Not just how good — what's good, what's off, and what to fix next.
Record one overhead swing. Pose Coach scores it across five dimensions, grades it S–D, and points to the one thing to work on next. This page explains how the score is calculated, how to read it, and how to use it.
One score. Five things behind it.
For each overhead stroke, Pose Coach reads five dimensions from your 3D skeleton, scores each 0–100, then weights them into one 0–100 overall score and an S/A/B/C/D grade. Speed is just one piece — completeness, angles, consistency, and energy transfer matter just as much.
A weighted blend of five dimensions. The grade is the overall score mapped to a letter — the same S–D scale that powers our running score, so grades are comparable across sports: your badminton B and your running B are one ruler.
Default weights: Completeness 25% · Tempo 20% · Joint Angles 20% · Stability 15% · Kinetic Chain 20%. A coach view auto-shifts to 30 / 15 / 25 / 10 / 20, weighting technical accuracy more.
| Grade | Label | Overall score |
|---|---|---|
| S | Outstanding | ≥ 90 |
| A | Excellent | ≥ 80 |
| B | Good | ≥ 70 |
| C | Pass | ≥ 60 |
| D | Needs Work | < 60 |
The five dimensions
Each dimension answers three questions: what it measures, what a top score looks like, and how to improve it. The order never changes — it matches the app's score card.
Completeness
Measures — A full overhead stroke has three phases: backswing → contact → follow-through. This checks whether each swing completes all three — backswing up above the shoulder, deep enough (not a shallow flick), an actual contact, and a follow-through that extends.
Top score — all three phases on every swing, backswing above the shoulder with depth. In-app: backswing 3/3 (2 deep), contact 3/3, follow-through 3/3.
- Backswing above the shoulder
- Full three-phase swings
- Don't cut the follow-through
Tempo
Measures — two things: how fast you swing (peak speed at contact) and how well you load (backswing as a share of the whole stroke). The sweet spot is a 40–60% backswing share — too fast and you don't load, too slow and you miss the release.
Top score — peak speed near the high-level range, backswing share inside 40–60%. In-app: avg peak 12.5 m/s; backswing share 48% (target 40–60%).
- Burst power at contact
- Slow the backswing to load, then accelerate
- Keep tempo steady
Speed is 60% of this dimension, rhythm 40%. A calibrated reference appears once enough same-stroke samples exist.
Joint Angles
Measures — how far your key-frame joint angles (shoulder / elbow / wrist / hip, across the three phases) deviate from a reference — the average degrees off. Smaller deviation, higher score.
Top score — average deviation near 0°. Reference scale: within 5° ≈ full marks, 15° ≈ 87, 30° ≈ 67, 50° ≈ 40, 80° → zero. In-app: avg deviation 18.5°, largest in the swing phase.
- Bend the elbow ~30° more before the swing
- Lock the wrist firm at contact
- Open the shoulder fully
Joint angles need a clear side view — facing the camera head-on can make this metric unavailable. Switch camera angle to get it.
Stability
Measures — how consistent you are swing-to-swing: body/device steadiness plus rhythm regularity across swings. Steadier and more regular scores higher.
Top score — stand steady, brace the core, racket arm doesn't wobble, every swing close in rhythm.
- Plant your feet, center your weight
- Brace the core to cut sway
- Keep the racket arm steady
Stability compares across swings, so record 3+ swings for a reliable read.
Kinetic Chain
Measures — how well power transfers along the chain — hips → shoulder → elbow → wrist — for each overhead stroke, based on a biomechanical model of the kinetic chain. Three sub-signals combine into one score: chain integrity (are your joints firing in the right order? — 50%), speed amplification (how much wrist speed multiplies from hip speed? — 30%), and hip engagement (are you starting from the hips or skipping to the arm? — 20%).
Top score — a clean proximal-to-distal sequence (hips → shoulder → elbow → wrist, each peaking in order), speed amplification ≥ 4.0× (full whip effect), and hip engagement ≥ 50 ms. In-app: 3/4 swings with intact chain, amplification 4.4×.
- Fire the hips before the shoulder — don't fire everything at once
- Let the elbow lead, then the wrist — a whip, not a push
- Finish the follow-through so the chain closes cleanly
Kinetic Chain is scored for overhead strokes only (clear / smash / drop). A clear side view at 60 fps or higher gives the most reliable read. When arm tracking degrades, this dimension is flagged as lower confidence.
Your score card, element by element
Open the score card and every element is telling you one thing.
- Score ring + grade badge — the overall 0–100 and its S/A/B/C/D letter. A Personal Best badge appears when you set a new high.
- One-line summary — names your strongest and weakest dimension in plain language (its tone adapts to your role — see below).
- Five dimension bars — Completeness / Tempo / Joint Angles / Stability / Kinetic Chain, each with its score and a one-line detail.
- Next Focus — points at your weakest dimension, e.g. "Focus on joint angles next."
- Tips to Improve — always three, ranked by leverage.
- Per-Swing Breakdown — each swing's score and weakest point; tap to replay that swing or save it as a reference.
- Engine version + notice — the scoring engine version and an honest reminder that scores are directional guidance.
Confidence: 3 or more swings counts as high confidence. Fewer shows "Low sample size — result is approximate." Record a few more swings and the score gets more trustworthy.
Not "keep practicing" — the exact three things to work on
Every score comes with three tips, ranked by leverage — the lowest-scoring dimension first. Each is concrete and quantified, not a platitude.
| 1 | Bend the elbow 30° more before the swing |
| 2 | Lock the wrist firm at contact |
| 3 | Plant your feet, center your weight |
Next Focus names the single dimension to drill. Tap Generate Training Plan to feed the score to the AI coach and get a targeted plan. When all five dimensions are already high (each ≥ 85), the tips switch to maintain / challenge mode.
Mixed a smash, a drop and a clear into one recording? The score is based on the most frequent stroke type, and the app suggests recording one type on its own for sharper, more targeted scoring.
Same swing — a different read for player, parent, coach
The numbers are identical for everyone; only the summary's tone changes. A coach view also shifts the weights toward technical accuracy (Completeness 25→30%, Joint Angles 20→25%) and eases off the noisier-when-sparse Tempo (20→15%) and Stability (15→10%). Kinetic Chain stays at 20% for both roles.
Player
Encouragement — "Scored A (82). Tempo is your strength — watch your joint angles!"
Parent
Reassurance — "Your child scored A (82). Tempo stands out; joint angles still has room to grow."
Coach
A prescription — "Overall A (82). Recommend focused joint-angles training."
What this score can — and can't — do
Scores reflect AI motion analysis and are directional guidance — not a clinical or professional assessment.
It can
- Quantify five dimensions of your overhead strokes (clear / smash / drop)
- Point to the one thing to work on, with actionable tips
- Track consistency across multiple swings
- Read joint angles from a clear side-view recording
Keep in mind
- Scoring currently focuses on overhead strokes — net shots and drives aren't scored yet
- Kinetic Chain is measured for overhead strokes only, and needs 60 fps or higher with a clear side view
- It doesn't replace a real coach's on-court judgment
- Fewer than 3 swings is flagged "result is approximate"
- A head-on camera may disable the joint-angle metric
If no complete swing is detected, or a clip can't be scored (low frame rate / screen recording), the app asks you to re-record in-app. When arm tracking degrades, the angle and completeness metrics are flagged as lower confidence rather than shown as exact.
Your next swing deserves a score.
Record one overhead swing and see your five dimensions, your grade, and the one thing to work on next.
Scoring engine v0.9.0 · Scores reflect AI motion analysis and are directional guidance, not a clinical or professional assessment.