Heart Rate Strap vs. Optical Watch: Which Wins in Heart Rate Monitoring Accuracy?

Introduction

“Do I still need a chest strap if I already have Garmin watch optical heart rate?” is a common question among cyclists. Optical heart rate (PPG) is convenient but has drawbacks; chest straps are accurate but troublesome. This article uses real-world test data to help you decide.

Two Heart Rate Monitoring Principles

Chest Strap Heart Rate Monitor (ECG-based)

• Directly reads the heart’s electrical signals
• Same principle as medical EKG
• Fast response, high accuracy

Optical Heart Rate (PPG-based)

• Uses LED to illuminate blood vessels in the wrist
• Detects changes in light reflection caused by blood flow
• Affected by limb movement, light, and sweat

Accuracy Comparison in Road Cycling Scenarios

Using a chest strap heart rate monitor as the baseline (HR 150 bpm steady state):

Why Optical Heart Rate Fails on Road Bikes?

1. Tight grip on handlebars: Muscle contraction interferes with blood flow signals
2. Vibration: Road bumps cause motion artifacts
3. Low body temperature + vasoconstriction: Outdoor optical readings are unreliable in winter
4. Wrist angle changes: Drop bar position differs from tops, sensor position shifts
5. Bright outdoor light: Direct sunlight on the sensor causes interference

Recommendations by Scenario

Indoor Training (Zwift, TrainerRoad)

Watch optical heart rate is sufficient (minimal vibration, stable lighting).

Outdoor Road Cycling

Chest strap heart rate monitor as primary, watch as backup recording.

Mountain Biking, CX, Gravel

Chest strap heart rate monitor is essential (extreme vibration interference).

Long-Distance Touring (Island Circumnavigation)

Arm band (such as Polar OH1) balances comfort and accuracy.

Triathlon (Including Swimming)

Choose a chest strap with memory function (such as Wahoo TICKR-X, Polar H10). Bluetooth transmission doesn’t work while swimming, so onboard storage is needed.

Heart Rate Strap Brand Comparison

Wearing Tips

• Chest strap: Wet the strap or apply conductive gel before wearing to improve signal
• Arm band: Wear on the lower edge of the deltoid muscle, avoid elbow movement interference
• Watch: Strap should be tight (not painful but unable to slide), sensor must be in firm contact with skin
• Cold weather: Warm up the body first (10 minutes) before trusting optical readings

Practical Recommendations

• Essential for advanced training: Chest strap heart rate monitor (Polar H10 or Wahoo TICKR-X)
• Limited budget: Magene MOVER H64, entry-level at NTD 1,500
• Watch pairing: Garmin HRM-Pro also transmits running dynamics
• Worried about chest strap skin irritation: Choose Polar Verity Sense arm band
• Triathlon needs: Polar H10 (swim memory transfer)
• Pairing issues: ANT+/BLE dual-mode can transmit to watch and trainer simultaneously

Conclusion

Watch optical heart rate is convenient, but accuracy is limited in outdoor road cycling scenarios. Advanced cyclists should definitely equip a chest strap heart rate monitor for precise heart rate zone training (Z2 base ride, Z4 threshold, Z5 VO2max, etc.). The Polar H10 is widely recognized as the gold standard; those on a budget can start with the Wahoo TICKR or Magene.

Related Reading

• Running Heart Rate Monitoring: In-Depth Accuracy Comparison of Heart Rate Straps vs Optical Heart Rate
• GPS Watch Optical Heart Rate vs Heart Rate Strap: Which Is More Accurate? A Practical Guide for Taiwanese Runners
• Heart Rate Strap vs Optical Heart Rate Watch for Road Running: Accuracy Differences and Best-Use Scenario Analysis
• Running Heart Rate Strap vs Optical Heart Rate: Measurement Accuracy and Wearing Comfort Comparison