I wanted to go back to the new articles today with Freisen et al. (2025) looking at ground reaction forces and peak throwing forces. The researchers studied 32 high school softball pitchers to examine whether ground reaction forces (GRFs) produced during the push-off phase of the pitch were related to peak shoulder forces later in the motion. Each pitcher threw fastballs for strikes while wearing 14 electromagnetic motion-capture sensors to track body movement. A force plate under the drive foot measured vertical, anterior/posterior, and medial/lateral GRFs at 1000 Hz. The propulsion phase was defined as push-off until the drive foot left the plate, and the acceleration phase lasted from stride-foot contact to follow-through. Shoulder forces (distraction, anterior, superior, medial, and resultant) were calculated during both phases and normalized to body weight. The researchers used regression and correlation analyses to determine whether peak GRFs and rate of force development (RFD) predicted peak shoulder forces.
They found:
Descriptive Values (from Table 1, page 4)
- Peak shoulder distraction during propulsion: ~34% body weight
- Peak shoulder distraction during acceleration: ~85% body weight
- Peak vertical GRF during propulsion: ~147% body weight
Correlation Findings
- Rate of Force Development (RFD) was negatively correlated with:
- Peak shoulder distraction force during propulsion (r = −0.367, p = 0.033)
- Peak shoulder resultant force during propulsion (r = −0.439, p = 0.009)
- No significant correlations were found during acceleration.
Regression Findings
- Peak vertical GRF during propulsion significantly predicted peak shoulder resultant force during propulsion
- Negative relationship (t = −3.176, p = 0.003)
- Higher vertical push-off force → lower shoulder force
- Model R² = 0.258
- No other GRF directions predicted shoulder forces.
- No significant relationships were found between propulsion GRFs and shoulder forces during the acceleration phase.
Implications: The main finding of this study is that stronger and faster push-off forces from the drive leg are associated with lower shoulder forces during the propulsion phase of the pitch. This supports the idea that effective lower-body force production may help reduce stress on the throwing shoulder early in the motion. Interestingly, these relationships did not carry into the acceleration phase, when shoulder forces are highest. This suggests that while lower-body force production helps during propulsion, other biomechanical factors (such as trunk rotation, sequencing, or muscular control) likely influence shoulder forces later in the pitch. The authors emphasize that pitchers may benefit from developing strong, explosive drive-leg mechanics to reduce shoulder loading. They also note that fatigue during games could reduce ground reaction forces, which might increase reliance on the shoulder and potentially elevate injury risk. Overall, the study reinforces the importance of the kinetic chain and lower-body training for both performance and injury prevention in softball pitchers.
Also…
I had a conversation this morning and even went over video of a pitcher who was struggling to gain velocity. What I saw was good technique, but a downfall in strength. I have decided to start working on 2 different master classes to start with regarding strength and conditioning in softball. One of the classes will be aimed at a more basic understanding of S&C in softball so that coaches can have conversations with their S&C coaches and begin to start to understand how to program for your own team. The second will be more advanced and allow coaches to start to become strength coaches for their own players. I have a lot to do, but I wanted to prime the group for that coming soon!