Rotational Acceleration
Also known as: rotational acceleration, rotational acceleration baseball, rotational acceleration swing, bat acceleration into the swing plane, rotational acceleration g's
Rotational acceleration is a swing-sensor metric for how quickly the bat accelerates into the swing plane early in the swing. It is reported in g's. One sensor maker lists an MLB average of 17 g and calls 15 g or more high. It reflects how well the body, not just the hands, starts the swing.
The sensor measures it from the moment the swing starts until the back elbow slots into place. That captures how explosively the bat leaves the load. It is not bat speed at contact. A hitter can still reach good bat speed late with a slow, hand-driven start.
High readings come from good sequencing. The pelvis turns first, then the torso, lead arm and hands. Casting the hands early or starting the swing with the arms usually lowers it. One maker's tiers are below 10 g low, 10 to just under 15 g medium, and 15 g or more high.
Compare a hitter with himself on the same sensor. A big drop from tee work to live pitching can point to a load or stride that costs time. A high reading with poor on-plane efficiency can mean the barrel gets going fast but in the wrong direction. Check it with video.
Tips by skill level
Start your swing with your hips and let the hands follow. That order usually raises rotational acceleration.
Track rotational acceleration from tee to front toss to live pitching. A big drop between stages shows where your load or stride is costing time.
Example
A college hitter reads 11 g off the tee. Video shows his hands starting the swing before his hips. He works on hip-first drills and medicine-ball throws. A month later he reads 14 g with the same bat.
Why it matters
Getting the bat moving quickly gives a hitter more time to see the pitch. Rotational acceleration shows whether the body is doing that work.
Common mistakes
- Trying to raise it by jerking the hands
- Comparing readings with different bats or sensors
- Ignoring on-plane efficiency while chasing a higher number
- Testing only off the tee
Frequently asked questions
What is rotational acceleration?
It is a swing-sensor reading for how quickly the bat accelerates into the swing plane at the start of the swing. It is reported in g's.
What is a good rotational acceleration in baseball?
One sensor maker lists an MLB average of 17 g and calls 15 g or more high. Below 10 g is low. Compare your own readings over time on the same sensor.
How do I increase rotational acceleration?
Improve your sequence so the hips start the swing before the hands. Rotational strength and medicine-ball throws can help. Avoid casting the hands early.
Sources
Related terms
- Hip-Shoulder SeparationHip-shoulder separation is the difference in rotation between the hips and the shoulders during the swing. The hips fire first while the shoulders stay back, creating stored torque that whips the bat through.
- Casting (Batting)Casting is a swing fault where the hands and barrel arc wide instead of taking a direct path to the ball. It kills bat speed and limits inside coverage.
- Time to ContactTime to contact is the split-second a swing takes from trigger to ball. It sets how late a hitter can afford to start swinging against a given velocity.
- On-Plane EfficiencyOn-plane efficiency is a swing-sensor metric for the percentage of the swing in which the bat stays on the plane it will meet the ball on. A higher number means the barrel spends longer in line with the pitch. One sensor maker recommends an average of 70 percent or higher, within a range of about 65 to 85 percent.
- Kinematic ChainThe kinematic chain is the order in which body segments, from the ground up, pass force and speed through a swing. Each segment hands its speed on to the next.
Related guides & benchmarks
Work on the cause
Video shows how you move, not the ball itself. Film one swing to find the movement behind this result — free to start.
See a sample Baseball report first