Dimensions
Required Inputs for processing:- handedness: the handedness of the batter [‘left’, ‘right’]
Variables
Output variables from hitting analysis.Events
Identify specific time points during the hit.| Event | Short Description | Column Name |
|---|---|---|
| Initiation | When the lead foot begins to move prior to max knee raise. | initiation_frame |
| Max Foot Raise | The maximum height of the lead foot during the swing. | max_foot_raise_frame |
| Foot Contact | The instant the front foot contacts the ground. Determined by finding the max downward velocity of the lead ankle and then obtaining the index when the following 5 frames have a vertical velocity below 0.2 m/s. | foot_contact_frame |
| Pelvis Velocity Initiation (Launch) | The start of pelvis rotation - also known as launch event. Determined via the last local minimum before peak pelvis angular velocity. | pelvis_initiation_frame |
| Max X Factor | The instant of maximum separation between shoulders and hips before the twisting motion of the swing. | max_x_factor_frame |
| X Factor Zero Crossing | When the shoulder-hip separation crosses zero after Max X Factor. | x_factor_zero_crossing_frame |
| Wrist Initiation | The start of the wrist movement during the swing. Finds the last local minimum before peak wrist angular velocity. | wrist_movement_initiation_frame |
| Twist | The average timing of peak angular velocities for the pelvis, trunk, and arm. Used to identify the timing of the major twisting motion. | twist_frame |
| Peak Pelvis Ang Vel | The instant of pelvis peak angular velocity. Peak finding parameters: minimum height: 250 deg/s, minimum prominence: 250 deg/s, distance to next peak: 100 frames (~0.4 s), minimum width: 0.1 s (24 frames). | peak_pelvis_velocity_frame |
| Peak Trunk Ang Vel | The instant of trunk peak angular velocity. Peak finding parameters: minimum height: 250 deg/s, minimum prominence: 250 deg/s, distance to next peak: 100 frames (~0.4 s), minimum width: 0.1 s (24 frames). | peak_trunk_velocity_frame |
| Peak Arm Ang Vel | The instant of lead arm peak angular velocity. Peak finding parameters: minimum height: 250 deg/s, minimum prominence: 250 deg/s, distance to next peak: 100 frames (~0.4 s), minimum width: 0.05 s (12 frames). | peak_arm_velocity_frame |
| Peak Wrist Angular Velocity | The instant of maximum wrist angular velocity | peak_wrist_angular_velocity_frame |
| Ball Contact | The estimated timing of ball contact - determined by audio signal (primary) or swing through event (secondary, if ball contact not detected or detected outside of foot contact and end twist events) | ball_contact_frame |
| Swing Through | The instant the rear wrist passes in front of the lead wrist, corresponding to a batter committing to a swing (would be a strike). | swing_through_frame |
| Pelvis Velocity Termination | The first local minimum after peak pelvis velocity. | pelvis_velocity_termination_frame |
| End Twist | Finds the end of the twisting motion: after X Factor zero crossing, when X Factor velocity returns to 0 deg/s | end_twist_frame |
Movement Flags
Find inefficiencies during the hitting motion.| Metric | Units | Short Description | Column Name |
|---|---|---|---|
| Leads With Wrist | boolean | Binary indicator if wrist leads the swing, if wrist initiation event occurs before pelvis initiation event. | leads_with_wrist |
| Sway | boolean | Binary indicator of excessive lateral movement, determined by difference in farthest forward and backward pelvis position (forward = towards the pitcher) around max knee raise event. Distance threshold for sway fault is 8 cm (~3 in). | sway |
| Sway Leg | boolean | Binary indicator of excessive lateral movement, determined by rear ankle and knee joint centers. Considered a leg sway fault if the rear knee passes behind the ankle (further from pitcher). | sway_leg |
| Knee Dominant | boolean | Binary indicator if swing is knee-dominant, determined by if the rear hip and ankle joint angles differ by more than 25 deg at launch and if the rear ankle is dorsiflexed less than 15 deg at launch. | knee_dominant_swing |
| Vertical Pelvis Hike | boolean | Binary indicator of excessive vertical pelvis movement, determined if the pelvis keypoint finishes the swing (to ball contact) higher than where it started (at launch event). | vertical_pelvis_hike |
| Lateral Pelvis Tilt | boolean | Binary indicator of excessive lateral pelvis tilt, determined by whether the pelvis tilts upwards more than 10 deg during the swing (initiation to ball contact). | excessive_lateral_pelvis_tilt |
| Drifting Forward | boolean | Binary indicator of excessive forward movement, determine by whether the pelvis drifts forward (towards the pitcher) more than 15 cm (~6 in) from launch to ball contact events. | drifting_forward |
Kinematic Sequence
Order and magnitude of pelvis, trunk, and upper arm peak rotational velocity (deg/s) during the swing.| Metric | Units | Short Description | Column Name |
|---|---|---|---|
| Kinematic Sequence | N/A | Sequence of segment peak angular velocities (twist speed) during the swing. Correct sequencing is pelvis-trunk-arm. | kinematic_sequence_order |
| Peak Pelvis Angular Velocity | deg/s | Max angular velocity of the pelvis segment. | peak_pelvis_angular_velocity |
| Peak Trunk Angular Velocity | deg/s | Max angular velocity of the trunk segment. | peak_trunk_angular_velocity |
| Peak Arm Angular Velocity | deg/s | Max angular velocity of the lead upper arm segment. | peak_arm_angular_velocity |
| Trunk to Arm Speed Up | ratio | Ratio (multiplication factor) of speed increase from trunk to arm. | trunk_to_arm_velocity_speedup |
| Pelvis to Trunk Speed Up | ratio | Ratio (multiplication factor) of speed increase from pelvis to trunk. | pelvis_to_trunk_velocity_speedup |
Body Metrics
Distances, angles, angular velocities, and other descriptors of body motion during a baseball hit.| Metric | Units | Short Description | Column Name |
|---|---|---|---|
| Handedness | N/A | Handedness of the athlete [‘right’ or ‘left’] (as input) | handedness |
| Drifting Forward Magnitude | m | Distance drifted forward during the swing - see Drifting Forward. | drifting_forward_magnitude |
| Time to Ball Contact | s | Duration between initiation and ball contact events. | time_to_ball_contact |
| Time to Launch | s | Duration beween initiation and pelvis velocity initiation (launch) events. | time_to_launch |
| Pelvis Acceleration Time | seconds | Time from pelvis initiation (start of rotation) to peak pelvis angular velocity. | “ |
| Pelvis Deceleration Time | seconds | Time from peak pelvis angular velocity to pelvis termination (end of rotation). | “ |
| Hip Hinge | deg | Max amount of rear hip flexion between max foot raise and foot contact events. | hip_hinge |
| Trunk Coil | deg | Max rotation angle that the trunk turns away from the pitcher - facing directly to the pitcher is 0 deg. | trunk_coil |
| Trunk Tilt at Launch | deg | Amount of side-to-side trunk tilt at launch event (pelvis velocity initiation). Positive values indicate tilting towards the pitcher and vice versa. | trunk_tilt_at_launch |
| Scap Load at Launch | deg | Amount of rear shoulder flexion (+) or extension (-) at launch event. Flexion/Extension translates to horizontal adduction (+) and abduction (-), respectively. | rear_scap_load_at_launch |
| Elbow Flexion at Launch | deg | Amount of rear elbow flexion at launch event. | rear_elbow_flexion_at_launch |
| Elbow Flexion at Ball Contact | deg | Amount of rear elbow flexion at ball contact event. | rear_elbow_flexion_at_ball_contact |
| Lead Knee Angle at Ball Contact | deg | Amount of lead knee flexion at ball contact. | lead_knee_angle_at_ball_contact |
| Stride Length | m | Distance between the lead ankle at foot contact and the rear ankle at max foot raise event. | stride_length |
| Rear Arm Connection | m | Average distance between the rear elbow and mid-torso (halfway between mid-shoulder and mid-hip joint centers) between launch and ball contact events. | rear_arm_connection |
| Shoulder Rotation Plane Flexion | deg | Amount of trunk flexion required to reach the average plane of rotation of the shoulder joint centers. | shoulder_rotation_plane_flexion |
| Shoulder Rotation Plane Tilt | deg | Amount of trunk tilt (+ = towards pitcher) to reach the average plane of rotation of the shoulder joint centers. | shoulder_rotation_plane_tilt |
| Relative Hand Position - Towards Pitcher | m | Distance along the axis towards the pitcher (+) between mid-shoulders and the average of the two wrists at the foot contact event. | relative_hand_position_towards_pitcher |
| Relative Hand Position - Up | m | Distance along the up axis (+) between mid-shoulders and the average of the two wrists at the foot contact event. | relative_hand_position_up |
| Relative Hand Position - Away from Body | m | Distance along the axis away from the body (+) between mid-shoulders and the average of the two wrists at the foot contact event. | relative_hand_position_away_from_body |
| Linear Stretch | m | Distance between the lead ankle and center of both wrists along the pitch direction at foot contact. | linear_stretch |
| Ball Contact Method | N/A | Ball contact event detection method: [both audio, single audio, swing through]. | ball_contact_method |
Time Series
Metrics describing motion over the duration of the capture, changing values with every frame. Use in combination with the keypoints and kinematics from Generic Outputs.| Metric | Units | Short Description | Column Name |
|---|---|---|---|
| Trunk Center of Mass Position X | m | Trunk center of mass X position - for use with keypoint positions. [time series metric] | trunk_center_of_mass_x |
| Trunk Center of Mass Position Y | m | Trunk center of mass Y position (up/down) - for use with keypoint positions. [time series metric] | trunk_center_of_mass_y |
| Trunk Center of Mass Position Z | m | Trunk center of mass Z position - for use with keypoint positions. [time series metric] | trunk_center_of_mass_z |
| Body Center of Mass Position X | m | Whole body center of mass X position - for use with keypoint positions. [time series metric] | whole_body_center_of_mass_x |
| Body Center of Mass Position Y | m | Whole body center of mass Y position (up/down) - for use with keypoint positions. [time series metric] | whole_body_center_of_mass_y |
| Body Center of Mass Position Z | m | Whole body center of mass Z position - for use with keypoint positions. [time series metric] | whole_body_center_of_mass_z |
| Trunk Global Flexion | deg | Amount of trunk sagittal plane flexion relative to the global coordinate system. [time series metric] | trunk_global_flexion |
| Trunk Global Tilt | deg | Amount of trunk frontal plane side-to-side tilt relative to the global coordinate system. [time series metric] | trunk_global_tilt |
| Trunk Global Rotation | deg | Amount of trunk transverse plane rotation relative to the global coordinate system. [time series metric] | trunk_global_rotation |
| Pelvis Global Tilt | deg | Amount of pelvis frontal plane side-to-side tilt relative to the global coordinate system. [time series metric] | pelvis_global_tilt |
| Pelvis Global Rotation | deg | Amount of pelvis transverse plane rotation relative to the global coordinate system. [time series metric] | pelvis_global_rotation |
Bat Metrics
Descriptors of bat positions, speeds, and more during the swing.| Metric | Units | Short Description | Column Name |
|---|---|---|---|
| Bat Speed - Resultant Sweet Spot | mph | Linear velocity of bat sweet spot | “ |
| Bat Speed - Angular to Linear | mph | Converted angular velocity to linear velocity | “ |
| Attack Angle | degrees | Angle of bat path relative to horizontal | attack_angle |
| On Plane Efficiency | % | Percentage of swing path aligned with optimal plane (within 10 deg) between foot contact and ball contact events. | on_plane_efficiency |
| Launch Position | deg | Angle of the bat relative to the batter’s spine in the sagittal plane at launch event (when the pelvis begins to rotate). | launch_position |
| Connection at Impact | deg | horizontal plane angle of the bat relative to the batter’s torso at the instant of ball contact | “ |
| Sweet Spot Fore Aft Position At Contact | m | fore/aft position of the bat sweet spot relative to the pelvis (mid point of the hip joint centers) | sweet_spot_fore_aft_position_at_contact |
| Attack Direction | deg | horizontal plane angle of the bat relative to the front of home plate, generally determines direction (right/left) of the hit. | attack_direction |
| Swing Path | deg | Vertical plane angle of the bat swing path relative to horizontal using the 0.04 s leading up to ball contact. | swing_path_angle |
Notes
- Kinematic data typically captured at 240Hz for Baseball Hitting
- All boolean variables (true/false = 1/0) return -1 if metric unable to be calculated.