A position player throw is not a mound delivery, and judging it by pitching rules gets it wrong. The chain is the same, roughly 80% of throwing velocity comes from rotational mechanics below the shoulder, but the crow hop and the transfer out of the glove are the parts that decide whether an infielder or outfielder gets rid of it on time.
The sequencing principle carries over exactly: legs and hips fire first, then trunk, then arm, with hand speed peaking last. Three things are genuinely different, and they are where most throwing faults live.
| Element | On a throw |
|---|---|
| The crow hop | Replaces the windup. Its job is linear momentum toward the target, gathered before rotation starts. A throw with no momentum makes the arm supply everything. |
| The transfer | Glove to hand has to happen while the feet are already working. Most late throws are late in the transfer, not slow in the arm. |
| Arm slot | Genuinely variable by position and by throw. A higher slot is not inherently better. An infielder throwing on the run should not look like a pitcher. |
These are the areas our throwing framework scores, in weight order. Each window is a reference range, not a template.
| Checkpoint | What good looks like | Most common fault |
|---|---|---|
| Sequencing weight 20 | Hips peak, then trunk, then elbow, then hand, in clear order. | Arm dominant throws, where hand speed ramps with no prior hip or trunk peak. |
| Hip to shoulder separation weight 20 | Hips opening ahead of the chest, peaking during the throw. 25 to 40 degrees on video corresponds to the 40 to 60 degree 3D reference. | Hips and shoulders rotating as one unit, so nothing elastic is stored. |
| Crow hop, stride, and momentum weight 15 | A gather that builds speed toward the target and converts to rotation on landing. | Standing and throwing with no momentum, or drifting sideways off the target line. |
| Trunk and posture weight 15 | Quiet head, forward flex over a stable base with moderate tilt. | Staying tall, which shortens the acceleration path, or excessive tilt that loads the shoulder. |
| Arm action and timing weight 15 | Elbow near 90 degrees at shoulder height when the front foot lands, hand speed peaking last, glove side firm. | Arm drag, where hand speed peaks well after the window it should. |
| Deceleration and finish weight 15 | Smooth decay with the chest continuing over the front leg toward the target. | Recoil, or falling off to the side rather than finishing through the throw. |
Field a rolled ball, crow hop, and throw to a target at 75% effort, feeling the rear leg drive you forward before you rotate. Six reps, adding distance gradually.
Cue: gather and go, then fire.
Take a crossover step behind the stride foot, shuffle toward the target, and throw at 75% as the momentum carries you. The feet arriving first forces the hips to fire before the trunk can cheat.
Cue: feet first, hands last.
From the throwing side knee, rotate the chest back, show the goalpost, and throw at 60%, letting the hand come through last. Ten easy reps.
Cue: chest turns, then the whip cracks.
Throw at 75% with one rule: the glove stops over the front foot at chest height and the chest travels to meet it. A partner watches that the glove never flies behind the hip.
Cue: bring your chest to the glove.
Everything above reads from a single camera as a 2D approximation, labeled that way, with basis landmarks and a confidence value on every number. What a clip cannot give you: arm health or workload, which need data from outside the video, and grip detail, which is below the resolution of a full body frame. Film from the side at 120 frames per second with the whole body in frame.
Send one practice clip and we will return the full breakdown, so your staff judges the engine on your players rather than a demo reel.
Request a breakdownWhere velocity comes from and the leaks that cost the most.
The same chain on the mound, with six checkpoints and windows.
The hitting side: load, sequence, contact, balance, timing.