I am going to go back old school to one of the seminal articles of softball biomechanics. Werner et al. (2006) measured 24 elite pitchers from the 1996 Olympic games with a mean age of 25 to determine specific kinematics of the pitch. Their sample had a mean velocity of 60.4 mph, much faster than almost all studies ever published. They found:
- Elbow distraction forces were 61% of bodyweight.
- Shoulder distraction forces were 80% of bodyweight.
- Seven factors contributed significantly to shoulder distraction force: Shoulder flexion at SFC, shoulder abduction at SFC, knee flexion angle at SFC, stride length and stride angle, and both elbow angle and hip angle at REL.
Implications: There are many other findings in this article, but let’s dig into shoulder distraction. Distraction force is the force of the segments trying to separate from the body. Our body is built to resist these forces, and in the shoulder, it is the main function of the rotator cuff. Other studies have reported that shoulder distraction force is positively correlated with velocity, but no evidence has been reported (yet) regarding shoulder distraction and injury. However, this study showed a negative correlation (not significantly) between shoulder distraction and pitch velocity. This means that these elite pitchers threw harder when shoulder distraction went down. Therefore, it could be possible (just like baseball) to throw harder with less stress. Longer stride length leads to more shoulder distraction force but more importantly, straighter strides lead to LESS shoulder distraction force. Also, the straighter the lead leg is at stride foot contact, the less the shoulder distraction force. This is a lot, but it shows some variables that we can help pitchers to mitigate possible injury risk.
People to Follow
Just a quick plug for Softball Premier TV, a YouTube channel that televises international softball around the world. This weekend there will be a men’s tournament in Florida called the USA Softball Winter Classic. If you are pining for some softball to watch, check out some of the best in the world this weekend.