About

High-Intensity Interval Training (HIIT) and metabolic conditioning rely on precise work-to-rest ratios to trigger the EPOC (Excess Post-exercise Oxygen Consumption) effect. Manual timekeeping introduces cognitive load and timing errors that degrade training stimulus. This tool provides a laboratory-grade timing solution designed for athletes, coaches, and therapists. Unlike basic timers, this engine incorporates Warmup and Cooldown phases, customizable cycle counts, and distinct audio-visual phases to optimize the ATP-CP and Glycolytic energy systems. It utilizes a separate browser thread (Web Worker) to guarantee millisecond accuracy even when the device is locked or the tab is backgrounded, solving the notorious "timer drift" issue found in standard JavaScript timers.

Formulas

To program an effective interval session, one must calculate the Total Session Duration (T_total). This comprises the Warmup (t_warm), the core Interval Cycles, and the Cooldown (t_cool). For a session with N sets, where each set consists of Work (t_work) and Rest (t_rest):

T_total = t_warm + [

N × t_work + t_rest

] − t_rest + t_cool

Intensity is often gauged using the Heart Rate Reserve (HRR) method (Karvonen Formula). To find the Target Heart Rate (THR) for a specific intensity percentage (p):

THR = HR_max − HR_rest × p + HR_rest

Reference Data

Training Protocol	Ratio (Work:Rest)	Physiological Target	Primary Energy System	Typical Duration	RPE (1-10)
Tabata (Izumi)	2:1 (20s : 10s)	VO₂ Max & Anaerobic Capacity	Phosphagen / Glycolytic	4 min	10 (Max)
Gibala Method	1:1.25 (60s : 75s)	Insulin Sensitivity & Aerobic Power	Oxidative / Glycolytic	30 min	8-9
Little Method	1:1.25 (60s : 75s)	Mitochondrial Density	Oxidative	18-27 min	9
Zuniga (Hypertrophy)	1:1 (30s : 30s)	Muscle Size & Lactate Tolerance	Glycolytic	10-20 min	7-8
Boxing (Amateur)	3:1 (120s : 60s)	Skill Endurance	Mixed	3 rounds	8
Boxing (Pro)	3:1 (180s : 60s)	Aerobic Conditioning	Mixed	12 rounds	8
MMA Championship	5:1 (300s : 60s)	Metabolic Conditioning	Mixed	5 rounds	9
Sprint 8	1:3 (30s : 90s)	Growth Hormone Release	Phosphagen	20 min	10 (Sprint)
EMOM (CrossFit)	Variable (~50s : 10s)	Work Capacity	Phosphagen	10-20 min	Variable
Fartlek (Speed Play)	Random (e.g. 3:2)	Aerobic Base	Oxidative	20-60 min	6-8
GVT (Rest Timer)	N/A (0s : 90s)	Hypertrophy (Volume)	ATP Replenishment	45 min	7
Plyometrics	1:5 (10s : 50s)	Explosive Power (CNS)	Phosphagen (ATP-CP)	10 min	10
Tempo Run	Continuous	Lactate Threshold	Oxidative	20-40 min	7-8
Aerobic Interval	1:0.5 (4m : 2m)	Cardiac Output	Oxidative	30-60 min	7
Phosphagen Power	1:10 (5s : 50s)	Max Velocity	ATP-CP	10 min	10

Frequently Asked Questions

Peripheral visual cues allow athletes to identify the training phase without focusing on the digits. We use distinct color psychology: Yellow for Warmup (Preparation), Green for Work (Go), Blue for Rest (Recover), and Purple for Cooldown (Finish).

The application utilizes a dedicated Web Worker thread. This technology runs independently of the main visual interface, ensuring the internal clock continues to tick accurately even if the device sleeps or the user switches browser tabs.

EMOM stands for "Every Minute on the Minute". In our presets, this is typically configured as a 60-second cycle. You perform your prescribed reps (e.g., 10 burpees) at the start of the minute and rest for the remainder of that 60 seconds. The beep signals the start of the next round.

Yes. The tool automatically caches your last configuration in the browser's Local Storage. Additionally, you can select from over 50 physiological standard presets which instantly configure the timer for specific goals like fat loss, hypertrophy, or endurance.

It is an estimate based on MET (Metabolic Equivalent of Task) values for general high-intensity circuit training (approx 8.0 METs). Actual expenditure varies significantly based on body weight, gender, and specific exercise intensity.