Calculating Heart Rate Reserve

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Heart Rate Reserve (HRR) Calculator

Measure this while sitting quietly for 5 minutes.
Moderate: 50-70%, Vigorous: 70-85%.
Max Heart Rate: –
Heart Rate Reserve (HRR): –
Target Heart Rate: –
function calculateHRR() { var age = parseFloat(document.getElementById('hrr_age').value); var restingHR = parseFloat(document.getElementById('hrr_resting').value); var intensity = parseFloat(document.getElementById('hrr_intensity').value); var resultsDiv = document.getElementById('hrr_results'); if (isNaN(age) || isNaN(restingHR) || isNaN(intensity) || age <= 0 || restingHR <= 0 || intensity < 0) { alert("Please enter valid positive numbers for all fields."); return; } // Calculations var maxHR = 220 – age; var hrr = maxHR – restingHR; var targetHR = (hrr * (intensity / 100)) + restingHR; // Display document.getElementById('res_max_hr').innerText = Math.round(maxHR) + " bpm"; document.getElementById('res_hrr').innerText = Math.round(hrr) + " bpm"; document.getElementById('res_target').innerText = Math.round(targetHR) + " bpm"; resultsDiv.style.display = 'block'; }

Understanding Heart Rate Reserve (HRR) and the Karvonen Formula

In the world of cardiovascular fitness, Heart Rate Reserve (HRR) is considered one of the most accurate ways to determine exercise intensity. Unlike the simple Maximum Heart Rate method, which only accounts for age, HRR takes your resting heart rate into account, providing a personalized training zone that reflects your current level of aerobic fitness.

What is Heart Rate Reserve?

Heart Rate Reserve is the difference between your measured or predicted maximum heart rate and your resting heart rate. It represents the "range" of heart beats you have available for physical activity. Generally, a higher HRR indicates better cardiovascular efficiency and physical conditioning.

The Mathematical Formula

To calculate your training zones using the HRR method (also known as the Karvonen Formula), follow these three steps:

  • Step 1: Calculate Max Heart Rate (MHR). Standard formula: 220 – Age.
  • Step 2: Calculate Heart Rate Reserve (HRR). HRR = MHR – Resting Heart Rate.
  • Step 3: Calculate Target Heart Rate (THR). THR = (HRR × Intensity%) + Resting Heart Rate.

Practical Example

Imagine a 40-year-old individual with a resting heart rate of 60 bpm who wants to exercise at 70% intensity.

  1. Max HR = 220 – 40 = 180 bpm
  2. HRR = 180 – 60 = 120 bpm
  3. Target HR = (120 × 0.70) + 60 = 144 bpm

For this person, maintaining a pulse of approximately 144 beats per minute would ensure they are training at exactly 70% of their aerobic capacity.

Recommended Intensity Zones

The American College of Sports Medicine (ACSM) suggests the following intensity levels based on HRR:

Intensity Level % of HRR Goal
Light 30% – 39% Recovery & Beginners
Moderate 40% – 59% Weight Management/General Health
Vigorous 60% – 89% Aerobic Fitness/Performance

Why Resting Heart Rate Matters

Your resting heart rate is a snapshot of your cardiovascular health. As you become more fit, your heart becomes stronger and pumps more blood with each beat, meaning it has to beat less often. By including this metric in the HRR calculation, the formula adjusts as your fitness improves, preventing you from overtraining or undertraining as your body adapts.

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