Game-Day Pitch and Throw Count Feasibility Using a Single Sensor to Quantify Workload in Youth Baseball Players

Michael T Freehill; Michael J Rose; Katherine A McCollum; Cristine Agresta; Stephen M Cain

doi:10.1177/23259671231151450

Game-Day Pitch and Throw Count Feasibility Using a Single Sensor to Quantify Workload in Youth Baseball Players

Orthop J Sports Med. 2023 Mar 21;11(3):23259671231151450. doi: 10.1177/23259671231151450. eCollection 2023 Mar.

Authors

Michael T Freehill¹, Michael J Rose¹, Katherine A McCollum^{1

2}, Cristine Agresta^{1

3}, Stephen M Cain^{1

4}

Affiliations

¹ Department of Orthopaedic Surgery, Stanford University School of Medicine, Stanford, California, USA.
² Department of Orthopaedic Surgery, University of Michigan School of Medicine, Ann Arbor, Michigan, USA.
³ Department of Rehabilitation Medicine, University of Washington, Seattle, Washington, USA.
⁴ Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, West Virginia, USA.

Abstract

Background: Pitch count recommendations are used to reduce injury risk in youth baseball pitchers and are based chiefly on expert opinion, with limited scientific support. Furthermore, they only account for pitches thrown against a hitter and do not include the total number of throws on the day a player pitched. Currently, counts are recorded manually.

Purpose: To provide a method using a wearable sensor to quantify total throws per game that is compliant with Little League Baseball rules and regulations.

Study design: Descriptive laboratory study.

Methods: Eleven male baseball players (age, 10-11 years) from an 11U (players 11 years and younger) competitive travel team were evaluated over a single summer season. An inertial sensor was placed above the midhumerus of the throwing arm and was worn during baseball games across the season. A throw identification algorithm capturing all throws and reporting linear acceleration and peak linear acceleration was used to quantify throwing intensity. Pitching charts were collected and used to verify actual pitches thrown against a hitter in a game versus all other throws identified.

Results: A total of 2748 pitches and 13,429 throws were captured. On the day a player pitched, he averaged 36 ± 18 pitches (23%) and 158 ± 106 total throws (pitches in game as well as all warm-up pitches and other throws during game). In comparison, on a day a player did not pitch, he averaged 119 ± 102 throws. Across all pitchers, 32% of all throws were low intensity, 54% were medium intensity, and 15% were high intensity. The player with one of the highest percentages of high-intensity throws did not pitch as their primary position, while the 2 players who pitched most often had the lowest percentages.

Conclusion: Total throw count can be successfully quantified using a single inertial sensor. Total throws tended to be higher on days a player pitched compared with regular game days without pitching.

Clinical relevance: This study provides a fast, feasible, and reliable method to obtain pitch and throw counts so that more rigorous research on contributing factors to arm injury in the youth athlete can be achieved.

Keywords: adolescent; arm; elbow; pitchers; sensors; wearables.