SIMULATION OF THE AIRBORNE PHASE OF THE GRAND JET IN BALLETD. Gordon E. Robertson, PhD, FCSBPamela Galler, BScLisa Stanley, BSc

Biomechanics Laboratory,School of Human Kinetics,University of Ottawa, Ottawa, CANADA

IntroductionGrand jet is one of the strongest jumps in balletIt is characterized by a leap that travels horizontallyLaws (2002) proposed that it is possible for the upper body to appear to translate in flight while the centre of gravity follows its parabolic path

Grand Jet

MethodsTwo experienced ballet dancers/instructorsPerformed several grand jets in sequence with a step in between jumpsSome trials were done landing on a force platformVideo taped at 60 fps10-segment model of body (i.e., hands and feet ignored)Planar motion analysis

MethodsTakeoff velocity determined from data preceding and after takeoffInitial estimate of total body angular momentum taken from average of flight phase momentaJoint displacements, initial position at takeoff, initial velocity and angular momentum were then used to iteratively obtain changes in trunk angle during flight (Lemaire & Robertson 1990)Total body angular momentum was adjusted by comparing simulated motion with actual motion

Methods

MethodsOnce a successful simulation was achieved:Hip joint displacements were modified to elevate lower extremities to produce full split in the air prior to reaching peak heightShoulder joint displacements were then modified to raise the upper extremities until a flat trajectory of the head and shoulders was achieved

ResultsNeither dancer had a flat trajectory of the upper body during their jumpsRaising the legs to achieve a split configuration in the air was insufficient to achieve a flat trajectoryRaising the arms past the horizontal was necessary to achieve the linear translation illusion with both dancers

Arms High, Legs Horizontal

Initial Jump

Jump after Legs Raised to Horizontal

Jump with Legs and Arms Raised

Jump Height versus Shoulder Rise

DiscussionThe illusion of floating through the air or linear translating while airborne could be achieved but required that the arms elevate above horizontalIn some dance traditions this is not a permissible motionThe illusion could be extended further by lowering the arms and legs after the jump apex, however, this may result in a hazardous landing

ReferencesLemaire, E.D. & Robertson, D.G.E. (1990) Validation of a computer simulation for planar airborne human motions. Journal of Human Movement Studies, 18:213-28.Laws, K. (2002) Physics and the Art of Dance. New York: Oxford Press.

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