Anthropometric Study of Foot Breadth of 5-10 Years Aged Bangladeshi Children.

The present anthropometric study was designed to construct data of 5-10 years aged Bangladeshi children regarding foot breadth and an attempt has been made out to grow interest among the researchers for future study and also to compare the data with the data of the people of other races. This cross-sectional, descriptive and analytic type study was conducted among 5-10 years aged 109 Bangladeshi children (70 male and 39 female) at different areas of Mymensingh district (Fulpur, Muktagacha, Fulbaria, Trisal and Haluaghat), Bangladesh from January 2016 to December 2016. Non-random purposive sampling technique was taken for sample collection. Any kind of foot deformity due to either from congenital or physical injury was excluded to construct standard measurement. Foot breadth was measured using slide caliper. The children were asked to stand with weight distributed equally on both feet. The legs were perpendicular to the feet. The mean foot breadth of right side of 5, 6, 7, 8, 9 and 10 years aged male children were 7.08±.61 cm, 7.11±.30 cm, 7.61±.45 cm, 7.44±.43 cm, 8.12±.38 cm and 8.17±.44 cm respectively and those of female children were 6.55±.64 cm, 7.17±.27 cm, 7.04±.70 cm, 7.62±.54 cm, 7.48±.88 cm and 7.85±.72 cm respectively. The mean foot breadth of left side of 5, 6, 7, 8, 9 and 10 years aged male children were 7.04±.60 cm, 7.03±.30 cm, 7.52±.47 cm, 7.36±.45 cm, 8.03±.38 cm and 8.08±.43 cm respectively and those of female children were 6.46±.63 cm, 7.10±.31 cm, 6.95±.71 cm, 7.54±.52 cm, 7.37±.89 cm and 7.77±.71 cm respectively. Comparison of foot breadth between male and female children was done by Unpaired Students 't' test and the differences of means were statistically non-significant. Data were tabulated and statistically analyzed using Microsoft excel and SPSS software. The results of present study would be useful in anatomy, orthopedics, forensic science, plastic surgery, radiology, podiatry, archeology, anthropology and nutrition science.

The effect of hallux valgus on the anatomy of the nerves around the first metatarsal bone.

OBJECTIVE: To identify the variations in the location of the nerves that may be at risk in hallux valgus (HV) surgery, and to reveal whether these nerves are affected by the anatomical changes associated with HV. METHOD: In the formalin fixed, 46 lower extremities (19 female, 27 male) (9 normal, 14 mild HV, 21 moderate/severe HV), extensor hallucis longus tendon (EHL), deep plantar artery, medial dorsal cutaneous (MDCN), deep fibular (DFN), common plantar digital (CPDN) and proper plantar digital (PPDN) nerves were examined. The branches of MDCN extending to the medial side of foot were recorded in three segments. The positional topography of nerves according to EHL were analyzed on 360° circle and clock models. RESULTS: Sex-related differences observed in some parameters in direct measurements were not found in the clock model comparisons. In advanced HV angles (> 20°), DFN was closer to EHL in the distal part of the metatarsal bone, while there was no difference in the proximal. The intersection of the medial branch of the MDCN with the EHL was more proximal in HV cases than in normal feet. The location of the nerves in the clock pattern did not change in HV. Of the nerve branches reaching the medial side of the foot, 65.2% were in Part I, 71.7% in Part II, and 4.3% in Part III. CONCLUSION: Sex differences in the distance of the nerves to the EHL disappeared when the size effect of the cross-section of the first metatarsal bone region was eliminated with the clock model. Only in advanced HVA (>20°) (not in mild HV), the DFN being closer to the EHL distally and the intersection of the medial branch of the MDCN with the EHL in HV being more proximal than in normal can be interpreted as specific reflections of HV progress. The variations we revealed in the number of branches reaching the inside of the foot may explain the diversity of neuromas or nerve injuries associated with HV surgery.

Exploring flatfeet morphology in children aged 6-12 years: relationships with body mass and body height through footprints and three-dimensional measurements.

The aim of the study was to determine the relationship between flatfoot morphology and body mass and height in children aged 6-12 years. A total of 6471 Chinese children (mean age 9.0 ± 1.9 years, 41% female) were assessed for foot morphometry, body height, and body mass index. Foot morphology, including foot length, width, girth, arch height, hallux valgus angle, and rearfoot valgus angle, was measured using a 3D laser scanner. Flatfoot evaluations were conducted using the Sztriter-Godunov index (KY) from footprints. All measurements were analyzed by age and sex using the mean values of the left and right sides. Comparisons were performed between flatfoot groups, between body mass index (BMI) groups, and between body height groups. The study revealed a significant decrease in the incidence of bipedal flatfoot with age (p < 0.001), whereas the prevalence of obesity remained consistent (p > 0.05). Bipedal flatfoot was associated with distinct morphological changes, including lower arches, reduced instep height, diminished ankle heights and a greater rearfoot valgus angle (p < 0.05). When comparing the BMI groups, overweight children had larger and thicker feet (p < 0.05), but no differences were found in arch height and ankle height (p > 0.05). When comparing the body height groups, short-statured children had a shorter feet girth, shorter arches, and shorter ankle height (p < 0.05), but no differences were found in the rearfoot valgus angle (p > 0.05). CONCLUSION: The main characteristics of flat feet include lower arches and instep heights and ankle heights but higher rearfoot valgus angles. In general, overweight children's feet do not have the common features of flat feet. In contrast, short children had similar features of flatfoot except for rearfoot valgus. Assessment of posture, such as rearfoot valgus, can be critical in identifying children with flat feet. WHAT IS KNOWN: • The morphology of children's feet is associated with body growth, but the relationship between flatfeet and body mass and height remains controversial. WHAT IS NEW: • Three-dimensional foot measurement shows that body mass is generally not associated with flatfeet, while short children have lower arches but no rearfoot valgus.

Anatomical analysis of ligaments surrounding calcaneocuboid joint; implications for role in foot stability.

PURPOSE: The calcaneocuboid joint is located in the lateral part of the foot and acts as a major stabilizer for the foot. Injuries to this joint often occur in association with ankle or foot injuries and are frequently overlooked, subsequently causing chronic pain or osteoarthritis. However, the relationship between ligaments surrounding the joint and joint instability remains unclear. Therefore, this study aimed to clarify the morphology and position of the ligaments surrounding the calcaneocuboid joint, and to reveal the relationship between the ligament structure. METHODS: The position and morphology of the bifurcate ligament (subdivided into calcaneonavicular and calcaneocuboid ligaments), dorsal calcaneocuboid ligament, lateral calcaneocuboid ligament, long plantar ligament, and short plantar ligament were measured (N = 11 feet in 6 Japanese cadavers). The circumference of the joint was quartered, while the ligament-uncovered area and the estimated cross-sectional area of each ligament were compared between the four sides. Furthermore, the estimated cross-sectional area of each ligament was calculated as an index for the ligament strength. RESULTS: The inferolateral side of the calcaneocuboid joint had the most uncovered area (54.63%) by the ligaments. In addition, the cross-sectional area of the ligaments on the lateral side was considerably smaller than that on the medial side. CONCLUSION: Our results suggest that ligament weakness on the inferolateral side may cause instability of the calcaneocuboid joint, especially after an inversion sprain injury, and may decrease the lateral longitudinal arch function, which results in chronic foot pain.

Technical note: A volumetric method for measuring the longitudinal arch of human tracks and feet.

Fossil footprints (i.e., tracks) were believed to document arch anatomical evolution, although our recent work has shown that track arches record foot kinematics instead. Analyses of track arches can thereby inform the evolution of human locomotion, although quantifying this 3-D aspect of track morphology is difficult. Here, we present a volumetric method for measuring the arches of 3-D models of human tracks and feet, using both Autodesk Maya and Blender software. The method involves generation of a 3-D object that represents the space beneath the longitudinal arch, and measurement of that arch object's geometry and spatial orientation. We provide relevant tools and guidance for users to apply this technique to their own data. We present three case studies to demonstrate potential applications. These include, (1) measuring the arches of static and dynamic human feet, (2) comparing the arches of human tracks with the arches of the feet that made them, and (3) direct comparisons of human track and foot arch morphology throughout simulated track formation. The volumetric measurement tool proved robust for measuring 3-D models of human tracks and feet, in static and dynamic contexts. This tool enables researchers to quantitatively compare arches of fossil hominin tracks, in order to derive biomechanical interpretations from them, and/or offers a different approach for quantifying foot morphology in living humans.

Fit of fire boots: exploring internal morphology using computed tomography.

Fit of fire boots is a crucial factor in the safety and performance of firefighters on the hostile fireground. Firefighters have reported that ill-fitting fire boots restrict their lower body movement and sometimes cause very dangerous situations by falling off behind the wearer. By using computed tomography, this study demonstrates the potential to quantify and visualize the fit of fire boots, which previously relied on subjective feedback from the wearers. The high-resolution three-dimensional (3D) models of two fire boot products allowed a detailed observation and measurement of the internal space of the boots. Also, the boot's internal dimension was compared to the foot measurement of local firefighters, showing the significant differences between the two boots. Lastly, simulation wrapping the 3D scanned foot with the boot revealed large void spaces around the toe box and ankle, as well as the narrower ball width of the boot than the foot.

Tracking 'transitional' diadectomorphs in the earliest Permian of equatorial Pangea.

Diadectomorpha was a clade of large-bodied stem-amniotes or possibly early-diverging synapsids that established a successful dynasty of late Carboniferous to late Permian high-fiber herbivores. Aside from their fairly rich record of body fossils, diadectomorphs are also well-known from widely distributed tracks and trackways referred to as Ichniotherium. Here, we provide detailed description of a diadectomorph trackway and a manus-pes couple originating from two different horizons in the Asselian (lowermost Permian) of the Boskovice Basin in the Czech Republic. The specimens represent two distinct ichnotaxa of Ichniotherium, I. cottae and I. sphaerodactylum. Intriguingly, the I. cottae trackway described herein illustrates a 'transitional' stage in the posture evolution of diadectomorphs, showing track morphologies possibly attributable to a Diadectes-like taxon combined with distances between the successive manus and pes imprints similar to those observable in earlier-diverging diadectomorphs, such as Orobates. In addition, this trackway is composed of 14 tracks, including six well-preserved manus-pes couples, and thus represents the most complete record of Ichniotherium cottae described to date from the Asselian strata. In turn, the manus-pes couple, attributed here to I. sphaerodactylum, represents only the second record of this ichnotaxon from the European part of Pangea. Our study adds to the diversity of the ichnological record of Permian tetrapods in the Boskovice Basin which had been essentially unexplored until very recently.

The oldest fossil bird-like footprints from the upper Triassic of southern Africa.

Footprint morphology reflects the anatomy of the trackmaker's foot and is direct evidence for the animal's behaviour. Consequently, fossil tracks can be used to infer ancient diversity, ethology, and evolutionary trends. This is particularly useful for deep-time intervals during which the early history of an animal group is reliant upon limited fossil skeletal material. Fossil tracks of early birds and theropods, the co-existing dinosaurian ancestors of birds, co-occur in the rock record since the Early Cretaceous. However, the evolutionary transition from dinosaur to bird and the timing of the birds' origin are still contested. Skeletal remains of the basal-most birds Aurornis, Anchiornis, Archaeopteryx and Xiaotingia are Middle to Late Jurassic, while tracks with tentative bird affinities, attributed to dinosaurs, are known from as early as the Late Triassic. Here, we present numerous, well-provenanced, Late Triassic and Early Jurassic tridactyl tracks from southern Africa, with demonstrable bird-like affinities, predating basal bird body fossils by c. 60 million years.

Morphological and evolutionary insights into the keystone element of the human foot's medial longitudinal arch.

The evolution of the medial longitudinal arch (MLA) is one of the most impactful adaptations in the hominin foot that emerged with bipedalism. When and how it evolved in the human lineage is still unresolved. Complicating the issue, clinical definitions of flatfoot in living Homo sapiens have not reached a consensus. Here we digitally investigate the navicular morphology of H. sapiens (living, archaeological, and fossil), great apes, and fossil hominins and its correlation with the MLA. A distinctive navicular shape characterises living H. sapiens with adult acquired flexible flatfoot, while the congenital flexible flatfoot exhibits a 'normal' navicular shape. All H. sapiens groups differentiate from great apes independently from variations in the MLA, likely because of bipedalism. Most australopith, H. naledi, and H. floresiensis navicular shapes are closer to those of great apes, which is inconsistent with a human-like MLA and instead might suggest a certain degree of arboreality. Navicular shape of OH 8 and fossil H. sapiens falls within the normal living H. sapiens spectrum of variation of the MLA (including congenital flexible flatfoot and individuals with a well-developed MLA). At the same time, H. neanderthalensis seem to be characterised by a different expression of the MLA.

3D Foot Anthropometric Measurements Under Two Weight- Bearing Conditions for Ergonomic Design of Foot-Related Products / Mediciones Antropométricas del Pie en 3D Bajo Dos Condiciones de Soporte de Peso para el Diseño Ergonómico de Productos Relacionados con los Pies

SUMMARY: This study collected 3D models of the left and right feet from 317 Chinese youth (155 females and 162 males) under half weight-bearing and no weight-bearing conditions. Thirteen dimensions and one angle were taken for each sample. By measuring 13 foot dimensions and 1 angle, this study comprehensively investigated the differences in foot shape between genders and the bilateral differences, as well as the foot shape differences under different conditions. The results showed that regardless of the condition, male foot dimensions were significantly larger than those of females. However, female foot shape was not simply a scaled-down version of male foot shape. On the contrary, the average angle of female feet was greater than that of males under both conditions, indicating a higher prevalence of hallux valgus in females. Both males and females exhibited significant correlation in foot dimensions between the left and right feet, with minimal differences. Under the half weight-bearing condition, the average foot length, width, and circumference were significantly larger than the corresponding measurements under the no weight-bearing condition, while the average height and angle were significantly smaller. Therefore, when designing footwear and foot-related medical rehabilitation aids, it is important to consider foot shape and dimensions under different conditions as a reference. The results of this study provide manufacturers of foot- related products with more detailed data support and are of significant value to the field of medical foot morphology research.

Este estudio recolectó modelos 3D de los pies izquierdo y derecho de 317 jóvenes chinos (155 mujeres y 162 hombres) en condiciones de carga media de peso y sin carga de peso. Para cada muestra se tomaron trece dimensiones y un ángulo. Al medir 13 dimensiones del pie y 1 ángulo, se investigó exhaustivamente las diferencias en la forma del pie entre ambos sexos y sus diferencias bilaterales, así como las diferencias en la forma del pie en diferentes condiciones. Los resultados mostraron que, independientemente de la condición, las dimensiones del pie de los hombres, estos eran significativamente más grandes que los de las mujeres. Sin embargo, la forma del pie femenino no era simplemente una versión reducida de la forma del pie masculino. Por el contrario, el ángulo promedio de los pies de las mujeres fue mayor que el de los hombres en ambas condiciones, lo que indica una mayor prevalencia de hallux valgus en las mujeres. Tanto hombres como mujeres exhibieron una correlación significativa en las dimensiones del pie, entre el pie izquierdo y el derecho, con diferencias mínimas. Bajo la condición de medio soporte de peso, la longitud, el ancho y la circunferencia promedio del pie fueron significativamente mayores que las medidas correspondientes bajo la condición sin soporte de peso, mientras que la altura y el ángulo promedio fueron significativamente más pequeños. Por lo tanto, al diseñar calzado y dispositivos médicos de rehabilitación relacionados con los pies, es importante tener en consideración la forma y las dimensiones del pie en diferentes condiciones como referencia. Los resultados de este estudio, brindan a los fabricantes de productos relacionados con los pies un soporte de datos más detallado y son de gran valor para el campo de la investigación médica de la morfología del pie.

Anatomical study of the distal course of the posterior tibial artery: A cadaver study.

OBJECTIVE: This study aimed to describe the course, branches, and variances of the posterior tibial artery, which provides the arterial supply of the plantar surface of the foot, starting from the tarsal tunnel level to provide descriptive information for all surgical interventions, diagnostic radiological procedures, and promising endovascular therapies in the tarsal region. METHODS: In this study, a dissection of 48 feet was performed on 25 formalin-fixed cadavers (19 males and 6 females). Surgical instruments and a digital caliper were used for dissection and measurements, and the critical structures were recorded by a Canon 250D camera to be illustrated later. RESULTS: All parameters were significantly longer in male cadavers compared to females. According to the correlation analysis, while there was a significant and robust correlation between the axial line and pternion-deep plantar arch (R=.830, P .05), a moderate correlation was found between the axial line and sphyrion-bifurcation (R=.575; P < .05), axial line and deep plantar arch-2nd interdigital commissure (R=.457; P < .05), and sphyrion-bifurcation and pternion-deep plantar arch (R=.480; P < .05). Variation in any branch of the posterior tibial artery was observed in 27 of the 48 studied sides. CONCLUSION: In our study, the branching and variability of posterior tibial artery on the plantar surface of the foot were described in detail with the determined parameters. In conditions that cause tissue and function loss and require reconstruction, such as diabetes mellitus and atherosclerosis, the most critical factor in increasing treatment success is a better understanding of the region's anatomy.

Proximity of percutaneous tibial nerve stimulation needle insertion to surrounding anatomic structures: a cadaveric study.

BACKGROUND: Percutaneous tibial nerve stimulation is a third-line treatment for overactive bladder and urgency urinary incontinence. During the procedure, a needle is inserted cephalad to the medial malleolus and posterior to the tibia. In recent years, permanent implants and leads have been developed for insertion into the medial ankle via a small incision. There are many important structures present in the medial compartment of the ankle, including the great saphenous vein, saphenous nerve, tibial nerve, posterior tibial vessels, and tendons of the posterior compartment leg muscles. OBJECTIVE: The primary objective of this study was to identify the proximity of the percutaneous tibial nerve stimulation needle placed per Food and Drug Administration-approved device instructions to nearby important anatomic structures. The secondary objectives were to identify the proximity of the tibial nerve to the needle site, identify clinically relevant ankle anatomic structures, and confirm the tibial nerve and posterior tibial vasculature by histologic analysis. STUDY DESIGN: Detailed medial ankle dissections were performed bilaterally on 10 female lightly embalmed anatomic donors (cadavers) obtained from the Willed Body Program at the University of Louisville. A pin was inserted at the percutaneous tibial nerve stimulation needle site, and the medial ankle was minimally dissected so the surrounding anatomic structures were visible but not disrupted. The shortest distance from the pin to the selected structures of the medial ankle region was measured. On completion of each dissection and set of measurements, tissue was harvested for histologic examination. The distances between the pin and each structure were assessed using means and standard deviations. A paired t test was used to assess the difference in the locations between the left and right ankles. Statistical analysis was performed on left-sided, right-sided, and combined measurements. An 80% prediction interval was found to represent the expected range of values for the measurement of a new cadaver or patient, and the 95% confidence interval of the mean was computed to characterize the average distance across all cadavers or patients. RESULTS: The medial ankle of 10 adult female lightly embalmed cadavers were examined bilaterally. Dissections were completed from October 2021 to July 2022. Of note, 80% prediction intervals for the tibial nerve, the posterior tibial artery or vein, and the flexor digitorum longus tendon had a lower range of 0.0 mm from the pin and extending to 12.1, 9.5, and 13.9 mm, respectively. Moreover, 2 of the structures were found to be asymmetrical between the right and left ankles. The great saphenous vein was further from the pin on the left (20.5 mm [standard deviation of 6.4 mm] on the left vs 18.1 mm [standard deviation of 5.3 mm] on the right; P=.04). The calcaneal (Achilles) tendon was further from the pin on the right side (13.2 mm [standard deviation of 6.8 mm] vs 7.9 mm [standard deviation of 6.7 mm]; P=.04). Tibial neurovascular structures were confirmed with microscopic analysis. CONCLUSION: The anatomic structures within the medial ankle lie unexpectedly close to the percutaneous tibial nerve stimulation needle site as noted per Food and Drug Administration-approved device instructions. There is a possibility that some medial ankle structures are not symmetrical. It is crucial that practitioners understand medial ankle anatomy when performing percutaneous tibial nerve stimulation or permanent device insertion.

Early euprimates already had a diverse locomotor repertoire: Evidence from ankle bone morphology.

The morphological adaptations of euprimates have been linked to their origin and early evolution in an arboreal environment. However, the ancestral and early locomotor repertoire of this group remains contentious. Although some tarsal bones like the astragalus and the calcaneus have been thoroughly studied, the navicular remains poorly studied despite its potential implications for foot mobility. Here, we evaluate early euprimate locomotion by assessing the shape of the navicular-an important component of the midtarsal region of the foot-using three-dimensional geometric morphometrics in relation to quantified locomotor repertoire in a wide data set of extant primates. We also reconstruct the locomotor repertoire of representatives of the major early primate lineages with a novel phylogenetically informed discriminant analysis and characterize the changes that occurred in the navicular during the archaic primate-euprimate transition. To do so, we included in our study an extensive sample of naviculars (36 specimens) belonging to different species of adapiforms, omomyiforms, and plesiadapiforms. Our results indicate that navicular shape embeds a strong functional signal, allowing us to infer the type of locomotion of extinct primates. We demonstrate that early euprimates displayed a diverse locomotor behavior, although they did not reach the level of specialization of some living forms. Finally, we show that the navicular bone experienced substantial reorganization throughout the archaic primate-euprimate transition, supporting the major functional role of the tarsus during early primate evolution. This study demonstrates that navicular shape can be used as a reliable proxy for primate locomotor behavior. In addition, it sheds light on the diverse locomotor behavior of early primates as well as on the archaic primate-euprimate transition, which involved profound morphological changes within the tarsus, including the navicular bone.

Using surface markers to describe the kinematics of the medial longitudinal arch.

BACKGROUND: Static and dynamic assessment of the medial longitudinal arch (MLA) is an essential aspect for measuring foot function in both clinical and research fields. Despite this, most multi-segment foot models lack the ability to directly track the MLA. This study aimed to assess various methods of MLA assessment, through motion capture of surface markers on the foot during various activities. METHODS: Thirty general population participants (mean age 20 years) without morphological alterations to their feet underwent gait analysis. Eight measures, each representing a unique definition of the MLA angle using either real only, or both real and floor-projected markers, were created. Participants performed tasks including standing, sitting, heel lift, Jack's test and walking, and had their Arch Height Index (AHI) measured using callipers. Multiple-criteria decision analysis (MCDA) with 10 criteria was utilised for selecting the optimal measure for dynamic and static MLA assessment. RESULTS: In static tasks, the standing MLA angle was significantly greater in all measures but one when compared to sitting, Jack's test and heel lift. The MLA angle in Jack's test was significantly greater than in heel lift in all measures. Across the compared dynamic tasks, significant differences were noted in all measures except one for foot strike in comparison to 50% gait cycle. All MLA measures held significant inverse correlations with MLA measured from static and dynamic tasks. Based on MCDA criteria, a measure comprising the first metatarsal head, fifth metatarsal base, navicular and heel markers was deemed the best for MLA assessment. SIGNIFICANCE: This study aligns with the current literature recommendations for the use of a navicular marker for characterising the MLA. It contrasts with previous recommendations and advocates against the use of projected markers in most situations.

Automated plantar contact area estimation in a dynamic state using K-Means clustering.

BACKGROUND: Estimation of plantar contact area (PCA) can be used for a variety of purposes such as classification of foot types and diagnosis of foot abnormalities. While some techniques have been developed for assessing static PCA, understanding dynamic PCA may improve understanding of gait biomechanics. This study aims (1) to develop an approach to estimate PCA from video images of footprints during walking and (2) to assess the accuracy and generalizability of this method. METHODS: A sample of 41 ambulatory, young adults (age = 24.3 ± 3.2 years, mass = 67.2 ± 16.9 kg, height = 1.63 ± 0.08 m) completed 10 trials walking on a raised transparent plexiglass platform. Foot contact during walking was recorded using a video camera placed under the platform. An image processing algorithm, Clustering Segmentation, was developed based on identifying color intensity between the PCA and the rest of the foot and plantar contact morphology. RESULTS: The proposed approach was compared to manual hand tracing, which is widely accepted as the Gold Standard, as well as with an earlier automated approach (Lidstone et al., 2019). Results showed that Clustering Segmentation followed the Gold Standard closely in all phases of gait. The maximum PCA and the maximum PCA length and width generally increased with foot size, indicating that the algorithm could successfully estimate the PCA across a wide range of foot sizes. Results also showed that the proposed approach for obtaining the PCA may be used to characterize various foot types in a dynamic state. CONCLUSION: Clustering Segmentation algorithm eliminates the need for subjective interpretation of the PCA. The results showed that the algorithm was considerably faster and more accurate than the earlier automated method. The proposed algorithm will be appropriate for assessment of foot abnormalities and provides complementary information to gait analysis.

The Lower Limbs of Sprinters Have Larger Relative Mass But Not Larger Normalized Moment of Inertia than Controls.

PURPOSE: Sprinters exhibit inhomogeneous muscularity corresponding to musculoskeletal demand for sprinting execution. An inhomogeneous morphology would affect the mass distribution, which in turn may affect the mechanical difficulty in moving from an inertia perspective; however, the morphological characteristics of sprinters from the inertia perspective have not been examined. Here we show no corresponding differences in the normalized mass and normalized moment of inertia between the sprinters and untrained nonsprinters. METHODS: We analyzed fat- and water-separated magnetic resonance images from the lower limbs of 11 male sprinters (100 m best time of 10.44-10.83 s) and 12 untrained nonsprinters. We calculated the inertial properties by identifying the tissue of each voxel and combining the literature values for each tissue density. RESULTS: The lower-limb relative mass was significantly larger in sprinters (18.7% ± 0.7% body mass) than in nonsprinters (17.6% ± 0.6% body mass), whereas the normalized moment of inertia of the lower limb around the hip in the anatomical position was not significantly different (0.044 ± 0.002 vs 0.042 ± 0.002 [a. u.]). The thigh relative mass in sprinters (12.9% ± 0.4% body mass) was significantly larger than that in nonsprinters (11.9% ± 0.4% body mass), whereas the shank and foot relative masses were not significantly different. CONCLUSIONS: We revealed that the mechanical difficulty in swinging the lower limb is not relatively larger in sprinters in terms of inertia, even though the lower-limb mass is larger, reflecting their muscularity. We provide practical implications that sprinters can train without paying close attention to the increase in lower-limb mass and moment of inertia.