Caynax HIIT is a free, powerful interval timer for HIIT, Tabata, cardio and any timed workout — now with live Bluetooth heart-rate monitoring, color-coded heart-rate zones, full workout history and progress tracking. Want to burn fat, build stamina and get more out of every minute? High-intensity interval training (HIIT) alternates short bursts of all-out effort with brief recovery — proven to improve fitness and fat burning in workouts as short as 9–20 minutes. Caynax HIIT keeps the timing, the cues and the tracking for you, so you can focus on the work. ★ Trusted by hundreds of thousands of athletes — 4.7★ and growing. ❤️ LIVE BLUETOOTH HEART RATE + ZONES • Pair any Bluetooth LE heart-rate strap or armband (standard Heart Rate Profile). • Live BPM during your workout — current, min, average and max. • 5 color-coded zones from your age or a custom max-HR, with a live graph. 📈 HEART-RATE CHARTS & HISTORY • Every session records your full heart-rate curve, colored by zone. • A history detail screen overlays your HR on each stage (warm-up / work / rest / cool-down). 📊 WORKOUT HISTORY & PROGRESS TRACKING • Automatic history of every session: date, duration, rounds, calories. • Streaks, a calendar, weekly trends and personal records. • Per-workout history, time-in-zone, a weekly goal, notes and RPE. ✨ TRY PRO FREE FOR 7 DAYS All premium features — heart-rate monitoring, charts, advanced analytics and progress tracking — are unlocked free for your first 7 days. No commitment. WHAT IS HIIT? High-intensity interval training alternates short, intense anaerobic effort with less-intense recovery. A typical session lasts 9–20 minutes: a warm-up, six to ten high-intensity reps separated by medium-intensity recovery, then a cool-down. A common protocol uses a 2:1 work-to-rest ratio — e.g. 30–40s of hard sprinting, then 15–20s of jogging. It's one of the best ways to get a complete workout when you're short on time. ⚠️ Because of the intensity, this training isn't for everyone. Please consult a doctor and a qualified trainer first. KEY FEATURES ⏱️ Powerful, flexible interval timer • Build unlimited workouts: warm-up, work, rest, rounds and cool-down. • Create, edit, duplicate and delete your own workouts. • Built-in Tabata and Fartlek samples — no stingy 2-workout limit. 🔊 Voice & sound cues • Voice (TTS) counts down out loud — edit the spoken texts (PRO). • Beep countdown with built-in beeps or your own sound (PRO). • Flexible countdown: every second, every n-th second, or only the final seconds (some options PRO). 🎛️ Built for real training • Full-screen color-coded stages and a big, readable timer. • "Next interval" preview. • Rewind backward and forward (PRO). • Multi-window support; keeps running reliably in the background. PERFECT FOR: Tabata • HIIT • cardio • CrossFit-style circuits • Fartlek • kettlebell • jump rope • bodyweight • running intervals • boxing rounds • stretching • yoga • and any activity that needs a flexible timer. FREE vs PRO Caynax HIIT is free and fully usable. PRO unlocks editable voice texts, custom sounds, advanced countdown options, rewind, and the full heart-rate + analytics suite — try it all free for 7 days. A one-time in-app purchase removes ads forever. When you're done burning fat, try Caynax Aerobic Weider Six (A6W) to build a perfect six-pack. Download Caynax HIIT and turn any space into your interval gym. 💪