scholarly journals Small vertebrates running on uneven terrain: a biomechanical study of two differently specialised lacertid lizards

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
François Druelle ◽  
Jana Goyens ◽  
Menelia Vasilopoulou-Kampitsi ◽  
Peter Aerts
Keyword(s):  
High Speed ◽  
Mechanical Energy ◽  
Small Animals ◽  
Podarcis Muralis ◽  
Cost Of Transport ◽  
Running Performance ◽  
Uneven Terrain ◽  
Hind Limbs ◽  
Custom Made ◽  
Lacertid Lizards

AbstractWhile running, small animals frequently encounter large terrain variations relative to their body size, therefore, terrain variations impose important functional demands on small animals. Nonetheless, we have previously observed in lizards that running specialists can maintain a surprisingly good running performance on very uneven terrains. The relatively large terrain variations are offset by their capacity for leg adjustability that ensures a ‘smooth ride’ of the centre of mass (CoM). The question as to how the effect of an uneven terrain on running performance and locomotor costs differs between species exhibiting diverse body build and locomotor specializations remains. We hypothesise that specialized runners with long hind limbs can cross uneven terrain more efficiently than specialized climbers with a dorso-ventrally flattened body and equally short fore and hind limbs. This study reports 3D kinematics using high-speed videos (325 Hz) to investigate leg adjustability and CoM movements in two lacertid lizards (Acanthodactylus boskianus, running specialist; Podarcis muralis, climbing specialist). We investigated these parameters while the animals were running on a level surface and over a custom-made uneven terrain. We analysed the CoM dynamics, we evaluated the fluctuations of the positive and negative mechanical energy, and we estimated the overall cost of transport. Firstly, the results reveal that the climbers ran at lower speeds on flat level terrain but had the same cost of transport as the runners. Secondly, contrary to the running specialists, the speed was lower and the energy expenditure higher in the climbing specialists while running on uneven terrain. While leg movements adjust to the substrates’ variations and enhance the stability of the CoM in the running specialist, this is not the case in the climbing specialist. Although their legs are kept more extended, the amplitude of movement does not change, resulting in an increase of the movement of the CoM and a decrease in locomotor efficiency. These results are discussed in light of the respective (micro-)habitat of these species and suggest that energy economy can also be an important factor for small vertebrates.

Do elite soccer players cover longer distance when losing? Differences between attackers and defenders

2020 ◽  
pp. 174795412098227
Author(s):  
Carlos Lago-Peñas ◽  
Anton Kalén ◽  
Miguel Lorenzo-Martinez ◽  
Roberto López-Del Campo ◽  
Ricardo Resta ◽  
...  
Keyword(s):  
New York ◽  
High Speed ◽  
Large Scale ◽  
Tracking System ◽  
Soccer Players ◽  
Running Performance ◽  
Situational Variables ◽  
Total Distance ◽  
Professional Soccer ◽  
Score Line

This study aimed to evaluate the effects playing position, match location (home or away), quality of opposition (strong or weak), effective playing time (total time minus stoppages), and score-line on physical match performance in professional soccer players using a large-scale analysis. A total of 10,739 individual match observations of outfield players competing in the Spanish La Liga during the 2018–2019 season were recorded using a computerized tracking system (TRACAB, Chyronhego, New York, USA). The players were classified into five positions (central defenders, players = 94; external defenders, players = 82; central midfielders, players = 101; external midfielders, players = 72; and forwards, players = 67) and the following match running performance categories were considered: total distance covered, low-speed running (LSR) distance (0–14 km · h−1), medium-speed running (MSR) distance (14–21 km · h−1), high-speed running (HSR) distance (>21 km · h−1), very HSR (VHSR) distance (21–24 km · h−1), sprint distance (>24 km · h−1) Overall, match running performance was highly dependent on situational variables, especially the score-line condition (winning, drawing, losing). Moreover, the score-line affected players running performance differently depending on their playing position. Losing status increased the total distance and the distance covered at MSR, HSR, VHSR and Sprint by defenders, while attacking players showed the opposite trend. These findings may help coaches and managers to better understand the effects of situational variables on physical performance in La Liga and could be used to develop a model for predicting the physical activity profile in competition.

scholarly journals Suspending force modeling based on nonlinear acoustics and high-speed running experiments for an ultrasonic journal bearing

2020 ◽  
Vol 12 (7) ◽  
pp. 168781402094047
Author(s):  
He Li ◽  
Yu Wang ◽  
Deen Bai ◽  
Fuyan Lyu ◽  
Kuidong Gao ◽  
...  
Keyword(s):  
Lead Zirconate Titanate ◽  
Smart Materials ◽  
High Speed ◽  
Acoustic Radiation ◽  
Dynamic Performance ◽  
Force Model ◽  
Trajectory Data ◽  
Running Performance ◽  
High Speeds ◽  
Radiation Theory

As a kind of promising noncontact bearings, ultrasonic bearings actuated by smart materials such as lead zirconate titanate ceramics show a good application prospect in high-speed machines and precision-measuring devices. The suspending force is one of the most important parameters that play a dominated role on the bearing’s static and dynamic performance. A suspending force model based on acoustic radiation theory for cylindrical object near sound source is built to predict the radial carrying capacity of an ultrasonic bearing actuated by three piezoelectric transducers. To validate the model, an ultrasonic bearing prototype is developed and a testing system is established. For observing the bearing’s dynamic running performance at high speeds, the bearing’s running experiment is carried out and the rotor center’s trajectory data and frequency spectrum are acquired to analyze the bearing’s dynamic characteristics at high speeds. The suspending force model and running performance experiments will contribute to the design, detection, and test of this type of bearings.

Suspension Optimum Design Considering Tire and Vehicle Matching

2014 ◽  
Vol 496-500 ◽  
pp. 617-620
Author(s):  
Fan Bai ◽  
Kong Hui Guo ◽  
Dang Lu
Keyword(s):  
Optimum Design ◽  
Performance Index ◽  
High Speed ◽  
Objective Assessment ◽  
Driving Safety ◽  
Safety Index ◽  
Experiment Data ◽  
Evaluation Standards ◽  
Vehicle Handling ◽  
Running Performance

A method of suspension optimum design based on the tire and vehicle matching was introduced in this paper. Firstly, the vehicle handling stability evaluation standards considering tire matching with vehicle were determined by the subjective and objective assessment. Secondly, the quality, suspension kinematics and compliance characteristics and tire mechanics of prototype were tested. The vehicle model of prototype was built in Carsim with the corresponding experiment data. The model was verified by the results of the vehicle handling stability tests. Then a combination simulation platform was developed by making use of Isight, Matlab and Casim. Finally the optimal design of suspension kinematics and compliance characteristics and tire mechanics were conducted, taking straight running performance index, high-speed driving safety index and high-speed cornering performance index as the objective. The simulation results indicated that after optimization, the straight running performance and high-speed cornering performance of prototype could be improved.

Control of ATRIAS in three dimensions: Walking as a forced-oscillation problem

2020 ◽  
Vol 39 (7) ◽  
pp. 774-796
Author(s):  
Siavash Rezazadeh ◽  
Jonathan W Hurst
Keyword(s):  
Feedback Linearization ◽  
High Speed ◽  
Forced Oscillation ◽  
Vertical Motion ◽  
Three Dimensions ◽  
Singular Perturbation Theory ◽  
Foot Placement ◽  
Uneven Terrain ◽  
Walking Control ◽  
The Stability

In this article, we present a new controller for stable and robust walking control of ATRIAS, an underactuated bipedal robot designed based on the spring-loaded inverted pendulum (SLIP) model. We propose a forced-oscillation scheme for control of vertical motion, which we prove to be stable and contractive. Moreover, we prove that, through some mild assumptions, the dynamics of the system can be written in a hierarchical form that decouples the stability analyses of the horizontal and vertical directions. We leverage these properties to find a stabilizing class of functions for foot placement. The torso control is also proved to be decoupled using singular perturbation theory and is stabilized through a feedback linearization controller. We also take advantage of the proposed framework’s flexibility and extend it to include a new reflex-based uneven-terrain walking control scheme. We test the controller for various desired walking speeds (0 to 2.5 m/s), for stepping up and down unexpected obstacles (15 cm), and for high-speed walking on a random uneven terrain (up to 10 cm of step-ups and step-downs and up to 1.8 m/s). The results show successful performance of the controller and its stability and robustness against various perturbations.

Evaluating the Influence of Specific Mechanical Energy on Biopolymer Blends Prepared via High-Speed Reactive Extrusion

2019 ◽  
Vol 1 (6) ◽  
pp. 1410-1419 ◽  
Author(s):  
Bárbara A. Calderón ◽  
Matthew S. McCaughey ◽  
Conor W. Thompson ◽  
Vincenzo L. Barinelli ◽  
Margaret J. Sobkowicz
Keyword(s):  
High Speed ◽  
Mechanical Energy ◽  
Reactive Extrusion ◽  
Specific Mechanical Energy ◽  
Biopolymer Blends

Engineering of small diameter tubular compacted fibrin matrices

2016 ◽  
Vol 17 (1-2) ◽  
Author(s):  
Thomas Aper ◽  
Mathias Wilhelmi ◽  
Klaus Hoeffler ◽  
Nils Benecke ◽  
Axel Haverich
Keyword(s):  
Tissue Engineering ◽  
Uniform Distribution ◽  
High Speed ◽  
Vascular Grafts ◽  
Small Diameter ◽  
Biomechanical Stability ◽  
Cardiovascular Tissue ◽  
Burst Strength ◽  
Custom Made ◽  
Biomechanical Strength

AbstractFibrin is widely used in different approaches of tissue engineering. Nevertheless, poor biomechanical strength restricts its use namely in cardiovascular tissue engineering. We have recently developed a novel moulding technique for the generation of highly stable fibrin tubes. The purpose of this study was the application of this method to the generation of small calibre fibrin tubes for the generation of bioartificial vascular grafts with a diameter of 3 mm. Therefore, a fibrinogen preparation was separated from plasma by means of cryoprecipitation and applied to a high-speed rotating casting mould in a low concentration to achieve slow polymerization and thereby uniform distribution of the fibrinogen. Thus, uniformly moulded 10 cm long fibrin tubes with a diameter of 3 mm were generated from 145±22 mg fibrinogen precipitated from 50 mL plasma. Thickness of the wall (522±57 μm) and biomechanical strength (47.4±11.1 kPa) were equable over the whole length of the tubes. Burst strength was 367±49 mm Hg. Thus, the developed technique enables the generation of tubular fibrin segments with a high biomechanical stability and represents a powerful tool for the generation of custom-made bioartificial vascular grafts.

Regular- and postseason comparisons of playing time and measures of running performance in NCAA Division I women soccer players

2015 ◽  
Vol 40 (9) ◽  
pp. 907-917 ◽  
Author(s):  
Adam J. Wells ◽  
Jay R. Hoffman ◽  
Kyle S. Beyer ◽  
Mattan W. Hoffman ◽  
Adam R. Jajtner ◽  
...  
Keyword(s):  
Ncaa Division I ◽  
High Intensity ◽  
High Speed ◽  
Division I ◽  
Soccer Players ◽  
Running Performance ◽  
Transient Motion ◽  
Absolute Time ◽  
Low Intensity ◽  
Playing Time

The management of playing time in National Collegiate Athletic Association (NCAA) soccer athletes may be a key factor affecting running performance during competition. This study compared playing time and running performance between regular-season and postseason competitions during a competitive women’s soccer season. Nine NCAA Division I women soccer players (age, 21.3 ± 0.9 years; height, 170.3 ± 5.7 cm; body mass, 64.0 ± 5.8 kg) were tracked using portable GPS devices across 21 games during a competitive season (regular season (n = 17); postseason (n = 4)). Movements on the field were divided into operationally distinct thresholds defined as standing/transient motion, walking, jogging, low-speed running, moderate-speed running, high-speed running, sprinting, low-intensity running, and high-intensity running. A significant increase in minutes played (+17%, p = 0.010) was observed at postseason compared with the regular season. Concomitant increases in time spent engaged in low-intensity running (LIR: +18%, p = 0.011), standing/transient motion (+35%, p = 0.004), walking (+17%, p = 0.022), distance covered while walking (+14%, p = 0.036), and at low intensity (+11%, p = 0.048) were observed. Performance comparisons between the first and second half within games revealed a significant decrease (p ≤ 0.05) in high-speed and high-intensity runs during the second half of the postseason compared with the regular season. Changes in minutes played correlated significantly with changes in absolute time spent engaged in LIR (r = 0.999, p < 0.001), standing/transient motion (r = 0.791, p = 0.011), walking (r = 0.975, p = 0.001), jogging (r = 0.733, p = 0.025), distance covered while walking (r = 0.898, p < 0.001) and low-intensity activity (r = 0.945, p < 0.001). Negative correlations were observed between minutes played and absolute time sprinting (r = −0.698, p = 0.037) and distance covered sprinting (r = −0.689, p = 0.040). Results indicate that additional minutes played during the postseason were primarily performed at lower intensity thresholds, suggesting running performance during postseason competitions may be compromised with greater playing time in intercollegiate women’s soccer.

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