The purpose of Jump et al. (2026) Impact of the Lower Body on Softball Pitching Velocity was to find which lower body and pelvis movements and forces are tied to fastball velocity. Researchers at Auburn University’s Sports Medicine and Movement Laboratory tested 90 female high school and college pitchers (average age 18 ± 3 years; 76 right-handed, 14 left-handed), all free of injury, pain, and surgery for the 6 months before testing. Each pitcher wore 14 electromagnetic motion sensors (recording at 100 Hz) and landed her stride foot on a force plate (1200 Hz) that measured ground reaction force (GRF) in three directions: vertical, front-to-back (braking), and side-to-side. After her own warm-up, each pitcher threw max-effort fastballs from regulation distance, and the 3 fastest on the radar gun were averaged. The pitch was split into two phases: propulsion (first forward movement to stride foot contact) and acceleration (stride foot contact to ball release). The researchers measured pelvis rotation speed, drive and stride knee extension speed, stride-leg GRFs, stride length, and how fast the body’s center of mass (COM) moved up and forward. They used correlations and a backward stepwise regression (a model that keeps only the variables that best predict velocity), with body mass included.
They found:
The Fastest Pitchers Moved Their Center of Mass Up and Forward Faster (KEY FINDING)
- Peak vertical COM velocity had the strongest link to pitch velocity (r = 0.51, p < .001)
- Peak forward COM velocity (toward home plate) was next (r = 0.44, p < .001)
- In the regression model, these were the two strongest predictors:
- Every 1 m/s more vertical COM velocity went with about 7.5 mph more pitch velocity (p < .001), or 0.075 mph per 1 cm/s
- Every 1 m/s more forward COM velocity went with about 5.4 mph more (p < .001), or 0.054 mph per 1 cm/s
- Average peak forward COM velocity was 2.98 m/s; average peak vertical COM velocity was 0.90 m/s
How fast the whole body moves up and out during the drive mattered more than any single joint motion they measured.
Together, the Lower Body Explained 57% of Velocity
- Average fastball velocity was 54.0 mph (± 5.0)
- The final model explained 57% of the differences in pitch velocity (R² = 0.57, p < .001)
- Typical prediction error was 3.32 mph
- Predictors kept in the model: vertical and forward COM velocity, stride-leg vertical and braking GRF, side-to-side GRF, pelvis rotation speed during the drive, and body mass
Without measuring the arm at all, lower body variables accounted for more than half of what separated faster and slower pitchers.
Stride Length Did Not Predict Velocity
- Average stride was 100% of body height (± 12%)
- Stride length (relative to height) was not significantly related to pitch velocity
- The authors pointed to earlier work where longer strides, and the COM shifting back toward the drive leg (“anchoring”), were linked to upper extremity pain
“Stride out” is not the answer by itself. How fast the body gets there matters more than how far it goes.
Push Down on Landing, Don’t Put On the Brakes
- Average peak stride-leg vertical GRF was 1,867 N (± 551)
- Vertical GRF:
- Correlated with velocity (r = 0.31, p = .001)
- Every 1,000 N more went with about 3.0 mph more (p = .001)
- Front-to-back (braking) GRF:
- A negative predictor: every 100 N more braking force went with about 0.8 mph less (p < .001)
- Side-to-side GRF:
- Correlated with velocity (r = 0.38, p < .001), but was not significant in the final model (p = .08)
Faster pitchers put more force straight down into the ground through the stride leg and less force into braking.
Pelvis Rotation Toward the Throwing Arm During the Drive
- During propulsion, the pelvis rotates toward the throwing-arm side before stride foot contact (average peak 587 deg/s)
- Faster rotation in this direction went with higher velocity (r = −0.26, p = .006; the r is negative only because this direction is recorded as a negative number)
- Every 100 deg/s more went with about 0.5 mph more (p = .03)
- Pelvis rotation back toward the glove side during acceleration (average 397 deg/s) was not related to velocity
A quick pelvis turn toward the throwing-arm side during the drive may help clear room for the arm and add a stretch between the trunk and pelvis.
Heavier Pitchers Threw Harder
- Body mass was a significant positive predictor (β = 0.22, p = .01)
- Average body mass was 77 kg (± 13)
Body mass was kept in the model to account for its effect on force, so the force findings hold even after body size is considered.
Knee Extension Speed Didn’t Make the Cut
- Drive knee extension speed (average 378 deg/s), stride knee extension speed (average 294 deg/s), and stride knee excursion were not significantly related to velocity
- Lead knee extension is often named as a velocity factor in baseball research
In this softball group, knee speeds alone did not separate faster pitchers from slower ones.
Implications: The authors concluded that the lower body plays a critical role in generating pitch velocity in the windmill pitch. Pitchers aiming to maximize velocity should focus on a forceful push-off during the drive that moves the center of mass up and forward quickly, rather than only increasing stride length. A quick, well-timed pelvis rotation toward the throwing-arm side during the drive may also help, and producing more vertical force through the stride leg on landing may create a stable base so energy from the legs and trunk can be passed on to the throwing hand. They suggested that training lower body force production and effective landing may benefit pitchers, and may also reduce the demand on the upper extremity. They also cautioned that chasing velocity could cost accuracy for some pitchers, so an individual approach is best. Limitations included measuring GRF only on the stride leg, looking only at lower body variables (no arm or trunk data), a cross-sectional design that cannot prove cause and effect, mixing high school and college pitchers, testing fastballs only, and not measuring the timing of pelvis rotation. They called for future research on drive-leg GRF, the whole kinetic chain, training and long-term studies, and other pitch types.
Key Takeaways
- Drive speed beats drive distance. Coach a fast, powerful push that moves the body up and out, not just a longer stride.
- Don’t chase stride length. The average stride was about body height, and longer was not faster.
- Land and push down. More stride-leg vertical force went with more velocity; more braking force went with less (about 0.8 mph per 100 N).
- Let the pelvis turn toward the throwing-arm side during the drive. Faster rotation there went with higher velocity.
- Keep it individual. Velocity gains may cost command for some pitchers, so track both.
Important Biomechanics Connection
This study fits right into the kinetic-chain model we keep coming back to: force starts at the ground, moves through the pelvis and trunk, and ends at the hand. It builds on Nimphius et al. (2016) (March 6, 2025), which the authors cite as showing that drive-leg vertical force was linked to pitch velocity, and on Pletcher et al. (2021) on drive-leg force (February 13, 2025). This time the force plate was under the stride leg, so the two together cover both ends of the drive. It also lines up with Oliver et al. (2019) on upper extremity pain (July 3, 2025): longer strides and anchoring were tied to pain, and here longer strides didn’t add velocity. Same lab, same theme as Friesen, Jump & Oliver (2025) on ground reaction and shoulder forces (February 12, 2026) and Oliver, Yanagita & Bordelon (2024) on stride mechanics and shoulder distraction (November 6, 2025). And it’s another reminder that softball ≠ baseball. Baseball pitchers land on a more flexed knee and rely on braking force, but in this study braking force cost softball pitchers velocity, and the lead-knee extension speed that shows up in baseball research didn’t predict anything here. The legs aren’t just a base; they’re a big part of the engine.
Also…
There are new CSCS (Certified Strength and Conditioning Specialist) guidelines for the volume and intensity of plyometric training. This post is a good illustration of how we should look to train our athletes with plyometric training.
Newsletter subscribers got this review a week early. Sign up for the Pitch Better Newsletter to get each week’s research first.