Fitness & Freshness helps track your levels of fitness, fatigue, and form over time. The Fitness & Freshness chart is currently only available to power meter or heart rate users with a Premium membership. Any activities recorded with heart rate data are included in your Fitness and Freshness calculations.
How Fitness & Freshness is Calculated
While fitness is a complicated concept, it can be simplified to just an accumulation of training. The Fitness Score is calculated using Training Load and/or Suffer Score, to measure your daily training, and an impulse-response model to quantify its effect over time. This will intuitively capture the building up of fitness, as well as the loss of fitness during a break.
The Fitness & Freshness chart uses Training Load and/or Suffer Score to quantify your daily training. Training Load is calculated using power data and Suffer Score is calculated using heart rate data, so you'll need a power meter or heart rate monitor to take advantage of this feature.
For premium members with no power data available, we generate the chart using only Suffer Score. For those who have at least 10 rides with both Suffer Score and Training Load, the athlete-specific best-fit between the two is calculated and used to fill in Training Load for rides with heart rate but not power.
While this type of fitness and freshness chart is popular among endurance athletes it can be difficult to understand at first. In general, the overall numbers aren't as important as general trends. If possible, it's best to compare where you are now to times in the past when you were fit. This can help you determine your current fitness and how to get even better.
Viewing your Fitness & Freshness Graph
Hover over the Training tab at the top of any Strava page, then select Fitness & Freshness from the drop down menu - or simply visit http://www.strava.com/athlete/fitness.
From this page, you will be able to view and interact with your Fitness and Freshness curve. You can select the range of time represented by the graph, as well as enable plotlines to track your Fatigue and Form (more on those later). Clicking on any point in the graph will 'focus' on that time interval - and show your specific Fitness, Fatigue, and Form values at that date. Below the graph, you'll see the relevant activities that contributed to your Fitness values, as well as their Training Impulse. Simply click again anywhere in the chart to 'unfocus.'
Races are marked in red to help you analyze fitness over longer chunks of time. The fitness delta next to the fitness score will show how your fitness has changed over the last seven days.
A bit more information...
Our method for calculating Fitness, Fatigue and Form is based off an impulse-response model first developed by Dr. Eric W. Banister in 1975. It was later applied to cycling by Dr. Andy Coggan.
The concepts apply to any measure of training stress. For example, the first models used average heart rate and time. We use Training Load, computed using power data collect with a dedicated power meter.
Conceptually, fatigue is easy to understand; it's that tired feeling which limits your performance. We model it the same way as fitness, but on a shorter time scale. You'll notice the score go up quickly after a couple hard days, but also go down quickly as you take a few days off.
Being in form, or "peaking," happens when one is very fit but not fatigued. Here we model this as the difference between your Fitness Score and your Fatigue Score.
For more information, please visit our training glossary or our blog post on the addition of Suffer Score.