Understanding your fat-burning heart rate zone can help you optimize your workouts for fat loss. This zone is typically between 60% and 70% of your maximum heart rate.
function calculateFatBurningZone() {
var age = parseFloat(document.getElementById("age").value);
var restingHeartRate = parseFloat(document.getElementById("restingHeartRate").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = "; // Clear previous results
if (isNaN(age) || isNaN(restingHeartRate) || age <= 0 || restingHeartRate <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for age and resting heart rate.";
return;
}
// Calculate Maximum Heart Rate (MHR) using the Tanaka formula (208 – 0.7 * age)
var maxHeartRate = 208 – (0.7 * age);
// Calculate Heart Rate Reserve (HRR)
var heartRateReserve = maxHeartRate – restingHeartRate;
// Calculate Fat Burning Zone (60% to 70% of MHR) – a simpler approach
// For a more precise calculation considering HRR (Karvonen Formula):
// Lower end of fat burning zone: (0.6 * heartRateReserve) + restingHeartRate
// Upper end of fat burning zone: (0.7 * heartRateReserve) + restingHeartRate
// We will present both a simpler MHR-based zone and the Karvonen-based zone for thoroughness.
// Simpler MHR-based zone (60-70% of MHR)
var fatBurnLowerMHR = 0.60 * maxHeartRate;
var fatBurnUpperMHR = 0.70 * maxHeartRate;
// Karvonen Formula-based zone (60-70% of HRR + Resting HR)
var fatBurnLowerKarvonen = (0.60 * heartRateReserve) + restingHeartRate;
var fatBurnUpperKarvonen = (0.70 * heartRateReserve) + restingHeartRate;
// Ensure values are within reasonable limits (e.g., not exceeding MHR)
fatBurnLowerKarvonen = Math.max(fatBurnLowerKarvonen, restingHeartRate); // Cannot be lower than resting HR
fatBurnUpperKarvonen = Math.min(fatBurnUpperKarvonen, maxHeartRate); // Cannot be higher than max HR
fatBurnLowerMHR = Math.max(fatBurnLowerMHR, restingHeartRate);
fatBurnUpperMHR = Math.min(fatBurnUpperMHR, maxHeartRate);
resultDiv.innerHTML =
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