Biomechanics of Youth Windmill Softball Pitching

Werner, S.L., Guido J.A., McNeice, R.P., Richardson, J.L., Delude, N.A., & Stewart, G.W. (2005). Biomechanics of Youth Windmill Softball Pitching. The American Journal of Sports Medicine, 33, pp. 552-560.

Dr. Sherry Werner and her colleagues (2005) recruited 53 pitchers from ages 11 to 19 (M = 14) to participate in their study. On average, they were 1.65 m tall and 59 kg in weight. Each pitcher warmed up and threw 10 pitches and selected their 3 best pitches for the study. Their mean pitching speed was 55 mph and the average time from stride foot contact to release was .117 s.

Average stride foot knee angle at contact was 33˚ and stride length was 1.03 m. The elbow was flexed at 20˚ at release. Peak upper trunk rotational velocity was 901˚/s and peak lower trunk rotational velocity was 544˚/s. The study also measured the ground reaction forces of the stride foot. Peak vertical reaction force was 139% bodyweight (BW) and horizontal peak force (braking force) was 115% BW just after stride foot contact. Peak medial ground force was 42% BW. The hips closed to 43˚ at release.

This was the first study to discuss the reaction forces of the stride foot at contact and, although they didn’t measure the velocity of the athletes at contact. We can presume that the higher forces would be related to higher velocities and, or more mass. None of the measures were analyzed to their relationship to the speed of the pitch. It is interesting that the vertical force was larger than the horizontal force. This means that the pitchers were coming down at a greater velocity than going forward. One might theorize that the better the relationship between the forces, as in more horizontal force than vertical force, that there is more horizontal velocity than vertical velocity. Theoretically, the more horizontal velocity the higher rate of speed the pitcher can throw the ball. Future research would do well to determine this relationship. Also, force measurements on take off may also be warranted.

The study noted a relationship between stride leg knee angle and the velocity of the ball as the less the knee angle, the greater the speed of the pitch. This is a significant finding. If the knee angle is less and the speed is higher then we can assume that “resistance” or the “block” at release is extremely important. Both Werner, Jones, Guido, and Brunct (2006) and Oliver and Plummer (2011) have also found relationships between hip angle and gluteus maximus activation, respectively, to be related to the speed of the pitch. So the block is also related to the hip angle as well. This means that the block is an entire body movement and the knee and hip angle should be as straight as possible.

Another analysis determined a relationship between upper trunk rotational velocity and the speed of the pitch. The faster the upper trunk rotates, the slower the ball velocity. Therefore, the more the shoulders rotate, or “close the door”, the slower the pitch. That may be food for thought for those who still believe in it. This also means that the front shoulder is stabilized at release in pitchers that throw harder, which would mean that the front knee, hip, and shoulder must be stable to generate more ball velocity.

Dr. Werner is a pioneer in the research of the windmill softball pitch. One thing about her articles is that she always has a lot of participants. Therefore, the conclusions that can be drawn from them are much more reliable than most other studies. This study lends significant evidence toward the importance of two important biomechanics: the stride leg knee angle and the stability, or lack of rotation, of the shoulders. Both can be addressed through drill work on a regular basis in your pitching workouts. One last quick note: Michelle Smith once asserted that the hip angle should be a “perfect 45”, meaning that the hips should be at 45˚, instead of the previous thought that 90˚ was more ideal. According to this study, 43˚ was the average. Even though this sample is not the most elite athletes in the game, we can assert that 45˚ is not far off.

“When I let go of what I am, I become what I might be.” ~Lao Tsu

Ps. Lao Tsu is the author of “The Art of War”. Every coach should read this book and I believe it’s free on Ibooks.