Zone Two training is a crucial component of endurance sports and general cardiovascular health. It refers to a moderate intensity level where your heart rate is typically between 60% and 70% of your maximum heart rate. At this intensity, your body primarily uses fat for fuel, which is beneficial for building aerobic base, improving fat metabolism, and enhancing mitochondrial function without causing excessive fatigue. This makes it an excellent zone for building endurance and recovering from harder training sessions.
If unsure, you can use a common estimation formula like 220 – age, or consult a professional.
Your Zone Two Heart Rate Range:
function calculateZoneTwoHR() {
var age = parseFloat(document.getElementById("age").value);
var maxHeartRateInput = parseFloat(document.getElementById("maxHeartRate").value);
var resultDiv = document.getElementById("result");
var zoneTwoLowerP = document.getElementById("zoneTwoLower");
var zoneTwoUpperP = document.getElementById("zoneTwoUpper");
// Clear previous results
zoneTwoLowerP.textContent = "";
zoneTwoUpperP.textContent = "";
resultDiv.style.display = "none";
var calculatedMaxHeartRate;
// If maxHeartRateInput is not provided or is 0, estimate it using age
if (isNaN(maxHeartRateInput) || maxHeartRateInput <= 0) {
if (isNaN(age) || age <= 0) {
alert("Please enter your age or estimated maximum heart rate.");
return;
}
calculatedMaxHeartRate = 220 – age;
document.getElementById("maxHeartRate").value = calculatedMaxHeartRate; // Update input for clarity
} else {
calculatedMaxHeartRate = maxHeartRateInput;
}
// Validate calculatedMaxHeartRate
if (isNaN(calculatedMaxHeartRate) || calculatedMaxHeartRate <= 0) {
alert("Invalid maximum heart rate calculated or entered. Please check your age and input.");
return;
}
// Zone Two is typically 60% to 70% of Max Heart Rate
var zoneTwoLowerBound = calculatedMaxHeartRate * 0.60;
var zoneTwoUpperBound = calculatedMaxHeartRate * 0.70;
zoneTwoLowerP.textContent = "Lower Limit: " + Math.round(zoneTwoLowerBound) + " BPM";
zoneTwoUpperP.textContent = "Upper Limit: " + Math.round(zoneTwoUpperBound) + " BPM";
resultDiv.style.display = "block";
}
.calculator-container {
font-family: sans-serif;
max-width: 600px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ddd;
border-radius: 8px;
background-color: #f9f9f9;
}
.calculator-container h2 {
text-align: center;
color: #333;
margin-bottom: 15px;
}
.calculator-container p {
color: #555;
line-height: 1.6;
margin-bottom: 20px;
}
.input-section {
margin-bottom: 20px;
}
.input-section label {
display: block;
margin-bottom: 8px;
font-weight: bold;
color: #444;
}
.input-section input[type="number"] {
width: calc(100% – 22px);
padding: 10px;
margin-bottom: 10px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
}
.input-section small {
display: block;
color: #777;
font-size: 0.85em;
margin-top: -5px;
margin-bottom: 10px;
}
button {
display: block;
width: 100%;
padding: 12px 15px;
background-color: #007bff;
color: white;
border: none;
border-radius: 5px;
font-size: 16px;
cursor: pointer;
transition: background-color 0.3s ease;
margin-bottom: 20px;
}
button:hover {
background-color: #0056b3;
}
#result {
background-color: #e9ecef;
padding: 15px;
border-radius: 5px;
text-align: center;
display: none; /* Hidden by default */
}
#result h3 {
margin-top: 0;
color: #333;
margin-bottom: 10px;
}
#result p {
margin-bottom: 5px;
font-size: 1.1em;
color: #007bff;
font-weight: bold;
}