Dimensions
Required Inputs for processing:- handedness: the handedness of the player [‘left’, ‘right’]
- serve stance position: the stance type used for the serve [‘pinpoint’, ‘platform’]
Phases of the serve
Stages adopted from Kovacs & Ellenbecker, 2011. ( Video )| Phase | Stage | Start | End | Event or Phase |
|---|---|---|---|---|
| Preparation | Start | Initiation | Initiation | Event |
| Preparation | Release | Initiation | Ball Release | Phase |
| Preparation | Loading | Ball Release | Low Arm | Phase |
| Preparation | Cocking | Low Arm | Max Shoulder Ext Rot | Phase |
| Acceleration | Acceleration | Max Sho ER | Ball Contact | Phase |
| Acceleration | Ball Contact | Ball Contact | Ball Contact | Event |
| Follow Thru | Deceleration | Ball Contact | Termination | Phase |
| Follow Thru | Finish | Termination | Termination | Event |
Variables
Output variables from tennis overhand serve analysis.Normative Ranges
See Tennis Overhand Serve Norms for the full 5th–95th percentile reference tables by competition level (Youth, Professional, Broad).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 | Description | Column Name |
|---|---|---|
| Initiation | the start of the tennis serve | initiation_event |
| Ball Release | the estimated timing of ball toss release | ball_release_event |
| Low Arm | the low point of the dominant arm prior to ball contact | low_arm_event |
| Max Shoulder ER | the instant of maximum shoulder external rotation between ball release and apex | max_shoulder_external_rotation_event |
| Apex | maximum height of the dominant-side wrist joint center during the serve | apex_event |
| Termination | end of the tennis serve | termination_event |
| Peak Forearm Velocity | the instant of peak forearm forward angular velocity, used to determine forward kinematic sequence | “ |
| Peak Upper Arm Velocity | the instant of peak upper arm forward angular velocity, used to determine forward kinematic sequence | “ |
| Peak Torso Velocity | the instant of peak torso forward angular velocity, used to determine forward kinematic sequence | “ |
Forward Kinematic Sequence Metrics
| Metric | Units | Description | Column Name |
|---|---|---|---|
| Peak Torso Forward Angular Velocity | degrees/second | Peak forward angular velocity of the torso segment in the serve direction | peak_torso_forward_angular_velocity |
| Peak Upper Arm Forward Angular Velocity | degrees/second | Peak forward angular velocity of the upper arm segment in the serve direction | peak_upper_arm_forward_angular_velocity |
| Peak Forearm Forward Angular Velocity | degrees/second | Peak forward angular velocity of the forearm segment in the serve direction | peak_forearm_forward_angular_velocity |
| Forward Kinematic Sequence | N/A | Sequence of peak forward angular velocities. Optimal sequence is ‘torso-upper_arm-forearm’ | forward_kinematic_sequence |
| Forward Trunk Arm Speedup | N/A | Speedup factor of peak forward angular velocities from the torso to the upper arm. | forward_trunk_arm_speedup |
| Forward Upper Arm Forearm Speedup | N/A | Speedup factor of peak forward angular velocities from the upper arm to the forearm. | forward_upper_arm_forearm_speedup |
| Upper Arm Forward Angular Velocity | deg/s | Time series values of the instantaneous forward angular velocity (serve direction) of the upper arm segment. Evaluate near apex (ball contact event) to visualize kinematic sequencing | upper_arm_forward_angular_velocity |
| Torso Forward Angular Velocity | deg/s | Time series values of the instantaneous forward angular velocity (serve direction) of the torso segment. Evaluate near apex (ball contact event) to visualize kinematic sequencing | torso_forward_angular_velocity |
| Forearm Forward Angular Velocity | deg/s | Time series values of the instantaneous forward angular velocity (serve direction) of the forearm segment. Evaluate near apex (ball contact event) to visualize kinematic sequencing | forearm_forward_angular_velocity |
Twist Kinematic Sequence Metrics
| Metric | Units | Description | Column Name |
|---|---|---|---|
| Peak Pelvis Twist Angular Velocity | degrees/second | Peak twist angular velocity of the pelvis segment in the serve direction | pelvis_peak_twist_angular_velocity |
| Peak Torso Twist Angular Velocity | degrees/second | Peak twist angular velocity of the torso segment in the serve direction | trunk_peak_twist_angular_velocity |
| Peak Upper Arm Twist Angular Velocity | degrees/second | Peak twist angular velocity of the upper arm segment in the serve direction | arm_peak_twist_angular_velocity |
| Twist Kinematic Sequence | N/A | Sequence of peak twist angular velocities. Optimal sequence is ‘torso-upper_arm-forearm’ | twist_kinematic_sequence |
| Twist Trunk Arm Speedup | N/A | Speedup factor of peak twist angular velocities from the torso to the upper arm. | twist_trunk_arm_speedup |
| Twist Pelvis Torso Speedup | N/A | Speedup factor of peak twist angular velocities from the pelvis to the trunk. | twist_pelvis_trunk_speedup |
Movement Flag Metrics
Movement flags identify poor or suboptimal mechanics for timing and body positioning during the serve.| Metric | Description | Column Name |
|---|---|---|
| Release Phase Off-Arm to Body Position | Ball toss angle is outside the acceptable 90°–180° range at ball release. | release_phase_off_arm_to_body_position |
| Release Phase Elbow Not Straight | Non-dominant elbow flexion exceeds 30° at ball release. | release_phase_elbow_not_straight |
| Loading Phase Knee Asymmetry | Front-to-back knee flexion difference exceeds 15° during loading. | loading_phase_knee_asymmetry |
| Loading Phase Pinpoint Break | Athlete breaks from a pinpoint stance during loading. | loading_phase_pinpoint_break |
| Loading Phase Lack of Trunk Coil | Trunk coil is below 110° during loading. | loading_phase_lack_trunk_coil |
| Loading Phase Lack of Pelvis Coil | Pelvis coil is below 110° during loading. | loading_phase_lack_pelvis_coil |
| Loading Phase Lack of Shoulder Drop | Trunk does not tilt toward the rear by at least 5° during loading. | loading_phase_lack_shoulder_drop |
| Loading Phase Lack of Pelvis Drop | Pelvis does not tilt toward the rear during loading. | loading_phase_lack_pelvis_drop |
| Loading Phase Excessive Knee Valgus | Front or back knee valgus classified as “high” during loading. | loading_phase_excessive_knee_valgus |
| Cocking Phase Lack of External Rotation | Max shoulder external rotation is below 180° during cocking. | cocking_phase_lack_external_rotation |
| Contact Phase Arm Out of Slot Position | Shoulder abduction is outside the 110°–140° range at ball contact. | contact_phase_arm_out_of_slot_position |
| Contact Phase Open Trunk Rotation | Trunk rotation has not passed -20° by ball contact. | contact_phase_open_trunk_rotation |
| Contact Phase Open Pelvis Rotation | Pelvis rotation has not passed -30° by ball contact. | contact_phase_open_pelvis_rotation |
| Landing Phase Excessive Forward Lean | Trunk forward flexion exceeds 60° at finish. | landing_phase_excessive_forward_lean |
| Landing Phase Excessive Side Lean | Absolute trunk side tilt exceeds 30° at finish. | landing_phase_excessive_side_lean |
| Landing Phase Excessive Forward Drift | Forward body displacement exceeds 0.50x height between contact and finish. | landing_phase_excessive_forward_drift |
| Landing Phase Excessive Side Drift | Open-side body displacement exceeds 0.30x height (or -0.10x height) between contact and finish. | landing_phase_excessive_side_drift |
Loading Phase Metrics
| Metric | Units | Description | Column Name |
|---|---|---|---|
| Loading Phase Max Knee Flexion Front Leg | degrees | Maximum amount of front leg knee flexion during the loading phase of the serve | loading_phase_max_front_knee_flexion |
| Loading Phase Max Knee Flexion Back Leg | degrees | Maximum amount of back leg knee flexion during the loading phase of the serve | loading_phase_max_back_knee_flexion |
| Loading Phase Trunk Tilt | degrees | Maximum amount of trunk side-side tilt towards the rear during the loading phase of the serve | loading_phase_trunk_tilt |
| Loading Phase Pelvis Tilt | degrees | Maximum amount of pelvis side-side tilt towards the rear during the loading phase of the serve | loading_phase_pelvis_tilt |
| Loading Phase Shoulder Hip Separation | degrees | Maximum difference in rotation of the shoulders and hips during the loading phase of the serve | loading_phase_shoulder_hip_separation |
| Loading Phase Ball Release Angle | degrees | Transverse plane arm angle at the instance of ball release | loading_phase_ball_toss_angle |
| Trunk Coil | deg | Maximum amount of trunk twist rotation away from the serve direction, like preloading the twist before the serve. | trunk_coil |
| Pelvis Coil | deg | Maximum amount of pelvis twist rotation away from the serve direction, like preloading the twist before the serve. | pelvis_coil |
| Release Phase Elbow Angle | degrees | Non-dominant (tossing) elbow flexion angle at ball release | release_phase_elbow_angle |
| Max Front Knee Valgus (Normalized) | × height | Maximum inward collapse of the front knee during the serve, normalized to athlete height | max_front_knee_valgus_upward_per_ht |
| Max Back Knee Valgus (Normalized) | × height | Maximum inward collapse of the back knee during the serve, normalized to athlete height | max_back_knee_valgus_upward_per_ht |
Cocking and Acceleration Phase Metrics
| Metric | Units | Description | Column Name |
|---|---|---|---|
| Cocking Phase Max Shoulder External Rotation | degrees | Maximum amount of shoulder external rotation during the cocking phase of the serve | cocking_phase_max_shoulder_external_rotation |
| Cocking Phase Shoulder Hyperangulation | degrees | Maximum amount of shoulder horizontal abduction during the cocking phase of the serve | cocking_phase_shoulder_hyperangulation |
| Cocking Phase Max X Factor | degrees | Maximum hip-shoulder separation during the cocking phase of the serve | cocking_phase_max_x_factor |
| Cocking Phase Shoulder Horizontal Abduction | degrees | Maximum horizontal abduction of the dominant shoulder during the cocking phase of the serve | cocking_phase_shoulder_horizontal_abduction |
| Acceleration Phase Max Knee Extension Velocity Front Leg | degrees/second | Maximum knee extension velocity of the front leg during the acceleration phase of the serve | acceleration_phase_max_front_knee_extension_velocity |
| Acceleration Phase Max Knee Extension Velocity Back Leg | degrees/second | Maximum knee extension velocity of the back leg during the acceleration phase of the serve | acceleration_phase_max_back_knee_extension_velocity |
| Acceleration Phase Max Elbow Extension Velocity | degrees/second | Maximum extension velocity of the dominant elbow during the acceleration phase of the serve | max_elbow_extension_velocity |
Contact Phase Metrics
| Metric | Units | Description | Column Name |
|---|---|---|---|
| Contact Phase Elbow Flexion | degrees | Amount of elbow flexion at apex | contact_phase_elbow_flexion |
| Contact Phase Shoulder Abduction | degrees | Amount of shoulder abduction at apex | contact_phase_shoulder_abduction |
| Contact Phase X Factor | degrees | Angle between the shoulders to hips in the transverse plane (twisting) at apex | contact_phase_x_factor |
| Time to Contact | seconds | Duration from initiation to ball contact | time_to_contact |
| Contact Phase Trunk Tilt | degrees | Degrees of side-side trunk tilt at apex | contact_phase_trunk_tilt |
| Contact Phase Trunk Flexion | degrees | Forward/backward trunk flexion at apex | contact_phase_trunk_flexion |
| Contact Phase Trunk Rotation | degrees | Trunk rotation relative to its starting orientation at apex | contact_phase_trunk_rotation |
| Contact Phase Pelvis Rotation | degrees | Pelvis rotation relative to its starting orientation at apex | contact_phase_pelvis_rotation |
| Contact Phase Wrist Height (Normalized) | × height | Wrist height at apex, normalized to athlete height | contact_phase_wrist_height_per_ht |
| Contact Phase Wrist Velocity (Normalized) | unconfirmed | Wrist speed at apex, reported alongside the height-normalized dataset | contact_phase_wrist_velocity_per_ht |
| Trunk Stretch | deg | Twist range of motion of the trunk. | trunk_stretch |
| Pelvis Stretch | deg | Twist range of motion of the pelvis. | pelvis_stretch |
Landing Phase Metrics
| Metric | Units | Description | Column Name |
|---|---|---|---|
| Finish Phase Trunk Flexion | degrees | Forward/backward trunk flexion at the finish of the serve | finish_phase_trunk_flexion |
| Finish Phase Trunk Tilt | degrees | Lateral trunk tilt at the finish of the serve | finish_phase_trunk_tilt |
| Forward Displacement (Normalized) | × height | Forward body displacement between contact and finish, normalized to athlete height | displacement_forward |
| Open-Side Displacement (Normalized) | × height | Open-side body displacement between contact and finish, normalized to athlete height | displacement_open_side |
| Vertical Displacement (Normalized) | × height | Vertical body displacement between contact and finish, normalized to athlete height | displacement_vertical |
Notes
- Kinematic data typically captured at 240Hz for Tennis Overhand Serve