Heart Rate During Exercise: What Happens Inside Your Body?

Your heart rate during training is one of the most direct signals your body gives you. Yet, many cyclists and runners don't fully understand what lies behind that number. If you know what's happening physiologically when your heart rate rises, you can approach your training much more effectively.

Why does your heart rate increase during exercise?

As soon as you start moving, your working muscles need more oxygen. Your heart responds by beating faster: it pumps more blood per minute to keep up with that oxygen demand. At the same time, your heart also increases its stroke volume with each beat, which is the amount of blood pumped out per heartbeat.

During light exertion, your heart rate gradually rises. As the intensity increases, your nervous system steps up a gear, and the frequency increases faster. Your body constantly tries to maintain a balance between the supply and demand of oxygen in the muscles.

What does your heart rate tell you about your training intensity?

Your heart rate is a reliable measure of how hard your body is working at any given moment. This is what makes heart rate monitoring so valuable for training. By guiding your training using heart rate zones, you ensure you're training the correct energy systems.

• Zone 1 and 2 (low to moderate): you primarily burn fat and build your aerobic base. Recovery is quick.
• Zone 3 (medium): you stress the aerobic system more intensely. Useful, but not the zone to always train in.
• Zone 4 (high): you train your threshold. Your body learns to deal with lactic acid better.
• Zone 5 (maximal): you approach your maximum heart rate. Can only be sustained for short periods, intended for interval training.

By consistently training in the correct zone, you specifically improve your endurance without unnecessarily overstressing yourself.

Heart Rate Drift: What is it and how do you deal with it?

A phenomenon that surprises many athletes is heart rate drift. This means your heart rate slowly continues to rise, even if your pace or wattage remains constant. This happens because your body heats up during prolonged exertion, loses fluids, and your blood plasma volume slightly decreases. Your heart then has to beat more often to pump the same amount of blood around.

On warm April days, when the season truly kicks off, you'll notice this effect more strongly. Heart rate drift is not a sign of weakness but a normal physiological phenomenon. You'll learn to recognize it by consistently tracking your heart rate during longer rides and runs.

Measuring Heart Rate: How to get more out of your training

To truly benefit from heart rate data, you need a reliable sensor that measures accurately. A chest strap measures electrical signals from your heart, providing a very accurate reading, even with varying intensity. Coospo offers affordable heart rate sensors that connect directly to your cycling computer or sports watch.

Check out the heart rate sensors in Vetturino's collection and choose the model that suits your training approach. Do you also want to track your cadence and speed for a more complete picture? Then the collection of speed and cadence sensors is a logical addition.

With the right data, you don't just know how hard you're working, but also why. And that's precisely the difference between just training and purposefully getting better.