What Should My Heart Rate Target Be When Running?

"I'm a 37-year-old woman, and I've just started running over the past summer. I'm up to running 40 minutes, and my heart rate reaches 190 beats per minute (bpm) during those runs without me ever feeling strained. My husband is worried this is dangerous. I've already lost 43 pounds and I'm about 7 pounds from my goal weight. What should my heart rate be when I'm running, to be safe? Thank you for any help you can give! — Wendy

– Wendy, Salem, Iowa

Answer by Dominique: Hi Wendy,
Thanks for your question about your target heart rate, and well done on building up to 40 minutes of running in your first summer.

For most runners, a sensible target sits roughly 60-80% of max heart rate, depending on your goal — there's no single number that fits everyone. Seeing 190 bpm on a 40-minute run at 37 isn't automatically dangerous. It depends on how it was measured, how it felt, and whether it came back down afterwards.

I'll break my response down as follows:

1. Why a Formula Alone Can't Fully Answer This
2. The Three Methods, and How to Use Them as a Starting Point
3. Is 190 BPM Actually Worth Worrying About?
4. Does a Lower Heart Rate Zone Actually Burn More Fat?
5. Building Into a Lower Training Zone
6. Bottom Line for You

1. Why a Formula Alone Can't Fully Answer This

Let's face it — a number on its own can't tell you whether you're safe. Every age-based max-heart-rate formula, like the old 220-minus-age rule, is a population average, not a personal measurement. Maffetone's 180-minus-age works differently — it's a rule of thumb for aerobic training heart rate, not a max-heart-rate estimate — but it's still an age-based shortcut rather than a personal measurement. Current comparisons of formula-estimated versus actually tested max heart rate put the typical gap at 10-15+ bpm, in either direction.

That matters directly for you, Wendy. Any Karvonen or Zoladz result you calculate shifts if your true maximum heart rate differs meaningfully from the age-based guess. Your Maffetone target of 138 doesn't use max heart rate at all, so it can't be checked that way — it's a rule of thumb, and your own effort and breathing are the check. The formula isn't wrong to use. It's just a starting point, not a verdict.

The trick is to sanity-check it. Compare what the formula predicts against how the effort actually feels — a proper guide to how to work out your maximum heart rate first will get you closer than the formula alone.

2. The Three Methods, and How to Use Them as a Starting Point

You've got three sensible ways to estimate your training zone, and I've written a full guide to heart rate training that covers all of them in more depth. Each gives you a starting estimate to refine, not a fixed answer.

The Maffetone approach takes 180 minus your age as your maximum for cardio work. For you, that's 180 − 37 = 143 — and because you're new to regular exercise, the method says to subtract another 5, landing at 138. Alternatively, the Karvonen heart rate calculator and the Zoladz heart rate calculator use your age and resting heart rate to work out a similar range. Whichever method you use, you'll land somewhere in the 130-150 range. Most of your running, especially as a beginner, should sit in the lower zones — zone 1 and zone 2. That pace will feel slow and stop-start to begin with. That's normal, not a sign you're doing it wrong.

3. Is 190 BPM Actually Worth Worrying About?

Here's a simple way to tell the difference. Generally fine: your heart rate rises with effort, comes back down within a few minutes of easing off, there's no chest pain, dizziness, or unusual breathlessness during the run, and you feel recovered rather than wiped out within an hour or so afterwards. Worth checking with a doctor promptly: any of those symptoms, especially alongside a family history of heart disease.

Wendy, your own description — no strain felt at 190 bpm, a history of obesity and limited exercise, both of which independently raise your exercise heart rate — is consistent with normal adaptation, not a red flag. Your husband's instinct to ask the question was the right call, not an overreaction. Beware treating this as a diagnosis, though. I'm not in a position to rule anything out from a forum post. This is triage, not diagnosis.

If long-term heart health is what's actually on your mind, I've covered that separately: worried about long-term heart health effects?

4. Does a Lower Heart Rate Zone Actually Burn More Fat?

Here's a myth worth clearing up, given where you're at with your weight loss. Training in a lower-intensity zone does burn a higher percentage of calories from fat as fuel — that's where the "fat-burning zone" idea comes from. But a higher percentage isn't the same as more total fat, or more total calories burned. Higher-intensity effort burns more calories overall per minute, even though a larger share of that comes from carbohydrate.

For someone in your position, Wendy, total training volume and consistency over time matter more than chasing a specific zone for its own sake. The lower-zone training I'm already recommending is the right call for building your aerobic base — not because it's uniquely a "fat-burning" number, but because it's the sensible, sustainable way to build up your fitness without breaking down.

5. Building Into a Lower Training Zone

Running at a much lower heart rate than you're used to will feel frustrating at first. You'll need walk breaks, and your pace will be stop-start. Stick with it for about a month, and your body adjusts. Soon you'll keep running while sticking to your target zone — then you'll find you get faster without your heart rate climbing.

As this happens, your resting heart rate will most likely drop over time, and so will your heart rate at any given easy pace. Your maximum heart rate is largely set by age and doesn't reliably change with training. That brings real benefits: reduced training stress, better sleep, and a fitter heart that does more work for less effort.

6. Bottom Line for You

Your 190 bpm on its own isn't a red flag, given how you describe feeling during and after your runs. But it's worth treating any formula-based target — 138 via Maffetone, or the Karvonen and Zoladz alternatives — as a starting estimate rather than an exact number. Your husband was right to ask the question, and the honest answer is: probably fine, worth a quick gut-check against the symptom list above.

Your weight-loss progress is real and well-earned. Slowing down for lower-zone training isn't a step backward from that — it's the next stage, building genuine cardiovascular fitness underneath the fitness you've already built.

Kind regards,
Dominique

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