Internal Rotation Strength
Why it matters, how it’s analyzed and what the research says
Internal Rotation Strength
Why it matters, how it’s analyzed and what the research says
Why it matters
Internal shoulder rotation strength (IR Strength) is an important performance metric related directly to the throwing motion. The strength of you internal rotators (pecs, lat, anterior deltoid, teres, major and subscapularis) accelerate the arm during throwing and maintain shoulder stability by regulating the speed of external rotation, being the layback of the throwing arm. IR strength is essential for throwing at high velocity. A decrease in IR strength can influence both velocity and accuracy under fatigue.

Analyzing Internal

Rotation Strength

There are three ways that the app
compares internal rotation strength:

1. Percentile

Percentile compares your internal rotation strength to other players your age. If you are in the lower third for players your age, you know that this is an area that you need to improve.

A solid goal would be to raise your strength to the 80th percentile or better. That means that your strength is better than 80% of the population.

2. Symmetry

Symmetry compares the internal rotation strength of your throwing side to your non-throwing side, in which most players are stronger on their throwing arm.

2. Symmetry

Symmetry compares the internal rotation strength of your throwing side to your non-throwing side, in which most players are stronger on their throwing arm.

In some cases, pitchers can show greater non-throwing side strength in their shoulder. When this is noticed, our customized program becomes modified to correct imbalance.

3. Trend

Trend analyzes how your strength has changed compared to previous tests. It’s normal for a player’s strength to fluctuate throughout the season, but these changes should be monitored and addressed.

Decreased strength by more than 10% will automatically modify your arm care and provide a recovery-based program of reduced training load. Along with your symmetry score, the trend score is an excellent marker to identify arm fatigue.

Summary of Research
  • Internal rotation strength is shown to be one of the biggest influencers of throwing performance (Clements, 2001).
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  • In a study comparing professional to amateur pitchers, the pro guys were much better at recruiting the internal rotators of the shoulder during the acceleration phase of throwing (Gowan, 1987).

 

  • Throwing puts a lot of stress on the internal rotators, so it shouldn’t be surprising that pitchers lose an average of 17% of their internal rotation strength following a start (Mullany, 2005).
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  • Spotting these drops are crucial as both velocity and accuracy decrease when the internal rotators become fatigued (Erickson et al, 2016). Players who pitch when tired are also 36x more likely to be injured (Flessig et al, 2011).
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  • Decreased rotator cuff strength can signify injury to the arm. A 2015 study showed that players with UCL tears had more significant reductions in strength in both their throwing and non-throwing arms when compared to uninjured players. (Garrision, 2015.)

TAKE HOME MESSAGE: IR strength losses over the course of the season will reduce velocity and may affect the balance between strength at the back of the shoulder versus the front of the shoulder increasing injury risk. Use the Arm Care app to minimize IR strength loss.

Research
Research
Toyoshima S., Hoshikawa T., Miyashita M., Oguri T. (1974) Contribution of the body parts to throwing performance. In: Nelson R.C., Morehouse C.A. (eds) Biomechanics IV. International Series on Sport Sciences. Palgrave, London.

Gowan ID, Jobe FW, Tibone JE, Perry J, Moynes DR. A comparative electromyographic analysis of the shoulder during pitching. Professional versus amateur pitchers. Am J Sports Med. 1987 Nov-Dec;15(6):586-90.

Mullaney MJ, McHugh MP, Donofrio TM, Nicholas SJ. Upper and lower extremity muscle fatigue after a baseball pitching performance. Am J Sports Med. 2005 Jan;33(1):108-13.

Erickson BJ, Sgori T, Chalmers PN, Vignona P, Lesniak M, Bush-Joseph CA, Verma NN, Romeo AA. The Impact of Fatigue on Baseball Pitching Mechanics in Adolescent Male Pitchers. Arthroscopy. 2016 May;32(5):762-71.

Fleisig GS, Andrews JR, Cutter GR, Weber A, Loftice J, McMichael C, Hassell N, Lyman S. Risk of serious injury for young baseball pitchers: a 10-year prospective study. Am J Sports Med. 2011 Feb;39(2):253-7.

Garrison, J Craig et al. “Baseball players with ulnar collateral ligament tears demonstrate decreased rotator cuff strength compared to healthy controls. International journal of sports physical therapy vol. 10,4 (2015): 476-81.