The Most Common Mistake with Fitness Trackers: Why You Should Follow the Two Finger Rule

The Most Common Mistake with Fitness Trackers: Why You Should Follow the Two Finger Rule

Fitness trackers and smartwatches are popular for monitoring your fitness levels. However, you will want to make sure you are using them correctly for accurate readings.

Fitness trackers or smartwatches are affordable accessories used by people who want to monitor their health and physical activity levels.

Many of these smartwatches also offer health functions, such as measuring heart rate and recording related data throughout the day. But this is exactly where many users make a mistake that can skew the values. Therefore, it's essential to remember the two finger rule.

Heart rate measurement on the wrist uses LEDs to determine blood flow. This eliminates the need for a chest strap, which many find uncomfortable in daily life. However, it's crucial to wear the fitness tracker or smartwatch correctly, as improper placement can lead to inaccurate readings; depending on the person and device, optical measurements can deviate by up to 5 percent.

Suunto recommends on its website that the smartwatch should be worn two fingers above the wrist bone while exercising, which is about three to four centimeters depending on the individual.

The device should sit snugly and evenly on the skin without shifting; no external light should hit the sensor. For daily wear, it is sufficient to keep the watch just one finger from the wrist bone.

There are other sources of errors when using it. If you exercise in cold temperatures, there may be less blood in the extremities as the body prioritizes keeping the core warm. Therefore, the values during exercise might only be accurate after warming up.

In sports involving arm movements, there might also be inaccuracies in measurement as skin contact can briefly be disrupted. This includes activities like tennis, mountain biking, or intense CrossFit. Even swimming can cause water to get between the skin and the sensor, affecting the optical sensor.

If you are serious about your training, maybe consider purchasing a supplementary chest strap which will give you more reliable readings when you exert yourself. For example, you could wear this when going for a run or bike ride, and then revert back to your smartwatch for general daily use and other activities.