Heart Rate vs RPE: Understanding When Each Matters

Which Should You Trust to Guide Your Training?

Technology has changed the way we train.

Not long ago, most people judged a workout with one simple question:

"How did that feel?"

Today, we have wearables that estimate heart rate, training load, recovery time, VO₂ max, sleep quality, heart rate variability, readiness scores and much more.

That's an incredible amount of information.

But it's also created a new problem.

Many people have become so focused on what their watch is telling them that they've stopped paying attention to what their body is telling them.

At The Training Ground, we see it every week.

Someone finishes a workout feeling fantastic.

Then they glance at their watch.

"Recovery: 72 Hours."

Suddenly, they're worried they've overtrained.

Another member arrives feeling flat, sore and exhausted.

Their watch says they're "Ready to Train."

So they ignore how they feel and push through anyway.

The problem isn't the technology.

The problem is expecting one number to tell the whole story.

Because training isn't that simple.

The best results come from understanding what each metric actually measures and knowing when to use it.

The Biggest Mistake We See

One of the biggest misconceptions in fitness is that there's one "best" way to measure training intensity.

Some people swear by heart rate.

Others insist RPE is all you'll ever need.

The reality?

Neither is universally better.

They're answering different questions.

Heart rate asks:

How hard is my cardiovascular system working?

RPE asks:

How difficult does this effort feel, and how close am I to my limit?

Neither replaces the other.

They complement each other.

Good coaches don't choose one.

They know when each provides the most useful information.

What Is RPE?

RPE stands for Rate of Perceived Exertion.

It's simply a way of rating how difficult an exercise feels using a scale from 1 to 10.

It isn't based on your watch.

It isn't based on the person training beside you.

It's based on your own perception of effort.

Generally:

RPE	How it feels
1–2	Very easy
3–4	Comfortable
5–6	Moderate effort
7	Challenging but controlled
8	Hard, with a little left in the tank
9	Very hard, maybe one more repetition
10	Maximum effort

RPE During Strength Training

In strength training, RPE is commonly linked to Repetitions in Reserve (RIR).

Instead of simply asking:

"Was that hard?"

We ask:

"How many good repetitions could you still have completed?"

As a guide:

RPE	Approximate reps left
6	4 reps remaining
7	3 reps remaining
8	2 reps remaining
9	1 rep remaining
10	0 reps remaining

This allows coaches to adjust training loads without asking every set to be an all-out effort.

If today's RPE 8 squat is 100 kg and next month your RPE 8 squat is 110 kg, you've become stronger, even though both sets felt equally difficult.

What Does Heart Rate Tell You?

Heart rate measures how your cardiovascular system responds to exercise.

It's one of the best ways to monitor internal training load during aerobic exercise.

But heart rate doesn't only respond to exercise.

It also changes because of:

• Sleep

• Stress

• Heat

• Humidity

• Hydration

• Caffeine

• Illness

• Altitude

• Fatigue

That's why the same workout may produce different heart-rate readings on different days.

Your fitness may not have changed.

Your physiology has.

Heart Rate Has a Delay

One important limitation is that heart rate doesn't respond instantly.

If you sprint for 20 seconds, your heart rate may still be climbing after you've already stopped.

That's why heart rate works exceptionally well during:

• Steady aerobic exercise

• Longer intervals

• Continuous cardio

But becomes less useful for:

• Short maximal sprints

• Olympic lifting

• Heavy strength work

• Explosive movements

The shorter the effort, the less useful heart rate becomes as an immediate guide.

When Heart Rate Matters Most

If your goal is improving cardiovascular fitness, heart rate is one of the most valuable tools available.

Think about activities like:

• Running

• Walking

• Cycling

• Rowing

• SkiErg

• Stair Climber

• Swimming

  
  

These are continuous efforts where your cardiovascular system is usually the limiting factor.

Imagine you're heading out for a Zone 2 run.

Your goal isn't to run as fast as possible.

Your goal is to spend time at a specific aerobic intensity.

Heart rate provides objective feedback.

RPE confirms whether that intensity feels appropriate.

Now imagine today your usual pace produces a heart rate that's 15 beats higher than normal, and the run feels unusually difficult.

That's valuable information.

Perhaps:

• You slept poorly.

• It's much hotter today.

• You're becoming dehydrated.

• You're fighting off a virus.

Neither heart rate nor RPE alone tells the whole story.

Together, they do.

When RPE Matters Most

Now let's move into the gym.

You're performing five sets of squats.

Will your heart rate increase?

Absolutely.

Does that tell us whether the weight is appropriate?

Not really.

Imagine two people both squat 100 kg for five repetitions.

One finishes the set and comfortably has another five reps left.

The other barely stands up with the final repetition.

Their heart rates might look remarkably similar.

The training stimulus is completely different.

That's where RPE becomes invaluable.

Rather than asking:

"How high did my heart rate get?"

We're asking:

"How close was I to my limit?"

That information helps us:

• Select appropriate loads

• Manage fatigue

• Progress safely

• Apply progressive overload

• Avoid unnecessary failure

  
  

Whether you're building strength, gaining muscle or returning from injury, RPE is often the more useful guide.

Heart Rate vs RPE: Which Should You Use?

Training situation	Primary guide	Secondary guide
Zone 2 cardio	Heart rate	RPE
Long runs	Heart rate	RPE
Cycling	Heart rate	RPE
Longer intervals	Heart rate	RPE
Short maximal intervals	RPE / Pace / Power	Heart rate
Strength training	RPE	Heart rate
Hypertrophy	RPE	Heart rate
Olympic lifting	RPE & technique	Heart rate
Rehabilitation	Symptoms & RPE	Heart rate when appropriate

Different training asks different questions.

Use the tool that best answers the question.

What About Fitness Wearables?

We genuinely love fitness wearables.

Garmin.

Apple Watch.

COROS.

Polar.

WHOOP.

They've helped millions of people become more engaged with their health.

But remember:

Your watch measures data.

It doesn't understand context.

Your watch might tell you:

• You slept poorly.

• Your resting heart rate increased.

• Your recovery score dropped.

• Your heart-rate variability changed.

What it cannot fully understand is why.

It doesn't know:

• Work has been unusually stressful.

• Your child was awake all night.

• You're mentally exhausted.

• Your shoulder has become painful.

• You're losing motivation.

• You're developing a cold.

It simply reports measurable signals.

Interpreting those signals still requires common sense.

What We Do at The Training Ground

When someone starts a session, we have them do a Readiness questionnaire:

We ask:

Then, once finished, we get them to provide the session RPE.

We don't just ask what their watch says.

We ask:

"How did that feel?"

If someone tells us:

"My easy run felt much harder than usual."

That matters.

If their heart rate was unusually high...

That matters too.

If their squat moved slowly despite feeling easy last week...

That's important as well.

Good coaching comes from putting all the pieces together.

Heart rate.

RPE.

Sleep.

Nutrition.

Stress.

Recovery.

Training history.

Goals.

The more pieces you understand, the clearer the picture becomes.

The Bottom Line

If you're trying to decide whether heart rate is better than RPE...

You're asking the wrong question.

The better question is:

What am I trying to measure?

If you're monitoring aerobic intensity, heart rate is incredibly valuable.

If you're managing strength training, RPE often tells you far more.

When you combine both?

You begin training with real intent.

Technology has made us incredibly good at collecting data.

Our job as coaches is helping you understand what that data actually means.

Because collecting more numbers doesn't produce better results.

Knowing how to use those numbers does.