Why Does My Heart Rate Increase?

What is Cardiac Drift?

Cardiac Drift refers to the gradual increase in heart rate during prolonged, steady-state exercise, even though the intensity remains constant. This phenomenon occurs during endurance activities, such as running or cycling, especially when exercise lasts 30 minutes or more.

Why Does Cardiac Drift Happen?

Several factors contribute to cardiac drift:

1. Dehydration: As you sweat during exercise, you lose fluids. Dehydration reduces blood volume, making it harder for the heart to pump blood efficiently, which results in an elevated heart rate to maintain the same output.

2. Increased Core Temperature: Prolonged exercise raises body temperature. To manage this, the body diverts more blood to the skin for cooling, reducing the amount of blood available for muscle delivery. The heart compensates by increasing its rate.

3. Fatigue: As you exercise for longer periods, muscle fatigue sets in. The body needs more blood flow to sustain muscle activity, which can elevate heart rate to meet these demands.

4. Reduced Blood Volume: As exercise continues, blood volume can decrease due to fluid loss through sweat and other mechanisms. This can reduce the blood's oxygen-carrying capacity, prompting the heart to pump faster to deliver sufficient oxygen.

When Does Cardiac Drift Occur?

• Duration: Cardiac drift typically becomes noticeable during longer sessions, especially those lasting more than 30 minutes at moderate to high intensities.
• Endurance Activities: It’s most noticeable during endurance sports like running, cycling, or swimming, where heart rate is sustained for extended periods.
• Environmental Conditions: Hot and humid conditions exacerbate cardiac drift, as the body works harder to regulate temperature and fluid balance.

How Does Cardiac Drift Affect Performance?

• Increased Effort: As heart rate increases due to cardiac drift, it can indicate rising fatigue or dehydration, making it harder to sustain the same intensity without increasing perceived effort.
• Fatigue Management: Athletes need to recognize cardiac drift to adjust hydration levels, pacing, or effort. If your heart rate is rising, it may be a sign to slow down or take in fluids.

How to Manage Cardiac Drift

1. Hydration: Drink enough fluids before, during, and after exercise to avoid dehydration.
2. Pacing: Start at a sustainable pace and avoid going out too hard, as this can exaggerate the effects of cardiac drift.
3. Temperature Management: If training in heat, wear light clothing, stay in the shade, or take breaks to cool down.
4. Fueling: Proper carbohydrate and electrolyte fueling supports endurance activities and prevents early fatigue.
5. Monitoring: Use a monitor to monitor your heart rate. A sustained increase may indicate that you need to adjust your intensity or take a break.

Conclusion

Cardiac drift is a natural response to prolonged exercise, often influenced by factors like dehydration, temperature, and fatigue. By recognizing and managing cardiac drift, athletes can optimize their performance, prevent excessive fatigue, and maintain endurance throughout their workouts.

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