Calculate Zone 2 Heart Rate Range

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Zone 2 Heart Rate Calculator

Measure this while sitting quietly or immediately upon waking.

Your Zone 2 Range:

Target: Keep your heart rate between these numbers during your endurance training to maximize mitochondrial efficiency and fat oxidation.

function calculateZone2() { var age = parseFloat(document.getElementById("ageInput").value); var rhr = parseFloat(document.getElementById("rhrInput").value); var resultsDiv = document.getElementById("resultsArea"); var resultDisplay = document.getElementById("resultText"); if (isNaN(age) || age 120) { alert("Please enter a valid age."); return; } if (isNaN(rhr) || rhr 120) { alert("Please enter a valid resting heart rate (typical range 30-120 BPM)."); return; } // Using Karvonen Formula for better accuracy // Max HR estimate (Fox Formula) var maxHR = 220 – age; // Heart Rate Reserve var hrr = maxHR – rhr; // Zone 2 is generally 60% to 70% of HRR + RHR var lowerLimit = Math.round((hrr * 0.60) + rhr); var upperLimit = Math.round((hrr * 0.70) + rhr); resultDisplay.innerHTML = lowerLimit + " – " + upperLimit + " BPM"; resultsDiv.style.display = "block"; }

Understanding Zone 2 Heart Rate Training

Zone 2 training is often referred to as "base training" or "aerobic threshold training." It is the intensity level where your body primarily uses fat as its main fuel source and builds mitochondrial density. For athletes and fitness enthusiasts, staying within this specific range is crucial for building a massive aerobic engine without overtaxing the central nervous system.

How This Range is Calculated

While many simple calculators just take 60-70% of your maximum heart rate, our tool uses the Karvonen Formula. This method is considered more accurate because it incorporates your Heart Rate Reserve (HRR)—the difference between your maximum heart rate and your resting heart rate. By accounting for your individual fitness level (via your resting pulse), the resulting range is far more personalized than generic formulas.

The Benefits of Training in Zone 2

  • Improved Fat Oxidation: Your body becomes more efficient at using fat for fuel at higher intensities.
  • Mitochondrial Health: Zone 2 specifically stimulates the growth and function of mitochondria, the powerhouses of your cells.
  • Faster Recovery: Because the intensity is moderate, you can perform Zone 2 workouts frequently without the long recovery times required by HIIT or Zone 4 sessions.
  • Lower Stress: It builds cardiovascular health without the massive cortisol spikes associated with high-intensity training.

A Practical Example

Let's look at a 40-year-old individual with a resting heart rate of 60 BPM:

  1. Estimated Max HR: 220 – 40 = 180 BPM.
  2. Heart Rate Reserve (HRR): 180 – 60 = 120 BPM.
  3. 60% Intensity: (120 × 0.60) + 60 = 132 BPM.
  4. 70% Intensity: (120 × 0.70) + 60 = 144 BPM.

For this person, the ideal Zone 2 training range is 132 to 144 beats per minute. During a run or cycle, they should aim to keep their heart rate within this window for the majority of their session to reap the aerobic benefits.

The "Talk Test"

If you don't have a heart rate monitor handy, a classic way to verify you are in Zone 2 is the talk test. You should be able to maintain a full conversation in complete sentences without gasping for air, but your breathing should be deep and rhythmic. If you can only speak in short bursts, you have likely drifted into Zone 3.

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