Option selection in whole-body rotation movements in gymnastics

Abstract When a gymnast performs a somersault, the linear and angular momentum along with a particular control of inertia during the flight phase constrain the possibilities for action. Given the complexity and dynamic nature of the human moving system, one could argue that there exist a particular amount of stable coordination states when performing somersaults. The goal of this study was to explore the manifold of movement options and coordination states along with their differentiating parameters for a single somersault in gymnastics based on a simple mathematical model reflecting gymnast’s rotation behavior during the flight phase. Biomechanical parameters determining rotation behavior during a somersault were systematically varied with regard to a particular set of biomechanical constraints defining a successful somersault performance. Batch simulations revealed that from 10229760 simulation cycles only 655346 (approximately 6.41%) led to successful somersault performance. A subsequent analysis of the movement option landscape for the optimum angular momentum revealed ten coordination states for a single somersault that could be clearly distinguished based on the simulation parameters. Taken the results together, it becomes apparent that it may be most advisable to perform a single somersault with a larger moment of inertia when achieving the tucked position, a longer duration to achieve the tucked position, a longer duration of staying tucked, and an intermediate moment of inertia during landing. This strategy comprises the largest amount of movement options associated with an upright landing and thus the highest probability of success when performing a single somersault.

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Using Biofeedback to Reduce Step Length Asymmetry Impairs Dynamic Balance in People Poststroke

Neurorehabilitation and Neural Repair ◽

10.1177/15459683211019346 ◽

2021 ◽

pp. 154596832110193

Author(s):

Sungwoo Park ◽

Chang Liu ◽

Natalia Sánchez ◽

Julie K. Tilson ◽

Sara J. Mulroy ◽

...

Keyword(s):

Angular Momentum ◽

Sagittal Plane ◽

Dynamic Balance ◽

Objective Measure ◽

Frontal Plane ◽

Step Length ◽

Berg Balance Scale ◽

Whole Body ◽

Functional Gait ◽

Full Body

Background People poststroke often walk with a spatiotemporally asymmetric gait, due in part to sensorimotor impairments in the paretic lower extremity. Although reducing asymmetry is a common objective of rehabilitation, the effects of improving symmetry on balance are yet to be determined. Objective We established the concurrent validity of whole-body angular momentum as a measure of balance, and we determined if reducing step length asymmetry would improve balance by decreasing whole-body angular momentum. Methods We performed clinical balance assessments and measured whole-body angular momentum during walking using a full-body marker set in a sample of 36 people with chronic stroke. We then used a biofeedback-based approach to modify step length asymmetry in a subset of 15 of these individuals who had marked asymmetry and we measured the resulting changes in whole-body angular momentum. Results When participants walked without biofeedback, whole-body angular momentum in the sagittal and frontal plane was negatively correlated with scores on the Berg Balance Scale and Functional Gait Assessment supporting the validity of whole-body angular momentum as an objective measure of dynamic balance. We also observed that when participants walked more symmetrically, their whole-body angular momentum in the sagittal plane increased rather than decreased. Conclusions Voluntary reductions of step length asymmetry in people poststroke resulted in reduced measures of dynamic balance. This is consistent with the idea that after stroke, individuals might have an implicit preference not to deviate from their natural asymmetry while walking because it could compromise their balance. Clinical Trials Number: NCT03916562.

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DESCRIPTIVE ANALYSIS OF WHOLE BODY AND SEGMENTAL ANGULAR MOMENTUM ABOUT THE CENTER OF MASS DURING THE BACKSTROKE

Medicine & Science in Sports & Exercise ◽

10.1249/00005768-199505001-01297 ◽

1995 ◽

Vol 27 (Supplement) ◽

pp. S232

Author(s):

J. M. Cappaert

Keyword(s):

Angular Momentum ◽

Descriptive Analysis ◽

Center Of Mass ◽

Whole Body

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Muscle contributions to whole-body sagittal plane angular momentum during walking

Journal of Biomechanics ◽

10.1016/j.jbiomech.2010.08.015 ◽

2011 ◽

Vol 44 (1) ◽

pp. 6-12 ◽

Cited By ~ 69

Author(s):

R.R. Neptune ◽

C.P. McGowan

Keyword(s):

Angular Momentum ◽

Sagittal Plane ◽

Whole Body

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Whole-body walking pattern using pelvis-rotation for long stride and arm swing for yaw angular momentum compensation

10.1109/humanoids47582.2021.9555794 ◽

2021 ◽

Author(s):

Beomyeong Park ◽

Myeong-Ju Kim ◽

Eunho Sung ◽

Junhyung Kim ◽

Jaeheung Park

Keyword(s):

Angular Momentum ◽

Whole Body ◽

Arm Swing ◽

Walking Pattern ◽

Pelvis Rotation

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The Near-Synchronous Polar Candidate V4633 Sgr (Nova Sagittarii 1998)

International Astronomical Union Colloquium ◽

10.1017/s0252921100002049 ◽

2004 ◽

Vol 190 ◽

pp. 176-177

Author(s):

Y. Lipkin ◽

E. M. Leibowitz

Keyword(s):

Angular Momentum ◽

Momentum Transfer ◽

White Dwarf ◽

Moment Of Inertia ◽

The Other ◽

Angular Momentum Transfer ◽

Classical Nova ◽

Order Of Magnitude ◽

Photometric Monitoring ◽

The Moment

AbstractThe classical nova V4633 Sgr (1998) exhibits two photometric periodicities. The shorter period (P1=3.01 hr) is stable, while the other one, longer by ~2.5%, has decreased monotonically since shortly after the nova eruption, with Ṗ2 ≈ –10−6 (Lipkin et al. 2001).Here we report on results of photometric monitoring of the star in 2001 and 2002. During our observations, the longer period decreased more, and in 2002 it was only 1.8% longer than P1 The decrease rate (Ṗ2) in 2001-2002 was an order of magnitude smaller than in 1998-2000.These new results support the Near-Synchronous Polar classification which was suggested for V4633 Sgr (Lipkin et al. 2001). In this model, the longer period of V4633 Sgr is the spin of the white dwarf, and its variation since 1998 reflects changes in the moment of inertia of the white dwarf, and angular momentum transfer in the system following the nova eruption.

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Magnetic Field Amplification and Polar Jet Formation in Protostars

Symposium - International Astronomical Union ◽

10.1017/s0074180900096017 ◽

1987 ◽

Vol 115 ◽

pp. 384-384

Author(s):

S. Hinata

Keyword(s):

Magnetic Field ◽

Angular Momentum ◽

Kinetic Energy ◽

Accretion Disk ◽

Outer Edge ◽

Moment Of Inertia ◽

Simple Relationship ◽

Field Amplification ◽

Background Magnetic Field ◽

The Moment

There is a simple relationship among moment of inertia I, rotational kinetic energy K, and momentum L given by (David Layzer, private communication), 2IK ≧ L. During the Hayashi phase a rotating protostar will amplify the trapped magnetic field by a dynamo-like process. Since the rotation is expected to be fast, many unstable modes will be excited and will grow exponentially in time until some nonlinear processes saturate the amplitude. However, it may happen that the reduction in rotational kinetic energy becomes so large that without increasing the moment of inertia the inequality given above may not be satisfied. The only way to increase the moment of inertia is to move the mass outward. This can be done by transferring the angular momentum outward through the magnetic field. So we will have a fast rotating mass shell at the outer edge of the star. Further transfer of angular momentum will push the shell against the accretion disk; the moving masses of the disk will divert the mass flow along the background magnetic field which extends perpendicular to the accretion disk. This results in the hollow cone jets from both poles because the outward motion is primarily on the equatorial plane.

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PARTICLE-NUMBER CONSERVING TREATMENT FOR THE GROUND STATE BANDS IN EVEN-EVEN TRANSFERMIUM NUCLEI

International Journal of Modern Physics E ◽

10.1142/s0218301308011860 ◽

2008 ◽

Vol 17 (supp01) ◽

pp. 208-218 ◽

Cited By ~ 3

Author(s):

XIAO-TAO HE ◽

ZHONG-ZHOU REN

Keyword(s):

Angular Momentum ◽

Shell Model ◽

Single Particle ◽

Ground State ◽

Particle Number ◽

Rotational Frequency ◽

Moment Of Inertia ◽

Particle Level ◽

Pairing Correlations ◽

Band Crossing

The ground state bands observed in even-even transfermium nuclei 250 Fm and 252,254 No are investigated by the cranked shell model with the particle-number conserving treatment for the monopole and quadrupole pairing correlations. The experimental variations of the kinematic moment of inertia with rotational frequency are reproduced very well in our calculation. Our results show bankbendings of [Formula: see text] at ħω ≈ 0.275 and 0.300 MeV in 252 No and 254 No , respectively. The detailed information about the contribution to alignment from each cranked single particle level exhibits that the backbending is mainly due to the rapidly aligned angular momentum of proton 1j15/2 [770]1/2 pairs and neutron 2h11/2 [761]3/2, 1j15/2 [734]9/2 pairs the band crossing.

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Boundary conditions for the formation of the Moon

Netherlands Journal of Geosciences – Geologie en Mijnbouw ◽

10.1017/njg.2015.24 ◽

2015 ◽

Vol 95 (2) ◽

pp. 131-139 ◽

Cited By ~ 1

Author(s):

M. Reuver ◽

R.J. de Meijer ◽

I.L. ten Kate ◽

W. van Westrenen

Keyword(s):

Angular Momentum ◽

Boundary Conditions ◽

Total Angular Momentum ◽

Nuclear Explosion ◽

Moment Of Inertia ◽

The Moon ◽

Moon System ◽

Giant Impact ◽

The Earth ◽

The Impact

AbstractRecent measurements of the chemical and isotopic composition of lunar samples indicate that the Moon's bulk composition shows great similarities with the composition of the silicate Earth. Moon formation models that attempt to explain these similarities make a wide variety of assumptions about the properties of the Earth prior to the formation of the Moon (the proto-Earth), and about the necessity and properties of an impactor colliding with the proto-Earth. This paper investigates the effects of the proto-Earth's mass, oblateness and internal core-mantle differentiation on its moment of inertia. The ratio of angular momentum and moment of inertia determines the stability of the proto-Earth and the binding energy, i.e. the energy needed to make the transition from an initial state in which the system is a rotating single body with a certain angular momentum to a final state with two bodies (Earth and Moon) with the same total angular momentum, redistributed between Earth and Moon. For the initial state two scenarios are being investigated: a homogeneous (undifferentiated) proto-Earth and a proto-Earth differentiated in a central metallic and an outer silicate shell; for both scenarios a range of oblateness values is investigated. Calculations indicate that a differentiated proto-Earth would become unstable at an angular momentum L that exceeds the total angular momentum of the present-day Earth–Moon system (L0) by factors of 2.5–2.9, with the precise maximum dependent on the proto-Earth's oblateness. Further limitations are imposed by the Roche limit and the logical condition that the separated Earth–Moon system should be formed outside the proto-Earth. This further limits the L values of the Earth–Moon system to a maximum of about L/L0 = 1.5, at a minimum oblateness (a/c ratio) of 1.2. These calculations provide boundary conditions for the main classes of Moon-forming models. Our results show that at the high values of L used in recent giant impact models (1.8 < L/L0 < 3.1), the proposed proto-Earths are unstable before (Cuk & Stewart, 2012) or immediately after (Canup, 2012) the impact, even at a high oblateness (the most favourable condition for stability). We conclude that the recent attempts to improve the classic giant impact hypothesis by studying systems with very high values of L are not supported by the boundary condition calculations in this work. In contrast, this work indicates that the nuclear explosion model for Moon formation (De Meijer et al., 2013) fulfills the boundary conditions and requires approximately one order of magnitude less energy than originally estimated. Hence in our view the nuclear explosion model is presently the model that best explains the formation of the Moon from predominantly terrestrial silicate material.

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