The Intensity Factor (IF) is a useful value that says a lot. This article explains why it is a useful value and how to interpret the number. First we look at how it is calculated. The intensity factor is obtained by dividing the NP (Normalized Power) by the FTP (Functional Treshold Power). The result should be somewhere between 0.6 (very long or slow rides) and 1.2 (short or very intensive rides).
Because it is based on Normalized Power and not on average power, it takes into account the variation in power during a workout. But it does not look at the length of the ride which means that it is not affected by, for example, muscle fatigue during a long ride (which can sometimes cause a distorted image). Unlike the Training stress score (TSS), the intensity factor really shows how intensive a workout was. A TSS of 100 can be a very long endurance ride of three hours or an all-out time trial of one hour on FTP.
The importance of the intensity factor only really becomes clear when you start training as effectively as possible. Effective training means that your training contributes to achieving your goal. When you know what is needed to achieve your goal, it becomes clearer how to train for this. By evaluating the intensity factor (in combination with other factors) of your training you know whether you have achieved the intended training effect. And by knowing whether you have completed the right training you know if you are on the right track to achieve your goal.
How to use intensity factor?
This may all be a little abstract. So let’s get some typical intensity factor values. An intensity factor lower than 0.65 are recovery rides that ensure that the muscles actively recover after heavy training. Between 0.65 and 0.85 are endurance rides to improve your endurance. Between 0.85 and 0.90 are tempo training sessions where the fat burning is maximal and a lot of energy from carbohydrate burning is needed. This zone is often called the ‘sweet spot zone’. Between 0.95 and 1.05 are FTP intensity workouts, i.e. an all-out workout on a long climb, time trial or criterion of 20 minutes to an hour. Above 1.05 are short intensive workouts like a prologue or a short steep climb. Let’s go back to effective training. If you want to ride a cyclo like La Marmotte, you have to ride 5000 altitude meters and 175 kilometers and you will especially need endurance to get through 8 hours in the saddle. A high FTP is not essential in this case because an hour on your FTP ride will not bring you to the finish but only halfway the first climb.
So what do you pay attention to when you evaluate your training or make a plan? You will have to complete a lot of endurance trainings and an intensity factor between 0,75 and 0,85. If you train with a higher or lower intensity factor you train too heavy or too light and you don’t train effectively.
Having said that, you’ll always have to remember not to train too monotonously. The body adapts best when the training stimulus is neither too heavy nor too light. If you always train the same thing, the effectiveness of that training gradually decreases. Also mentally it is tiring to always do the same training. So always keep training a little varied. The intensity factor becomes your best friend who helps you keep an eye on that.
How to get better?
Getting better is all about timing. There are actually not good or bad workouts. There is only a bad combination or the wrong workout on the wrong time. The path of progression is therefore a training plan with the right training stimulus according to your level, goal and available time. To help you with that we developed an algorithm in the JOIN Cycling application. It provides you with a highly flexible training plan to makes sure you get the most out of your rides. You can download JOIN in the App Store and Play store. Or check this page for more info.