Your heart rate during exercise should generally stay between 50% and 85% of your maximum heart rate, depending on how intense your workout is. For a 40-year-old, that means roughly 90 to 153 beats per minute. The exact range shifts with your age, fitness level, and whether you’re aiming for a moderate or vigorous workout.
How to Find Your Maximum Heart Rate
The simplest formula is 220 minus your age. A 35-year-old would have an estimated max of 185 beats per minute. This method is widely used, but it can be off by 10 to 12 beats per minute in either direction. A slightly more refined formula, sometimes called the Tanaka method, multiplies your age by 0.7 and subtracts that from 207. For the same 35-year-old, that gives a max of about 182. Neither formula is perfect since individual variation is real, but both give you a workable starting point.
Your actual maximum heart rate is influenced by genetics, fitness history, and other factors that no formula can capture. If you want a precise number, a supervised exercise stress test is the gold standard. For most people planning everyday workouts, the formula estimate is close enough.
Target Zones for Moderate and Vigorous Exercise
The American Heart Association breaks exercise intensity into two main zones based on your maximum heart rate:
- Moderate intensity: 50% to about 70% of max. Think brisk walking, casual cycling, or light swimming. You can carry on a conversation comfortably.
- Vigorous intensity: 70% to about 85% of max. This covers running, fast cycling, competitive sports, and high-intensity interval training. Talking becomes difficult.
Here’s what those zones look like across different ages, using the 220-minus-age formula:
- Age 20: Max 200 bpm, target range 100 to 170
- Age 30: Max 190 bpm, target range 95 to 162
- Age 40: Max 180 bpm, target range 90 to 153
- Age 50: Max 170 bpm, target range 85 to 145
- Age 60: Max 160 bpm, target range 80 to 136
- Age 70: Max 150 bpm, target range 75 to 128
If you’re just starting to exercise or returning after a long break, stay in the lower half of your target range. As your cardiovascular fitness improves, you can push into the upper range for shorter bursts.
A More Personalized Calculation
The basic percentage method treats everyone the same, but two people the same age can have very different resting heart rates. Someone with a resting pulse of 55 and someone at 80 will experience the same “70% of max” workout very differently. The Karvonen method accounts for this by using something called heart rate reserve: the gap between your resting heart rate and your maximum.
To use it, subtract your resting heart rate from your estimated max. That number is your heart rate reserve. Then multiply it by the intensity percentage you want (say, 60% for moderate exercise) and add your resting heart rate back. So a 40-year-old with a resting heart rate of 65 would calculate: (180 – 65) × 0.60 + 65 = 134 bpm. This tends to give a more accurate reflection of actual effort, especially if your resting heart rate is unusually high or low.
Warning Signs You’ve Pushed Too Hard
Exceeding 85% of your max for short intervals during high-intensity training is common and generally safe for healthy people. But certain symptoms signal that something beyond normal exertion is happening. A racing, pounding heartbeat that feels irregular or like a flip-flopping sensation in your chest is worth paying attention to. Chest pain, dizziness, lightheadedness, or near-fainting during exercise are red flags regardless of what your heart rate monitor says.
The talk test is a simple real-world check. During moderate exercise, you should be able to hold a conversation. During vigorous exercise, you can manage a few words at a time but not a full sentence. If you can’t speak at all, you’re likely working harder than intended. If you feel like your heart is pounding out of proportion to how hard you’re actually working, or if your heart rate spikes and won’t come down when you ease off, stop and rest.
Why Your Heart Rate Might Not Match the Chart
Several common medications change how your heart responds to exercise. Beta-blockers, prescribed for high blood pressure and other heart conditions, slow the heart rate so much that you may never reach your calculated target no matter how hard you push. If you take one, heart rate zones become unreliable as a guide.
In that case, the Borg Rating of Perceived Exertion scale is a better tool. It’s essentially a structured version of asking yourself “how hard does this feel?” Most workouts should feel somewhat hard, meaning they take real effort but you can keep going. Caffeine, dehydration, heat, stress, and poor sleep can all temporarily inflate your heart rate during the same workout that felt easy last week. A number that’s 10 to 15 beats higher than usual on a hot day or after a rough night doesn’t necessarily mean something is wrong.
What Your Recovery Heart Rate Tells You
How quickly your heart rate drops after you stop exercising is one of the best indicators of cardiovascular fitness. A healthy benchmark is a drop of at least 18 beats per minute within the first minute of rest. If you finish a run at 165 bpm and you’re at 147 or lower after 60 seconds of standing still, your heart is recovering well.
Over weeks and months of consistent training, you’ll typically notice two things: your resting heart rate drops, and your recovery gets faster. Both are signs that your heart is pumping more efficiently. If your recovery rate stalls or worsens despite consistent training, it can be an early sign of overtraining or accumulated fatigue. Tracking this number over time gives you more useful information about your fitness trajectory than any single workout heart rate reading.