Do you have atrial fibrillation and have an irregular pulse-curve during workouts? Here is why..

“Why does my heart rate graph look so messy when I work out?” That’s what Kari, who lives with permanent atrial fibrillation, asked me recently. She often trains with her friend Lise, whose heart rhythm is normal — sinus rhythm.

They do the same workout, yet their heart rate graphs look completely different: Kari’s curve is irregular and jagged, while Lise’s is smooth and predictable.

💡 Read more about permanent atrial fibrillation

📊 The Heart Rate Graphs: Kari vs. Lise

In the figure below, you can see both heart rate curves during a typical workout:

• Lise’s curve: even, controlled, and predictable

• Kari’s curve: uneven, with small spikes and dips — both during and after exercise

Pulse-curve under physical activity during sinusrythm

Pulse-curve under physical activity during atrial fibrillation

💬 The difference between Kari and Lise

Lise has what’s called sinus rhythm — the heart’s normal rhythm. When she starts exercising, the brain sends signals through the nervous system saying:

“We need more oxygen now!”

Her heart responds by beating faster in a controlled and coordinated way. When the workout ends, the heart rate gradually slows down again. The whole process is smooth and well-regulated.

Kari, on the other hand, has atrial fibrillation (AF).In her heart, the electrical activity in the upper chambers (the atria) has become chaotic. Instead of one organized electrical impulse per heartbeat, there are hundreds of tiny, uncoordinated impulses firing at once.

The connection between the atria and the ventricles — called the AV node — acts like a gatekeeper, allowing only some of these impulses to pass through. But which impulses get through is completely random.

🏃‍♀️ What happens when Kari exercises?

When Kari starts her workout, her body sends the same signal as Lise’s:

“We need more oxygen!”

But because her heart’s electrical control is already chaotic, exercise amplifies the irregularity. The AV node starts letting more signals through — but still at unpredictable intervals.

The result? Her heart rate goes up — as it should — but not smoothly. One minute it’s 110, the next it’s 140, then back to 125, even though she’s keeping a steady pace.

When the exercise ends, her heart rate gradually falls, but again in an uneven pattern — up a bit, down, up again, then slowly settling. It often takes longer for the heart rate to return to baseline.

📉 Why do the curves look so different?

Here’s what a typical 30-minute workout might look like:

🔵 Lise (sinus rhythm):

• Smooth, predictable rise as exercise begins

• Stable heart rate during steady effort

• Controlled decrease after exercise

• A “clean” and easy-to-read curve

  
  

🔴 Kari (atrial fibrillation):

• Irregular rise at the start

• Variable heart rate during steady exercise — up and down

• Unpredictable drop after exercise

• A “messy” curve with many fluctuations

  
  

⚠️ Is this dangerous?

The irregular heart rate pattern itself is not dangerous — it simply reflects atrial fibrillation. However, many people with permanent AF experience an overly rapid heart rate during activity.

When the heart rate rises too quickly, it can cause:

• Shortness of breath (dyspnea)

• Fatigue

• Longer recovery time after exercise

  
  

🫁 Why does atrial fibrillation make you short of breath?

One of the most common reasons is that the heart rate increases too quickly and irregularly during activity.

When that happens, the heart doesn’t have enough time to fill properly between beats, meaning less blood is pumped out with each contraction. The body then gets less oxygen, and you feel short of breath and tired, even with moderate effort.

This isn’t about poor fitness — it’s about how the heart beats.

💊 Treatment: Slowing the heart rate — not necessarily fixing the rhythm

For people like Kari, the goal is not always to restore normal rhythm, but to control the heart rate so it stays in a comfortable range.

This is usually achieved with medications such as:

• Beta blockers (e.g., metoprolol, bisoprolol)

• Calcium channel blockers (e.g., verapamil, diltiazem)

• Digoxin (often used in older adults or those with low activity levels)

  
  

When medication is properly adjusted, many patients notice:

✅ A calmer heart rate

✅ Easier workouts

✅Less shortness of breath

✅ Better quality of life

Many patients feel significantly better once their heart rate–control medications are optimized.

💡 In summary

• A jagged, irregular heart rate graph is typical in atrial fibrillation.

• Shortness of breath often comes from a heart rate that increase too fast during activity.

• Treatment focuses on slowing the rate, not necessarily restoring sinus rhythm.

• With proper medication, patients can exercise more comfortably and live well with AF.

  
  

🩺 In short: Even if your smartwatch shows a “messy” graph, it’s simply revealing that your heart beats in a different rhythm. With the right follow-up and treatment, you can stay active and live well — even with atrial fibrillation. ❤️