scholarly journals Variaciones cinemáticas de ascenso en los ciclistas de montaña (Kinematic variations of uphill in mountain bikers)

Retos ◽  
2020 ◽  
pp. 257-263
Author(s):  
Esteban Aedo Muñoz ◽  
Alberto Rötger Guarda ◽  
Ignacio Ria Gamboa ◽  
Natalia Rodríguez Zárate ◽  
Cristian Rojas Reyes ◽  
...  
Keyword(s):  
Angular Velocity ◽  
Cycle Time ◽  
Sagittal Plane ◽  
Recovery Phase ◽  
Mountain Bike ◽  
Kinematic Indicators ◽  
Left Ankle ◽  
Preparatory Phase ◽  
Cross Country

  El propósito de este estudio fue determinar los indicadores cinemáticos relevantes entre categorías Elite y Sub-23 de ciclistas de cross country mountain bike (MTB) en la técnica de ascenso. La muestra fue compuesta por ciclistas Sub-23 (n=5; 18.8±0.5 años) y Elite (n=7; 24.2±2.0 años), todos los participante varones, diestros y ciclistas federados de competiciones de cross country MTB. Los datos fueron registrados desde el plano sagital al ascender por un terreno con una pendiente de 9.5±0.5% con la técnica de videofotogrametría. Los indicadores que presentaron diferencias entre categorías fueron: velocidad angular ciclo pedaleo izquierdo (p=0.04; g=-1.22), tiempo ciclo pedaleo izquierdo (p=0.02; g=1.44), velocidad angular ciclo pedaleo izquierdo de la fase preparatoria (p=0.03; g=-1.37), mientras que para la velocidad articular; velocidad de la cadera izquierda en fase de envión (p=0.029; g=-1.38), velocidad del tobillo izquierdo (p=0.005; g=-1.94) y tobillo derecho (p=0.002; g=-2.17) en fase de recuperación. Abstract. The purpose of this study was to determine the relevant kinematic indicators between Elite and Under-23 categories of cross country mountain bike (MTB) cyclists in the climbing technique. The sample was made up of Under-23 (n=5; 18.8±0.5 years) and Elite (n=7; 24.2±2.0 years) cyclists, all male and right-handed, federated participants of cross-country MTB competitions. The data were recorded from the sagittal plane to the ascending one through a terrain with a slope of 9.5±0.5% with videophotogrammetry. The indicators that showed differences between categories were: left pedaling cycle angular velocity (p=0.04; g=-1.22), left pedaling cycle time (p=0.02; g=1.44), left pedaling cycle angular velocity of the preparatory phase (p=0.03; g=-1.37), while for joint speed; speed of the left hip in clean and jerk phase (p=0.029; g =-1.38), speed of the left ankle (p=0.005; g=-1.94) and right ankle (p=0.002; g=-2.17) in recovery phase.

scholarly journals Joint torque and velocity optimization for a redundant leg of quadruped robot

2017 ◽  
Vol 14 (5) ◽  
pp. 172988141773189 ◽  
Author(s):  
Taihui Zhang ◽  
Honglei An ◽  
Hongxu Ma
Keyword(s):  
Angular Velocity ◽  
Sagittal Plane ◽  
Load Capacity ◽  
Optimization Criterion ◽  
Quadruped Robot ◽  
Joint Torque ◽  
Quadratic Program ◽  
Hydraulic Actuator ◽  
Joint Torques ◽  
Physical Limitations

Hydraulic actuated quadruped robot similar to BigDog has two primary performance requirements, load capacity and walking speed, so that it is necessary to balance joint torque and joint velocity when designing the dimension of single leg and controlling its motion. On the one hand, because there are three joints per leg on sagittal plane, it is necessary to firstly optimize the distribution of torque and angular velocity of every joint on the basis of their different requirements. On the other hand, because the performance of hydraulic actuator is limited, it is significant to keep the joint torque and angular velocity in actuator physical limitations. Therefore, it is essential to balance the joint torque and angular velocity which have negative correlation under the condition of constant power of the hydraulic actuator. The main purpose of this article is to optimize the distribution of joint torques and velocity of a redundant single leg with joint physical limitations. Firstly, a modified optimization criterion combining joint torques with angular velocity that takes both support phase and flight phase into account is proposed, and then the modified optimization criterion is converted into a normal quadratic programming problem. A kind of recurrent neural network is used to solve the quadratic program problem. This method avoids tremendous matrix inversion and fits for time-varying system. The achieved optimized distribution of joint torques and velocity is useful for aiding mechanical design and the following motion control. Simulation results presented in this article confirm the efficiency of this optimization algorithm.

Power Output and Pacing During International Cross-Country Mountain Bike Cycling

2018 ◽  
Vol 13 (9) ◽  
pp. 1243-1249 ◽  
Author(s):  
Cyril Granier ◽  
Chris R. Abbiss ◽  
Anaël Aubry ◽  
Yvon Vauchez ◽  
Sylvain Dorel ◽  
...  
Keyword(s):  
Power Output ◽  
Aerobic Power ◽  
Maximal Aerobic Power ◽  
Mass Ratio ◽  
Mountain Bike ◽  
Fast Start ◽  
World Class ◽  
Physiological Profiles ◽  
Road Cyclists ◽  
Cross Country

Purpose: To characterize the physiological profiles of elite cross-country mountain-bike (XCO-MTB) cyclists and to examine their pacing and power-output (PO) distribution during international races. Methods: Over 2 competitive seasons, 8 male XCO-MTB cyclists (VO2max 79.9 [5.2] mL·min−1·kg−1, maximal aerobic power [MAP] 411 [18] W and 6.3 [0.4] W·kg−1) regularly undertook incremental tests to assess their PO and heart rate (HR) at first and second ventilatory thresholds (VT1 and VT2) and at VO2max. During the same period, their PO, HR, speed, and cadence were recorded over 13 international races (total of 30 recorded files). Results: Mean PO, speed, cadence, and HR during the races were 283 (22) W (4.31 [0.32] W·kg−1, 68% [5%] MAP), 19.7 (2.1) km·h−1, 68 (8) rpm, and 172 (11) beats·min−1 (91% [2%] HRmax), respectively. The average times spent below 10% of MAP, between 10% of MAP and VT1, between VT1 and VT2, between VT2 and MAP, and above MAP were 25% (5%), 21% (4%), 13% (3%), 16% (3%), and 26% (5%), respectively. Both speed and PO decreased from the start loop to lap 1 before stabilizing until the end of the race.Conclusions: Elite off-road cyclists demonstrated typical values of world-class endurance cyclists with an excellent power-to-mass ratio. This study demonstrated that XCO-MTB races are performed at higher intensities than reported in previous research and are characterized by a fast start followed by an even pace.

Aerobic and Anaerobic Power Distribution During Cross-Country Mountain Bike Racing

2020 ◽  
pp. 1-6
Author(s):  
Bernhard Prinz ◽  
Dieter Simon ◽  
Harald Tschan ◽  
Alfred Nimmerichter
Keyword(s):  
Power Output ◽  
Power Distribution ◽  
Anaerobic Power ◽  
Energy System ◽  
Mountain Bike ◽  
Mean Power ◽  
Anaerobic Energy ◽  
Cross Country ◽  
Mean Power Output ◽  
Aerobic And Anaerobic

Purpose: To determine aerobic and anaerobic demands of mountain bike cross-country racing. Methods: Twelve elite cyclists (7 males;  = 73.8 [2.6] mL·min-1·kg−1, maximal aerobic power [MAP] = 370 [26] W, 5.7 [0.4] W·kg−1, and 5 females;  = 67.3 [2.9] mL·min−1·kg−1, MAP = 261 [17] W, 5.0 [0.1] W·kg−1) participated over 4 seasons at several (119) international and national races and performed laboratory tests regularly to assess their aerobic and anaerobic performance. Power output, heart rate, and cadence were recorded throughout the races. Results: The mean race time was 79 (12) minutes performed at a mean power output of 3.8 (0.4) W·kg−1; 70% (7%) MAP (3.9 [0.4] W·kg−1 and 3.6 [0.4] W·kg−1 for males and females, respectively) with a cadence of 64 (5) rev·min−1 (including nonpedaling periods). Time spent in intensity zones 1 to 4 (below MAP) were 28% (4%), 18% (8%), 12% (2%), and 13% (3%), respectively; 30% (9%) was spent in zone 5 (above MAP). The number of efforts above MAP was 334 (84), which had a mean duration of 4.3 (1.1) seconds, separated by 10.9 (3) seconds with a mean power output of 7.3 (0.6) W·kg−1 (135% [9%] MAP). Conclusions: These findings highlight the importance of the anaerobic energy system and the interaction between anaerobic and aerobic energy systems. Therefore, the ability to perform numerous efforts above MAP and a high aerobic capacity are essential to be competitive in mountain bike cross-country.

Physiological determinants of elite mountain bike cross-country Olympic performance

2018 ◽  
Vol 37 (10) ◽  
pp. 1154-1161 ◽  
Author(s):  
Jacob Bejder ◽  
Thomas Christian Bonne ◽  
Michael Nyberg ◽  
Kim Anker Sjøberg ◽  
Nikolai Baastrup Nordsborg
Keyword(s):  
Mountain Bike ◽  
Cross Country

scholarly journals Understanding the Physiological Requirements of the Mountain Bike Cross-Country Olympic Race Format

2018 ◽  
Vol 9 ◽  
Author(s):  
Arnaud Hays ◽  
Simon Devys ◽  
Denis Bertin ◽  
Laurie-anne Marquet ◽  
Jeanick Brisswalter
Keyword(s):  
Mountain Bike ◽  
Cross Country

Head Kinematics in Mini-Sled Tests of Foam Padding: Relevance of Linear Responses From Free Motion Headform (FMH) Testing to Head Angular Responses

2003 ◽  
Vol 125 (4) ◽  
pp. 523-532 ◽  
Author(s):  
J. Ivarsson ◽  
D. C. Viano ◽  
P. Lo¨vsund ◽  
Y. Parnaik
Keyword(s):  
Angular Velocity ◽  
Brain Injuries ◽  
Motor Vehicle ◽  
Sagittal Plane ◽  
Angular Acceleration ◽  
Linear Acceleration ◽  
Free Motion ◽  
Constant Thickness ◽  
Head Impacts ◽  
Hybrid Iii

The revised Federal Motor Vehicle Safety Standard (FMVSS) No. 201 specifies that the safety performance of vehicle upper interiors is determined from the resultant linear acceleration response of a free motion headform (FMH) impacting the interior at 6.7 m/s. This study addresses whether linear output data from the FMH test can be used to select an upper interior padding that decreases the likelihood of rotationally induced brain injuries. Using an experimental setup consisting of a Hybrid III head-neck structure mounted on a mini-sled platform, sagittal plane linear and angular head accelerations were measured in frontal head impacts into foam samples of various stiffness and density with a constant thickness (51 mm) at low (∼5.0 m/s), intermediate (∼7.0 m/s), and high (∼9.6 m/s) impact speeds. Provided that the foam samples did not bottom out, recorded peak values of angular acceleration and change in angular velocity increased approximately linearly with increasing peak resultant linear acceleration and value of the Head Injury Criterion HIC36. The results indicate that the padding that produces the lowest possible peak angular acceleration and peak change in angular velocity without causing high peak forces is the one that produces the lowest possible HIC36 without bottoming out in the FMH test.

Sign in / Sign up

Export Citation Format

Share Document