scholarly journals Centre of mass movement and mechanical energy fluctuation during gallop locomotion in the Thoroughbred racehorse

2006 ◽  
Vol 209 (19) ◽  
pp. 3742-3757 ◽  
Author(s):  
T. Pfau
Keyword(s):  
Mechanical Energy ◽  
Mass Movement ◽  
Centre Of Mass ◽  
Energy Fluctuation

scholarly journals Changes in Energy Cost and Total External Work of Muscles in Elite Race Walkers Walking at Different Speeds

2014 ◽  
Vol 44 (1) ◽  
pp. 129-136 ◽  
Author(s):  
Wiesław Chwała ◽  
Andrzej Klimek ◽  
Wacław Mirek
Keyword(s):  
Kinetic Energy ◽  
Total Energy ◽  
Energy Cost ◽  
Direct Method ◽  
Mechanical Energy ◽  
Mass Movement ◽  
Average Energy ◽  
Centre Of Mass ◽  
External Work ◽  
Race Walking

Abstract The aim of the study was to assess energy cost and total external work (total energy) depending on the speed of race walking. Another objective was to determine the contribution of external work to total energy cost of walking at technical, threshold and racing speed in elite competitive race walkers. The study involved 12 competitive race walkers aged years with 6 to 20 years of experience, who achieved a national or international sports level. Their aerobic endurance was determined by means of a direct method involving an incremental exercise test on the treadmill. The participants performed three tests walking each time with one of the three speeds according to the same protocol: an 8-minute walk with at steady speed was followed by a recovery phase until the oxygen debt was repaid. To measure exercise energy cost, an indirect method based on the volume of oxygen uptake was employed. The gait of the participants was recorded using the 3D Vicon opto-electronic motion capture system. Values of changes in potential energy and total kinetic energy in a gate cycle were determined based on vertical displacements of the centre of mass. Changes in mechanical energy amounted to the value of total external work of muscles needed to accelerate and lift the centre of mass during a normalised gait cycle. The values of average energy cost and of total external work standardised to body mass and distance covered calculated for technical speed, threshold and racing speeds turned out to be statistically significant. The total energy cost ranged from 51.2 kJ.m-1 during walking at technical speed to 78.3 kJ.m-1 during walking at a racing speed. Regardless of the type of speed, the total external work of muscles accounted for around 25% of total energy cost in race walking. Total external work mainly increased because of changes in the resultant kinetic energy of the centre of mass movement.

Body Centre of Mass Movement in the Sound Horse

2000 ◽  
Vol 160 (3) ◽  
pp. 225-234 ◽  
Author(s):  
H.H.F. BUCHNER ◽  
S. OBERMÜLLER ◽  
M. SCHEIDL
Keyword(s):  
Mass Movement ◽  
Centre Of Mass

scholarly journals Spring-like leg behaviour, musculoskeletal mechanics and control in maximum and submaximum height human hopping

2011 ◽  
Vol 366 (1570) ◽  
pp. 1516-1529 ◽  
Author(s):  
Maarten F. Bobbert ◽  
L. J. Richard Casius
Keyword(s):  
Energy Expenditure ◽  
Muscle Activation ◽  
Mechanical Energy ◽  
Reaction Force ◽  
Ground Reaction Forces ◽  
Centre Of Mass ◽  
Leg Stiffness ◽  
Reaction Forces ◽  
And Control ◽  
The Relationship

The purpose of this study was to understand how humans regulate their ‘leg stiffness’ in hopping, and to determine whether this regulation is intended to minimize energy expenditure. ‘Leg stiffness’ is the slope of the relationship between ground reaction force and displacement of the centre of mass (CM). Variations in leg stiffness were achieved in six subjects by having them hop at maximum and submaximum heights at a frequency of 1.7 Hz. Kinematics, ground reaction forces and electromyograms were measured. Leg stiffness decreased with hopping height, from 350 N m −1 kg −1 at 26 cm to 150 N m −1 kg −1 at 14 cm. Subjects reduced hopping height primarily by reducing the amplitude of muscle activation. Experimental results were reproduced with a model of the musculoskeletal system comprising four body segments and nine Hill-type muscles, with muscle stimulation STIM( t ) as only input. Correspondence between simulated hops and experimental hops was poor when STIM( t ) was optimized to minimize mechanical energy expenditure, but good when an objective function was used that penalized jerk of CM motion, suggesting that hopping subjects are not minimizing energy expenditure. Instead, we speculated, subjects are using a simple control strategy that results in smooth movements and a decrease in leg stiffness with hopping height.

scholarly journals A method for tracking centre of mass displacement during non-seated cycling using an inertial sensor

2020 ◽  
Author(s):  
Ross D. Wilkinson ◽  
Glen A. Lichtwark
Keyword(s):  
Repeated Measures ◽  
Inertial Sensor ◽  
Mechanical Energy ◽  
Vertical Displacement ◽  
Cycling Performance ◽  
Measurement Unit ◽  
Centre Of Mass ◽  
Joint Power ◽  
Lower Back ◽  
Marker Cluster

Abstract Instantaneous crank power does not equal total joint power if a rider's centre of mass (CoM) gains and loses mechanical energy. Thus, estimating CoM motion and the associated energy changes can provide valuable information about cycling performance. To date, an accurate and precise method for tracking CoM motion during outdoor cycling has not been validated. Purpose: To assess the suitability of an inertial measurement unit (IMU) for tracking CoM motion during non-seated cycling by comparing vertical displacement derived from an inertial sensor mounted to the lower back of the rider to an attached marker cluster and to a kinematic estimate of vertical CoM displacement from a full-body musculoskeletal model (Model). Methods: IMU and motion capture data were collected synchronously for 10 seconds while participants (n = 7) cycled on an ergometer in a non-seated posture at three power outputs and two cadences. A limits of agreement analysis, corrected for repeated measures, was performed on the range of vertical displacement between the IMU and the two other measures. A total of 303 crank cycles were analysed. Results: The IMU measured vertical displacement of the marker cluster with high accuracy (1.6 mm) and precision (3.5 mm) but substantially overestimated the kinematic estimate of rider CoM displacement. Conclusion: We interpret these findings as evidence that a single IMU placed on the lower back is unsuitable for tracking rider CoM displacement during non-seated cycling if the linearly increasing overestimation is unaccounted for.

scholarly journals Collision-based mechanics of bipedal hopping

2013 ◽  
Vol 9 (4) ◽  
pp. 20130418 ◽  
Author(s):  
Anne K. Gutmann ◽  
David V. Lee ◽  
Craig P. McGowan
Keyword(s):  
Mass Velocity ◽  
Mechanical Energy ◽  
Large Fraction ◽  
Center Of Mass ◽  
Reaction Force ◽  
Centre Of Mass ◽  
Cost Of Transport ◽  
Kangaroo Rats ◽  
Muscle Work ◽  
Collision Angle

The muscle work required to sustain steady-speed locomotion depends largely upon the mechanical energy needed to redirect the centre of mass and the degree to which this energy can be stored and returned elastically. Previous studies have found that large bipedal hoppers can elastically store and return a large fraction of the energy required to hop, whereas small bipedal hoppers can only elastically store and return a relatively small fraction. Here, we consider the extent to which large and small bipedal hoppers (tammar wallabies, approx. 7 kg, and desert kangaroo rats, approx. 0.1 kg) reduce the mechanical energy needed to redirect the centre of mass by reducing collisions. We hypothesize that kangaroo rats will reduce collisions to a greater extent than wallabies since kangaroo rats cannot elastically store and return as high a fraction of the mechanical energy of hopping as wallabies. We find that kangaroo rats use a significantly smaller collision angle than wallabies by employing ground reaction force vectors that are more vertical and center of mass velocity vectors that are more horizontal and thereby reduce their mechanical cost of transport. A collision-based approach paired with tendon morphometry may reveal this effect more generally among bipedal runners and quadrupedal trotters.

scholarly journals The three-dimensional locomotor dynamics of African ( Loxodonta africana ) and Asian ( Elephas maximus ) elephants reveal a smooth gait transition at moderate speed

2007 ◽  
Vol 5 (19) ◽  
pp. 195-211 ◽  
Author(s):  
Lei Ren ◽  
John R Hutchinson
Keyword(s):  
Inverted Pendulum ◽  
Mechanical Energy ◽  
Three Dimensional ◽  
The Body ◽  
Centre Of Mass ◽  
Slow Speed ◽  
Gait Transition ◽  
Asian Elephants ◽  
Weight Support ◽  
Running Mechanics

We examined whether elephants shift to using bouncing (i.e. running) mechanics at any speed. To do this, we measured the three-dimensional centre of mass (CM) motions and torso rotations of African and Asian elephants using a novel multisensor method. Hundreds of continuous stride cycles were recorded in the field. African and Asian elephants moved very similarly. Near the mechanically and metabolically optimal speed (a Froude number (Fr) of 0.09), an inverted pendulum mechanism predominated. With increasing speed, the locomotor dynamics quickly but continuously became less like vaulting and more like bouncing. Our mechanical energy analysis of the CM suggests that at a surprisingly slow speed (approx. 2.2 m s −1 , Fr 0.25), the hindlimbs exhibited bouncing, not vaulting, mechanics during weight support. We infer that a gait transition happens at this relatively slow speed: elephants begin using their compliant hindlimbs like pogo sticks to some extent to drive the body, bouncing over their relatively stiff, vaulting forelimbs. Hence, they are not as rigid limbed as typically characterized for graviportal animals, and use regular walking as well as at least one form of running gait.

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