What a heart rate monitor shows
A heart rate monitor reports your pulse in beats per minute. On a bike it gives a live picture of how hard your body is working. Unlike speed, it is not affected by wind or hills in the same way, so it can show that a climb or a headwind is costing you more effort even when your speed drops.
This is general fitness information, not medical advice. If you have a heart condition, symptoms such as chest pain or dizziness, or any doubt about exercise, speak to a doctor before using heart rate to push yourself.
Chest straps and wrist sensors
Two types of sensor are common.
Chest straps sit around the ribcage and detect the heart’s electrical signal. They tend to respond quickly to changes in effort and are often preferred for steady riding data. They need to be snug but comfortable, and the contact area usually works best slightly damp, so follow the manufacturer’s advice for wetting or using contact gel.
Wrist or arm sensors shine light through the skin to detect blood flow. They are convenient because there is nothing to wear around the chest. On a bike, though, bumps, grip pressure and wrist movement can disturb the reading, and the response to sudden effort changes can lag. Armband styles worn on the forearm are often steadier than a watch on the wrist, but this varies by device.
Neither is perfect. Cold, sweat, a loose fit or a low battery can all give strange numbers.
Pairing with your computer
Most computers connect to heart rate sensors wirelessly. Check the manual of both devices to be sure they use a compatible standard.
- Put the sensor on, since many only switch on when they detect skin contact.
- Open the computer’s sensor menu and search for devices.
- Pick your sensor from the list and confirm that it shows a reading.
- Move around a little and check the number looks plausible.
If you ride with others, pair at home rather than in a group, so the computer does not pick up a neighbour’s sensor.
What effort zones roughly mean
Computers often divide heart rate into zones, typically a handful of bands from very easy to very hard. The idea is simple:
- Lower zones feel easy. You can talk in full sentences and could keep going for a long time.
- Middle zones feel steady but purposeful. Talking is possible in shorter phrases.
- Upper zones feel hard. Breathing is heavy, and you can only hold them briefly.
The exact boundaries differ between people, and the default zones on a device are usually estimates based on age or a general formula, so treat them as a rough guide. Heart rate also varies with heat, sleep, stress, illness, caffeine and tiredness, so a higher number on a hot day does not mean you are less fit. How you feel, including your breathing, is a useful cross-check.
A beginner does not need to chase a particular zone. A simple use is to keep most rides at a level where you can chat comfortably, which supports the idea of pacing effort rather than going out too hard.
Using it on a ride
- Start gently. Heart rate takes a little while to settle, so expect the early numbers to climb as your body warms up.
- Expect a delay. Your pulse reacts a few moments after your legs do, so a sudden sprint or climb shows up slightly later on the screen.
- On hills, watch for the number rising steadily and ease off or change gear before you are out of breath. The article on climbing gears has more on that side.
- Use it as a check, not a command. If the number says one thing and your body clearly says another, such as feeling unwell or dizzy, stop and rest.
Keeping glances short
Heart rate changes slowly, so there is no need to look often. A glance every few minutes on a quiet, straight section is usually enough. Some computers can colour the field by zone or give a gentle alert, which lets you notice a change without staring.
In traffic, on descents, over rough surfaces and in groups, ignore the number and watch the road. If the data is making you anxious, put the field on a second page and ride by feel.
Care and cleaning
Rinse and dry a chest strap’s sensor pads after rides, following the manufacturer’s care instructions, and replace the battery or recharge when readings turn unreliable. A fresh battery is the quickest fix for a sensor that keeps dropping out.