressure sensors were implanted in a 1-mm thick insole, with a total weight of 29 g. Plantar pressure was recorded with 200 Hz during 3 s of standing and while walking 10 steps. The maximum loads during standing and walking were analyzed in each sensor, and the results were compared between different areas of the foot in the antero-posterior direction and the medio-lateral direction and between different time points. The movement of the center of pressure (COP) during walking was also evaluated. Analyses were adjusted for body mass index and gait speed. RESULTS: The movement of COP was constant for both sexes. In all cases, the maximum load was observed on the medial of the foot. Women had a significantly higher peak pressure on the hallux, toes, forefoot, and medial aspect of the foot compared to men while standing and walking (p < .05). CONCLUSIONS: A newly introduced in-shoe plantar pressure sensor demonstrated a typical loading transition pattern of the foot. Furthermore, higher plantar pressure in the forefoot was detected in healthy women as compared to men during standing and walking activities.

Effect of sensory stimulation applied under the great toe on postural ability in patients with fibromyalgia.

Fibromyalgia (FM) is a chronic pain syndrome, characterised by several symptoms. One of the most prevalent symptoms in FM is balance impairment that compromise the autonomy, function and performance status of patients.Purpose: The main objective of the present study was to evaluate the effect of sensory stimulation provided by the use of a low additional thickness of 0.8 mm placed under the great toes bilaterally on the centre of pressure (CoP) measures in patients with FM. It was hypothesised that postural ability would change with a low focal additional thickness used to compute these measures.Materials and Method: Twenty-four patients with FM voluntarily participated in this study. Postural performance during quiet standing was investigated through the CoP displacements recorded using a force-plate. Sensory stimulation was provided by a small additional thickness of 0.8 mm placed under the great toe bilaterally and two conditions were compared: additional thickness 0 (control) and 0.8 mm.Results: An improvement of body balance through spatial parameters with sensory cutaneous stimulation applied under the great toe bilaterally were observed in patients with FM. Our results showed a significant decrease of surface area and mean speed of CoP, associated to a significant decrease of variance of speed. An additional observation is that sagittal (Y) mean position of the CoP gets more anterior (+ 5 mm) relative to control condition.Conclusion: These findings brings new clinical perspectives in the development of intervention strategies in the management of patients with FM and balance disorders, completing validated therapeutic strategies.

Strength properties of extant hominoid hallucal and pollical metapodials.

Functional comparisons of cortical bone strength properties between hominoid hallucal and pollical metapodials (Mt1 and Mc1, respectively) are lacking. Determining which of these two elements is stronger, and by how much, could be informative because the hallux and pollex are used differently both within and among extant hominoids during locomotion and manipulation (i.e., functional differentiation between autopod pairs). Here, we compare Mt1 and Mc1 midshaft cortical area, polar section modulus, and polar second moment of area, calculated from high-resolution computed tomography images in humans (n = 21), chimpanzees (n = 47), gorillas (n = 24), orangutans (n = 20), siamangs (n = 8), and gibbons (n = 21). Intraindividual comparisons between bones within species were made using paired t-tests. Log10-transformed Mt1:Mc1 ratios were created to assess relative strength asymmetry between bones, and interspecific comparisons of these proportions were made using analyses of variance. Absolute strength differences between the Mt1 and Mc1 for all variables were significantly larger in the Mt1 for all species (p < 0.05). Significant differences across species in Mt1:Mc1 proportions were also found, thereby demonstrating that strength asymmetry between bones differs among taxa (p < 0.05); asymmetry was lowest in orangutans, intermediate in gorillas, and greatest in humans, chimpanzees, siamangs, and gibbons. These findings support the hypothesis that the Mt1 is better adapted structurally than the Mc1 for bearing mechanical loads during weight support of locomotion in all extant hominoids and that pedal hallucal grasping likely engenders higher loads than manual pollical grasping in nonhuman hominoids. Thus, functional differentiation in autopod use within and among hominoids is reflected in hallucal and pollical metapodial strength properties.

Properties and Function of the Flexor Hallucis Capsularis Interphalangeus Tendon.

INTRODUCTION: The fibrocartilagenous plantar plates of the forefoot are biomechanically important, forming the primary distal attachment for the plantar aponeurosis. They are integral to the function of the windlass mechanism in supporting the arches of the foot in gait. Dissection of the cadaveric hallux revealed an organised sagittal thickening of the dorsal side of the flexor hallucis longus (FHL) sheath, which attached the interphalangeal plantar plate to the metatarsophalangeal (MTP) plantar plate. A description of a similar structure was made in 1984 when it was termed the flexor hallucis capsularis interphalangeus (FHCI) - however, it has not been researched since, and we aim to study it further and identify its characteristics. METHOD: Eight specimens were dissected from four cadavers. Two were stained and examined under magnification in both polarized and non polarized light. The remaining 6 were subjected to micrometer testing of their tensile properties. RESULTS: Both the histological features and mechanical properties were consistent with tendon; with cross sectional area, ultimate tensile strength and stiffness varying between specimens. CONCLUSIONS: Based on its location and properties, the FHCI tendon may be involved in limiting dorsiflexion of the first MTP joint and could have clinical relevance in pathological processes around both the first and second MTP joints. Clin. Anat., 33:689-695, 2020. © 2019 Wiley Periodicals, Inc.

Technical report: dynamic assessment of plantar fasciitis and plantar fascia tears utilising dorsiflexion of the great toe.

Discrimination between plantar fasciitis and partial tears of the plantar fascia can be difficult on ultrasound given laxity of the plantar fascia in the region of its calcaneal insertion and anisotropy. Dynamic assessment with great toe dorsiflexion can improve visualisation of the proximal portion of the plantar fascia on ultrasound, by straightening the plantar fascia due to the windlass mechanism. This article describes the technique and its anatomical basis.

Falls rate increase and foot dorsal flexion limitations are exhibited in patients who suffer from asthma: A novel case-control study.

Purpose: Based on the possible association between reduced foot dorsiflexion and high risk of falls, the main objective was to determine the ankle and 1º metatarsophalangeal joint (1stMTTP) dorsiflexion range of motion and falls rate in patients with asthma compared to healthy matched-paired controls. Methods: A case-control study was carried out. Eighty participants were recruited and divided into patients with asthma (case group; n=40) and matched-paired healthy participants (control group; n=40). Foot dorsal flexion range of motion (assessed by the Weight-Bearing Lunge Test [WBLT]) and falls rate (evaluated as falls number during the prior year) were considered as the primary outcomes. Indeed, ankle dorsiflexion was measured by a mobile app (º) and a tape measure (cm) as well as 1stMTTP dorsiflexion was determined by and universal goniometer (º). Results: Statistically significant differences (P<.05) showed that patients with asthma presented a greater falls rate than healthy participants and reduced bilateral ankle and 1stMTTP dorsiflexion ranges of motion than healthy participants, except for the left ankle dorsiflexion measured as degrees (P>.05). Conclusions: These study findings showed that a falls rate increase and bilateral foot dorsal flexion limitations of the ankle and 1stMTTP joints are exhibited in patients who suffer from asthma.

A biomechanical assessment of running with hallux unstable shoes of different material stiffness.

PURPOSE: Functional footwear with different unstable profiles has been widely used to mimic barefoot condition and offload plantar loading for pathological or injury prevention. However, little research investigates the effect of unstable structure on particular foot functions. In this study, a prototype of unstable shoe design with unstable element of different stiffness placed at the hallux (a regionalized rocker) was used. The primary objective was to analyse the biomechanical performance of running with hallux unstable shoes, aiming to potentially stimulate and increase the toe gripping function. METHODS: The lower limb kinematics and plantar pressure distribution were measured to comparatively analyse the soft (SS) and hard (SH) unstable shoes with flat control shoes (CS). RESULTS: The SS showed increased big toe and reduced forefoot plantar pressure. The SS led to similar lower limb kinematics to baseline CS except for reduced hip abduction, increased rotation range of motion (ROM), increased peak ankle plantar flexion and ROM. The SH presented significantly altered lower limb kinematics across hip, knee and ankle, and laterally distributed plantar pressure. CONCLUSIONS: Unstable shoes with soft material led to reduced medial metatarsal loading by increasing the support area and modified joint kinematics minimally. Unstable shoes with stiffer material presented compensatory kinematic movements across all joints and laterally shifted plantar loading distribution. These findings may provide implications on toe grip function training for foot pressure off-loading.

The relationship between hallux grip force and balance in people with diabetes.

BACKGROUND: Diabetes accelerates the decline in muscle strength in older people and substantially increases the risk for fall and injury. Weakening of lower extremity muscles, in particular, is a strong predictor for falls, but currently there is no established method for its assessment in clinics. The paper grip test (PGT) offers a qualitative assessment of hallux plantar flexor strength and its usefulness for predicting falls has been demonstrated in non-diabetic populations. RESEARCH QUESTION: The aim of this study is to test whether the PGT can be used for a quantitative assessment of lower-extremity strength and to investigate its relationship with isometric muscle strength and balance in people with diabetes and peripheral neuropathy. METHODS: Isometric muscle strength of all muscle groups of the foot-ankle was assessed using a dynamometer in sixty-nine people with diabetes and neuropathy. Postural sway and the gripping force exerted by the participants during the PGT was measured for the same participants using a plantar pressure assessment system. These measurements were repeated in regular intervals for 18 months in a longitudinal observational cohort study. RESULTS: Cross-sectional analysis of baseline data showed that people who failed the PGT swayed more. Analysis of longitudinal data showed that increasing hallux grip force is significantly associated with reduced postural sway. No significant association was found between dynamometry-based measurements of strength and postural sway. Hallux grip force was significantly correlated to the strength of all muscle groups of the foot-ankle complex. SIGNIFICANCE: These results indicate that hallux grip force can assess the strength of the foot-ankle muscles and could potentially be used to identify people at risk of falling. This sets the basis for the development of new screening protocols to assess weakening of the muscles of the foot-ankle and to enhance risk assessment for falls in people with diabetes and peripheral neuropathy.

Hallux plantar flexor strength in people with diabetic neuropathy: Validation of a simple clinical test.

AIM: To validate the paper grip test for assessing plantar flexion strength of the hallux. METHODS: Plantar flexor strength for 69 people with diabetic neuropathy was assessed: (a) using the paper grip test while simultaneously a plantar pressure platform quantified the force under the hallux, and (b) using a hand-held dynamometer. Following testing, participants were divided into groups: (1) passed vs. failed paper grip test (2) males vs. females. Statistical analyses determined if differences were evident between the groups and assessed the relationship between the paper grip test and the hand-held dynamometer. The discrimination ability, sensitivity, specificity, and reproducibility of the paper grip test was established. RESULTS: Participants who passed the paper grip test demonstrated greater grip force at the hallux than those who failed, and they also exhibited greater isometric maximum force during the hand-held dynamometry test (p ≤ 0.05). Grip force for males was significantly higher than for females. A moderate positive correlation between the paper grip test and the hand-held dynamometer was evident. CONCLUSIONS: In the population examined the paper grip test was found to be a valid clinical tool; it offers a non-invasive, inexpensive, and quick method to assess plantar flexion strength of the hallux.

The extent of skin bending rather than action possibilities explains why holes feel larger with the tongue than with the finger.

When small holes are felt with the tongue, they are perceived to be larger compared with when felt with the index finger. This oral illusion has not yet been consistently explained. From present action-specific accounts of perception, we derived a high-level sticking-action hypothesis to explain the oral illusion. In 5 experiments, we contrasted this hypothesis' predictions with predictions from the low-level bending hypothesis, which states that felt hole size decreases with decreasing bending of the skin at the hole's edges. Results from Experiments 1 to 3 showed that felt hole size decreases with the pliability of the exploring effector (tongue > index finger > big toe, big fingers > small fingers), which affects skin bending, and that size perception with the highly pliable tongue is more accurate than with the less pliable finger and toe. Experiment 4 showed that holes of intermediate size are perceived to be larger with the tongue's tip than with its dorsum. Finally, exploration styles that lessen the skin's bending (using low vs. high tongue forces in Experiment 5) decreased perceived hole size. Overall, the results favor the low-level bending hypothesis over the high-level sticking-action hypothesis. (PsycINFO Database Record

Movement coordination patterns between the foot joints during walking.

BACKGROUND: In 3D gait analysis, kinematics of the foot joints are usually reported via isolated time histories of joint rotations and no information is provided on the relationship between rotations at different joints. The aim of this study was to identify movement coordination patterns in the foot during walking by expanding an existing vector coding technique according to an established multi-segment foot and ankle model. A graphical representation is also described to summarise the coordination patterns of joint rotations across multiple patients. METHODS: Three-dimensional multi-segment foot kinematics were recorded in 13 adults during walking. A modified vector coding technique was used to identify coordination patterns between foot joints involving calcaneus, midfoot, metatarsus and hallux segments. According to the type and direction of joints rotations, these were classified as in-phase (same direction), anti-phase (opposite directions), proximal or distal joint dominant. RESULTS: In early stance, 51 to 75% of walking trials showed proximal-phase coordination between foot joints comprising the calcaneus, midfoot and metatarsus. In-phase coordination was more prominent in late stance, reflecting synergy in the simultaneous inversion occurring at multiple foot joints. Conversely, a distal-phase coordination pattern was identified for sagittal plane motion of the ankle relative to the midtarsal joint, highlighting the critical role of arch shortening to locomotor function in push-off. CONCLUSIONS: This study has identified coordination patterns between movement of the calcaneus, midfoot, metatarsus and hallux by expanding an existing vector cording technique for assessing and classifying coordination patterns of foot joints rotations during walking. This approach provides a different perspective in the analysis of multi-segment foot kinematics, and may be used for the objective quantification of the alterations in foot joint coordination patterns due to lower limb pathologies or following injuries.

Effect of Bipartite Hallucal Sesamoid on Hallux Valgus Surgery.

BACKGROUND: Bipartite hallucal sesamoids are often found in patients with hallux valgus. However, it is unknown whether bipartite hallucal sesamoids affect the results of hallux valgus surgery or not. The purpose of the present study was to evaluate the outcomes of chevron osteotomy for hallux valgus with and without bipartite hallucal sesamoid. METHODS: A total of 152 patients (168 feet) treated with distal or proximal chevron osteotomy for hallux valgus constituted the study cohort. The 168 feet were divided into 2 groups: bipartite hallucal sesamoid (31 feet) and without bipartite hallucal sesamoid (137 feet). Hallux valgus angle (HVA), intermetatarsal angle (IMA), distal metatarsal articular angle (DMAA), tibial sesamoid position, and first metatarsal length were measured for radiographic outcomes and the American Orthopaedic Foot & Ankle Society (AOFAS) hallux metatarsophalangeal-interphalangeal (MTP-IP) score was measured for clinical outcomes. RESULTS: All radiographic measurements and the AOFAS score showed significant ( P < .05) improvement at the time of final follow-up compared with preoperative measurements in both groups. No significant differences ( P > .05) were found between the 2 groups in terms of HVA, IMA, DMAA, tibial sesamoid position, metatarsal shortening, and AOFAS score on final follow-up. CONCLUSIONS: This study suggests that bipartite hallucal sesamoids do not affect the results of hallux valgus surgery. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Outcomes of the Distal Metatarsal Dorsiflexion Osteotomy for Advanced Hallux Rigidus.

BACKGROUND: Hallux rigidus can be treated using several different methods and the best treatment option depends on the severity of degenerative changes of the metatarsophalangeal (MTP) joint. However, the ideal operative option for advanced hallux rigidus remains debatable. This prospective study was performed to evaluate the intermediate-term clinical outcomes of distal metatarsal osteotomy used as a joint-preserving method for the treatment of advanced hallux rigidus. METHODS: Forty-two cases (39 patients) were followed for more than 3 years after distal metatarsal dorsiflexion osteotomy for advanced hallux rigidus of grade III-IV. Clinical evaluations included the American Orthopaedic Foot & Ankle Society (AOFAS) scores, Foot and Ankle Ability Measure (FAAM) scores, and patient subjective satisfaction scores. Range of motion (ROM) of great toe, complications, reoperation rates, width of the MTP joint space, and times to union were evaluated. RESULTS: Mean AOFAS hallux and mean FAAM scores significantly improved from 56.4 and 61.2 points preoperatively to 87.6 and 88.7 points at final follow-up, respectively ( P < .001). Grade III and IV groups had significantly different AOFAS and FAAM scores at final follow-up. Mean dorsiflexion of great toe significantly improved from 14.8° preoperatively to 35.5° at final follow-up ( P < .001). Mean patient satisfaction score at final follow-up was 92.8 points. There were 4 cases (9.5%) of subsequent fusion and 2 cases (4.8%) of transfer metatarsalgia. CONCLUSIONS: Distal metatarsal dorsiflexion osteotomy using bio-compression screws appears to be an effective operative option for grade III advanced hallux rigidus with viable cartilage on >50% of the first metatarsal articular surface, as it restored joint motion, provided reliable pain relief, and did not require implant removal. However, based on the unsatisfactory clinical results and the high rate of reoperation observed, the authors cannot recommend this operative method for the treatment of end-stage (grade IV) hallux rigidus. LEVEL OF EVIDENCE: Level IV, prospective case series.

Investigating biomechanical function of toes through external manipulation integrating analysis.

PURPOSE: This study was aimed to investigate the function of toes while running through comparing bound toes by external- manipulation with natural separate toes by evaluating kinematics and plantar pressure analysis. METHODS: Seven habitually barefoot male runners participated in the running test under toes binding and non-binding conditions, and Vicon and Novel insole plantar pressure measurement were conducted synchronously to collect kinematics and foot loading. RESULTS: Ankle kinematics showed larger non-significant range of motion in the frontal plane while running with toes non-binding.The medial forefoot had a smaller force time integral, and with hallux had a larger force time integral than those of running with toes binding, with significance level p < 0.05. CONCLUSIONS: While no significance existed between bound and non-bound toes in kinematics, the medial forefoot had a smaller foot impulse and the hallux had a larger foot impulse for those with non-binding feet. This suggests that other functions such as the active gripping action of toes might be important for the efficiency of the foot windlass mechanism (the plantar fascia support), which would be beneficial for running performance improvement and foot injury prevention.

Toe Flexor Strength, Flexibility and Function and Flexor Hallucis Longus Tendon Morphology in Dancers and Non-Dancers.

Tendinopathy of the flexor hallucis longus (FHL), colloquially referred to as "dancer's tendinitis," is a common condition in dancers and attributed to high demand on this muscle in positions of extreme ankle plantarflexion and metatarsophalangeal (MTP)) flexion and extension. Despite such a high prevalence, there has been little research into preventative or nonsurgical interventions. As a means to identify potential targets for prevention and intervention, this study aimed to characterize toe flexors in dancers by measuring strength, flexibility, function, and FHL tendon morphology. Dancers (n=25) were compared to non-dancers (n=25) in toe flexor isometric strength, first MTP joint range of motion, foot longitudinal arch flexibility, balance ability, endurance during modified heel raises without use of the toes, and FHL tendon thickness, cross-sectional area, and peak spatial frequency. Significant differences were found in functional first MTP joint extension (dancers 101.95°, non-dancers 91.15°, p<0.001), balance ability during single-leg stance on the toes (dancers 11.43 s, non-dancers 5.90 s, p=0.013), and during modified heel raises (dancers 22.20 reps, non-dancers 28.80 reps, p=0.001). Findings indicate that dancers rely on toe flexors more than non-dancers to complete balance and heel raise tasks. Efficacy of using this modified heel raise task with the toes off the edge of a block as a means to train larger plantarflexors and as a nonsurgical intervention should be studied in the future. Improving interventions for FHL tendinopathy will be impactful for dancers, in whom this condition is highly prevalent.

EMG and force production of the flexor hallucis longus muscle in isometric plantarflexion and the push-off phase of walking.

Large forces are generated under the big toe in the push-off phase of walking. The largest flexor muscle of the big toe is the flexor hallucis longus (FHL), which likely contributes substantially to these forces. This study examined FHL function at different levels of isometric plantarflexion torque and in the push-off phase at different speeds of walking. FHL and calf muscle activity were measured with surface EMG and plantar pressure was recorded with pressure insoles. FHL activity was compared to the activity of the calf muscles. Force and impulse values were calculated under the big toe, and were compared to the entire pressed area of the insole to determine the relative contribution of big toe flexion forces to the ground reaction force. FHL activity increased with increasing plantarflexion torque level (F=2.8, P=0.024) and with increasing walking speed (F=11.608, P<0.001). No differences were observed in the relative contribution of the force under the big toe to the entire sole between different plantarflexion torque levels (F=0.836, P=0.529). On the contrary, in the push-off phase of walking, peak force under the big toe increased at a higher rate than force under the other areas of the plantar surface (F=3.801, P=0.018), implying a greater relative contribution to total force at faster speeds. Moreover, substantial differences were found between isometric plantarflexion and walking concerning FHL activity relative to that of the calf muscles, highlighting the task-dependant behaviour of FHL.

A comparative biomechanical analysis of habitually unshod and shod runners based on a foot morphological difference.

Running is one of the most accessible physical activities and running with and without footwear has attracted extensive attention in the past several years. In this study 18 habitually male unshod runners and 20 habitually male shod runners (all with dominant right feet) participated in a running test. A Vicon motion analysis system was used to capture the kinematics of each participant's lower limb. The in-shoe plantar pressure measurement system was employed to measure the pressure and force exerted on the pressure sensors of the insole. The function of a separate hallux in unshod runners is analyzed through the comparison of plantar pressure parameters. Owing to the different strike patterns in shod and unshod runners, peak dorsiflexion and plantarflexion angle were significantly different. Habitually shod runners exhibited a decreased foot strike angle (FSA) under unshod conditions; and the vertical average loading rate (VALR) of shod runners under unshod conditions was larger than that under shod conditions. This suggests that the foot strike pattern is more important than the shod or unshod running style and runners need to acquire the technique. It can be concluded that for habitually unshod runners the separate hallux takes part of the foot loading and reduces loading to the forefoot under shod conditions. The remaining toes of rearfoot strike (RFS) runners function similarly under unshod conditions. These morphological features of shod and unshod runners should be considered in footwear design to improve sport performance and reduce injury.