VO2 Flow vs Intervalla

VO2 Flow is built for the Norwegian 4x4 protocol, the research-backed interval method athletes use to raise VO2max. Four 4-minute intervals at 90 to 95% max heart rate, with 3-minute recoveries. Studies show a 10% VO2max increase in 8 weeks. Run Norwegian 4x4 or build your own protocol. Tabata. 10x1. 8x2. Any work and rest combination, any number of rounds. Free in the app: - Norwegian 4x4 protocol built-in and ready to start - Workout history, every completed session logged and grouped by month - One custom interval profile - Apple Music integration, album art and controls during your session - Audio cues and haptic feedback on every phase transition - Keep screen awake during workouts - Landscape and portrait support Pro upgrade, $4.99 one-time: - Remove all ads forever - Unlimited custom interval profiles - Achievement badges, 7 milestones you can share - Every future Pro feature, no subscription This is a timer, not a fitness platform. No social feed. No subscription. No complexity. Launch, pick a profile, start.

Free. No ads. No account required. Intervalla is a precision interval timer built for serious training. Whether you follow the classic Tabata protocol, push through an AMRAP session, or design your own custom intervals — this app keeps you on pace with a clean, distraction-free interface. THREE TRAINING MODES • Tabata — 20s work / 10s rest with configurable rounds • AMRAP — As many reps as possible in one timed block • Custom — Set your own work, rest, rounds, warm-up and cool-down LIVE HEART RATE Connect any Bluetooth Low Energy heart rate monitor (Polar, Garmin, Wahoo, etc.) and see your BPM in real-time. Switch to HR mode for a live sparkline graph that tracks your intensity throughout the session. After your workout, get a full summary with avg/max/min BPM and time in each heart rate zone. WORKS WITH YOUR SCREEN LOCKED Put your phone in your pocket and train. Audio cues play reliably in the background, and your heart rate monitor stays connected — even with the screen off. DESIGNED FOR FOCUS • Circular progress ring with phase-specific colors • Distinct audio cues for work, rest, and transitions • Lock controls to prevent accidental taps mid-workout • Dark interface that's easy to read mid-workout SAVE YOUR FAVORITES Save up to 5 custom presets and start any workout with a single tap. Three built-in presets included to get you started immediately. AUDIO THAT WORKS Plays through the silent switch on iOS — never miss a cue. Different tones for work start, rest start, countdown, and workout complete. SHARE WORKOUTS Create a workout and share it with friends, training partners, or your community. One link opens a ready-to-run timer. COMPLETELY FREE No ads, no subscriptions, no account required. Just open and train. Built with care in Norway.