Using the Base Fitness Metric

While it may be great to have a Base Fitness of 120 before your marathon, it won’t help if you achieved this through 200 meter sprints.”

Have you ever wondered how fit you are? How this year compares to last year? What about how 5 days off in a row affects your fitness? All of these questions can be answered by using the Base Fitness metric within the COROS EvoLab software. 

What Is Base Fitness and Where Can I Find It?

Base Fitness can be found in your training load management chart on the COROS Training Hub. You can also locate it in the Calendar view as it will display across the top of the screen. Once you have located the metric, the next question is what does this mean? Base Fitness is a rolling 42 day average of your training load. Every workout you complete will have a training load associated with it. Essentially, how stressful was this workout for your body. While this number can be insightful for day-to-day monitoring, its importance magnifies when you add it to the past 42 days.  

Practical Use of Base Fitness

Base Fitness is a great metric to track throughout the year. When in your off-season, it would make sense to see this number lower. You actually want to see this number lower to ensure a proper off-season and recovery period. During your base season, you would like to see this number return to your base level. Build season will see the number grow, and peak season will have you at your highest levels of the year. Use this metric to ensure you are achieving your desired outcome with training. It’s great to have a plan, but ensure that plan is producing the results you want!

Building Fitness

The question of “how much can I build” is the next logical question. That answer will be different for individuals based on training history, life stressors, your body’s ability to recover, and other factors. Also to note, if you are just starting out with data, you will see large spikes due to your data catching up with your actual abilities. While the software is fantastic, it needs the right data to calculate these values (see Data in, Data out article for more information). Once you have 42 days worth of training, we would recommend athletes build between 2-6 base fitness points/week. Some athletes may be able to build more, but we always recommend keeping an eye on your fatigue levels. Any time an athlete gets above 70 fatigue, they need to consider resting over training. By increasing too fast, athletes risk overtraining injuries. It’s best to plan long term and build this metric in a manageable way.

Peak Fitness

All athletes have a different “peak” number they can achieve. Some athletes may be able to build towards 100 while others can build towards 180. The important thing to understand here is that life stressors begin to play a major role the higher you build. Be sure to listen to your body and always recover when necessary. Once you reach your peak for the season, its best to take an off-season. Without an off-season and lowering your base fitness, you run the risk of burnout.

Coaching Tips

Base Fitness should be one of the top metrics you look at when actively training for an event. It helps you understand if your training is enough, or possibly too much. Once you understand how base fitness works, you also want to include the principle of specificity with it. While it may be great to have a Base Fitness of 120 before your marathon, it won’t help if you achieved this through 200 meter sprints. You want to ensure your Base Fitness comes from specific training needed for your event. Once you are tracking this metric, and your training is specific, the last step is using the Calendar function of the Training Hub to plan appropriately. If you have a Marathon coming up in 6 weeks, you can plan training in advance to see where your Base Fitness will be in the future. Predictive modeling allows you to better plan and prepare for any upcoming event. Make sure you’re training properly and setting yourself up for success at future events. 


Base Fitness is one of the first metrics every athlete should learn. It provides instant feedback on how much you’re training and how your fitness is progressing or regressing throughout the year. Once you learn where to find this tool and how to utilize it, you can begin to dial in your training even further. While training without a plan may still create fitness, it’s best to track your data and ensure you’re accomplishing what you intended. Start using Base Fitness and watch as your training and race results begin to explore perfection!

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