Track and Field: Discus

Overview

The discus throw is a track and field throwing event in which the athlete rotates one and a half turns within a circle to accelerate a discus before releasing it at speed and at an optimal angle. The thrower begins with a preparatory wind-up, pivots off the non-dominant foot into an airborne turn, plants the dominant foot in the center of the circle, and drives through the legs and trunk before releasing the discus off the fingers with the arm extended. Distance depends on release speed, release angle, and the sequencing of the legs, hips, and trunk ahead of the arm. Biomechanical analysis of the discus throw can address foot-off and foot-down timing through the turn, hip-shoulder separation built during the turn, arm and shoulder positioning at release, and release speed, height, and angle.

Dimensions

Required inputs for processing are not yet defined. When supported, typical dimensions may include:

handedness: the handedness of the athlete [‘left’, ‘right’], which determines throw direction and rotation

Output Variables

Generic Outputs

Every capture includes session metadata, standard joint angle/velocity time series, and 3D keypoint positions common to all movements. See Generic Outputs for the full list.

Events

Metric	Acronym	Description
Peak Backswing	PB	the peak backswing position prior to the throw
Dominant Foot Off	DFO	the instance when the dominant foot leaves the ground
NonDominant Foot Off	NDFO	the instance when the nondominant foot leaves the ground
Dominant Foot Down	DFO	the instance when the dominant foot touches the ground
NonDominant Foot Down	NDFO	the instance when the nondominant foot touches the ground
Release	R	release of the discus

Phases and Stages of the Discus Throw

Phase	Start	End
Preparation	PB	DFO
Entry	DFO	NDFO
Airborne	NDFO	DFD
Transition	DFD	NDFD
Delivery	NDFD	R

Discrete Metrics

Metric	Units	Description
Handedness	N/A	Calculated handedness of the athlete (‘right’ or ‘left’)
Preparation Phase	seconds	Time between peak backswing and dominant foot off
Entry Phase	seconds	Time between dominant foot off and non-dominant foot off
Airborne Phase	seconds	Time between non-dominant foot off and dominant foot down
Transition Phase	seconds	Time between dominant foot down and non-dominant foot down
Delivery Phase	seconds	Time between non-dominant foot down and release
Speed at DFO	m/s	Speed of the discus at dominant foot off
Speed at NDFO	m/s	Speed of the discus at non-dominant foot off
Speed at DFD	m/s	Speed of the discus at dominant foot down
Speed at NDFD	m/s	Speed of the discus at non-dominant foot down
Speed at Release	m/s	Speed of the discus at release
Horizontal Release Speed	m/s	Horizontal component of discus speed at release
Vertical Release Speed	m/s	Vertical component of discus speed at release
Hip-Shoulder Separation at DFO	degrees	Transverse angle between hips and shoulders at dominant foot off
Hip-Shoulder Separation at NDFO	degrees	Transverse angle between hips and shoulders at non-dominant foot off
Hip-Shoulder Separation at DFD	degrees	Transverse angle between hips and shoulders at dominant foot down
Hip-Shoulder Separation at NDFD	degrees	Transverse angle between hips and shoulders at non-dominant foot down
Hip-Shoulder Separation at Release	degrees	Transverse angle between hips and shoulders at release
Arm Elevation Angle at DFO	degrees	Angle of throwing arm relative to horizontal at dominant foot off
Arm Elevation Angle at NDFO	degrees	Angle of throwing arm relative to horizontal at non-dominant foot off
Arm Elevation Angle at DFD	degrees	Angle of throwing arm relative to horizontal at dominant foot down
Arm Elevation Angle at NDFD	degrees	Angle of throwing arm relative to horizontal at non-dominant foot down
Arm Elevation Angle at Release	degrees	Angle of throwing arm relative to horizontal at release
Shoulder-Arm Separation at DFO	degrees	Angle between shoulder line and arm at dominant foot off
Shoulder-Arm Separation at NDFO	degrees	Angle between shoulder line and arm at non-dominant foot off
Shoulder-Arm Separation at DFD	degrees	Angle between shoulder line and arm at dominant foot down
Shoulder-Arm Separation at NDFD	degrees	Angle between shoulder line and arm at non-dominant foot down
Shoulder-Arm Separation at Release	degrees	Angle between shoulder line and arm at release
Base of Support Width	meters	Distance between ankles at non-dominant foot down
Relative Release Height	meters	Vertical distance between discus and shoulder at release
Height at Release	meters	Absolute height of discus at release
Release Angle	degrees	Angle of discus trajectory at release
Distance	meters	Estimated distance thrown
Trunk Flexion at Release	degrees	Trunk sagittal flexion angle at release (forward = positive, backward = negative)
Release Style	N/A	Classification of release style (‘Reverse’ or ‘Fixed Foot’)

Notes

Kinematic data typically captured at 240Hz

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Biomechanics

Track and Field: Discus

Overview

Dimensions

Output Variables

Generic Outputs

Events

Phases and Stages of the Discus Throw

Discrete Metrics

Notes

​Overview

​Dimensions

​Output Variables

​Generic Outputs

​Events

​Phases and Stages of the Discus Throw

​Discrete Metrics

​Notes

Overview

Dimensions

Output Variables

Generic Outputs

Events

Phases and Stages of the Discus Throw

Discrete Metrics

Notes