Apple Watch Ultra IRON

A strength-first Ultra designed for squats, deadlifts, bench, and real 1RM days.

Not “fitness.” Not “movement rings.” This is a wrist-mounted coach + logbook + timer that survives steel, chalk, wraps, and PR chaos.

0) Design rules (the non-negotiables)

  1. Zero fumble UI: everything important must work with Action Button + Crown + Side Button.
  2. Chalk + wraps = normal: touch input is optional, never required.
  3. Strength reality: long rests, heavy singles, top sets + back-offs, RPE, e1RM, meet-style attempts.
  4. Don’t lie: auto-detection is conservative and always confirmable.
  5. Barbell-contact survival: bezel + strap + forearm mounting exist for a reason.

1) Hardware spec (Ultra body, gym-mutant edition)

1.1 “Knurl Guard” bezel + recessed crystal

  • Raised, replaceable sacrificial bezel ring (think: bumper for steel contact).
  • Slightly recessed display to avoid knurl kisses turning into permanent scars.
  • Anti-glare priority for harsh gym LEDs and mirror walls.

1.2 “Chalk Lock” physical-first controls

  • Touch gets de-emphasized.
  • Big hit zones and “reject accidental wrist flex” filtering.
  • Screen stays readable and stable during front rack, low-bar squat, and bench arch.

1.3 Haptics tuned for a loud gym

  • End-of-rest haptic is not polite.
  • Attempt Mode haptics feel like: “3…2…1… MOVE.”

1.4 WrapBand system (the headline feature)

WrapBand: band + wrist wrap hybrid

  • Normal band attachment + integrated wrap tail.
  • Micro-adjust pull tab: tighten between sets, loosen between sets, no re-threading.
  • Sweat + chalk tolerant fabric with a low-profile lock so it doesn’t snag.

Forearm Mount Sleeve (for squats/cleans/front rack)

  • Moves the watch 2–3 inches up the forearm.
  • Auto-rotates UI into Forearm Orientation.
  • Solves: front squat pain, clean contact, wrist wrap interference, and bar-to-watch collisions.

1.5 Optional accessory: Bar Tag (for serious velocity/ROM)

A tiny IMU puck that clips onto the bar (or collar). Used only when you want precision.

  • Watch does the session flow.
  • Bar Tag provides real bar motion, especially useful for:
    • velocity-based training
    • deadlift (wrist motion can be subtle)
    • bench (wrist motion ≠ bar motion)

2) StrengthOS (software) — information architecture

Core surfaces

  1. Lift Stack (Home)
  2. Workout Session
  3. Attempt Mode
  4. Rest / Timer
  5. Plate Math
  6. Video Proof (iPhone companion)
  7. Post-workout Review
  8. PR & Trend dashboard

Core philosophy

During the workout, you’re a lifter, not a data clerk.

The watch captures just enough in the moment, and gives you the deep analytics later.

3) Control mapping (always consistent)

Physical controls

  • Action Button = SET
    • Press: Start/Confirm set
    • Double press: End set
    • Long press: Mark as “Top set” / “PR”
  • Digital Crown = Adjust
    • Turn: change weight / reps / RPE (contextual)
    • Press: confirm / next field
  • Side Button = TIMER / MODE
    • Press: Start rest timer
    • Double press: +30 seconds (or +15s configurable)
    • Long press: Enter/Exit Attempt Mode

“Chalk Lock” touch rules

  • Tap targets must be huge
  • Swipe gestures become secondary or disabled during movement
  • Touch is best for review, not for in-set logging

4) Screen-by-screen UI flow (watch)

I’ll write this like a product spec + storyboard. Each screen includes: purpose, layout, and interactions.

4.1 Onboarding flow (first launch)

Screen A: Units + Bar defaults

Title: “IRON Setup”

  • Units: lb / kg
  • Default bar: 45 lb / 20 kg (editable)
  • Plates available: toggle common sets (gym A / gym B)

Interactions

  • Crown selects, press confirms.
  • Action Button advances.

Screen B: Training style (pick your brain’s language)

  • Powerlifting / Strength
  • Hypertrophy
  • Olympic lifting
  • Mixed

Default if you pick powerlifting:

  • Enable: RPE, Attempt Mode, warm-up autopilot, meet-style commands.

Screen C: Wrist situation

  • “I lift with wraps often” ✅
  • “I front squat / clean” ✅
  • “I want Forearm Mount mode suggested” ✅

Screen D: Camera pairing (optional but savage)

  • “Pair iPhone camera for set recording” (QR-like pairing)
  • “Auto-record: attempts + top sets” ✅

Screen E: Accessibility + gym noise

  • Haptic intensity: Normal / Strong / Nuclear
  • Rest end: haptic only / haptic + sound

4.2 Home: Lift Stack

Purpose: instant launch into today’s plan, no distraction.

Layout

  • Date + battery + “Gym-ready” status
  • Big tile list:
    1. Squat — “Work up to heavy single”
    2. Bench — “Top set + 3 back-offs”
    3. Deadlift — “3×3”
    4. Accessories — optional

Interactions

  • Action Button: Start today’s workout immediately
  • Crown: scroll
  • Tap: open a tile (optional)

4.3 Workout Session: Exercise Overview

Example: SQUAT

Layout

  • Header: SQUAT + current goal
  • “Warm-up Autopilot” ladder
  • “Work sets” list (empty until you log)
  • Small bottom bar: Plate Math | Timer | Notes

Interactions

  • Action Button: Start the next prescribed set (warm-up or work)
  • Crown: adjust target weight before starting
  • Side Button: start rest timer (even before you set, if you’re pacing)

4.4 Pre-Set Screen (the “you’re about to lift” moment)

Layout (big, stupid readable)

  • Lift name
  • Target weight (huge)
  • Target reps
  • Optional: Tempo / Pause cue (if programmed)
  • Tiny line: last set summary

Actions

  • Action Button: START SET
  • Crown: adjust weight
  • Tap: toggles between “Target” and “Actual” mode (optional)

4.5 In-Set Screen (minimal + locked)

When a set is running, the UI becomes a locked HUD.

Layout

  • Timer (set duration)
  • Rep count (if confident) with confidence indicator:
    • “Reps: 3 (High)”
    • or “Reps: — (Low)” and it waits for confirmation after

Actions

  • Double Action Button: END SET
  • Side Button: does nothing (prevents accidental mode switches mid-lift)

4.6 Post-Set Confirm Screen (where the log becomes real)

This is the key. Fast, one-handed, no nonsense.

Layout

  • “LOG SET”
  • Weight: 315
  • Reps: 5
  • RPE: 8.5 (optional)
  • Tags: Belt / Wraps / Straps / Paused / PR (quick toggles)

Interactions

  • Crown changes highlighted field
  • Crown press moves to next field
  • Action Button: CONFIRM
  • Side Button: START REST (immediate)

If detection is uncertain, it asks:

  • “I think that was 4 reps. Correct?”
    • Crown: adjust
    • Action: confirm

4.7 Rest Screen (coach mode)

Layout

  • Big rest countdown
  • Next set preview: “Next: 325 × 3”
  • Tiny options: +30s | -30s | Plate Math

Interactions

  • Side Button: start/pause rest
  • Double Side: +30s
  • Crown: adjust rest target
  • Action Button: jump straight into next set screen

4.8 Plate Math Screen (zero-brain loading)

Layout

  • Target: 405 lb
  • Bar: 45
  • Per side: 180
  • Plates per side: 45 + 45 + 25 + 10 + 2.5

Interactions

  • Crown cycles between “Gym A / Gym B plate sets”
  • Action: back

4.9 Attempt Mode (1RM day / meet-day brain)

Enter: long press Side Button

Exit: long press Side Button

Attempt Mode Screen: “ONE JOB”

Layout

  • Big: “405 × 1”
  • Under: “Command: Standby”
  • Tiny: last attempt + result

Flow

  1. You’re ready → press Action Button
  2. Watch haptics: boom… boom… boom
  3. Screen says: “GO”
  4. You lift
  5. After you rack/lock: double Action Button (end)
  6. Post-attempt prompt:
    • ✅ Good lift
    • ❌ Miss
    • If miss: “Where?” (out of hole / mid / lockout / grip)

Then it does:

  • Updates PR if new
  • Updates e1RM trend
  • Suggests next attempt jump:
    • “Next: 420 (+15)” or “Next: 410 (+5)”
    • Suggestion is conservative if fatigue is flagged

4.10 Accessories mode (simple, fast, optional)

Accessories are chaos. The watch treats them like quick logging blocks:

  • Pick movement (row / pull-up / curls / lunges)
  • “Quick sets” logging:
    • weight + reps
    • rest optional
    • superset toggle available

5) iPhone companion (the “proof + analysis” machine)

The watch is the controller. The phone is the camera + review bay.

5.1 Set Recording

  • Watch can trigger iPhone camera:
    • record next set
    • auto-trim clip around set start/end
  • Auto-record rules:
    • attempts
    • top sets
    • any set you long-press PR on

5.2 Clip + Metadata sync

Each clip stores:

  • lift, weight, reps, RPE
  • timestamp
  • attempt result
  • optional tags (belt/wraps/etc)

Review later:

  • Tap a set → jumps to exact clip
  • Scrub with crown (feels insanely good)

5.3 “Depth Coach” (phone vision, watch haptics)

Optional for squat:

  • Phone analyzes depth (below parallel) and consistency.
  • Watch can give:
    • post-set feedback (“2 reps high”)
    • or silent haptic cue (only if you choose)

No pretending the watch alone can see your hips. The phone does the vision work.

6) Set detection + rep counting logic (the nerd engine)

This is the “don’t embarrass me” section. The system must avoid fake sets.

6.1 Sensor inputs

From the watch:

  • Accelerometer + gyroscope (IMU)
  • Heart rate (PPG) for exertion gating
  • Wrist orientation / rotation patterns
  • Optional: microphone for “clank” cue (only if user enables; not required)

From Bar Tag (optional):

  • Bar acceleration + orientation
  • Much stronger signal for deadlift and bench

From iPhone (optional):

  • Video analysis for depth/lockout (post-hoc or live)

6.2 Set detection: conservative classifier + confirmation

High-level approach

A set is detected only when multiple gates align:

Gate 1 — Movement burst

  • Detect a sustained movement window (e.g., 5–60 seconds) above a threshold.

Gate 2 — Strength cadence

  • Repetitive pattern consistent with reps (peaks/troughs), not random waving.

Gate 3 — Wrist posture plausibility

  • Bench and squat have distinctive wrist orientations.
  • If orientation is “typing on phone” or “walking,” reduce confidence.

Gate 4 — Exertion support

  • HR rises (or HRV drops) around the window OR user initiated set manually.

Gate 5 — Rest context

  • If user is in “rest screen” and movement begins, confidence increases.
  • If user is browsing home, confidence decreases.

Output

  • The model produces a confidence score:
    • High: auto-create set, then quick confirm screen
    • Medium: prompt “Was that a set?”
    • Low: ignore completely

Why this works

  • In lifting, false positives are worse than missed detections.
  • Missed detection is recoverable with one Action Button press.
  • False detection ruins logs and trust.

6.3 Rep counting: template-based segmentation + learning

Rep counting uses:

  • Peak detection on filtered acceleration/rotation signals
  • Exercise template chosen by:
    • user-selected lift (best)
    • or classifier guess (backup)

Templates (examples)

  • Squat
    • descent phase: smooth acceleration change + orientation shift
    • “bottom event”: velocity crosses near-zero + direction change
    • ascent phase: strong acceleration peak(s)
  • Bench
    • eccentric-lower peak → pause detection → concentric press peak
  • Deadlift
    • from floor: sharp initiation
    • lockout: stabilization plateau
    • down: controlled negative or drop signature

Paused reps detection

A pause is detected when:

  • bar/wrist velocity stays near zero for > X ms at bottom/top depending on lift.

Tempo

Tempo is derived from phase durations (eccentric / pause / concentric).

Learning your technique

Over time:

  • it adjusts thresholds to your cadence and range
  • it remembers your typical rep timing at different intensities

6.4 e1RM + PR logic (strength math that lifters actually use)

True 1RM tracking

  • Only from:
    • Attempt Mode singles
    • or manually tagged “True 1RM”

e1RM (estimated)

Calculated from:

  • your best sets, weighted toward:
    • top sets
    • high intensity (≥ ~80%)
    • high confidence rep count

The system supports multiple formulas internally and picks the best fit per user:

  • Rep-based estimators (e.g., Epley/Brzycki-style)
  • RPE-based adjustment (if you use RPE)

If you log RPE:

It converts RPE → estimated reps-in-reserve → adjusts e1RM to avoid overestimating grindy sets.

“PRs that matter”

  • 1RM PR
  • Rep PRs at key weights
  • Best e1RM
  • Best volume PRs (e.g., squat tonnage in a session)

6.5 Attempt jump suggestion model

Inputs:

  • last attempt success/fail
  • velocity proxy trend (if available)
  • rest adherence
  • historical jump patterns (you personally)
  • fatigue flags (HR + bar speed collapse proxy)

Outputs:

  • suggested next jump: +2.5 / +5 / +10 / +15 etc
  • confidence indicator (“Safe”, “Aggressive”)

This is a coach vibe, not a dictator. You can override with crown.

7) Data model (how sessions are stored)

Entities

  • AthleteProfile
    • units, bars, plate sets, preferred rest, RPE usage
  • Program
    • blocks, weeks, sessions, exercise prescriptions
  • Session
    • start/end, location (optional), notes, readiness
  • Exercise
    • name, variation, cues
  • Set
    • weight, reps, RPE, tags, timestamps, confidence
  • Attempt
    • weight, outcome, fail point, attempt number
  • Clip
    • video reference + trimming points + metadata
  • PR
    • type, value, date, linked set/attempt

Sync

  • Watch stores locally first
  • Phone merges video + analytics
  • Cloud sync optional (privacy-first)

8) Edge cases (where most lifting products die)

8.1 Deadlifts: wrist motion can be minimal

Solutions:

  • Encourage manual start/end via Action Button (fast)
  • Boost detection using:
    • grip change + HR + rest context
  • Optional Bar Tag for clean rep segmentation

8.2 Front squat / cleans: bar hits wrist area

Solutions:

  • Forearm Mount mode
  • Screen rotation + button behavior unchanged

8.3 Bench: wrist extension + touch disasters

Solutions:

  • Chalk Lock auto-engages for bench set
  • “In-set screen” ignores touch

8.4 Straps/wraps/belt

Solutions:

  • Quick tags on post-set screen
  • WrapBand designed to coexist (and forearm mount avoids wrap conflict)

8.5 Supersets and circuits

Solutions:

  • “Accessory block” mode favors quick logging
  • Optional auto-rest (or none)

9) Default “powerlifting-first” setup (since you said squat/deadlift/1RM)

Here’s a built-in template called IRON: Strength Block:

Day A (Squat focus)

  • Squat: warm up → top single @ RPE 8 → 3×5 @ ~75%
  • Bench: 4×6 @ moderate
  • Accessories: rows + posterior chain

Day B (Bench focus)

  • Bench: top single @ RPE 8 → 5×3 @ ~80%
  • Squat variation: 3×5
  • Accessories: triceps + upper back

Day C (Deadlift focus)

  • Deadlift: top single @ RPE 8 → 3×3 @ ~80%
  • Bench variation: 4×5
  • Accessories: hamstrings + core

On watch: you don’t see percentages unless you want them.

You see “Next: 315 × 3” and you smash it.

10) What makes Ultra IRON feel different (the vibe)

  • You hit SET, lift, hit SET, and you’re back to breathing.
  • Your rest timer ends like a coach: NOW.
  • Attempt Mode turns your wrist into meet-day command center.
  • Plate math deletes mental friction.
  • Video proof makes every PR permanent.

If you want to go even deeper, I can also write:

  • the exact button-state machine (every press in every screen)
  • the ML feature list for the classifiers (what signals it uses and why)
  • a full end-to-end product PRD (requirements, QA cases, metrics, launch plan)

But honestly? You already have a watch concept that would bully every “fitness tracker” in the room.