:root {
–primary-color: #e63946; /* Heart red */
–secondary-color: #1d3557;
–light-bg: #f1faee;
–border-radius: 8px;
–spacing: 20px;
}
body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
margin: 0;
padding: 0;
}
.calculator-container {
max-width: 800px;
margin: 40px auto;
padding: var(–spacing);
background: #fff;
border: 1px solid #ddd;
border-radius: var(–border-radius);
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.calc-header {
text-align: center;
margin-bottom: 30px;
}
.calc-header h2 {
color: var(–secondary-color);
margin-bottom: 10px;
}
.input-group {
margin-bottom: 20px;
}
.input-group label {
display: block;
font-weight: 600;
margin-bottom: 8px;
color: var(–secondary-color);
}
.input-group input {
width: 100%;
padding: 12px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.input-group input:focus {
border-color: var(–primary-color);
outline: none;
}
.hint-text {
font-size: 0.85em;
color: #666;
margin-top: 5px;
}
.calc-btn {
display: block;
width: 100%;
background-color: var(–primary-color);
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background-color 0.3s;
}
.calc-btn:hover {
background-color: #c1121f;
}
#results-area {
margin-top: 30px;
background-color: var(–light-bg);
padding: 20px;
border-radius: var(–border-radius);
display: none;
border-left: 5px solid var(–primary-color);
}
.result-row {
display: flex;
justify-content: space-between;
align-items: center;
padding: 10px 0;
border-bottom: 1px solid rgba(0,0,0,0.1);
}
.result-row:last-child {
border-bottom: none;
}
.result-label {
font-weight: 600;
color: var(–secondary-color);
}
.result-value {
font-weight: 700;
font-size: 1.2em;
color: var(–primary-color);
}
.content-article {
max-width: 800px;
margin: 40px auto;
padding: 0 20px;
}
.content-article h2, .content-article h3 {
color: var(–secondary-color);
}
.content-article p {
margin-bottom: 20px;
}
.info-box {
background: #eef4ed;
padding: 15px;
border-radius: 8px;
margin: 20px 0;
}
@media (max-width: 600px) {
.result-row {
flex-direction: column;
align-items: flex-start;
}
.result-value {
margin-top: 5px;
}
}
function calculateMinHeartRate() {
// 1. Get input values
var ageInput = document.getElementById('ageInput').value;
var rhrInput = document.getElementById('rhrInput').value;
var resultsArea = document.getElementById('results-area');
// 2. Validate Age
if (!ageInput || isNaN(ageInput) || ageInput 110) {
alert("Please enter a valid age between 10 and 110.");
return;
}
var age = parseFloat(ageInput);
var rhr = 0;
var useKarvonen = false;
// 3. Validate RHR if provided
if (rhrInput && !isNaN(rhrInput)) {
rhr = parseFloat(rhrInput);
if (rhr > 30 && rhr < 150) {
useKarvonen = true;
}
}
// 4. Calculate Max Heart Rate (Fox Formula: 220 – Age)
// Note: For more precision in seniors, sometimes 208 – (0.7 * age) is used,
// but 220-age is the standard expectation for general web calculators.
var maxHR = 220 – age;
// 5. Initialize variables for zones
var minTrainingHR = 0; // 50%
var fatBurnStart = 0; // 60%
var cardioStart = 0; // 70%
var methodText = "";
// 6. Logic Switch: Karvonen vs Standard
if (useKarvonen) {
// Karvonen Formula: TargetHR = ((MaxHR – RHR) * %Intensity) + RHR
var hrr = maxHR – rhr; // Heart Rate Reserve
minTrainingHR = (hrr * 0.50) + rhr;
fatBurnStart = (hrr * 0.60) + rhr;
cardioStart = (hrr * 0.70) + rhr;
methodText = "Karvonen Formula (Personalized)";
} else {
// Standard Formula: TargetHR = MaxHR * %Intensity
minTrainingHR = maxHR * 0.50;
fatBurnStart = maxHR * 0.60;
cardioStart = maxHR * 0.70;
methodText = "Standard Age-Based (220 – Age)";
}
// 7. Display Results (Rounded to nearest whole number)
document.getElementById('res-max-hr').innerHTML = Math.round(maxHR) + " bpm";
document.getElementById('res-min-hr').innerHTML = Math.round(minTrainingHR) + " bpm";
document.getElementById('res-fat-burn').innerHTML = Math.round(fatBurnStart) + " bpm";
document.getElementById('res-cardio').innerHTML = Math.round(cardioStart) + " bpm";
document.getElementById('res-method').innerHTML = methodText;
// Show results area
resultsArea.style.display = 'block';
}
What is the Minimum Heart Rate for Exercise?
When starting a fitness journey or monitoring cardiovascular health, understanding your minimum heart rate is crucial. In the context of exercise, this usually refers to the lowest heart rate required to achieve a therapeutic or training effect on your heart and lungs.
Generally, for an activity to qualify as "moderate-intensity" aerobic exercise, your heart rate needs to reach at least 50% of your maximum heart rate. Below this threshold, while you are burning calories, you are not significantly stressing the cardiovascular system enough to improve aerobic capacity.
How to Calculate Minimum Training Heart Rate
There are two primary methods used by our calculator above to determine your training floor:
1. The Standard Method (Maximum Heart Rate)
This is the simplest way to estimate your zones. It first calculates your theoretical maximum heart rate (MHR) using the formula:
MHR = 220 – Age
Your minimum training heart rate is then calculated as 50% of this number. For example, a 40-year-old has an MHR of 180 bpm. Their minimum training rate would be 90 bpm.
2. The Karvonen Formula (Heart Rate Reserve)
If you input your Resting Heart Rate (RHR), our calculator switches to the Karvonen formula. This method is widely considered more accurate because it takes into account your specific fitness level.
It calculates your Heart Rate Reserve (HRR), which is the difference between your maximum and resting rates. The formula for your minimum target (50% intensity) is:
Target HR = ((Max HR – Resting HR) × 0.50) + Resting HR
This method prevents fit individuals with low resting heart rates from receiving training targets that are too low to be effective.
Why "Minimum" Matters
Identifying your minimum heart rate helps you avoid "junk miles"—exercise that is too hard to be recovery but too easy to elicit physiological adaptation. Staying above this minimum ensures:
- Improved Heart Efficiency: Strengthening the heart muscle itself.
- Capillary Growth: Increasing the blood vessels supplying muscles.
- Fat Metabolism: The lower zones (50-60%) are often called the "Fat Burn Zone" because the body relies more on fat stores for fuel at this lower intensity.
Resting Heart Rate vs. Minimum Training Rate
It is important not to confuse Minimum Training Heart Rate with Resting Heart Rate.
- Resting Heart Rate (RHR): The number of times your heart beats per minute while you are at complete rest (usually 60-100 bpm for adults, lower for athletes).
- Minimum Training Rate: The floor of your exercise zone (usually 90-110 bpm depending on age).
If your resting heart rate is consistently below 60 bpm (bradycardia) and you are not an athlete, or if it is consistently above 100 bpm (tachycardia), you should consult a physician before starting a new exercise program.