Maximum Heart Rate During Exercise
The maximum heart rate (MHR) during exercise can be most accurately predicted using the formula 208 - 0.7 × age in healthy adults, which is more precise than the traditional 220 - age formula, especially for older individuals. 1, 2
Understanding Maximum Heart Rate
Maximum heart rate is a critical physiological parameter that:
- Increases linearly with workload and oxygen demand during dynamic exercise
- Is primarily influenced by age and age-related neural influences
- Serves as an indicator of maximal or near-maximal effort during exercise testing
- Helps guide exercise prescription and intensity
Physiological Basis
Heart rate response to exercise occurs through:
- Initial increase due to decreased vagal tone
- Followed by increased sympathetic outflow 1
- Linear relationship with increasing workload and oxygen consumption
Prediction Equations
Several formulas exist for predicting MHR, with varying accuracy:
| Formula | Equation | Notes |
|---|---|---|
| Traditional | 220 - age | Widely used but underestimates MHR in older adults [1] |
| Tanaka | 208 - 0.7 × age | More accurate across age groups [2] |
| Fox | 220 - age | Tends to overestimate MHR in children/adolescents [3] |
| Sex-specific (men) | 220 - 0.95 × age | May be more accurate for men [4] |
| Sex-specific (women) | 210 - 0.79 × age | Women have different HR responses than men [4] |
Important Considerations
- High variability exists among individuals of identical age (±12 beats per minute) 1
- MHR is largely determined by age and is relatively independent of gender and physical activity status in adults 2
- Using 85% of age-predicted MHR to define sufficient effort during exercise testing has limitations and should not be used in isolation as a termination criterion 1
Clinical Applications
Exercise Prescription
For exercise prescription, target heart rate ranges are typically set at 50-75% of MHR:
| Age (years) | Target HR (bpm) | Average Maximum HR (bpm) |
|---|---|---|
| 60 | 80 to 120 | 160 |
| 65 | 78 to 116 | 155 |
| 70 | 75 to 113 | 150 |
| 75 | 73 to 109 | 145 |
Exercise Testing Interpretation
When interpreting exercise test results:
- Achievement of age-predicted MHR suggests maximal or near-maximal effort 1
- A normal increase in HR during exercise is approximately 10 bpm per metabolic equivalent (MET) 1
- Heart rate reserve (HRR) is the difference between age-predicted MHR and maximal HR achieved during exercise 1
- Respiratory exchange ratio (RER) ≥1.10 is a more reliable indicator of maximal effort than heart rate alone 1
Factors Affecting Maximum Heart Rate
Several factors can influence MHR and should be considered:
- Medications: Beta-blockers significantly reduce MHR 1
- Cardiovascular disease: May reduce peak HR in many patients 1
- Exercise capacity: Poor exercise capacity can lower peak HR 4
- Current smoking, diabetes, and obesity: All have significant peak HR-lowering effects 4
- Body position and exercise type: Dynamic exercise increases HR more than isometric or resistance exercise 1
Heart Rate Recovery
Heart rate recovery (HRR) after exercise:
- Exhibits a rapid fall during the first 30 seconds after exercise
- Is influenced by the peak heart rate achieved during exercise 5
- Has prognostic value - abnormal recovery predicts adverse cardiovascular events 1, 5
Practical Implications
When using MHR for exercise prescription or testing:
- Consider using the Tanaka equation (208 - 0.7 × age) for more accurate predictions, especially in older adults
- Recognize the high individual variability in MHR response
- Account for medications and conditions that may affect heart rate
- Consider sex differences in HR response when precise measurements are needed
- Use RER as an additional indicator of maximal effort during exercise testing
By understanding the factors that influence maximum heart rate and using the most appropriate prediction equation, clinicians can more accurately assess exercise capacity and prescribe appropriate exercise intensity for improved cardiovascular health.