Understanding Your Resting Heart Rate and Training Zones
Your resting heart rate (RHR) is a key indicator of your cardiovascular fitness. It's the number of times your heart beats per minute when you are completely at rest, typically measured first thing in the morning before getting out of bed. A lower RHR generally signifies a more efficient heart muscle that can pump more blood with each beat, thus requiring fewer beats per minute to circulate blood throughout your body.
Regular aerobic exercise, especially endurance training, can lead to a decrease in your RHR over time. While a lower RHR is often associated with better fitness, it's important to consider it in conjunction with other health markers. Sudden significant changes in RHR can sometimes indicate illness, overtraining, or other health issues, so it's wise to monitor it consistently.
The heart rate zones are percentages of your maximum heart rate (MHR) and are used to guide the intensity of your workouts. While this calculator focuses on deriving zones from your resting heart rate and age, a more comprehensive approach typically uses age-predicted MHR (220 – age) as a baseline. However, this calculator provides a practical way to understand training intensity relative to your current fitness level.
How the Resting Heart Rate Zone Calculator Works:
This calculator uses a simplified approach to estimate your training zones based on your resting heart rate and age. The primary goal is to help you understand what different heart rate levels might mean for your training intensity and recovery.
Age-Predicted Maximum Heart Rate (MHR): Calculated as 220 – Age. This is a common, albeit general, estimation of your highest possible heart rate during strenuous activity.
Heart Rate Reserve (HRR): Calculated as MHR – Resting Heart Rate (RHR). This represents the range between your resting heart rate and your maximum heart rate. It's the capacity your heart has to increase its rate during exercise.
Training Zones (based on HRR):
Very Light Zone (Recovery/Warm-up): Approximately 50-60% of HRR + RHR. This zone is for very light activity, warm-ups, cool-downs, and active recovery. It aids in blood flow and muscle recovery without significant cardiovascular stress.
Light Zone (Endurance): Approximately 60-70% of HRR + RHR. This is often referred to as the "fat-burning" zone, good for building aerobic base and endurance.
Moderate Zone (Aerobic): Approximately 70-80% of HRR + RHR. This zone improves cardiovascular fitness and is suitable for longer duration workouts.
Hard Zone (Anaerobic Threshold): Approximately 80-90% of HRR + RHR. Training here improves speed and performance by pushing your anaerobic threshold.
Maximum Zone (Max Effort): Approximately 90-100% of HRR + RHR. This zone is for very short bursts of high intensity, improving peak performance.
By inputting your age and resting heart rate, this calculator provides an estimate of these zones, helping you to train smarter and more effectively towards your fitness goals. Remember to consult with a healthcare professional before starting any new exercise program.
function calculateHeartRateZones() {
var age = parseFloat(document.getElementById("age").value);
var restingHeartRate = parseFloat(document.getElementById("restingHeartRate").value);
var resultDiv = document.getElementById("result");
var resultValueDiv = document.getElementById("result-value");
var resultExplanationDiv = document.getElementById("result-explanation");
// Input validation
if (isNaN(age) || age 120) {
resultExplanationDiv.innerHTML = "Please enter a valid age between 1 and 120.";
resultValueDiv.innerHTML = "";
resultDiv.style.display = "block";
return;
}
if (isNaN(restingHeartRate) || restingHeartRate 250) {
resultExplanationDiv.innerHTML = "Please enter a valid resting heart rate between 1 and 250 BPM.";
resultValueDiv.innerHTML = "";
resultDiv.style.display = "block";
return;
}
// Calculations
var maxHeartRate = 220 – age;
var heartRateReserve = maxHeartRate – restingHeartRate;
// Ensure HRR is not negative (e.g., if restingHR > predicted maxHR)
if (heartRateReserve < 0) {
heartRateReserve = 0;
}
var veryLightMin = Math.round(0.50 * heartRateReserve + restingHeartRate);
var veryLightMax = Math.round(0.60 * heartRateReserve + restingHeartRate);
var lightMin = Math.round(0.60 * heartRateReserve + restingHeartRate);
var lightMax = Math.round(0.70 * heartRateReserve + restingHeartRate);
var moderateMin = Math.round(0.70 * heartRateReserve + restingHeartRate);
var moderateMax = Math.round(0.80 * heartRateReserve + restingHeartRate);
var hardMin = Math.round(0.80 * heartRateReserve + restingHeartRate);
var hardMax = Math.round(0.90 * heartRateReserve + restingHeartRate);
var maxEffortMin = Math.round(0.90 * heartRateReserve + restingHeartRate);
var maxEffortMax = Math.round(1.00 * heartRateReserve + restingHeartRate);
// Ensure zone upper bounds don't exceed predicted max heart rate
veryLightMax = Math.min(veryLightMax, maxHeartRate);
lightMax = Math.min(lightMax, maxHeartRate);
moderateMax = Math.min(moderateMax, maxHeartRate);
hardMax = Math.min(hardMax, maxHeartRate);
maxEffortMax = Math.min(maxEffortMax, maxHeartRate);
// Ensure zone lower bounds are not less than resting heart rate
veryLightMin = Math.max(veryLightMin, restingHeartRate);
lightMin = Math.max(lightMin, restingHeartRate);
moderateMin = Math.max(moderateMin, restingHeartRate);
hardMin = Math.max(hardMin, restingHeartRate);
maxEffortMin = Math.max(maxEffortMin, restingHeartRate);
// Adjust for potential overlaps and ensure progression
lightMin = Math.max(lightMin, veryLightMax);
moderateMin = Math.max(moderateMin, lightMax);
hardMin = Math.max(hardMin, moderateMax);
maxEffortMin = Math.max(maxEffortMin, hardMax);
var explanation = "Age-Predicted Maximum Heart Rate: " + maxHeartRate + " BPM" +
"Heart Rate Reserve (HRR): " + heartRateReserve + " BPM" +
"Zone 1 (Very Light / Recovery): " + veryLightMin + " – " + veryLightMax + " BPM (50-60% of HRR + RHR)" +
"Zone 2 (Light / Endurance): " + lightMin + " – " + lightMax + " BPM (60-70% of HRR + RHR)" +
"Zone 3 (Moderate / Aerobic): " + moderateMin + " – " + moderateMax + " BPM (70-80% of HRR + RHR)" +
"Zone 4 (Hard / Anaerobic Threshold): " + hardMin + " – " + hardMax + " BPM (80-90% of HRR + RHR)" +
"Zone 5 (Maximum Effort): " + maxEffortMin + " – " + maxEffortMax + " BPM (90-100% of HRR + RHR)";
resultValueDiv.innerHTML = "Your estimated heart rate zones are shown above.";
resultExplanationDiv.innerHTML = explanation;
resultDiv.style.display = "block";
}