Kinesiological Testing Information

Videographic Set-up
Surface Electromyography
Videographic and Electromyographic Protocol
Analysis of Videographic Data
How We Use the Information



Videographic Set-up



  1. Two high-speed cameras will be positioned perpendicular to the planes of motion, equidistant from the pitching rubber. Tripod positioning will be established with taping to ensure consistency throughout the recording sessions. One regular camera will be set up behind the pitcher to record the feet.

  2. Bubble levels will be used to level the cameras in fore, aft and lateral directions.

  3. Appropriate zoom magnification will maximize the portion of the motion to be captured.

  4. The environment will have maximum lighting available and a background that will provide contrast to the reflective markers. Direct Linear Transformation Model will be placed on the mound for referencing three-dimensional calibration as per Wang (1995).

  5. Shutter speed should be set at 249Hz to allow enough light for clear definition of the image.

  6. Iris settings will be set to automatic or set manually to correspond with the shutter speed so as to provide the most bright, clear image. [A larger iris opening will allow more light but will be less clear, as the depth of field is decreased. A smaller opening will permit less light to pass through the lens, but will provide a more crisp image.]

  7. If adjustable, the brightness signal should be set to a higher frequency to increase SVHS quality.

  8. Event markers will be videotaped to identify the subject and to allow the software to recognize the landmarks. Activity of the two cameras will be synchronized.

  9. Once the environment has been established, filming of the Direct Linear Translation Model placed in the filming field will be performed.

  10. One minute of videotape leader will procede the recorded events for each individual, ensuring that the VCR controller has enough frames available for the digitizing process.

  11. A logbook will be used to record events and times during the videotaping process.

  12. Reference markers will be removed during recording of the desired activity.

  13. After a supervised warm-up and the placement of the EMG electrodes and video markers (in addition to recording the one minute leader) the pitcher will throw 10 pitches. Strikes and balls will be recorded in the log book.



    Surface Electromyographic Procedure

    The sEMG electrode placement sites will focus on scapular and upper extremity muscles. Four muscle sites will be utilized: serratus anterior, latissimus dorsi, infraspinatus and biceps brachii. All the muscles being tested are isolated by using techniques described by Kendall, McCreary and Provence in Muscles Testing and Function 4th Edition. The palpation skills of a experienced clinician will determine electrode placement in accordance with the following protocol.

    Site preparation for the electrode-skin interface will include shaving of the area followed by abrasion using and alcohol soaked pad, rubbing the site of electrode application vigorously, eight times. A slightly abrasive pad will be used. The skin preparation will elicit a slight histochemical effect (Cram & Kasman, 1998).

    The electrode is 0.5cm in diameter and will be placed at an interelectrode distance of 1cm, which is recommended for facial and upper extremity muscles (Cram et al., 1998). Smaller electrodes with a closer interelectrode spacing will allow for a higher level of selectivity. Leads and cables will be kept as short as possible and be shielded to prevent any artifacts from the surrounding structures. This also helps in preventing any unnecessary wire sway to deter artificial amplitude artifacts (Cram et al., 1998)

    In the interest of minimizing contamination of the recordings, the following principles should be considered when selecting the appropriate sites for electrode placement:

    1. Minimize the chance of other muscles being recorded and maximize the isolation of the selected muscle through anatomical considerations.
    2. Position the electrodes parallel to the muscle fibers. [Knowledge of the anatomy and palpation skills enhances electrode placement proficiency.]
    3. Place the electrodes slightly off center to assure that the motor points are not straddled.
    4. Be consistent with the electrode placements and use anatomical landmarks to facilitate the reproducibilty.
    5. Be sensitive to anatomical differences and be flexible whn using satndardized electrode placement protocols.
    6. Keep the electrode size and placement consistent to allow adequate isolation of selected muscle, while decreasing the amount of activity picked up from the surrounding musclulature.
    7. The reference electrode should be placed over a adjacent, electrically neutral area, such as the bony spinous process of C7 (or equidistant from active electrodes as a second choice)

      To ascertain that the placement of the electrode is in the optimal location, specific muscle testing of the target muscle should produce the sEMG signal while contraction of neighboring and synergistic muscles should contribute little or nothing to the recordings. The following protocols will be utilized to ensure optimal sEMG signal reception:

      Serratus Anterior (Lower fibers)

      The fibers of the serratus anterior muscle arise from the first to ninth ribs and insert on the costal surface of the scapula. The serratus anterior muscle is hard to isolate because of its location under the scapula and overlying muscles. Misinterpretation of the recordings occurs because of interference from the costal and latissimus dorsi muscles. In order to minimize this interference, the electrode location should be just anterior to the border of the latissimus dorsi muscle at the level of the inferior angle of the scapula. Place the two active electrodes horizontally 2cm apart, just below the axilla at the level of the inferior angle of the scapula and just medial to the latissimus dorsi muscle.
      To confirm the best placement of the electrodes, have the person perform forward flexion of the arms and do a push-up. An alternative task is to have the operator resist scapular protraction. This protraction of the scapula should facilitate the contraction of the serratus anterior muscle. The serratus anterior must contract with the other scapular stabilizers to provide an adequate force couple for correct shoulder elevation. The serratus anterior will increase its contribution during shoulder flexion and decrease its contribution during shoulder abduction.

      Infraspinatus

      For placement of the electrodes on the infraspinatus, divide the spine of the scapula in half, move caudally 4 cm in a vertical line parallel with the medial border of the spine of the scapula. The electrodes should be placed approximately 2 cm apart and should follow the fiber orientation from the infraspinous fossa to the attachment on the greater trochanter of the humerus. The infraspinatus is an important rotator cuff muscle for humeral head stabilization that can be effectively isolated for interpretation and treatment. This muscle is significant for its role in humeral stabilization during deceleration associated with the pitching motion.

      Latissimus Dorsi

      Two active electrodes will be placed 2 cm apart and approximately 4 cm below the inferior border of the scapula, half the distance between the spine and the lateral edge of the torso. They are obliquely oriented at approximately 25 degrees from horizontal. Evaluation of extension, adduction and medial rotation of the arm will assure appropriate placement.

      Biceps Brachii

      The biceps brachii will be located by having the subject flex the arm with the forearm in a supinated position. The muscle mass in the ventral aspect of the upper arm that emerges will be palpated. Two active electrodes will be placed parallel to the muscle fibers and in the center of the muscle mass. Placement of the active electrodes more laterally will emphasize detection of shoulder flexion and forearm flexion. Caution must be exercised in electrode placement as an excessively distal placement will tend to receive primary conduction from the brachialis muscle. To assure proper placement of the electrodes, resistance to forearm flexion should augment the signal.



      Videographic and Electromyographic Protocol

      The second day of data collection will involve videographic and sEMG analysis of the pitch. Each of the participants will follow a standardized warm-up protocol. Subjects will perform their warm-up throws with the sEMG electrodes and associated wires in place to allow them to habituate to the testing environment. After warm-up and when the participant feels comfortable and adequately familiarized with environment, 10 fastballs will be thrown at maximal effort to a target behind home plate 46 feet away. Pitchers will throw from the wind-up position off an elevated pitching mound to a catcher behind home plate. A JUGGS radar gun will be used from behind the backstop to measure pitch velocities. Of the ten fastbals thrown, at least three must be videotaped that are strikes and recorded as being faster than 50 mph. If these criteria are not met, additional throws must be completed until this data has been collected. The synchronization of the two cameras with the sEMG data will be accomplished using a visual analog switch.



      Analysis of the Videographic Data

      A three-dimensional analysis of videographic data will be completed utilizing two 120 Hz high-speed cameras, synchronized with a Butterworth fourth order zero lag filter with a cutoff frequency of 10 Hz. The following landmarks will be manually digitized utilizing Motus video and analog motion measurement system (Peak Performance Technologies, Inc.) protocol:

      1. Ball - center
      2. Head - center of occiput
      3. Right/Left hand - middle distal meatcarpal
      4. Right/Left wrist - joint line, equidistant from radial and ulnar styloid process
      5. Right/Left elbow - joint center
      6. Right/Left shoulder - joint center
      7. Lower cervical - C7 spinous process
      8. Middle thorax - T12 spinous process
      9. Lower lumbar - L5 spinous process

      Lower extremity parameters will be collected using reflectors placed on the landmarks specified below:

      1. Greater trochanter
      2. Lateral femoral condyle
      3. Lateral malleolus
      4. Base of the fifth metatarsal
      5. Lateral calcaneous

      Extrapolation of the data points with computer analysis of the statistics will be performed using the Peak Performance's Motus System. Direct linear transformation will be used to obtain three-dimensional data for each landmark. Segmental analysis of the data points individually and in relation to eachother will be carried out for each phase of the pitching motion (wind-up, arm cocking, arm acceleration and follow through).



      How We Use the Information

      Analysis for quality of the pitching motion occurs through intergration of the videographic data providing information as to the relative positioning of the joints with the sEMG data providing information regarding the firing of the muscles. These components are interpreted in relation to expected values for each of the four phases of the pitching motion. Previous studies of the pitching motion have provided data on expected joint positions and muscle firing ratios for each phase of the pitching motion.

      1. The Wind-Up Phase - The phase of the baseball pitch represents the initiation of the pitch, where positioning of the joints of both the lower and upper extremities is vital for storage of energy which can be utilized in the later stages. Accordingly, early detection and correction of inefficiencies during this phase of force loading can enhance the force production and safe positioning for the rest of the pitch.

      2. The Arm Cocking Phase - During this phase, the upper extremity is positioned in an extreme range of external rotation, which will facilitate optimal arm acceleration and force production in the next stage of the pitch. This extreme range of motion creates the torsional (twisting) forces through the arm bone and may be a dominant factor in pathological growth changes and shoulder injuries among young pitchers. Positioning of the trunk and lower extremity are also of pinnacle impotance in that less force production from the shoulder may be required if the trunk and lower extremities are positioned appropriately. Activation of specific muscles of the shoulder are essential in protecting the shoulder from injury during this extreme positioning of the shoulder joint.

      3. The Arm Acceleration Phase - The main goal and chief clinical finding for this phase of the baseball pitch is attainment of maximal arm acceleration. The fact that increased acceleration creates increased forces on tissues is fairly intuitive. The extreme forces distributed through these tissues requires an appropriate attenuation of these forces in order for avoid tissue damage. The greater the forces produced, the lower the margin of error available for muscle activation and joint positioning before tissue injury occurs. As would be expected, the incidence of elbow conditions such as medial epicondylitis, fascial compression syndrome, ulnar nerve injury and posteromedial osteophyte development are associated with the increased forces during this phase. For this reason, kinematics and kinetics of this phase of the pitching motion are of great importance.

      4. The Follow-through Phase - The follow-through phase has also been referred to as the deceleration phase, with the primary goal being the safe deceleration of the arm after the baseball has left the hand. Slowing the arm down from such a rapid velocity in such a short distance requires forces just as large as the forces initiating the movement. Oftentimes, the focus of the pitcher, however, is elsewhere (namely, where the ball is travelling) and proper deceleration of the arm does not occur. The chief focus for deceleration is to resist the valgus and distractive forces inherent in the motion. Muscles from the entire body, especially the upper extremity must contract eccentrically in coordination to properly decelerate the moving limb.

      Analysis of each of these phases with regards to the muscle and joint positioning requirements allows us to interpret whether the pitching mechanisms used by the young pitchers are biomechanically correct. These findings can be compared to those of their peers to discern to what extent young pitchers have the muscular and coordinative capacity to pitch without probability of injury. Based on the findings of videographic and sEMG data, we will be able to identify the components of the baseball pitching motion with the highest likelihood of predisposing children to injury. This would allow coaches to emphasize proper mechanics in those particular components of the pitch. The dynamic data recorded through videographic and sEMG also serve to clarify the findings from the anthropometric and CT scan data, explaining to what extent the forces of pitching affect the children's growth.