Oliver et al. (2022) studied 55 NCAA Division I softball pitchers to see whether the amount of energy flowing through the trunk was related to how much force was placed on the shoulder during pitching. Each pitcher threw three full-effort rise-ball pitches while wearing electromagnetic motion-capture sensors that recorded body movement at 100 Hz. A force plate was used to identify the moment the stride foot contacted the ground. The researchers focused on the acceleration phase of the pitch, from foot contact to ball release. Using a segment-power analysis, they calculated how much energy flowed into the trunk (proximal energy inflow) and how much energy flowed out of the trunk toward the arm (distal energy outflow). These energy values were then compared to each pitcher’s peak shoulder distraction force using regression analysis to see if trunk energy flow predicted shoulder stress.
They found:
- Proximal trunk energy inflow was NOT related to peak shoulder distraction force
- Very weak relationship (r = 0.02, p = .87)
- Distal trunk energy outflow was also NOT related to peak shoulder distraction force
- Weak relationship (r = 0.13, p = .34)
- Average peak shoulder distraction force was ~931 N·m
- Trunk energy-flow curves showed consistent patterns across pitchers but did not predict shoulder loading
Implications: The authors expected that pitchers who transferred more energy through the trunk would experience lower shoulder stress, but the results did not support this idea. Unlike baseball pitching studies, where trunk energy flow has been linked to elbow stress, softball pitching did not show the same relationship with shoulder distraction force. One possible explanation is that this study measured trunk energy inflow and outflow differently than prior baseball research, which often looked at whole-segment power or energy transfer across joints. The authors also suggest that trunk energy flow alone may not explain shoulder stress, and that how energy moves through the entire kinetic chain, including the pelvis, arm, and shoulder joints, may be more important. They emphasize that pitchers may maintain similar trunk energy patterns even when shoulder stress is high, possibly through compensations elsewhere in the body. Future research should look at energy generation, absorption, and transfer across multiple segments and include performance measures like pitch velocity. I would also add that ecological dynamics suggests that no two pitches, even by the same person, are the same. Therefore, key takeaways are: 1. There isn’t a relationship between the kinetic chain and shoulder distraction, but there is a relationship between the kinetic chain and velocity. 2. There is a relationship between shoulder distraction and velocity. 3. There isn’t a relationship between shoulder distraction and injury (in softball). Therefore, it’s still important to transfer energy efficiently to increase velocity, and we can be relatively confident that we won’t be risking injury by doing so.
Also…
I like to use social media to learn, interact and add to it. However, sometimes it’s good to just get fired up. Jocko Willink always fires me up. Here is a recent post to add to your New Year!