Heart Rate Zone Calculator Threshold

Lactate Threshold Heart Rate (LTHR) Zone Calculator

This is the average heart rate you can sustain for about 40-60 minutes.

Your Custom Training Zones

Zone	Description	Range (BPM)

Pro Tip: These zones are based on the Joe Friel method, the industry standard for endurance athletes like runners and cyclists.

function calculateLTHRZones() { var lthr = parseFloat(document.getElementById('lthr').value); var resultsArea = document.getElementById('results-area'); var tableBody = document.getElementById('zone-table-body'); if (isNaN(lthr) || lthr 220) { alert("Please enter a realistic Lactate Threshold Heart Rate (typically between 120 and 190 BPM)."); return; } var zones = [ { name: "Zone 1", desc: "Recovery / Active Recovery", min: 0, max: 0.85 }, { name: "Zone 2", desc: "Aerobic / Endurance", min: 0.85, max: 0.89 }, { name: "Zone 3", desc: "Tempo / Intensive Aerobic", min: 0.90, max: 0.94 }, { name: "Zone 4", desc: "Sub-Threshold / Sweet Spot", min: 0.95, max: 0.99 }, { name: "Zone 5a", desc: "Super-Threshold", min: 1.00, max: 1.02 }, { name: "Zone 5b", desc: "Aerobic Capacity (VO2 Max)", min: 1.03, max: 1.06 }, { name: "Zone 5c", desc: "Anaerobic Capacity", min: 1.06, max: 1.15 } ]; var html = ""; for (var i = 0; i < zones.length; i++) { var z = zones[i]; var low = Math.round(lthr * z.min); var high = Math.round(lthr * z.max); // Adjustment for Zone 1 which has no floor in this simplified model var displayRange = (i === 0) ? "Below " + high : low + " – " + high; if(i === 6) displayRange = "Above " + low; html += ""; html += "" + z.name + ""; html += "" + z.desc + ""; html += "" + displayRange + " BPM"; html += ""; } tableBody.innerHTML = html; resultsArea.style.display = 'block'; resultsArea.scrollIntoView({ behavior: 'smooth' }); }

Understanding the Heart Rate Zone Calculator Threshold (LTHR)

In endurance sports, training by "Max Heart Rate" is often inaccurate because formulas like "220 minus age" have a high margin of error. Using your Lactate Threshold Heart Rate (LTHR) is the gold standard for personalized training. This calculator helps you define your specific zones based on the physiological point where lactate begins to accumulate in your bloodstream faster than it can be removed.

How to Find Your LTHR

To use this heart rate zone calculator threshold, you first need to determine your LTHR. The most common DIY method is the 30-Minute Time Trial:

1. Warm up thoroughly for 10-15 minutes.
2. Perform a 30-minute solo time trial (running or cycling) at the hardest effort you can sustain for that duration.
3. Capture your average heart rate for the LAST 20 minutes of the test.
4. This average is your estimated Lactate Threshold Heart Rate.

The 7 Training Zones Explained

Based on the Joe Friel intensity model, we break your training into seven distinct zones:

• Zone 1 (Recovery): Used for easy days and between intervals. It promotes blood flow without adding fatigue.
• Zone 2 (Endurance): The "all-day" pace. This builds mitochondrial density and teaches your body to burn fat efficiently.
• Zone 3 (Tempo): A moderate-hard effort. Useful for building muscular endurance but requires more recovery than Zone 2.
• Zone 4 (Threshold): This is the "comfortably uncomfortable" zone. Training here improves your ability to clear lactate and sustain higher speeds.
• Zone 5a-5c: These zones target your VO2 Max and anaerobic capacity. These are short, high-intensity intervals used to build top-end power and speed.

Example Calculation

If an athlete performs a 30-minute test and their average heart rate for the final 20 minutes is 170 BPM, their zones would look like this:

• Zone 2 (85-89%): 145 – 151 BPM. This is where the majority of "base" training should occur.
• Zone 4 (95-99%): 162 – 168 BPM. This is the sweet spot for threshold intervals.

Disclaimer: This calculator is for informational purposes only. Always consult with a physician before beginning a high-intensity exercise program. Heart rate can be affected by caffeine, stress, heat, and hydration levels.