Peroration: Hip Width and Metabolic Energy Expenditure of Abductor Muscles.

Objectives: We recently reported that functional pelvic width is not a statistically significant predictor of the metabolic energy expenditure of the hip abductor muscles during walking when mass, stature, and progression velocity were controlled. Others revised this analysis, suggesting that a different statistical approach would yield statistical significance. In order to address this suggestion, herein we refine our original analysis and increase our sample size.

Hip stabilization in an australopithecine-like hip: the influence of shape on muscle activation.

Hip stabilization through muscular activation of the gluteals is a key feature of hominin walking, but the role of pelvic shape on muscular activation remains uncertain. Coupled with this is the uncertainty regarding whether the kinematics and kinetics of modern humans are appropriate in extinct hominins. We apply modern human kinematics and kinetics to musculoskeletal models with modern human-like and australopithecine-like hips.

Implications of variability in triceps surae muscle volumes on peak lower limb muscle forces during human walking.

Musculoskeletal modeling can be used to estimate forces during locomotion. These models, however, are dependent on underlying assumptions about the model inputs, such as muscle volumes and fiber lengths, to calculate muscle forces. Triceps surae (gastrocnemius medialis, gastrocnemius lateralis, soleus) muscle volume distributions vary among humans.

An Introduction to the Orbital Buttresses.

Facial buttresses are supportive bony structures of the facial skeleton that form a thick, strong, and protective framework for the face. Surgical fixation may be required to restore morphology and function when damage to these buttresses occurs. The authors sought to determine whether, similar to buttresses of the facial skeleton, buttresses of the internal orbit exist.

Macroscopic differences in adult human femora are linked to body mass index.

Bone functional adaptation is routinely invoked to interpret skeletal morphology despite ongoing debate regarding the limits of the bone response to mechanical stimuli. The wide variation in human body mass presents an opportunity to explore the relationship between mechanical load and skeletal response in weight-bearing elements. Here, we examine variation in femoral macroscopic morphology as a function of body mass index (BMI), which is used as a metric of load history.

Variation in human limb joint articular morphology.

Objectives: Synovial joints in human limbs strike a balance between mobility, stability, and articular fit, yet little is known about how these conflicting demands pattern intraspecific variation in articular shape. In this study, we use geometric morphometrics to establish the apportionment and magnitude of morphological variance of the articular surfaces of the human shoulder, elbow, hip, and knee. We hypothesize that variances will be comparable between articulating surfaces within a joint and will be larger in joints with smaller ranges of motion, given their plurality of functional demands.

Morphological variation of the Pan talus relative to that of Gorilla.

Objectives: Differences in talar articular morphology relative to locomotion have recently been found within Pan and Gorilla. Whole-bone talar morphology within, and shared variation among, Pan and Gorilla (sub)species, however, has yet to be investigated. Here we separately analyze talar external shape within Pan (P.

Hip width and metabolic energy expenditure of abductor muscles.

Despite a paucity of physiological evidence, simplistic biomechanical analyses have led researchers to assume that humans who have wider hips use more energy to walk. Pitting biomechanical first principles against physiological data has led to little deepening of our understanding of bipedalism and its evolution. Both approaches, however, use proxies for the energy used by muscles.

Carpal allometry of African apes among mammals.

Objectives: Morphological variation in African ape carpals has been used to support the idea that Pan and Gorilla evolved knuckle-walking independently. Little work, however, has focused on the effect of body mass on carpal morphology. Here, we compare carpal allometry in Pan and Gorilla to that of other quadrupedal mammals with similar body mass differences.

Effects of obesity on talar micro- and macro-morphology.

The addition of information regarding obesity status to the forensic anthropological biological profile could significantly contribute to the identification of human skeletal remains since over 40% of the U.S. adult population is currently obese.

Two Late Pleistocene human femora from Trinil, Indonesia: Implications for body size and behavior in Southeast Asia.

Late Pleistocene hominin postcranial specimens from Southeast Asia are relatively rare. Here we describe and place into temporal and geographic context two partial femora from the site of Trinil, Indonesia, which are dated stratigraphically and via Uranium-series direct dating to ca. 37-32 ka.

Sensitivity of musculoskeletal models to variation in muscle architecture parameters.

Musculoskeletal models, like all theoretical models of physical processes, depend on the assumptions needed to construct the model. For musculoskeletal models, these assumptions include, among other things, the kinematic data, the kinetic data and the muscle parameters. The former (dynamic) data can be acquired relatively easily from living subjects, but the latter are usually based on limited information, frequently determined from cadaver studies performed on elderly individuals.

A morphometric analysis of early Eocene Euprimate tarsals from Gujarat, India.

Early Eocene primate postcranial bones from the Vastan lignite mine of Gujarat, India, have proven useful for understanding the haplorhine and strepsirrhine divergence. Previous analyses of material assigned to Asiadapidae supported interpretations that these primates were generalized arboreal quadrupeds, while the omomyid Vastanomys was likely to have been more proficient leaper than asiadapids. More recent examinations of long bone cross-sectional properties and calcaneal elongation have complicated the behavioral interpretations of these fossils.

A review of musculoskeletal modelling of human locomotion.

Locomotion through the environment is important because movement provides access to key resources, including food, shelter and mates. Central to many locomotion-focused questions is the need to understand internal forces, particularly muscle forces and joint reactions. Musculoskeletal modelling, which typically harnesses the power of inverse dynamics, unites experimental data that are collected on living subjects with virtual models of their morphology.

Comparing and combining sliding semilandmarks and weighted spherical harmonics for shape analysis.

Quantifying morphological variation is critical for conducting anatomical research. Three-dimensional geometric morphometric (3D GM) landmark analyses quantify shape using homologous Cartesian coordinates (landmarks). Setting up a high-density landmark set and placing it on all specimens, however, can be a time-consuming task.

Calcaneal shape variation in humans, nonhuman primates, and early hominins.

The foot has played a prominent role in evaluating early hominin locomotion. The calcaneus, in particular, plays an important role in weight-bearing. Although the calcanei of early hominins have been previously scrutinized, a three-dimensional analysis of the entire calcaneal shape has not been conducted.

Muscle forces and the demands of human walking.

Reconstructing the locomotor behavior of extinct animals depends on elucidating the principles that link behavior, function, and morphology, which can only be done using extant animals. Within the human lineage, the evolution of bipedalism represents a critical transition, and evaluating fossil hominins depends on understanding the relationship between lower limb forces and skeletal morphology in living humans. As a step toward that goal, here we use a musculoskeletal model to estimate forces in the lower limb muscles of ten individuals during walking.

Scaling and relative size of the human, nonhuman ape, and baboon calcaneus.

Among human and nonhuman apes, calcaneal morphology exhibits significant variation that has been related to locomotor behavior. Due to its role in weight-bearing, however, both body size and locomotion may impact calcaneal morphology. Determining how calcaneal morphologies vary as a function of body size is thus vital to understanding calcaneal functional adaptation.

Bilateral asymmetry and developmental plasticity of the humerus in modern humans.

Objective: This study investigates bilateral asymmetry in the humerus of modern human populations with differing activity patterns to assess the relative plasticity of different bone regions in response to environmental influences, particularly the biomechanical demands of handedness.

Methods: External breadths, cross-sectional properties, and centroid sizes were used to quantify directional and absolute asymmetry of humeral diaphyseal, distal periarticular, and articular regions in six populations with differing subsistence strategies (total n = 244). Geometric section properties were measured using computed tomography at six locations along the distal humerus, while centroid sizes of the distal articular and periarticular regions, as well as eight segments of the diaphysis, were extracted from external landmark data.

Gorilla calcaneal morphological variation and ecological divergence.

Objectives: The primate foot has been extensively investigated because of its role in weight-bearing; however, the calcaneus has been relatively understudied. Here we examine entire gorilla calcaneal external shape to understand its relationship with locomotor behavior.

Materials And Methods: Calcanei of Gorilla gorilla gorilla (n = 43), Gorilla beringei graueri (n = 20), and Gorilla beringei beringei (n = 15) were surface or micro-CT scanned.

Internal architecture of the mandibular condyle of rabbits is related to dietary resistance during growth.

Although there is considerable evidence that bone responds to the loading environment in which it develops, few analyses have examined phenotypic plasticity or bone functional adaptation in the masticatory apparatus. Prior work suggests that masticatory morphology is sensitive to differences in food mechanical properties during development; however, the importance of the timing/duration of loading and variation in naturalistic diets is less clear. Here, we examined microstructural and macrostructural differences in the mandibular condyle in four groups of white rabbits () raised for a year on diets that varied in mechanical properties and timing of the introduction of mechanically challenging foods, simulating seasonal variation in diet.

Estimating the in vivo location of the talus from external surface landmarks.

Objectives: Finite element analysis has gained popularity in anthropological research to connect morphological form to measurable function but requires that loads are applied at appropriate anatomical locations. This is challenging for the ankle because the joint surfaces are not easily determined given their deep anatomical location. While the location of the talonavicular and subtalar joints can be directly determined via medical imaging, regression equations are a common, less invasive method to estimate joint locations from surface anatomy.

Effective Mechanical Advantage Allometry of Felid Elbow and Knee Extensors.

Larger terrestrial mammals have generally been found to use more extended limb postures, a mechanism which maintains muscular requirements at larger sizes by improving the effective mechanical advantage (EMA) of limb musculature. Felids, however, have been documented to maintain joint angles across body sizes. If felid morphology scales isometrically, it would mean larger felids have relatively weaker muscles, compromising locomotor activities.

Long bone diaphyseal shape follows different ontogenetic trajectories in captive and wild gorillas.

Objectives: A number of studies have demonstrated the ontogenetic plasticity of long bone diaphyseal structure in response to mechanical loading. Captivity should affect mechanical loading of the limbs, but whether captive apes grow differently than wild apes has been debated. Here, we compare captive and wild juvenile and adult Gorilla to ascertain whether growth trajectories in cross-sectional diaphyseal shape are similar in the two environments.