Static versus dynamic muscle modelling in extinct species: a biomechanical case study of the pelvis and lower extremity.

The force a muscle generates is dependent on muscle structure, in which fibre length, pennation angle and tendon slack length all influence force production. Muscles are not preserved in the fossil record and these parameters must be estimated when constructing a musculoskeletal model. Here, we test the capability of digitally reconstructed muscles of the model (specimen AL 288-1) to maintain an upright, single-support limb posture.

Three-dimensional volumetric muscle reconstruction of the pelvis and limb, with estimations of limb leverage.

To understand how an extinct species may have moved, we first need to reconstruct the missing soft tissues of the skeleton, which rarely preserve, with an understanding of segmental volume and muscular composition within the body. The specimen AL 288-1 is one of the most complete hominin skeletons. Despite 40+ years of research, the frequency and efficiency of bipedal movement in this specimen is still debated.

Modern three-dimensional digital methods for studying locomotor biomechanics in tetrapods.

Here, we review the modern interface of three-dimensional (3D) empirical (e.g. motion capture) and theoretical (e.

Anatomically grounded estimation of hindlimb muscle sizes in Archosauria.

In vertebrates, active movement is driven by muscle forces acting on bones, either directly or through tendinous insertions. There has been much debate over how muscle size and force are reflected by the muscular attachment areas (AAs). Here we investigate the relationship between the physiological cross-sectional area (PCSA), a proxy for the force production of the muscle, and the AA of hindlimb muscles in Nile crocodiles and five bird species.

Reconstructing Articular Cartilage in the Hip Joint and the Need for Modeling Six Degrees of Freedom.

The postcranial skeleton of (AL 288-1) exhibits clear adaptations for bipedality, although there is some debate as to the efficiency and frequency of such upright movement. Some researchers argue that AL 288-1 walked with an erect limb like modern humans do, whilst others advocate for a "bent-hip bent-knee" (BHBK) gait, although in recent years the general consensus favors erect bipedalism. To date, no quantitative method has addressed the articulation of the AL 288-1 hip joint, nor its range of motion (ROM) with consideration for joint spacing, used as a proxy for the thickness of the articular cartilage present within the joint spacing which can affect how a joint moves.

A Guide to Inverse Kinematic Marker-Guided Rotoscoping Using IK Solvers.

X-ray Reconstruction of Moving Morphology (XROMM) permits researchers to see beneath the skin, usually to see musculoskeletal movements. These movements can be tracked and later used to provide information regarding the mechanics of movement. Here, we discuss ""-a method that combines inverse kinematic solvers with that of traditional scientific rotoscoping methods to quickly and efficiently overlay 3D bone geometries with the X-ray shadows from XROMM data.

Three-dimensional polygonal muscle modelling and line of action estimation in living and extinct taxa.

Biomechanical models and simulations of musculoskeletal function rely on accurate muscle parameters, such as muscle masses and lines of action, to estimate force production potential and moment arms. These parameters are often obtained through destructive techniques (i.e.

One size fits all? Stature estimation from footprints and the effect of substrate and speed on footprint creation.

Estimation of stature from footprint lengths is a common prediction in forensic cases and in paleoanthropology upon the discovery of fossil footprints. Many studies, which have estimated stature from footprints, generally use a "one-size-fits-all" approach that usually involves applying a known ratio of foot length to total stature to do so, although this method has fallen out of practice in forensic cases in recent years but is still commonly used for fossil trace evidence. Yet, we know that substrate and speed can change the dimensions of a footprint, so why are these "one-size-fits-all" approaches still used today? We tested footprint production across different substrates at a walk, a fast walk, and a jog.

Musculoskeletal modelling of the Nile crocodile (Crocodylus niloticus) hindlimb: Effects of limb posture on leverage during terrestrial locomotion.

We developed a three-dimensional, computational biomechanical model of a juvenile Nile crocodile (Crocodylus niloticus) pelvis and hindlimb, composed of 47 pelvic limb muscles, to investigate muscle function. We tested whether crocodiles, which are known to use a variety of limb postures during movement, use limb orientations (joint angles) that optimise the moment arms (leverages) or moment-generating capacities of their muscles during different limb postures ranging from a high walk to a sprawling motion. We also describe the three-dimensional (3D) kinematics of the crocodylian hindlimb during terrestrial locomotion across an instrumented walkway and a treadmill captured via X-ray Reconstruction of Moving Morphology (biplanar fluoroscopy; 'XROMM').

The morphological affinity of the Early Pleistocene footprints from Happisburgh, England, with other footprints of Pliocene, Pleistocene, and Holocene age.

Fossil hominin footprints provide a direct source of evidence of locomotor behavior and allow inference of other biological data such as anthropometrics. Many recent comparative analyses of hominin footprints have used 3D analytical methods to assess their morphological affinities, comparing tracks from different locations and/or time periods. However, environmental conditions can sometimes preclude 3D digital capture, as was the case at Happisburgh (England) in 2013.