We provide quantitative anatomical data on the muscle–tendon units of the equine pelvic limb. Specifically, we recorded muscle mass, fascicle length, pennation angle, tendon mass and tendon rest length. Physiological cross sectional area was then determined and maximum isometric force estimated. There was proximal-to-distal reduction in muscle volume and fascicle length. Proximal limb tendons were few and, where present, were relatively short. By contrast, distal limb tendons were numerous and long in comparison to mean muscle fascicle length, increasing potential for elastic energy storage. When compared with published data on thoracic limb muscles, proximal pelvic limb muscles were larger in volume and had shorter fascicles. Distal limb muscle architecture was similar in thoracic and pelvic limbs with the exception of flexor digitorum lateralis (lateral head of the deep digital flexor), the architecture of which was similar to that of the pelvic and thoracic limb superficial digital flexors, suggesting a functional similarity.
The functional anatomy of the pelvic limb of the ostrich (Struthio camelus) was investigated in order to assess musculoskeletal specialization related to locomotor performance. The pelvic limbs of ten ostriches were dissected and detailed measurements of all muscle tendon units of the pelvic limb were made, including muscle mass, muscle length, fascicle length, pennation angle, tendon mass and tendon length. From these measurements other muscle properties such as muscle volume, physiological cross-sectional area (PCSA), tendon cross-sectional area, maximum isometric muscle force and tendon stress were derived, using standard relationships and published muscle data. Larger muscles tended to be located more proximally and had longer fascicle lengths and lower pennation angles. This led to an expected proximal to distal reduction in total muscle mass. An exception to this trend was the gastrocnemius muscle, which was found to have the largest volume and PCSA and also had the highest capacity for both force and power production. Generally high-power muscles were located more proximally in the limb, while some small distal muscles (tibialis cranialis and flexor perforatus digiti III), with short fibres, were found to have very high force generation capacities. The greatest proportion of pelvic muscle volume was for the hip extensors, while the highest capacity for force generation was observed in the extensors of the ankle, many of which were also in series with long tendons and thus were functionally suited to elastic energy storage.
We studied the strategies used by cursorial bipeds (ostriches) to maneuver during running. Eight ostriches were induced to run along a trackway and execute turns. Ground reaction forces and three-dimensional kinematics of the body and leg joints were simultaneously recorded, allowing calculation of joint angles and quasi-static net joint torques. Sidesteps, where the leg on the outside of the turn changes the movement direction, and crossovers using the inside leg, occurred with nearly equal frequency. Ostriches executed maneuvers using a simple control strategy that required minimal changes to leg kinematics or net torque production at individual joints. Although ostriches did use acceleration or braking forces to control body rotation, their morphology allowed for both crossovers and sidesteps to be accomplished with minimal net acceleratory/braking force production. Moreover, body roll and ab/adduction of the leg shifted the foot position away from the turn direction, reducing the acceleratory/braking forces required to prevent under-or over-rotation and aligning the leg with the ground reaction force.
Muscle moment arms were measured for major muscles of the pelvic limb of the ostrich (Struthio camelus) in order to assess specific functional behaviour and to apply this to locomotor performance. Pelvic limbs of six juvenile ostriches were used for this study. The tendon travel technique was used to measure moment arms of 21 muscles at the hip, knee, ankle and metatarsophalangeal joints throughout the ranges of motion observed during level running. Six of the 21 muscles measured were found to have moment arms that did not change with joint angle, whilst the remainder all demonstrated angle-dependent changes for at least one of the joints crossed. Moment arm lengths tended to be longest for the large proximal muscles, whilst the largest relative changes were found for the moment arms of the distal muscles. For muscles where moment arm varied with joint angle: all hip muscles were found to have increasing moment arms with extension of the joint, knee flexors were found to have moment arms that increased with extension, knee extensor moment arms were found to increase with flexion and ankle extensor moment arms increased with extension. The greatest relative changes were observed in the flexors of the metatarsophalangeal joint, for which a three-fold increase in moment arm was observed from flexion to full extension. Changes in muscle moment arm through the range of motion studied appear to optimize muscle function during stance phase, increasing the effective mechanical advantage of these muscles.
Kinematic and kinetic parameters of running gait were investigated through growth in the ostrich, from two weeks up to 10 months of age, in order to investigate the effects of increasing body size. Ontogenetic scaling relationships were compared with published scaling relationships found to exist with increasing body size between species to determine whether dynamic similarity is maintained during growth. During the study, ostrich mass (M(b)) ranged from 0.7 kg to 108.8 kg. Morphological measurements showed that lengths scaled with positive allometry during growth (hip height proportional to M(b)(0.40); foot segment length proportional to M(b)(0.40); tarsometatarsus length proportional to M(b)(0.41); tibiotarsus length proportional to M(b)(0.38); femur length proportional to M(b)(0.37)), significantly exceeding the close to geometric scaling observed between mammalian and avian species of increasing body size. Scaling of kinematic variables largely agreed with predicted scaling for increasing size and demonstrated relationships close to dynamic similarity and, as such, ontogenetic scaling of locomotor parameters was similar to that observed with increasing body mass between species. However, the ways in which these scaling trends were achieved were very different, with ontogenetic scaling of locomotor mechanics largely resulting from simple scaling of the limb segments rather than postural changes, likely to be due to developmental constraints. Small deviations from dynamic similarity of kinematic parameters and a reduction in the predicted scaling of limb stiffness (proportional to M(b)(0.59)) were found to be accounted for by the positive allometric scaling of the limb during growth.
It is unclear whether small animals, with their high stride frequency and crouched posture, or large animals, with more tendinous limbs, are more reliant on storage and return of elastic energy during locomotion. The ostrich has a limb structure that appears to be adapted for high-speed running with long tendons and short muscle fibres. Here we investigate biomechanics of ostrich gait through growth and, with consideration of anatomical data, identify scaling relationships with increasing body size, relating to forces acting on the musculoskeletal structures, effective mechanical advantage (EMA) and mechanical work. Kinematic and kinetic data were collected through growth from running ostriches. Joint moments scaled in a similar way to the pelvic limb segments as a result of consistent posture through growth, such that EMA was independent of body mass. Because no postural change was observed, relative loads applied to musculoskeletal tissues would be predicted to increase during growth, with greater muscle, and hence tendon, load allowing increased potential for elastic energy storage with increasing size. Mass-specific mechanical work per unit distance was independent of body mass, resulting in a small but significant increase in the contribution of elastic energy storage to locomotor economy in larger ostriches.
In this paper, we present a novel methodology to obtain imitative and innovative postural movements in a humanoid based on human demonstrations in a different kinematic scale. We collected motion data from a group of human participants standing up from a chair. Modeling the human as an actuated 3-link kinematic chain, and by defining a multi-objective reward function of zero moment point and joint torques to represent the stability and effort, we computed reward profiles for each demonstration. Since individual reward profiles show variability across demonstrating trials, the underlying state transition probabilities were modeled using a Markov chain. Based on the argument that the reward profiles of the robot should show the same temporal structure of those of the human, we used differential evolution to compute a trajectory that fits all humanoid constraints and minimizes the difference between the robot reward profile and the predicted profile if the robot imitates the human. Therefore, robotic imitation involves developing a policy that results in a temporal reward structure, matching that of a group of human demonstrators across an array of demonstrations. Skill innovation was achieved by optimizing a signed reward error after imitation was achieved. Experimental results using the humanoid HOAP-3 are shown.
To examine the effects of dysfunction of specific musculature of the shank a reliable and valid protocol can be used to induce a localised fatigue effect. A localised dynamometry based protocol was developed to illicit a fatigue effect in either plantar flexors or dorsiflexors. An isokinetic protocol allowing for movement through the full range of motion, set at an angular velocity of 45°s−1, was used to allow fatigue to be developed. Fatigue was established when three consecutive torque measures dropped below 50% of the average three peak contractions. Bouts of activity were based on a ratio of 40 contractions interspaced with a 30s rest. Results suggest that the protocol elicited a fatigue effect in the prime movers of either plantar flexion or dorsiflexion, supported through the analysis of power spectral density and amplitude shift of surface electromyography measures. The protocol demonstrated sound reliability with Interclass Correlation scores for all measures ranging from 0.441–0.962. The protocol is a valid and repeatable process for establishing muscular weakness in the working muscles of either plantar or dorsi flexion, as observed in the fatigued state. This can allow further examination of the effects of a localised muscular weakness on daily living tasks.
Humans are known to manage postural movements in a very elegant manner. In the task of standing up from a chair, a humanoid robot can benefit from the variability of human demonstrations. In this paper we propose a novel method for humanoid robots to imitate a dynamic postural movement demonstrated by humans. Since the kinematics of human participants and the humanoid robot used in this experiment are different, we solve the correspondence problem by making comparisons in a common reward space defined by a multimodal reward function composed of balance and effort terms. We fitted a fully actuated triple inverted pendulum to model both human and robot. We used Differential Evolution to find the optimal articular trajectory that minimizes the Kullback-Leibler difference between the human's and robot's reward profile subject to constraints.
In rapidly growing animals there are numerous selective pressures and developmental constraints underpinning the ontogenetic development of muscle–tendon morphology and mechanical properties. Muscle force generating capacity, tendon stiffness, elastic energy storage capacity and efficiency were calculated from muscle and tendon morphological parameters and in vitro tendon mechanical properties obtained from a growth series of ostrich cadavers. Ontogenetic scaling relationships were established using reduced major axis regression analysis. Ostrich pelvic limb muscle mass and cross-sectional area broadly scaled with positive allometry, indicating maintained or relatively greater capacity for maximum isometric force generation in larger animals. The length of distal limb tendons was found to scale with positive allometry in several tendons associated with antigravity support and elastic energy storage during locomotion. Distal limb tendon stiffness scaled with negative allometry with respect to body mass, with tendons being relatively more compliant in larger birds. Tendon material properties also appeared to be size-dependent, suggesting that the relative increased compliance of tendons in larger ostriches is due in part to compensatory distortions in tendon material properties during maturation and development, not simply from ontogenetic changes in tendon geometry. Our results suggest that the previously reported increase in locomotor economy through ontogeny in the ostrich is due to greater potential for elastic energy storage with increasing body size. In fact, the rate of this increase may be somewhat greater than the conservative predictions of previous studies, thus illustrating the biological importance of elastic tendon structures in adult ostriches. Summary: The ontogenetic scaling of muscle–tendon morphology and tendon material properties suggests maintained or relatively increased muscle force generation, increased elastic energy storage and locomotor economy in adult versus juvenile ostriches.
The study aimed to compare the effects of elastic and weight resistance exercise on muscular activation patterns. Twenty‐one moderately active males (age = 25 ± 8) performed ten bicep curls and leg extensions with weights (W), an equivalent elastic resistance (T), and a combined condition (TW) of half elastic tension and half weight resistance. Muscular activations of the biceps, triceps, rectus femoris, vastus medialis, and lateralis were recorded with Trigno wireless electrodes, and joint angles were recorded with Qualisys Track Manager. Biceps total activation was highest (P
The objective of this study was to investigate the changes in metabolic variables, running energetics and spatiotemporal gait parameters during an 80.5 km treadmill ultramarathon and establish which key predictive variables best determine ultramarathon performance. Twelve participants (9 male and 3 female, age 34 ± 7 years, and maximal oxygen uptake ([Formula: see text]O ) 60.4 ± 5.8 ml·kg ·min ) completed an 80.5 km time trial on a motorised treadmill in the fastest possible time. Metabolic variables: oxygen consumption ([Formula: see text]O ), carbon dioxide production ([Formula: see text]CO ) and pulmonary ventilation ([Formula: see text] ) were measured via indirect calorimetry every 16.1 km at a controlled speed of 8 km·h and used to calculate respiratory exchange ratio (RER), the energy cost of running (Cr) and fractional utilisation of [Formula: see text]O (F). Spatiotemporal gait parameters: stride length (SL) and cadence (SPM) were calculated via tri-axial accelerometery. Trial completion time was 09:00:18 ± 01:14:07 (hh:mm:ss). There were significant increases in [Formula: see text]O , Cr, F, [Formula: see text] and heart rate (HR) (p
Individuals with sarcoidosis are at risk of deconditioning and heightened non-communicable diseases through decreased muscle strength and physical activity. This systematic review analyzed published data to provide an overview of the associations of physical activity and physical fitness with sarcoidosis. A systematic search of PubMed and ScienceDirect, was conducted in April 2021 following PRISMA guidelines, to determine the association of sarcoidosis with levels of physical activity and fitness. Experimental studies of patients with sarcoidosis where cardio-respiratory capacity, physical activity and/or muscle strength were measured were selected. Twenty-one trials with 1442 participants met the inclusion criteria. Studies (published between 1986 and 2018) found reduced cardio-respiratory capacity (n = 17), physical activity levels (n = 2) and muscle strength (n = 8) within sarcoidosis patients, with those experiencing fatigue affected more than non-fatigued. Physical activity is reduced in sarcoidosis compared to normative values, including sedentary healthy individuals. In addition, muscle strength and cardio-respiratory capacity/fitness are reduced, with individuals affected by fatigue. Three clinical exercise-intervention trials demonstrated improved muscle strength and 6-minute walk distance alongside decreased fatigue ratings. The deconditioning effects of sarcoidosis, in addition to associated symptoms, can be overcome/improved by exercise. Further well-designed trials with exercise prescription are needed to establish standardized exercise recommendations specific to sarcoidosis.