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Looking for new opportunities in mechanical design, we are interested in studying the kinematic behaviour of biological joints. The real kinematic behaviour of the elbow of quadruped animals (which is submitted to high mechanical stresses in comparison with bipeds) remains unexplored. The sheep elbow joint was chosen because of its similarity with a revolute joint. The main objective of this study is to estimate the effects of elbow simplifications on the prediction of joint reaction forces in inverse dynamic simulations. Rigid motions between humerus and radius-ulna were registered during full flexion-extension gestures on five cadaveric specimens. The experiments were initially conducted with fresh specimens with ligaments and repeated after removal of all soft tissue, including cartilage. A digital image correlation system was used for tracking optical markers fixed on the bones. The geometry of the specimens was digitized using a 3D optical scanner. Then, the instantaneous helical axis of the joint was computed for each acquisition time. Finally, an OpenSim musculoskeletal model of the sheep forelimb was used to quantify effects of elbow joint approximations on the prediction of joint reaction forces. The motion analysis showed that only the medial-lateral translation is sufficiently large regarding the measuring uncertainty of the experiments. This translation assimilates the sheep elbow to a screw joint instead of a revolute joint. In comparison with fresh specimens, the experiments conducted with dry bone specimens (bones without soft tissue) provided different kinematic behaviour. From the results of our inverse dynamic simulations, it was noticed that the inclusion of the medial-lateral translation to the model made up with the mean flexion axis does not affect the predicted joint reaction forces. A geometrical difference between the axis of the best fitting cylinder and the mean flexion axis (derived from the motion analysis) of fresh specimens was highlighted. This geometrical difference impacts slightly the prediction of joint reactions. [ABSTRACT FROM AUTHOR]

Background: Neural injury to the motor cortex may result in long-term impairments. As a model for human impairments, rodents are often used to study deficits related to reaching and grasping, using the single-pellet reach-to-grasp task. Current assessments of this test capture mostly endpoint outcome. While qualitative features have been proposed, they usually involve manual scoring. Objective: To detect three phases of movement during the single-pellet reach-tograsp test and assess completion of each phase. To automatically monitor rat forelimb trajectory so as to extract kinematics and classify phase outcome. Methods: A top-view camera is used to monitor three rats during training, healthy and impaired testing, over 33 days. By monitoring the coordinates of the forelimb tip along with the position of the pellet, the algorithm divides a trial into reaching, grasping and retraction. Unfulfilling any of the phases results in one of three possible errors: miss, slip or drop. If all phases are complete, the outcome label is success. Along with endpoints, movement kinematics are assessed: variability, convex hull, mean and maximum reaching speed, length of trajectory and peak forelimb extension. Results: The set of behavior endpoints was extended to include miss, slip, drop and success rate. The labeling algorithm was tested on pre- and post-lesion datasets, with overall accuracy rates of 86% and 92%, respectively. These endpoint features capture a drop in skill after motor cortical lesion as the success rate of 59.6 ± 11.8% pre-lesion decreases to 13.9 ± 8.2% post-lesion, along with a significant increase in miss rate from 7.2 ± 6.7% pre-lesion to 50.2 ± 18.7% post-lesion. Kinematics reveals individualspecific strategies of improvement during training, with a common trend of trajectory variability decreasing with success. Correlations between kinematics and endpoints reveal a more complex pattern of relationships during rehabilitation (18 significant pairs of features) than during training (nine correlated pairs). Conclusion: Extended endpoint outcomes and kinematics of reaching and grasping are captured automatically with a robust computer program. Both endpoints and kinematics capture intra-animal drop in skill after a motor cortical lesion. Correlations between kinematics and endpoints change from training to rehabilitation, suggesting different mechanisms that underlie motor improvement. [ABSTRACT FROM AUTHOR]

Hummingbirds differentially modify flight kinematics in response to the type of challenge imposed. Weightlifting is associated with increases in stroke amplitude (the angle swept by the wings) to increase the angular velocity of the wings and generate the requisite lift, but only up to 160°. Conversely, flight in hypodense air is accomplished by increasing the angular velocity of the wing through increases in wingbeat frequency and stroke amplitudes, with larger increases in amplitude than seen in weightlifting flight. The kinematic differences between these two challenges may be facilitated by the lower energetic costs associated with overcoming drag and inertial forces over the wing during hypodense flight. Thus, we hypothesized that energetic expenditure is what limits the kinematics of weightlifting flight, with lower air densities permitting increases in angular velocity at comparatively lower costs. To explore the kinematic and energetic effects of air density and weightlifting on hovering flight performance, video and respirometric recordings of weightlifting were performed on four species of hummingbirds across an elevational gradient. Contrary to our hypothesis, wingbeat frequency did not vary due to elevation. Instead, wingbeat frequency seems to increase depending on the power requirements for sustaining hovering flight. Furthermore, metabolic rates during hovering increased with angular velocity alone, independent of elevation. Thus, it appears that the differential responses to flight challenges are not driven by variation in the flight media. [ABSTRACT FROM AUTHOR]

ABSTRACT While the mass distribution of limbs is known to influence the metabolic energy consumed during locomotion, it remains unknown how the mass distribution of limbs may influence overall limb kinematics and whether the influence of limb mass distribution on limb kinematics differs between fore- and hindlimbs. To examine limb mass distribution's influence upon fore- and hindlimb kinematics, temporal stride parameters and swing phase joint kinematics were recorded from four dogs trotting on a treadmill with 0.5% and 1.0% body mass added to each limb, forelimbs alone, and hindlimbs alone, as well as with no added mass. Under all loading conditions, stride period did not differ between fore- and hindlimbs; however, forelimbs exhibited greater duty factors and stance durations, whereas hindlimbs exhibited greater swing durations, which may be related to the hindlimb's greater mass. Changes in forelimb joint and hip range of motion (RoM), flexion, and extension were subject to a high amount of kinematic plasticity among dogs. In contrast, for the knee and ankle, distally loading all four limbs or hindlimbs alone substantially increased joint RoM and flexion. Increased flexion of the knee and ankle has the potential to reduce the hindlimb's rotational inertia during swing phase. The differing response of fore- and hindlimbs with regard to joint kinematics is likely due to differences in their mass and mass distribution and differences in the physiological traits of fore- and hindlimb protractors and joint flexors. [ABSTRACT FROM AUTHOR]

Maneuverability is one of the most important and least understood aspects of animal locomotion. The hydrofoil-like flippers of cetaceans are thought to function as control surfaces that effect maneuvers, but quantitative tests of this hypothesis have been lacking. Here, we constructed a simple hydrodynamic model to predict the longitudinal-axis roll performance of fin whales, and we tested its predictions against kinematic data recorded by on-board movement sensors from 27 free-swimming fin whales. We found that for a given swimming speed and roll excursion, the roll velocity of fin whales calculated from our field data agrees well with that predicted by our hydrodynamic model. Although fluke and body torsion may further influence performance, our results indicate that lift generated by the flippers is sufficient to drive most of the longitudinal-axis rolls used by fin whales for feeding and maneuvering. [ABSTRACT FROM AUTHOR]

When the head does not move, rapid movements of the eyes called saccades are used to redirect the line of sight. Saccades are defined by a series of metrical and kinematic (evolution of a movement as a function of time) relationships. For example, the amplitude of a saccade made from one visual target to another is roughly 90% of the distance between the initial fixation point (T0) and the peripheral target (T1). However, this stereotypical relationship between saccade amplitude and initial retinal error (T1-T0) may be altered, either increased or decreased, by surreptitiously displacing a visual target during an ongoing saccade. This form of motor learning (called saccadic adaptation) has been described in both humans and monkeys. Recent experiments in humans and monkeys have suggested that internal (proprioceptive) and external (target shape, color, and/or motion) cues may be used to produce context-dependent adaptation. We tested the hypothesis that an external contextual cue (target color) could be used to evoke differential gain (actual saccade/initial retinal error) states in rhesus monkeys. We did not observe differential gain states correlated with target color regardless of whether targets were displaced along the same vector as the primary saccade or perpendicular to it. Furthermore, this observation held true regardless of whether adaptation trials using various colors and intrasaccade target displacements were randomly intermixed or presented in short or long blocks of trials. These results are consistent with hypotheses that state that color cannot be used as a contextual cue and are interpreted in light of previous studies of saccadic adaptation in both humans and monkeys. [ABSTRACT FROM AUTHOR]

Limb amputation often represents the only treatment option for canine patients with certain diseases or injuries of the appendicular system. Previous studies have investigated adaptations to tripedal locomotion in dogs but there is a lack of understanding of biomechanical compensatory mechanisms. This study evaluated the kinematic differences between quadrupedal and tripedal locomotion in nine healthy dogs running on a treadmill. The loss of the right pelvic limb was simulated using an Ehmer sling. Kinematic gait analysis included spatio-temporal comparisons of limb, joint and segment angles of the remaining pelvic and both thoracic limbs. The following key parameters were compared between quadrupedal and tripedal conditions: angles at touch-down and lift-off, minimum and maximum joint angles, plus range of motion. Significant differences in angular excursion were identified in several joints of each limb during both stance and swing phases. The most pronounced differences concerned the remaining pelvic limb, followed by the contralateral thoracic limb and, to a lesser degree, the ipsilateral thoracic limb. The thoracic limbs were, in general, more retracted, consistent with pelvic limb unloading and previous observations of bodyweight re-distribution in amputees. Proximal limb segments showed more distinct changes than distal ones. Particularly, the persistently greater anteversion of the pelvis probably affects the axial system. Overall, tripedal locomotion requires concerted kinematic adjustments of both the appendicular and axial systems, and consequently preventive, therapeutic and rehabilitative care of canine amputees should involve the whole musculoskeletal apparatus. [ABSTRACT FROM AUTHOR]

The objective was to assess sows' lameness by measuring weight distribution on limbs using a force plate made up of 4 individual platforms each resting on 4 single-ended beam load cells. The weight was recorded at an average rate of 14 readings per s over a 15 min period. Ten sows (5 lame sows and 5 sound sows) were weighed twice on 2 different days to assess the repeatability of the measure. Sixty-one sows were then selected in 2 different sites and visually scored for lameness, using a 3-point scoring system (0 = normal gait; 1 = abnormal gait, and/or stiffness; and 2 = shortened stride, and/or the sow puts less weight or avoids putting weight on 1 leg). Various measures were recorded from each sow using the force plate (percentage of weight, the ratio between the weights applied by contralateral legs, weight shifting, and amplitude of weight bearing and weight removing), kinematics (speed, stride length, swing time, stance time, foot height, and carpal and tarsal joints angle average and amplitude), and accelerometers (time spent standing during 24 h, frequency of stepping behavior during feeding, and latency to lie down after feed delivery). The within-sow CV for each measure taken from the force plate were lower than 15%, which reflects a good repeatability. Among force plate measures, only the weight shifting frequency and the ratio between the weights applied by contralateral legs differed between lameness scores. Sows that scored 2 had a higher frequency of weight shifting for fore legs (P = 0.0003) and hind legs (P = 0.0007) than sows scored 0 and 1. The ratio between the weights applied by contralateral legs decreased with the increase of lameness score for the hind limbs (P = 0.014). However, these measures also differed between sites (P < 0.01). These differences may be due to various reasons, including but not limited to genetics and housing systems. Nevertheless, the results suggest that force plate measures such as the asymmetry in the weight applied between a pair of legs and weight shifting are good indicators of lameness. Multivariate analysis on fore and hind legs showed independency between variables related to animals in movement (measures from kinematics) and variables related to static animals (measures from the force plate and accelerometers). Therefore, both static and dynamic methods need to be used to detect various lame sows. [ABSTRACT FROM AUTHOR]

Sexual selection often results in males exhibiting exaggerated traits (e.g. bright colors, elaborate appendages) to attract potential mates and in some cases to also use as a weapon. These traits, however, can impose costs, such as an increase in energy expenditure and a decrease in locomotor performance, which could decrease foraging efficiency and increase an individual's vulnerability to predators. We examined the effect of the enlarged claw in male fiddler crabs U ca pugilator on ecologically relevant performance measures. We measured locomotor performance and kinematics during horizontal, uphill and downhill movements. Speed and stride mechanics were measured for clawed males, males after the claw was removed, and females while running on level (0°), uphill (15 and 30°) and downhill (−15 and −30°) slopes. Endurance capacities were measured on all crabs on horizontal and uphill inclines. Though claw removal had no significant effect on horizontal speeds, removal of the major claw significantly increased uphill speeds of male fiddler crabs at 15 and 30° inclines. Generally, as incline increased, the difference in performance between males with the enlarged claw and those with the claw removed increased. We also found that clawed males exhibit slower downhill speeds compared to clawless males and that claw removal significantly enhanced endurance on all inclines. This study indicates that an assessment of movement on level surfaces alone may not be entirely ecologically relevant when determining the actual costs of sexually selected ornaments. [ABSTRACT FROM AUTHOR]

The work describes and compares the conformation traits and gait characteristics in the main native Iberian dressage Purebreds (Lusitano, Spanish and Menorca horses). In total, 4 strides belonging to each of 66 males (4-14 years old) were recorded at handled trot, using a 3D semi-automatic movement analysis system. Principal component analysis (PCA) and intraclass Correlations (iC) were computed. The Menorca Purebred showed proportionally higher limbs (23.8 and 15.1 cm for the forelimb cannon and pastern lengths), the Lusitano Purebred had larger inclinations (66.1°, 37.7° and 47.9° for the scapula and pastern angles), and the Spanish Purebred presented a longer scapula (41.5 cm) and a larger hip angle (132.1°), apparently showing a better conformation for dressage gaits. However, the three breeds presented undesirable tarsus joint conformation (<155.5°) for dressage performance. In general, all of them showed good features in the kinematics of the forelimbs. Nevertheless, the functional capacity of their hindlimbs and linear parameters probably need to be improved for their competitiveness. [ABSTRACT FROM AUTHOR]

Background: Swinging limb lameness is defined as a motion disturbance ascribed to a limb in swing phase. Little is known about its biomechanics in dogs, particularly about the body motions that accompany it, such as vertical head and pelvic motion asymmetry. The aim of this study was to describe the changes in vertical head and pelvic motion asymmetry in dogs with induced swinging limb motion disturbance, mimicking a swinging limb lameness. Fore- and hind-limb lameness was induced in ten sound dogs by placing a weight (200 g) proximal to the carpus or tarsus, respectively. Marker-based motion capture by eight infrared light emitting video cameras recorded the dogs when trotting on a treadmill. Body symmetry parameters were calculated, including differences between the two highest positions of the head (HDmax) and pelvis (PDmax) and between the two lowest positions of the head (HDmin) and pelvis (PDmin), with a value of zero indicating perfect symmetry. Results: Induction of swinging forelimb lameness showed significant changes in HDmax (median and range: sound 1.3 mm [− 4.7 to 3.1], in the left side − 28.5 mm [− 61.2 to − 17.9] and in the right side 20.1 mm [− 4.4 to 47.5]) and, induction of swinging hind limb lameness showed significant changes in PDmax (sound 2.7 mm [− 7.4 to 7.2], in the left side − 10.9 mm [− 22.4 to 0.5] and in the right side 8.6 mm [− 3 to 30]), as well as an increased hip movement asymmetry (sound 1.6 mm [− 8.6 to 19.9], in the left side − 18.1 mm [− 36.7 to 5.4] and in the right side 15 mm [− 20.7 to 32.1]) (P < 0.05). Conclusions: Induced swinging fore- and hind limb lameness resulted in significant increased asymmetry of the maximal vertical displacement movement of the head and pelvis, due to decreased lifting of the head in forelimb lameness and of the pelvis in hind limb lameness. The results suggest that asymmetry of the maximal vertical displacement of the head and pelvis (i.e. lifting) is a key lameness sign to evaluate during examination of swinging limb lameness. [ABSTRACT FROM AUTHOR]

Ovine locomotion studies are rare, despite their relevance for medical research. The aim of this preliminary study was to investigate habituation and temporospatial parameters during treadmill walking of seven Austrian Mountain sheep. Sheep were naive to treadmill exercise. During five treadmill sessions, movement cycle duration (MCD), vertical trunk movement (VTM), stride height (SH), stride length (SL), and percentage of movement cycle at stance (%St) were assessed. Two sheep were excluded from the study because they would not walk on the treadmill. From the end measurement session, MCD (0.95 s) and %St (62%) were similar to reported kinetics of sheep walking over ground, although stride length (1.05 m) was longer in this study. These findings suggest that sheep may require more than five sessions to become habituated to treadmill walking. [ABSTRACT FROM AUTHOR]