Strength Coaching
METTLE
A strength coach that shows the reason behind every number.
Mettle is a strength coach that shows its work. Goals, experience, equipment, schedule, and training history shape an adaptive program on iPhone. Deterministic logic owns sets, reps, rest, load progression, and deloads. Apple’s on-device model can select and explain exercises only from curated candidates. Logged reps and loads drive the next prescription, while RPE can shape coaching depth. Mettle remains in active development, and final private iCloud behavior is not yet verified.
Why it exists
A strength coach that shows the reason behind every number.
Mettle gives deterministic training logic control of every prescription. On-device intelligence selects from curated candidates and explains the plan at the lifter’s level, so adaptation never becomes a black box.
No hidden data path
Useful from the first input to the final result.
- 01
Define the Training Context
Choose the goal, experience, equipment, training days, session length, units, and optional bodyweight.
- 02
Generate a Structured Program
On-device AI selects from curated exercise candidates while deterministic composition still produces a complete plan if the model is unavailable.
- 03
Run the Session
See the last performance and exact “Why this?” rationale, log sets, use the planned rest timer, and optionally control the phone session from Apple Watch.
- 04
Adapt the Next Prescription
Logged sets drive the next progression, the program calendar schedules deloads, and completed training, RPE history, and note language can inform competence and coaching depth.
What it does
Purpose-built for one private workflow.
Every Number Has a Reason
Double progression and scheduled deload logic produce the sets, reps, loads, and evidence behind “Why this?”, not an unconstrained language model.
Coaching that Changes Altitude
The same deterministic program can be explained gently to a new lifter or with more training detail to someone experienced, without hiding control.
Workout Continuity
Live Activity, a resumable session, optional HealthKit, a Watch remote, custom exercises, and CSV export keep the training record useful.
Privacy is architecture
A shorter data path.
A clearer privacy boundary.
Core programming and coaching run on-device and retain a deterministic fallback. The source prefers private iCloud when that capability is configured and falls back on-device; the reviewed entitlement currently lacks iCloud, so final sync behavior remains unverified. HealthKit is optional, and the Watch experience controls an active phone workout rather than acting as a standalone trainer.
Read the full privacy modelBefore release or install
Questions worth asking.
01Can Mettle’s AI invent an unsafe exercise, weight, or rep prescription?
The design prevents the language model from owning those decisions. Apple’s on-device model can select and explain exercises only from curated candidates; a deterministic engine owns sets, reps, loads, rest, double progression, and deload logic. The evidence behind a prescription is what Mettle shows in “Why this?”.
02Is Mettle useful for both beginner and experienced lifters?
That is the central product design. Goal, experience, equipment, schedule, training history, RPE, and optional bodyweight shape the program, while the coaching language and amount of detail adapt to the lifter’s level. Mettle can suggest a transparent level-up when the logged evidence supports it.
03Does Mettle work offline or without Apple Intelligence?
Core program composition, progression, exercise selection, and workout logging have a deterministic local path, so they do not depend on a network or supported Foundation Models hardware. Apple purchase verification and any user-initiated web link still use Apple or web services.
04Does Mettle upload my workouts or bodyweight?
Mettle has no Obsidian Ridge Labs account, analytics SDK, or developer workout server. Its persistence source prefers the user’s private iCloud when that capability is configured and falls back to an on-device store; the reviewed entitlement currently lacks iCloud, so final sync behavior is not yet a release promise. HealthKit access is optional and permission-based.
05Can I control a Mettle workout from Apple Watch?
The in-development Watch app acts as a remote for an active workout owned by the iPhone. It can help log sets and control the rest timer with haptic confirmation. A standalone Watch workout that runs independently from the phone is not part of the current scope.
06Can I export my Mettle training history?
Yes. The current implementation can export completed-set history as CSV. That user-initiated export leaves Mettle’s managed data store, so its privacy depends on the destination the user chooses.