Kinematic Sequencing of the Football Pass Using Inertial Motion Analysis.

Background: The kinematic sequencing of overhead throwing demonstrates a series of joint motions to generate the throwing force. The biomechanics of the overhead throw have been heavily researched in baseball players; however, more research is needed on the biomechanics of passing in football quarterbacks.

Purpose: The purpose of this pilot descriptive study was to identify the kinematic sequencing of a football quarterback's pass using wireless inertial motion technology.

Study design: Pilot descriptive cross-sectional study.

Methods: Eight young, healthy, right-handed, pain-free quarterbacks (four high school, four collegiate) performed three drop back passes each at three increasing distances (9 total passes at 10, 20 and 30 yards) while wearing Ultium wireless IMUs (Noraxon, Scottsdale AZ) as part of their pre-season assessment. Kinematic data of each pass were identified and marked at four points of interest: foot contact, maximal external rotation, ball release, and maximal internal rotation. Data were analyzed with Noraxon MyoMotion 3.18 using a customized kinematic sequence algorithm to provide mean angles at specific points of interest over the nine throws of each quarterback.

Results: Subjects were male, mean age 16.4 +/- 1.8 years (range 14-20). Kinematic sequencing of the extremities revealed shoulder abduction and external rotation peaked respectively at an average of 112° and 134° at the beginning of the acceleration phase, as did elbow flexion (100°). Stride knee flexion remained relatively consistent, increasing from 29° to 46° after maximal shoulder external rotation. The trunk remained relatively upright; however, quarterbacks experienced an average of 23° of lumbar extension at maximal shoulder external rotation. The trunk initiated rotation with an average of 40° to the right at foot contact, which reversed during the acceleration phase to a maximum of 21° to the left. Hip-shoulder separation remained about 20°, initially favoring right trunk rotation in the cocking phase, but quickly reversed to 20° favoring left trunk rotation in the follow-through. Minimal hip-shoulder separation (11°) occurred at ball release.

Conclusion: In the kinematic sequence from lower to upper extremity, stride knee flexion remains relatively unchanged, while trunk movement tends to shift away from the throwing side, converging toward a near-neutral position in all three planes just before ball release. This pilot study provided insight into the kinematic sequencing of football quarterbacks. Further research is warranted in evaluating the quarterback pass with inertial motion units.

Level of evidence: 3.