Open any popular fitness app and you'll find the same bloated feature set: workout videos you won't watch, AI coaches giving generic advice, meal plans you won't follow, social feeds you don't need, challenges you didn't ask for.
Intrvl does none of that.
It does exactly two things: time intervals with precision and track weights with speed.
That's not a limitation. That's a philosophy.
The Unix principle applied to training
The Unix philosophy says: do one thing and do it well. Build tools that work together, not monoliths that try to solve every problem.
Intrvl follows this principle because serious training doesn't need complexity — it needs precision where it counts.
Consider what actually matters during a training session:
- Timing rest periods accurately
- Recording what you lifted
- Seeing what you did last time
- Tracking progression over time
Everything else is noise.
Why two functions, not twenty
Most fitness apps add features to justify subscriptions. More features mean more perceived value, which means higher monthly fees and better retention metrics.
But feature bloat creates friction.
Every additional function adds cognitive load. Every extra screen adds navigation steps. Every new workflow adds decision points between you and the work that matters.
Why Serious Lifters Still Use Pen and Paper showed how paper logbooks dominate for a reason — they're fast, focused, and frictionless. But paper can't time your rest periods or calculate volume trends.
Less Screen Time, Better Workouts demonstrated that app-switching between separate timer and tracking tools breaks focus and costs time.
The solution isn't adding more features. It's unifying the two essential functions without adding anything else.
What "precision" actually means
When we say Intrvl times intervals with precision, we mean the timing engine never drifts — even when the app is backgrounded, even during long sessions, even when your phone locks.
That's not a trivial engineering problem. Most timer apps lose accuracy when iOS suspends them. Intrvl's countdown engine maintains second-level precision because timing rest periods is a training variable, not a convenience feature.
Live Activities integration means your timer runs on the Lock Screen and Dynamic Island. Background-safe operation means you can log sets, check previous weights, or switch apps without losing timing accuracy.
That's precision.
What "speed" actually means
When we say Intrvl tracks weights with speed, we mean the unified interface eliminates app-switching friction entirely.
Timer counts down. You finish your set. You tap the weight you lifted — right there, same screen, no navigation. You start the next rest period. Repeat.
No switching between apps. No searching for the exercise in a different tool. No losing your place in the session.
Fast enough that you won't reach for paper. Complete enough that you won't need spreadsheets later.
That's speed.
What we don't do (and why that matters)
Intrvl has no workout videos. You already know how to squat.
Intrvl has no AI coach. You already have a program — or you know how to design one.
Intrvl has no meal tracking. Nutrition apps exist. Use those.
Intrvl has no social feed. Training isn't content creation.
These aren't missing features. They're intentional omissions.
The target user is an intermediate to advanced lifter who understands training fundamentals, follows structured programs, and recognises rest periods as a variable worth controlling.
That person doesn't need hand-holding. They need tools that respect their intelligence and get out of their way.
The features that earn their place
Every function in Intrvl exists because it directly serves timing or tracking.
Analytics (Effective Volume, Strain Score, Muscle Heatmap, Training Density) exist because tracking without analysis is just data collection. These calculations process on-device, respect privacy, and answer the question: is this working?
Warm-up tagging exists because volume calculations shouldn't include sets that don't contribute to training stimulus.
Failure set marking exists because sets taken to failure impose greater recovery costs — Strain Score accounts for this.
Program import exists because structured training requires planned sessions. The JSON-based spec lets coaches distribute programs via simple file-sharing — no servers, no accounts, no infrastructure.
iCloud sync exists because losing training data isn't acceptable. It's optional, Apple-managed, and the company never sees your information.
Each feature serves the core functions. Nothing exists for feature-count padding.
Why this matters for your training
Feature bloat doesn't just waste screen space — it wastes cognitive resources during sessions.
Every decision point between you and the next set is friction. Every navigation step is delay. Every unrelated notification is distraction.
Intrvl's single-purpose philosophy means faster session execution, lower cognitive load, no subscription justification bloat, no features you'll never use, and no privacy compromises for social features you didn't want.
You get precision tools without complexity. Data without hand-holding. Progression tracking without video libraries.
The trade-off we made deliberately
Building a single-purpose tool means accepting limitations.
If you want guided workouts, Intrvl isn't for you. If you need exercise form videos, look elsewhere. If you want meal tracking integrated, use a nutrition app.
That's the trade-off.
But if you're an intermediate to advanced lifter who already knows how to train — if you value evidence-based programming over algorithmic suggestions — if you recognise that the difference between good and great sessions is often just proper rest and consistent tracking — then Intrvl's focused approach is exactly what you need.
Two functions. Done perfectly.
No workout videos. No AI coach. Just data that respects your intelligence.
One payment. Lifetime of gains.
Intrvl costs $24.99 USD with a 14-day free trial. No subscriptions. No ads. All features included — including advanced analytics. No premium tier.
One payment gets you precision timing, complete tracking, on-device analytics, and program management. Everything you need. Nothing you don't.
Because the single-purpose philosophy extends to pricing: pay once, train forever.
Time every interval. Track every lift. Know what works.