Understanding your fitness requires more than just tracking miles. The right data can help you train smarter, avoid burnout, and see real progress over time. COROS offers a range of powerful tools to measure your fitness, but these five metrics stand out as the most essential for monitoring improvements and optimizing training.

Base Fitness: The Foundation of Progress

Base Fitness is your long-term fitness tracker, calculated as a rolling 42-day average of your daily training load. Think of it as your fitness bank account—each workout is a deposit, and over time, you build a reserve of endurance and strength. A higher Base Fitness score generally means you’re adapting well to training and increasing your overall capacity. If you see it trending downward, it may be time to reassess consistency or ramp things back up.

Training Status: Finding the Right Balance

Training hard is important, but training smart is what leads to long-term success. Training Status helps you understand whether you’re progressing, maintaining, or overreaching based on recent training loads. If your Training Status shows optimized training, you're striking the right balance. If it indicates excessive training, you might need more recovery before pushing the intensity again.

Running Fitness: Measuring Aerobic Development

Running Fitness is a holistic measure of your running ability, factoring in multiple intensity zones. It provides an overall score based on the pace you can sustain in each zone. As EvoLab calculates your pace zones, Running Fitness reflects how well-rounded your abilities are across different intensities. A rising score suggests improvements in both aerobic and anaerobic capacity, while stagnation may indicate areas needing targeted training.

If your Running Fitness score hasn’t changed in a while, EvoLab may not have enough recent data to make adjustments. To recalibrate your zones and get a more accurate score, try taking a Running Fitness Test. This is a high-intensity effort, so COROS recommends scheduling it at least several weeks away from key races to avoid unnecessary fatigue.

VO2 Max: The Standard for Endurance

VO2 Max is widely considered one of the best indicators of cardiovascular fitness. It measures the maximum amount of oxygen your body can use during intense exercise. Higher numbers mean your heart and muscles are becoming more efficient, translating to better performance in races and workouts. While genetics play a role, consistent aerobic training can improve your VO2 Max over time.

Resting Heart Rate: A Window Into Recovery

Resting Heart Rate (RHR) is one of the simplest yet most valuable indicators of fitness and recovery. A lower RHR over time typically suggests improved fitness. Spikes in your resting heart rate can signal fatigue, stress, or the onset of illness—important cues to adjust your training load before small issues turn into setbacks.

Resting Heart Rate is not only an indicator of fitness, but also an indicator of recovery. Learn more about RHR and other recovery metrics.

Using These Metrics to Improve Your Training

The best athletes don’t just train hard—they train with purpose. By keeping an eye on these five key metrics, you can better understand how your body is adapting to training, when to push harder, and when to prioritize recovery. Whether you're chasing a personal best or just looking to stay consistent, these insights can help guide your journey to better fitness.

Ready to track your progress? Each of these five metrics is available on your COROS watch, the mobile app, and the Training Hub. Check in regularly to monitor your progress and make the most of your training.