Target Heart Rate Calculator
Calculate Your Target Heart Rate Zones for Optimal Exercise Training
Target Heart Rate Calculator
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Heart Rate Training Zones
What is Target Heart Rate?
Target heart rate is the ideal heart rate zone (measured in beats per minute, or bpm) for exercising safely and effectively to achieve specific fitness goals. By monitoring heart rate during exercise and keeping it within target zones, you optimize cardiovascular benefits while avoiding overexertion. Different intensity zones (50-100% of maximum heart rate) train different energy systems and produce different adaptations—from fat burning and endurance building to speed and power development.
Target heart rate is based on maximum heart rate (HRmax), the highest number of beats per minute your heart can achieve during maximum physical exertion. HRmax is estimated using age-based formulas since it decreases predictably with age—approximately 1 beat per year after age 20. The most accurate formula is Gellish (HRmax = 206.9 - 0.67 × age), which replaced the outdated "220 - age" formula. For a 30-year-old, HRmax ≈ 187 bpm; for a 50-year-old, HRmax ≈ 173 bpm.
Understanding and using target heart rate zones allows personalized, data-driven training. Instead of guessing exercise intensity ("Am I working hard enough?"), heart rate provides objective feedback. Beginners stay in 50-70% zones to build aerobic base safely. Intermediate exercisers train at 70-85% for cardiovascular improvements. Athletes use 85-100% zones for performance gains. Tracking heart rate during workouts ensures you're training at appropriate intensities for your goals while avoiding undertraining or dangerous overexertion.
Maximum Heart Rate Formulas
Gellish Formula (Most Accurate)
Example - 30 years old:
HRmax = 206.9 - (0.67 × 30)
HRmax = 206.9 - 20.1
HRmax = 187 bpm
Based on large-scale longitudinal study of over 1,700 participants. More accurate than older formulas, especially for older adults.
Percentage of Max HR Method
Example - 70% intensity:
HRmax = 187 bpm (from above)
Target HR = 187 × 0.70
Target HR = 131 bpm
Simple, widely used method. Good for general fitness and recreational exercisers.
Karvonen Formula (Heart Rate Reserve)
Example - 70% intensity with 60 bpm resting HR:
HRmax = 187 bpm, HRrest = 60 bpm
Heart Rate Reserve = 187 - 60 = 127 bpm
Target HR = (127 × 0.70) + 60
Target HR = 88.9 + 60
Target HR = 149 bpm
More personalized method accounting for individual fitness (resting heart rate). Preferred by athletes and advanced exercisers.
Detailed Heart Rate Training Zones
Zone 1: Very Light (50-60% HRmax)
Purpose: Warm-up, cool-down, recovery, and general health maintenance. At this intensity, you can easily hold a conversation without breathing hard. Zone 1 improves overall cardiovascular health, reduces blood pressure, lowers cholesterol, and decreases chronic disease risk. It's ideal for beginners starting exercise programs, recovery days between hard workouts, and active rest. Example activities: leisurely walking, gentle cycling, easy swimming. Time recommendation: 20-60 minutes. Most calories come from fat oxidation.
Zone 2: Light (60-70% HRmax)
Purpose: Fat burning and aerobic base building. This is the "fat-burning zone" where the body preferentially uses fat for fuel. You can still talk but may need occasional breaths between sentences. Zone 2 builds endurance, improves mitochondrial density, enhances fat metabolism, and develops aerobic capacity foundation. Ideal for weight loss, long slow distance (LSD) training, and building cardiovascular base. Example activities: brisk walking, easy jogging, recreational cycling. Time recommendation: 30-90 minutes. Approximately 60-70% of calories from fat.
Zone 3: Moderate (70-80% HRmax)
Purpose: Aerobic capacity improvement and cardiovascular fitness. This is "comfortably hard" intensity—you can speak short sentences but not hold long conversations. Zone 3 increases stroke volume (heart's pumping capacity), improves oxygen delivery to muscles, enhances lactate clearance, and builds cardiovascular endurance. Most recreational exercisers train predominantly in this zone. Example activities: steady-state running, cycling at moderate pace, swimming laps. Time recommendation: 20-60 minutes. Mix of carbohydrate and fat fuel sources.
Zone 4: Hard (80-90% HRmax)
Purpose: Anaerobic threshold training and performance improvement. At this intensity, speaking is difficult—only brief phrases possible. Zone 4 raises lactate threshold (ability to sustain hard efforts), increases VO2 max, improves speed endurance, and enhances race performance. This is tempo run or threshold training intensity. Sustainable for 20-60 minutes depending on fitness. Example activities: tempo runs, time trials, interval training. Predominantly carbohydrate fuel. Too much time here risks overtraining; limit to 20% of weekly training volume.
Zone 5: Maximum (90-100% HRmax)
Purpose: Peak power output and speed development. All-out effort—speaking is impossible. Zone 5 develops maximal oxygen uptake (VO2 max), increases anaerobic power, improves neuromuscular coordination, and builds sprint speed. This is interval training, hill sprints, or race-pace efforts. Sustainable for only 30 seconds to 5 minutes per interval. Example activities: track intervals, hill repeats, sprint training. Extremely high injury and overtraining risk—use sparingly (5-10% of training). Requires adequate warm-up, rest between intervals, and strong fitness base. Not recommended for beginners or those with cardiac risk factors.
How to Measure Heart Rate
Manual Pulse Measurement
Radial artery (wrist): Place index and middle fingers on the thumb side of opposite wrist, just below the wrist crease. Don't use thumb (it has its own pulse). Count beats for 15 seconds and multiply by 4, or count for 30 seconds and multiply by 2. For resting heart rate, measure first thing in morning while still in bed before moving. Carotid artery (neck): Place fingers gently on side of neck below jawbone. Don't press too hard (can trigger reflex slowing heart rate).
Heart Rate Monitors
Chest strap monitors (Polar, Garmin) are most accurate, using electrocardiogram (ECG) sensors. They detect electrical signals from heart and provide real-time, beat-by-beat accuracy (±1 bpm). Optical wrist monitors (Fitbit, Apple Watch, Garmin watches) use photoplethysmography (PPG)—LEDs detect blood flow changes. Convenient but less accurate during high-intensity exercise, arm movements, or poor skin contact. Accuracy ±5-10 bpm. Gym equipment monitors (treadmill, bike handgrips) use same optical technology—convenient but often inaccurate.
Resting Heart Rate (RHR)
Normal RHR ranges: 60-100 bpm for adults. Athletes often have 40-60 bpm due to increased stroke volume (more blood pumped per beat). Lower RHR generally indicates better cardiovascular fitness. Measure RHR upon waking before getting out of bed—take average over 3-5 days for accuracy. RHR increases with illness, stress, dehydration, overtraining, poor sleep, or caffeine. Decreasing RHR over weeks/months indicates improving fitness. RHR above 100 (tachycardia) or below 40 (bradycardia in non-athletes) warrants medical evaluation.
Heart Rate Recovery
Heart rate recovery (HRR) measures how quickly heart rate decreases after stopping exercise—a powerful predictor of cardiovascular health and mortality. Good recovery: heart rate drops 12+ bpm in first minute, 20+ bpm in two minutes. Poor recovery (< 12 bpm in one minute) indicates poor cardiovascular fitness or potential cardiac issues. To test: exercise at high intensity for 3 minutes, stop completely, measure heart rate at 1 and 2 minutes post-exercise. Improving HRR through consistent training indicates enhanced parasympathetic nervous system function and cardiac efficiency.
Tips for Effective Heart Rate Training
- Follow 80/20 rule: Spend 80% of training time in Zones 1-2 (easy), only 20% in Zones 3-5 (moderate to hard). This prevents overtraining and optimizes adaptations.
- Use heart rate variability (HRV): Low HRV indicates stress/fatigue—consider rest day or easy training. High HRV signals readiness for hard workouts.
- Account for cardiac drift: Heart rate gradually increases during long workouts at constant pace due to dehydration, heat, and fatigue. This is normal.
- Don't obsess over exact numbers: Target zones are ranges, not precise values. Being within ±5 bpm of target is sufficient.
- Adjust for heat and altitude: Heart rate is 5-10 bpm higher in hot weather and at altitude. Lower intensity targets accordingly.
- Warm up before hard efforts: Spend 10-15 minutes in Zone 1-2 before interval training or Zone 4-5 work to prepare cardiovascular system.
- Track resting heart rate trends: Consistently elevated morning RHR (+ 5-10 bpm) indicates inadequate recovery, illness, or overtraining.
- Test actual max HR: Formulas estimate HRmax—actual values vary ±10-15 bpm. Perform supervised max HR test for precision (3-minute all-out effort).
- Combine with perceived exertion: Use Rate of Perceived Exertion (RPE) alongside heart rate for comprehensive intensity monitoring, especially during intervals.
- Retest every 6-12 months: Resting heart rate and zone boundaries change with fitness improvements—recalculate targets periodically.
Medical Disclaimer
This target heart rate calculator provides estimates based on validated formulas but cannot account for individual variations, medical conditions, medications, or fitness levels. Calculated maximum heart rate may differ from actual values by ±10-15 bpm. People with heart conditions, high blood pressure, diabetes, respiratory diseases, or taking beta-blockers or other medications affecting heart rate should consult physicians before using heart rate targets for exercise planning. Beta-blockers significantly lower heart rate—standard formulas don't apply; use perceived exertion instead. Pregnant women, individuals over 65, and those with chronic conditions require modified targets. High-intensity training (Zones 4-5) carries injury and cardiac event risks—medical clearance recommended before starting. If experiencing chest pain, dizziness, excessive shortness of breath, irregular heartbeat, or unusual symptoms during exercise, stop immediately and seek medical attention. This tool is for educational purposes only, not medical advice. Always consult healthcare providers before beginning new exercise programs, especially high-intensity training.
About the Author
Adam
Co-Founder @ RevisionTown
Math Expert specializing in various curricula including IB, AP, GCSE, IGCSE, and more
When engaging in physical activity, it’s essential to monitor whether you’re exercising at the right intensity to achieve your fitness goals without overexerting yourself. One effective way to gauge this is by comparing your current heart rate during exercise with your estimated Target Heart Rate (THR). Our Target Heart Rate Calculator simplifies this process, offering accurate results tailored to your age and other personal factors.
Understanding Heart Rate
What is Heart Rate?
Heart Rate refers to the number of times your heart beats per minute (bpm). It is a vital indicator of cardiovascular health and overall fitness level. Monitoring your heart rate during exercise helps ensure that you are working within a safe and effective intensity range.
Normal Heart Rate
Your Resting Heart Rate (RHR) is the number of heartbeats per minute while at rest. For most adults, a normal resting heart rate ranges between 60 and 100 bpm. Athletes or highly active individuals may have a lower RHR, sometimes as low as 40 bpm, due to more efficient heart function.
How to Measure Your Resting Heart Rate:
- Find Your Pulse: Use your index and middle finger to locate your pulse on the side of your neck (carotid artery) or on your wrist (radial artery).
- Count the Beats: Count the number of beats you feel in 15 seconds.
- Calculate bpm: Multiply the count by 4 to get your heart rate in bpm.
Example: If you count 20 beats in 15 seconds, your RHR is 80 bpm.
Why Target Heart Rate Matters
Understanding your Target Heart Rate is crucial for:
- Optimizing Workout Efficiency: Ensures you’re working hard enough to improve cardiovascular fitness without overexertion.
- Preventing Injury: Helps avoid pushing your heart rate into unsafe zones.
- Achieving Specific Fitness Goals: Different intensity levels target fat burning, endurance, or high-intensity performance improvements.
Methods for Calculating Target Heart Rate
There are two primary methods for calculating your Target Heart Rate during exercise:
Percentage Method
The Percentage Method calculates your THR based on a percentage of your Maximum Heart Rate (HRmax). The formula is straightforward:
HRtarget=HRmax×Target Percentage\text{HR}_{\text{target}} = \text{HR}_{\text{max}} \times \text{Target Percentage}
Example:
- Max HR: 200 bpm
- Target Percentage: 80%
- Target HR: 200×0.80=160200 \times 0.80 = 160 bpm
This method provides a quick estimate of the ideal heart rate range for different exercise intensities.
Karvonen Method
The Karvonen Method incorporates your Resting Heart Rate (RHR) to calculate the Heart Rate Reserve (HRR), offering a potentially more personalized THR:
HRtarget=(HRmax−HRrest)×Target Percentage+HRrest\text{HR}_{\text{target}} = (\text{HR}_{\text{max}} – \text{HR}_{\text{rest}}) \times \text{Target Percentage} + \text{HR}_{\text{rest}}
Example:
- Max HR: 200 bpm
- Resting HR: 60 bpm
- Target Percentage: 80%
- Heart Rate Reserve: 200−60=140200 – 60 = 140 bpm
- Target HR: (140×0.80)+60=112+60=172(140 \times 0.80) + 60 = 112 + 60 = 172 bpm
Note: Due to the limited sample size and potential variability in individual responses, our calculator primarily utilizes the Percentage Method for broader applicability.
Estimating Maximum Heart Rate
Accurately determining your Maximum Heart Rate (HRmax) is essential for calculating your THR. HRmax can be estimated using different formulas based on age and other factors.
Old Formula: 220 – Age
For decades, the most commonly used formula to estimate HRmax has been:
HRmax=220−Age\text{HR}_{\text{max}} = 220 – \text{Age}
Example:
- Age: 30 years
- HRmax: 220−30=190220 – 30 = 190 bpm
Limitations:
- Accuracy: Research has shown that this formula can overestimate HRmax in younger individuals and underestimate it in older adults.
- Variability: Individual differences in fitness levels and genetics can affect HRmax, making this a rough estimate.
New Formula: Tanaka & Gellish
Recent studies suggest more accurate formulas based on larger sample sizes:
Tanaka Formula (2001, 2007): HRmax=208−(0.7×Age)\text{HR}_{\text{max}} = 208 – (0.7 \times \text{Age})
Gellish Formula (2007): HRmax=206.9−(0.67×Age)\text{HR}_{\text{max}} = 206.9 – (0.67 \times \text{Age})
Example Using Gellish Formula:
- Age: 30 years
- HRmax: 206.9−(0.67×30)=206.9−20.1=186.8206.9 – (0.67 \times 30) = 206.9 – 20.1 = 186.8 bpm
Comparison:
- Old Formula: 190 bpm
- Gellish Formula: 186.8 bpm
These newer formulas provide a more nuanced estimation of HRmax, aligning better with observed data across various age groups.
Adjusting for Body Fat Percentage
Individuals with a body fat percentage (BF%) higher than 30% may require an adjusted HRmax formula:
HRmax=200−(0.5×Age)\text{HR}_{\text{max}} = 200 – (0.5 \times \text{Age})
Example:
- Age: 40 years
- HRmax: 200−(0.5×40)=200−20=180200 – (0.5 \times 40) = 200 – 20 = 180 bpm
Rationale: Higher body fat can influence cardiovascular efficiency, potentially affecting HRmax. Adjusting the formula helps in providing a more accurate THR for individuals with higher BF%.
Our Target Heart Rate Calculator includes an option to adjust HRmax based on body fat percentage for enhanced accuracy.
Target Heart Rate Zones
Understanding the different Heart Rate Zones helps in tailoring your workouts to meet specific fitness objectives. These zones are defined as percentages of your HRmax and correspond to various levels of exercise intensity.
Key Target Zones for Exercise
| Zone | Effort | Effect & Purpose |
|---|---|---|
| 50-60% | Very Light Exercise | – Improves heart health – Lowers blood pressure – Increases muscle mass – Reduces cholesterol & risk of degenerative diseases. High safety |
| 61-70% | Light Effort | – High fat burn – Promotes muscle gains – Trains the body to burn fat – Increases mitochondria in muscles – Good for weight loss |
| 71-80% | Moderate Exercise | – Aerobic effort – Improves vital capacity and respiratory rate – Increases heart size & strength – Boosts cardiac output |
| 81-90% | Hard Exercise | – Maximum fat burn (if fit enough) – Enhances VO2 max – Reduces susceptibility to sore muscles |
| 91-100% | Extreme Effort | – Athlete-level intensity – Sustained for short periods (e.g., interval workouts) – Develops fast-twitch muscles – High risk of overtraining and injuries |
These zones serve as general guidelines. Always consider personal fitness levels and consult with healthcare or fitness professionals when determining appropriate exercise intensities.
Using the Target Heart Rate Calculator
Our Target Heart Rate Calculator is a user-friendly tool designed to provide accurate THR estimates based on your personal information. Here’s how to use it effectively:
Step-by-Step Guide
Step 1: Enter Personal Information
Provide the following details to initiate the calculation:
- Age: Your current age in years.
- Gender: Select your gender (Male/Female).
- Height: Your height in centimeters or inches.
- Weight: Your weight in kilograms or pounds.
- Activity Level: Choose the option that best describes your daily physical activity, including exercise routines.
Accurate input ensures precise THR results.
Step 2: Select Your Activity Level
Your activity level impacts your TDEE and, consequently, your THR. The calculator typically offers the following options:
- Sedentary: Little to no exercise.
- Lightly Active: Light exercise/sports 1-3 days a week.
- Moderately Active: Moderate exercise/sports 3-5 days a week.
- Very Active: Hard exercise/sports 6-7 days a week.
- Super Active: Very hard exercise/sports and a physical job or training twice a day.
Choose the most accurate activity level to align your THR with your actual energy expenditure.
Step 3: Choose Your Calculation Method
While our calculator primarily uses the Percentage Method, you may have options to select different calculation approaches based on your preferences or specific needs.
Step 4: Review Your Macro Breakdown
Once all inputs are provided, the calculator will display:
- Maximum Heart Rate (HRmax): Estimated based on age and other factors.
- Target Heart Rate Range: The ideal bpm range for your chosen exercise intensity.
- Current Heart Rate: Measured during exercise using a heart rate monitor or manual pulse counting.
This breakdown helps you adjust your workout intensity to stay within safe and effective heart rate zones.
Interpreting the Results
- Below Target Zone: Indicates low-intensity exercise. Useful for warm-ups or cool-downs but may not significantly improve cardiovascular fitness.
- Within Target Zone: Optimal for achieving specific fitness goals, such as fat loss or endurance improvement.
- Above Target Zone: High-intensity exercise, beneficial for advanced fitness levels but carries higher risks of overexertion and injury.
Use these insights to modify your workout routines accordingly.
Macronutrients in Common Diets
Different diets emphasize varying macronutrient distributions to achieve specific health and fitness outcomes. Our calculator includes predefined macro balances for six popular diets:
| Diet | Carbohydrates (%) | Proteins (%) | Fats (%) |
|---|---|---|---|
| High Carb | 60% | 25% | 15% |
| DASH Diet | 55% | 27% | 18% |
| Moderate Diet | 50% | 25% | 25% |
| Zone Diet | 40% | 30% | 30% |
| Low Carb | 30% | 40% | 30% |
| Keto Diet | 10% | 15% | 75% |
Predefined Diets
- High Carb Diet: Ideal for endurance athletes needing ample energy from carbohydrates.
- DASH Diet: Designed to combat hypertension, focusing on fruits, vegetables, and lean proteins.
- Moderate Diet: Balances macronutrients for a sustainable and well-rounded intake.
- Zone Diet: Balances macros in a 40-30-30 ratio to control insulin levels and promote weight loss.
- Low Carb Diet: Reduces carbohydrate intake significantly, increasing protein and fat consumption.
- Keto Diet: High-fat, adequate-protein, and very low-carbohydrate diet aimed at inducing ketosis for weight loss and metabolic benefits.
Custom Macro Balances
If none of the predefined diets align with your goals, our calculator allows you to input a custom macro balance. This feature is beneficial for individuals with unique dietary requirements or those following specialized nutrition plans.
Ensure that your custom macro percentages sum to 100% to maintain a balanced diet.
Optimal Macronutrient Balance
While various diets offer different macro distributions, a balanced approach is generally recommended for overall health:
- Carbohydrates: 50% of daily calories
- Proteins: 25% of daily calories
- Fats: 25% of daily calories
Benefits of a Balanced Macronutrient Approach:
- Energy Provision: Carbs and fats supply the necessary energy for daily activities and workouts.
- Muscle Maintenance: Adequate protein intake supports muscle repair and growth.
- Hormonal Health: Fats play a crucial role in hormone production and regulation.
IIFYM (If It Fits Your Macros) Approach:
The IIFYM philosophy allows flexibility in your diet by focusing on meeting daily macro targets rather than adhering to specific food restrictions. Our Macro Calculator serves as a free IIFYM tool, enabling you to tailor your diet to fit your lifestyle while achieving your nutritional goals.
Weight Loss and Macronutrient Control
Effective weight loss involves not just reducing caloric intake but also ensuring a balanced macronutrient distribution. Here’s how controlling your macros can aid in weight loss:
- Caloric Deficit: Creating a caloric deficit by consuming fewer Calories than your TDEE leads to weight loss.
- Macro Balance: Ensuring a healthy balance of carbs, proteins, and fats supports metabolic functions and prevents muscle loss.
- Nutrient-Dense Foods: Prioritizing nutrient-dense foods within your macro targets promotes satiety and overall health.
- Energy Levels: Adequate carbohydrate intake maintains energy levels, while sufficient protein preserves muscle mass.
Using the Macro Calculator for Weight Loss:
- Determine Caloric Needs: Use the calculator to estimate your TDEE.
- Set a Deficit: Aim for a sustainable caloric deficit (e.g., 500 Calories per day for ~0.5 kg/1 lb weight loss per week).
- Adjust Macros Accordingly: Ensure your protein intake remains sufficient to preserve muscle mass while adjusting carbs and fats to meet the deficit.
Our Macro Calculator provides both caloric counts and macronutrient distributions, enabling you to plan meals that align with your weight loss goals.
Practical Tips for Managing Your Macros
- Plan Your Meals: Use the macro breakdown to plan balanced meals that meet your daily requirements.
- Track Your Intake: Utilize food tracking apps to monitor your macronutrient consumption throughout the day.
- Choose Quality Sources: Opt for whole, unprocessed foods to ensure you get essential nutrients alongside your macros.
- Adjust as Needed: Regularly reassess your macros based on changes in weight, activity levels, or fitness goals.
- Stay Hydrated: Adequate water intake supports metabolic processes and overall health.
- Incorporate Variety: Ensure a diverse intake of protein, carbohydrate, and fat sources to cover all essential nutrients.
- Listen to Your Body: Pay attention to hunger cues and energy levels to adjust your macro intake as necessary.
Implementing these tips alongside our Macro Calculator can enhance your dietary adherence and success.
Cautions and Considerations
While our Macro Calculator is a powerful tool, it’s essential to use it responsibly:
Individual Variations
- Genetic Factors: Genetic predispositions can influence how your body processes and utilizes macronutrients.
- Health Conditions: Conditions like diabetes, thyroid disorders, or kidney disease may require specialized dietary adjustments.
- Fitness Levels: Your current fitness level and workout intensity can impact your macronutrient needs.
Consulting Professionals
- Healthcare Providers: Always seek advice from healthcare professionals before making significant dietary changes, especially if you have underlying health conditions.
- Nutritionists/Dietitians: Consult with nutrition experts to tailor your macronutrient distribution to your specific health and fitness goals.
Avoiding Extremes
- Balanced Diet: Strive for balance rather than extreme macro distributions, which can lead to nutrient deficiencies or health issues.
- Sustainable Changes: Adopt dietary changes that you can maintain long-term to ensure ongoing health and fitness benefits.
Responsible use of the Macro Calculator ensures that your dietary changes promote long-term health and well-being.
Conclusion
Understanding and calculating your Target Heart Rate and macronutrient needs are foundational steps toward achieving your fitness and health goals. By accurately determining your THR, you can optimize your workout intensity, ensuring that each exercise session contributes effectively to your cardiovascular fitness and overall well-being. Simultaneously, managing your macronutrient intake with the help of our Macro Calculator allows you to maintain a balanced diet that supports your energy needs, muscle maintenance, and weight management objectives.
Key Takeaways:
- Accurate Calculations: Use the latest formulas for estimating HRmax to ensure precise THR calculations.
- Balanced Macros: Aim for a balanced macronutrient distribution tailored to your specific goals and lifestyle.
- Professional Guidance: Consult with healthcare or nutrition professionals to personalize your fitness and dietary plans.
Empower yourself with the knowledge and tools to take control of your health, optimize your workouts, and achieve a balanced, nutritious diet.
References
- Tanaka, H., & Gellish, R. L. (2001). Age-predicted maximal heart rate revisited. Journal of the American College of Cardiology.
- Gellish, R. L., Tanaka, H., & Seals, D. R. (2007). Age-predicted maximal heart rate revisited: An update on the limitations of the 220-age formula. Journal of the American College of Cardiology.
- American Heart Association (AHA). Guidelines on heart rate monitoring and cardiovascular health.
- Karvonen, J., Kentala, E., & Mustala, O. (1957). The effects of training on heart rate; a longitudinal study. Annales Medicinae Experimentalis et Biologiae Fenniae.
- Mayo Clinic. Understanding your resting heart rate. Retrieved from Mayo Clinic