Complete Guide to Running Watch Features: In-Depth Comparison of GPS Accuracy, Heart Rate Monitoring, and Training Metrics

Introduction

Running watches have evolved from “timing tools” into “portable exercise laboratories.” Modern running watches can not only record pace, distance, and heart rate, but also estimate VO2max, predict race times, provide load management recommendations, and even detect sleep quality. However, more features do not necessarily mean better usability. Understanding the technical principles and practical limitations of each feature is what allows a watch to truly become a training partner rather than a tech toy.

GPS Accuracy: Choosing Satellite Systems

GPS accuracy is the most fundamental and important metric of a running watch, directly affecting the accuracy of distance recording.

Modern running watches typically support multi-constellation systems:

• GPS: US system, with the widest global coverage
• GLONASS: Russian system, performs better at high latitudes
• Galileo: EU system, performs better in urban canyons (dense high-rise areas)
• BeiDou: China’s BeiDou system, with denser signal coverage in the Asia-Pacific region

When running in Taiwan’s urban environments (such as the high-rise canyons of Xinyi District, Taipei City), watches using only the GPS single-constellation system often experience drift, with actual distance potentially differing from recorded distance by 2–5%. It is recommended to choose watches that support dual- or multi-constellation systems and to enable multi-constellation mode (at the cost of increased battery consumption).

Some high-end watches (such as the Garmin Fenix series and COROS Vertix series) are equipped with multi-band GNSS (L1 + L5 frequencies), significantly improving positioning accuracy in dense high-rise areas such as near Taipei 101.

Reliability of Optical Heart Rate Monitoring

Wrist-based optical heart rate (PPG technology) estimates heart rate by shining LED light onto subcutaneous blood vessels and detecting changes in blood flow. The reliability of this technology is affected by the following factors:

• Skin pigmentation: Darker skin absorbs light differently; some early studies suggested possible systematic errors, but recent sensor improvements have significantly narrowed the gap
• Wearing position: The watch should sit snugly against the wrist, about two finger-widths above the wrist bone; if too loose, movement can generate erroneous signals
• Exercise intensity: During high-intensity sprints, wrist-based optical heart rate has a response lag of approximately 5–15 seconds, causing peak heart rate to be underestimated
• Cold weather: Vasoconstriction reduces blood flow to the wrist, increasing optical heart rate errors during winter trail running

Interpreting Training Metrics

Modern running watches offer an increasing number of training metrics. Below are the most practical ones:

VO2max Estimation:
Both Garmin and Polar use the Firstbeat algorithm to estimate VO2max, with input data including heart rate, speed, and terrain information. Taiwanese runners should note that if training is predominantly conducted in hot, humid conditions, heart rate will be higher than in cooler weather, potentially causing VO2max to be underestimated. It is recommended to use steady aerobic runs (Zone 2 heart rate) during autumn and winter weather as the baseline condition for VO2max assessment.

Training Load:
Based on TRIMP (Training Impulse) or ATL/CTL models, it tracks acute and chronic training load to help prevent overtraining. This feature requires at least 4–6 weeks of continuous usage data before it can provide meaningful recommendations.

Running Dynamics Metrics:
Some watches (typically requiring a chest strap or Run Pod) can measure biomechanical metrics such as cadence, stride length, vertical oscillation, and ground contact time. Cadence is the easiest metric to monitor and holds the greatest training value; a target of 170–180 steps per minute is recommended.

Brand Comparison

• Garmin Forerunner series: The most widely used among Taiwanese runners, with a complete ecosystem, rich data on the Garmin Connect platform, and good map support (including Traditional Chinese maps for Taiwan)
• COROS PACE/APEX series: Excellent battery life and high value for money; has grown rapidly in Taiwan’s ultramarathon community in recent years
• Polar Vantage series: Well-regarded heart rate monitoring accuracy, comprehensive Training Load Pro features; suitable for runners who prioritize physiological data analysis
• Apple Watch Ultra: Multi-functional integration (daily use, fitness, emergency SOS), but its running-specific features lack the depth of dedicated running watches, and battery life remains a limitation

Practical Recommendations

1. Don’t chase the highest-end model: If your weekly mileage is below 50 km, a mid-range running watch (NT$5,000–10,000) already provides all necessary features; elite-level functions (multi-band GNSS, full map navigation) have limited utility in regular road running
2. Prioritize battery life: Taiwan’s ultramarathon events can sometimes last over 24 hours, and insufficient battery is a major risk. The COROS series excels in this regard
3. Utilize Taiwan-specific maps: If trail running in Taiwan’s mountains, confirm the watch supports OSM or official Taiwan maps—navigation features could be lifesaving in an emergency
4. Update firmware regularly: Brands continuously improve GPS algorithms and heart rate sensors; regular updates typically yield tangible performance gains

Conclusion

A running watch is a tool to assist training, not a measure of a runner’s worth. Understanding the principles and limitations of each feature is what allows you to extract maximum value from this expensive piece of hardware. For most Taiwanese runners, a mid-range watch that accurately records GPS, provides reliable heart rate data, and has a battery that can outlast the longest training day is already an excellent training partner.

Related Reading

• Choosing a Sports GPS Watch: Accuracy vs. Battery Life—How to Strike the Best Balance
• Road Running GPS Watch Buying Guide: Comprehensive Comparison of Garmin vs COROS vs Polar Features
• In-Depth GPS Running Watch Guide: Feature Analysis and Training Applications for Garmin and COROS
• Running Watch Buying Guide: Comparing Garmin vs COROS vs Apple Watch for Runner Needs