Shoulder Muscle Firing Patterns During the Windmill Softball Pitch

Maffett, M.W., Jobe, F.W., Pink, M.M., Brault, J., Mathiyakom, W. (1997). Shoulder Muscle Firing Patterns During the Windmill Softball Pitch. American Journal of Sports Medicine, 25(3), 369-374.

This study was actually a stand-alone study, and part of a comparison study in Escamilla and Andrews (2009). 45% of time-loss injuries were shoulder injuries and 27% of those were from overuse in Loosli, et al. (1992). This study tried to compare differences in the muscle firing patterns between elite underhand and overhand pitchers.

Participants in the softball portion were 10 collegiate pitchers with an average 20.1 years of age, and 53 mph per pitch. The external rotators peak muscle activation was between the 6 – 9 o’clock phase of the pitch (not after release like baseball), and the internal rotators peaked activation from 12 o’clock to release.  The most expressive way to put this is a table:

	6 – 3 o’clock	3 – 12 o’clock	12 – 9 o’clock	9 o’clock – REL	Follow-Through
External Rotators
Supraspinatus	78%	43%	22%	37%	19%
Infraspinatus	93%	92%	35%	29%	30%
Teres Minor	24%	87%	57%	41%	44%
Shoulder Flexion
Ant. Deltoid	38%	17%	22%	43%	28%
Pectoralis Major	17%	24%	63%	76%	33%
Post. Deltoid	37%	102%	52%	62%	34%
Internal Rotators
Subscapularis	34%	41%	81%	75%	26%
Serratus Anterior	38%	19%	45%	61%	40%

I highlighted those muscles that were most relevant during each movement. It’s interesting that the arm first externally rotates, then internally rotates. If we are looking to maximize the pitch in terms of muscle contraction, we should increase external rotation so that we can increase internal rotation. In real terms, that means that we would want the elbow facing away from the body and the ball and palm facing toward the body. I will let you conceptualize how that is supposed to work.

This also illustrates a few training notes:

• The Serratus Anterior is active the entire pitch, as it helps to maintain Scapular stability throughout the pitch. Scap pushups, etc. should become part of your routine.
• Those of you who stay away from bench because it’s “bad for your shoulder” should re-evaluate the value of training the Pectoralis Major
• Anterior and posterior Deltoid muscles are very active during the pitch. Therefore, you need to have a balanced shoulder routine with a lot of rear delt work since the anterior deltoid will work in all press movements.

Escamilla and Andrews (2009) also reviewed baseball muscle firing patterns for the overhand throw in their study. Here is a table with the firing patterns of similar muscles to the softball pitch:

	Stride	Arm Cocking	Arm Acceleration	Arm Deceleration	Follow-Through
External Rotators
Supraspinatus	60%	49%	51%	39%	10%
Infraspinatus	30%	74%	31%	37%	20%
Teres Minor	23%	71%	54%	84%	25%
Shoulder Flexion
Ant. Deltoid	40%	28%	27%	47%	21%
Pectoralis Major	11%	56%	54%	29%	31%
Post. Deltoid	42%	26%	68%	60%	13%
Internal Rotators
Subscapularis (Lower)	26%	62%	56%	41%	25%
Subscapularis (Upper)	37%	99%	115%	60%	16%
Serratus Ant.(6th rib)	44%	69%	60%	51%	32%
Serratus Ant. (4th rib)	40%	106%	50%	34%	41%

Quite a few studies have been done to illustrate the muscle firing patterns in the baseball pitch, as compared to the single study that has been done in the windmill softball pitch, so the data may not be as accurate. However, we can generalize a few conclusions in comparison to the baseball pitch that might help us understand more. Also, just as a note, the arm deceleration phase in the overhand pitch is more akin to the softball follow through. In the overhand pitch follow-through, the pitchers arm has all but stopped after the arm deceleration.

The first glaring thing I see is that the external rotators take more of the brunt of the action during the overhand deceleration (39% - 84% activation) than in the follow-through of the softball pitch (19% - 44% activation). This is probably why we don’t see the same injury rate in the rotator cuff in softball. That being said, the bigger muscles (Posterior Deltoid and Pectoralis Major) are activating a lot more during the softball pitch:

Peak firing:

	Softball	Baseball
Anterior Deltoid	43%	47%
Pectoralis Major	76%	56%
Posterior Deltoid	102%	68%

This would likely be why many unofficial experts say that the windmill is a more “natural motion”. That being said, injury incidence in softball is just as, if not more common, than it is in baseball, the difference being that most of the injury incidence in softball does not result in time lost (Loosli, et al., 1992). Baseball research is also more extensive, leading training protocols to be much more accurate and more preventative toward injury.

The other observation that I have that the authors didn’t is the activation of the internal rotators and the potential it has to the softball pitch. In non-scientific observations, I have noticed that girls who have above average overhand throws tend to also be the kids that throw underhand with above average speed. According to the baseball research, the internal rotators peak activation (115% in the upper subscapularis) is much higher than in softball (81% in the subscapularis). This likely is due to the extreme stretch reflex effect produced during the arm cocking of the overhand throw. This could be why the ball velocities of the overhand throw are still higher than the underhand throw. If we could activate the internal rotators more, possibly by increasing the stretch reflex, could we see velocities that we haven’t reached before? Food for thought.

Here is that reference as well:

Escamilla, R.F. & Andrews, J.R. (2009). Shoulder Muscle Recruitment Patterns and Related Biomechanics during Upper Extremity Sports. Journal of Sports Medicine, 39 (7), 569-590.