Take Home Points

  1. Preseason training program can improve posterior shoulder endurance and improvements in 20 weeks.
Shoulder injuries in high school baseball players are frequent, accounting for 17.6% of all reported injuries (Moore 2013). Muscular strength, imblances, and endurance weakness are the common factors when developing programs to reduce injury risk. Young pitchers with a history of shoulder pain show less supraspinatus and middle trapezius strength compared than healthy pitchers. High school pitchers also show increased internal rotation strength and decreased in external rotation strength in the throwing arm compared with the non-dominant arm (Moore 2013). The posterior aspect of the shoulder is most researched, due to the high deceleration required after the research of a baseball.  Arm fatigue has been identified as a risk factor for shoulder and elbow pain in youth baseball pitchers. However, endurance of the posterior shoulder muscles in overhead athletes is not routinely examined or conditioned. The hypothesis was that upper extremity muscular endurance can be improved in adolescent baseball players during a 20-week preseason training program. 

Moore (2013) researched the posterior shoulder muscles in maintaining shoulder function in throwing. Fourteen baseball players (16 years old) attended 3 supervised training sessions per week for 20 weeks. Strengthening of the upper extremity was performed with a specific. Testing was completed at baseline and at 4, 8, and 20 weeks. The posterior shoulder endurance test was performed to assess muscular endurance. The participant held a weight equal to 2% of his body weight (rounded to the nearest half-pound) to account for variance among participants. Starting with the arm perpendicular to the floor, the participant horizontally abducted his arm to 90 degrees at a cadence of 30 beats per minute. Repetitions were performed until the participant was fatigued, indicated by one of the following conditions: the inability to hold the arm at the top of the arc for the required duration (1 second), compensation with elevation of entire upper torso, or verbal report of the inability to continue. Posterior shoulder endurance improved from 30 repetitions at baseline to 66 at 4 weeks and 88 at 20 weeks. Glenohumeral internal rotation range of motion and the glenohumeral internal/external rotation strength ratio remained similar over the course of the program.It was thought that endurance and strength would increase with the preseason training sessions with no loss of ROM. The results suggest that a preseason training program can improve posterior shoulder endurance and improvements in 20 weeks. Upper extremity strength and range of motion remained the same across the 20-week program. 

The results show that this program did not improve Glenohumoral ROM. Another major finding is that this program did not affect either strength ratios or range of motion. This allowed it to be included in the overall conditioning program without concern of interference with other exercises (Moore 2013). 
This study uses an easily performed preseason training exercises for high school baseball players. This was found to be positive for posterior shoulder endurance without affecting shoulder strength or range of motion. This study provides us with some evidence that preseason training can have a positive effect on some muscle characteristics in adolescent baseball players. Previous findings support that a training program can improve throwing performance parameters. The equipment for the exercises was simple and inexpensive. The exercises can be included in more comprehensive programs that can be designed to target and improve the various kinetic chain parameters that have been identified as factors in injury risk, without concern that they may adversely affect other parameters (Moore 2013). 

Reference: 
  1. Moore SD, Uhl TL, Kibler WB. Improvements in shoulder endurance following a baseball-specific strengthening program in high school baseball players. Sports Health. 2013 May;5(3):233-8.
Written by Chris Barber, CPT