PitchTrak Operations Guide

The Motion Analysis Corp. pitching analysis application creates measurements of the critical biomechanical parameters during left handed and right handed baseball pitching. It supplies a complete kinematic and kinetic report of the upper extremity as well as measurements about the player's technique. The information can be used to indicate a potential for injury, compare the biomechanics among players, or show comparisons of the same player over time. This guide will step though the procedures to properly acquire the pitching trials and then operate PitchTrak.


What you need

Motion Analysis Corp. Motion Capture system 38 Retroreflective Markers and configured as shown below:

PitchTrak Marker Set

MARKERREQUIRED OR OPTIONALCOMMENTS
1R.AcromionrequiredEnd of the Clavicle (collar bone) - top of shoulder
2R.ClavicleoptionalPlaced at the middle of the clavicle, used for asymmetry
3L.AcromionrequiredEnd of the Clavicle - top of shoulder
4Back Headoptionalrear/center of head
5Top.HeadoptionalTop/center of head
6Front HeadoptionalFront/center of head
7L.Wrist.RadrequiredStyloid Process of the Radius. Wrist on thumbside.
8L.Wrist.UlnrequiredStyloid Process of the Ulna. Wrist on fingerside.
9L.Epi.LatrequiredLateral epicondyle of the humerus. Outside of elbow.
10L.Epi.MedrequiredMedial epicondyle of the humerus. Inside of elbow.
11L.Hand orrequiredBase of the 5th MCP joint. Left handed pitcher only
11R.HandrequiredBase of the 5th MCP joint. Right handed pitcher only
12L.Scap.InfrequiredRoot of scapular spine. Bottom of scapula. //en.wikipedia.org/wiki/Spine_of_scapula
13L.Scap.MedrequiredInferior angle of the scapula. Upper/Inside corner of the scapula.
14R.Scap.MedrequiredInferior angle of the scapula
15R.Scap.InfrequiredRoot of scapular spine
16R.Epi.LatrequiredLateral epicondyle of the humerus //act.downstate.edu/courseware/haonline/figs/L06/060200.htm
17R.Epi.MedrequiredMedial epicondyle of the humerus
18R.Wrist.RadrequiredStyloid Process of the Radius (Thumbside)
19R.Wrist.UlnrequiredStyloid Process of the ulna
20R.ASISrequiredOver the right front of the hip
21V.SacralrequiredOver the base of the spine, L5-S1 joint
22L.ASISrequiredOver the left front of the hip
23R.Thighoptionalabout 1/3 the distance from hip joint to knee joint
24R.Kneeoptionalon the Lateral Condyle
25R.Knee.Medoptionalon the Medial Condyle
26R.Shankoptionalabout 1/3 the distance from knee joint to ankle joint
27R.Ankleoptionalon the Lateral Malleolus
28R.Ankle.Medoptionalon the Medial Malleolus
29R.HeeloptionalCentered on the heel
30R.ToeoptionalOver the base of the second toe
31L.Thighoptionalabout 2/3 the distance from hip joint to knee joint
32L.Kneeoptionalon the Lateral Condyle
33L.Knee.Medoptionalon the Medial Condyle
34L.Shankoptionalabout 2/3 the distance from knee joint to ankle joint
35L.Ankleoptionalon the Lateral Malleolus
36L.Ankle.Medoptionalon the Medial Malleolus
37L.HeeloptionalCentered on the heel
38L.ToeoptionalOver the base of the second toe

Determining Your Marker Set

The full-body marker set combines a 7 segment upper body set (head, 2 upper arms, 2 lower arms, 2 shoulder girdles) with an 8 segment marker set for the lower body (trunk, pelvis, 2 thighs, 2 lower legs, 2 feet). Fifteen markers are required in order for PitchTrak to output any data. The optional markers determine whether certain kinematic parameters are calculated. For example, if markers are placed on the head, then head rotations will be calculated. Additionally, if markers are placed on the Left and Right Anterior Superior Iliac Spines (ASIS) and Sacral joint, then pelvic rotations will be calculated and trunk rotations are calculated relative to the pelvis. Otherwise, trunk rotations will be calculated relative to the global coordinate system. All six markers on the feet (#26-28,32-34) are needed to compute stride parameters. If any additional markers are used (e.g. more asymmetry markers), PitchTrak will simply ignore them for its calculations. Markers placed on the scapula are purely used to predict the location of the glenohumeral (GH) center during the pitch. Although scapular motion is compromised by skin motion, errors in regression have been found to be no less than those found with the GH center estimated with trunk based markers, particularly when the shoulder elevation is less than 120Ëš.

Angle Definitions

This section describes the plotting conventions used to define upper body movements. Sagittal and frontal plane movements are rotations of the long axis of the segment as observed down its medial-lateral and anterior-posterior axes, respectively. Transverse plane motion is the rotation about the long axis of the segment.

PitchTrak Head Angle

Head: Measured relative to the trunk.

Motions: sagittal plane: forward flexion (+) - ext (-) frontal plane: head tilt left (+) - right (-) transverse plane: left (+) - right (-) rotation.

Pitchtrak Trunk Angle

Trunk: Measured relative to the pelvis (if markers on pelvis).

Motions: sagittal plane: forward flexion (+) - ext (-) frontal plane: trunk tilt left (+) - right (-) transverse plane: left (+) - right (-) rotation.

PitchTrak Shoulder Angle

Shoulder: Measured relative to the shoulder girdle (ipsilateral trunk half segment).

Motions: plane of elevation: hor add (+) - hor abd (-) elevation: elevation (+) - depression (-) transverse plane: internal (+) - external (-) rotation.

Comments: The clinical rotations of shoulder flexion and abduction are described as shoulder elevation due to the ambiguity of these clinical descriptors.

PitchTrak Elbow Angle

Elbow: Measured relative to the humerus

Motions: sagittal plane: flexion (+) - extension (-) frontal plane: varus (+) - valgus (-).

PitchTrak Files

There are a number of files specific to this application that will be used by Cortex to help you set up, acquire and process your trials:

  • PitchTrak.mars - holds the marker and segment information.
  • PitchTrak.cal - holds the event information.

Data Collection Setup

Setup for data collection for PitchTrak with Cortex is done much the same as with any collection. There are some settings for calibration and data collection that will help ease the process. Learn about the recommended data collections settings in Data Collection Setup.

Trial Collection

You should already be familiar with how to collect 3D data using Cortex. However, PitchTrak requires some specific collection procedures to ensure correct calculations. Trial Collection describes the recommended procedures to collect your trials.

Running the PitchTrak Application

The PitchTrak software is simple to operate, and there are only a few fields to enter and several buttons to click. A video tutorial and some instructions for using the PitchTrak software are in Running the PitchTrak Application.

Output Definitions

The PitchTrak Report provides a series of biomechanical measures relevant to the pitching motion. Here is a brief explanation of each of their meanings.

MEASUREDESCRIPTION
1Stride Length (% body height)Distance between left and right feet at front-foot contact in the direction from rubber to home plate
2Shoulder Abduction at FC (deg)Abduction angle of the throwing shoulder (GH joint) at front foot contact
3Shoulder Horizontal Abduction at FC (deg)Horizontal abduction angle of the throwing shoulder (GH joint) at front foot contact
4Shoulder External Rotation at FC (deg)External rotation angle of the throwing shoulder (GH joint) at front foot contact
5Max Trunk Rotation (deg)Peak trunk rotation angle (with respect to the pelvis) during the pitching cycle
6Max Shoulder External Rotation (deg)Peak shoulder external rotation angle during pitching cycle
7Elbow Flexion at BR (deg)Elbow flexion angle at ball release
8Trunk Forward Flexion at BR (deg)Trunk forward flexion angle at ball release
9Max Shoulder Distraction Force (% body weight)1Peak reaction force directed along the longitudinal axis of the shoulder girdle coordinate system (parent reference frame)
10Max Shoulder Abduction Torque (% bw-h) 1,2Peak moment about the anterior-posterior axis of the shoulder girdle coordinate system (proximal reference frame)
11Max Shoulder Horizontal Abduction Torque (% bw-h) 1,2Peak moment about the superior-inferior axis of the shoulder girdle coordinate system (proximal reference frame)
12Max Shoulder ER Torque (% bw-h) 1,2Peak moment about the longitudinal axis of the shoulder girdle coordinate system (proximal reference frame)
13Max Elbow Flexion Torque (% bw-h) 1,2Peak moment about the medial-lateral axis of the humeral coordinate system (proximal reference frame)
14Max Elbow Valgus Torque (% bw-h) 1,2Peak moment about the anterior-posterior axis of the humeral coordinate system (proximal reference frame)

1All forces and net joint moments are resolved in the proximal segmental coordinate system.2Moments are expressed in external convention. bw = body weight; h = height.

References

References provides relevant articles and publications about pitching analysis.