When we are under stress, either mental or physical, our heart rates can increase quite dramatically. But how high can they safely go? Let’s take a look at the facts.
What is heart rate?
Heart rate, also known as pulse, is the number of times your heart beats per minute. A normal resting heart rate for adults ranges from 60 to 100 beats per minute (bpm).
Your heart rate is controlled by the sinoatrial node, which is like the pacemaker of the heart. This generates electrical impulses that make your heart muscles contract and pump blood around your body.
When you are stressed or undergoing physical activity, your heart needs to work harder to supply oxygen and nutrients to your tissues. So your heart rate increases to meet these extra demands.
How is heart rate measured?
Heart rate can be measured in several ways:
- Taking your pulse – Placing fingers (not thumb) on wrists, neck, or temples to feel heartbeats
- Using heart rate monitors – Wearable devices like fitness trackers and smartwatches
- Electrocardiogram (ECG) – Records electrical activity of the heart and shows heart rate
Taking your pulse manually or using heart rate monitors are convenient ways to check heart rate. But ECG gives the most accurate measurement.
What is a normal heart rate?
Normal resting heart rate varies by factors like age, fitness level, genetics, and medications. Here are typical normal ranges:
| Age | Normal resting heart rate |
|---|---|
| Newborns (0-3 months) | 70-190 bpm |
| Infants (3-11 months) | 80-160 bpm |
| Toddlers (1-2 years) | 80-130 bpm |
| Preschoolers (3-4 years) | 80-120 bpm |
| Children (5-11 years) | 70-115 bpm |
| Adolescents (12-15 years) | 60-105 bpm |
| Youth (15-17 years) | 60-100 bpm |
| Adults (18-64 years) | 60-100 bpm |
| Older adults (65+ years) | 60-100 bpm |
Athletes or very active individuals may have resting heart rates under 60 bpm. Rates under 40 bpm may need medical assessment.
Maximum heart rate
Maximum heart rate is the highest heart rate your body can safely achieve during intense physical activity. There are various formulas to estimate maximum heart rate based on age:
- 220 minus your age – Example: For a 30 year old, max HR = 220 – 30 = 190 bpm
- 208 minus (0.7 x your age)
- 206.9 minus (0.67 x your age)
However, these formulas only provide rough estimates. Your true max HR depends on individual factors. The most accurate way to determine it is through a maximal exercise stress test.
Target heart rate zones
Target heart rate zones provide guidance on safe and effective heart rate ranges during exercise. They are calculated based on your maximum heart rate. There are several different zone systems, but a common one is:
| Target zone | % of Max HR | Intensity |
|---|---|---|
| Zone 1 | 50-60% | Light/Easy |
| Zone 2 | 60-70% | Moderate |
| Zone 3 | 70-80% | Hard |
| Zone 4 | 80-90% | Very hard |
| Zone 5 | 90-100% | Maximal |
Staying in zones 1-3 provides cardiovascular benefits. Zone 4 is tough and zone 5 is unsustainable for long periods.
How does heart rate increase when stressed?
Both physical and psychological stress can increase your heart rate due to activation of the sympathetic nervous system. This triggers your body’s “fight or flight” response.
When stressed, your brain sends signals to release stress hormones like adrenaline and cortisol. These hormones cause physiological changes like:
- Increasing breathing rate and blood pressure
- Dilating blood vessels in muscles
- Constricting blood vessels in limbs and skin
- Increasing heart rate and strength of contractions
This helps deliver more oxygen and energy to your brain and muscles so you can respond to the perceived threat. Short bursts of stress and elevated heart rate are normal and even healthy. But chronic stress takes a toll on your cardiovascular system.
Physical stress
Vigorous exercise is a prime example of physical stress. During intense workouts, adrenaline and other hormones increase heart rate to supply working muscles.
Factors like exercise intensity, fitness level, and genetics influence how much your heart rate goes up. Well-conditioned athletes can exceed 80-90% of max heart rate during sustained high intensity training.
Psychological stress
Mental stressors like work deadlines, arguments, or anxiety can also spike your heart rate. Research shows heart rate reactivity to psychological stress is highly variable between individuals.
In a classic laboratory study, heart rates surged up to 143 bpm in some participants during a stressful mental arithmetic task, while others only reached 110 bpm. Heart rate rises more sharply when stress feels overwhelming or uncontrollable.
Stress heart rate vs. resting heart rate
Your resting heart rate is your baseline pulse when calm and relaxed. Stress heart rate is elevated above your baseline due to heightened sympathetic nervous system activation.
For example, if your resting heart rate is 70 bpm, it may jump to 100-130 bpm under acute stress. The exact increase depends on the stressor and your individual reactivity.
How high can heart rate safely go when stressed?
During intense physical exertion or emotional stress, heart rates can spike quite high in healthy people without issue. However, there are some safety cut-offs to keep in mind:
Max heart rate
As discussed earlier, maximum heart rate declines with age. Reaching your estimated max heart rate is extremely taxing and can only be sustained very briefly. It should never persist more than a few minutes.
Heart rate reserve
Heart rate reserve (HRR) is the difference between your maximum and resting heart rate. Guidelines generally recommend not exceeding 85-95% of HRR during exercise. This equates to about 90-98% max HR for younger adults.
220 bpm cut-off
Some organizations use 220 bpm as the highest safe heart rate limit for young healthy adults. Older adults are advised to stay under 180 bpm.
These thresholds provide rough guidance but everyone has unique heart rate responses. You should consult a doctor for personalized advice.
Dangers of excessively high heart rate
Sustained severely high heart rate is termed tachycardia and can be dangerous depending on the cause and your overall health. Potential consequences include:
- Reduced blood flow to vital organs
- Irregular heart rhythms (arrhythmias)
- Cardiac arrest
- Heart attack (myocardial infarction)
- Stroke
- Death
However, these severe outcomes are very rare in healthy young people without underlying heart conditions. During intense physical exertion, your body limits maximum heart rate once your cardio capacity is exceeded.
With extreme emotional stress, it is theoretically possible for your heart rate to keep climbing due to uncontrolled adrenaline release. But physically you would likely become unwell and be forced to rest before reaching perilous levels.
Managing heart rate during stress
Here are some tips to prevent excessive heart rate spikes when stressed:
- Monitor your heart rate using a fitness tracker or pulse checks.
- Recognize early signs of tachycardia like pounding heart, palpitations, chest pain, weakness, dizziness, or shortness of breath.
- Stop and rest immediately if heart rate feels dangerously high.
- Use stress management techniques like mindful breathing, meditation, or calming self-talk.
- Take prescribed medications for conditions like arrhythmias, hyperthyroidism, or anxiety disorders.
- Avoid stimulants like caffeine, nicotine, cold medicines, or recreational drugs.
- Stay well hydrated and don’t exercise in extreme heat.
See your doctor if you have recurrent episodes of unexplained tachycardia, heart palpitations, or other concerning symptoms with stress.
Key points
- Heart rate normally increases with physical and psychological stress due to hormonal changes.
- How high it goes depends on factors like fitness level, health status, genetics, and stressor severity.
- Extremely high heart rates above ~220 bpm can be dangerous but are rare in healthy young people.
- Listen to your body’s cues and stop exerting yourself if heart rate feels excessively high.
- Stress management and lifestyle changes can reduce exaggerated heart rate spikes.
The bottom line
In most healthy individuals, heart rates up to 90-100% max are well-tolerated during intense physical exercise. But chronically exceeding 85% heart rate reserve or 90% max heart rate is inadvisable.
With acute psychological stress, untrained and out-of-shape people can experience temporary spikes well over 150 bpm. However, your body limits heart rate at the point you start feeling unwell. Consult a doctor if stress frequently drives your heart rate to concerning levels.
While temporary tachycardia is normal, maintaining excessively high heart rates is risky. Monitor your stress reactions and vital signs. And see a professional if you have recurrent unexplained episodes or other troubling cardiac symptoms.