Understanding your heart rate zones can significantly enhance the effectiveness of your workouts. The Apple Watch, along with many other fitness trackers, uses your heart rate data to estimate these zones, which correspond to different exercise intensities. These zones are typically based on a percentage of your maximum heart rate (MHR).
function calculateHeartRateZones() {
var age = document.getElementById("age").value;
var restingHeartRate = document.getElementById("restingHeartRate").value;
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (age === "" || restingHeartRate === "") {
resultDiv.innerHTML = "Please enter both your age and resting heart rate.";
return;
}
age = parseInt(age);
restingHeartRate = parseInt(restingHeartRate);
if (isNaN(age) || isNaN(restingHeartRate) || age <= 0 || restingHeartRate <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for age and resting heart rate.";
return;
}
// 1. Calculate Estimated Maximum Heart Rate (MHR) using the Tanaka formula
// MHR = 208 – (0.7 * age)
var mhr = 208 – (0.7 * age);
// 2. Calculate Heart Rate Reserve (HRR)
// HRR = MHR – Resting Heart Rate
var hrr = mhr – restingHeartRate;
// 3. Calculate Heart Rate Zones (using common percentages)
// These percentages are general guidelines. The Apple Watch might use slightly different algorithms.
// Zone 1: Very Light (50-60% of MHR) – often calculated based on percentage of MHR
var zone1_lower_mhr = 0.50 * mhr;
var zone1_upper_mhr = 0.60 * mhr;
// Zone 2: Light (60-70% of MHR) – often calculated based on percentage of MHR
var zone2_lower_mhr = 0.60 * mhr;
var zone2_upper_mhr = 0.70 * mhr;
// Zone 3: Moderate (70-80% of MHR) – often calculated based on percentage of MHR
var zone3_lower_mhr = 0.70 * mhr;
var zone3_upper_mhr = 0.80 * mhr;
// Zone 4: Hard (80-90% of MHR) – often calculated based on percentage of MHR
var zone4_lower_mhr = 0.80 * mhr;
var zone4_upper_mhr = 0.90 * mhr;
// Zone 5: Maximum (90-100% of MHR) – often calculated based on percentage of MHR
var zone5_lower_mhr = 0.90 * mhr;
var zone5_upper_mhr = 1.00 * mhr;
// Alternative calculation using Heart Rate Reserve (HRR) for more personalized zones
// Often used for more accurate training zones, especially for intermediate to advanced athletes.
// Apple Watch might blend MHR and HRR approaches.
// Zone 1 (Recovery): 50-60% HRR + Resting HR
var zone1_lower_hrr = (0.50 * hrr) + restingHeartRate;
var zone1_upper_hrr = (0.60 * hrr) + restingHeartRate;
// Zone 2 (Endurance): 60-70% HRR + Resting HR
var zone2_lower_hrr = (0.60 * hrr) + restingHeartRate;
var zone2_upper_hrr = (0.70 * hrr) + restingHeartRate;
// Zone 3 (Tempo/Moderate): 70-80% HRR + Resting HR
var zone3_lower_hrr = (0.70 * hrr) + restingHeartRate;
var zone3_upper_hrr = (0.80 * hrr) + restingHeartRate;
// Zone 4 (Threshold/Hard): 80-90% HRR + Resting HR
var zone4_lower_hrr = (0.80 * hrr) + restingHeartRate;
var zone4_upper_hrr = (0.90 * hrr) + restingHeartRate;
// Zone 5 (Maximum/Peak): 90-100% HRR + Resting HR
var zone5_lower_hrr = (0.90 * hrr) + restingHeartRate;
var zone5_upper_hrr = (1.00 * hrr) + restingHeartRate;
var htmlOutput = "