Earlier this year Zwift introduced Category Enforcement. In races with category enforcement turned on, you can only enter your own category or higher – and this category is determined by your Critical Power, which is calculated by looking at any efforts you have done in the last 60 days between 2-50 minutes long.
Learn all about Category Enforcement here >
Category Enforcement has generally been a huge success. The majority of Zwift races now have it enabled, and the historical problems of sandbagging are now really a thing of the past. However, of course there is always scope for improvement! Here are the key problems with Zwift racing prior to the CE rollout, to have a look at what areas still need some work.
| The Problem | Solved by CE | Solved by suggestions below |
| Riders can enter lower categories than they should | ✔️ | |
| ZwiftPower only looks at 20-minute efforts, so avoiding 20-minute efforts can keep your category lower than your ability | ✔️ | |
| ZwiftPower needs 3 x 20m efforts, so only doing 2 can keep your category low | ✔️ | |
| Strong short duration power is a key Zwift asset, so certain rider types can benefit from high 3-5 minute power | ✔️ | |
| Only efforts in races are considered | ✔️ | |
| Races are normally won by sprints, but sprint ability is not factored in | – | – |
| Categories are determined by w/kg, when raw watts is often a better predictor of success | ✔️ | |
| By splitting on w/kg, the heaviest riders at the top of each category (below A) will be the strongest | ✔️ | |
| There is a need to introduce a ‘minimum wattage’ so super lightweight riders are not overly penalised | ✔️ | |
| Typically riders have very consistent race experiences – always at the front, always in the middle, always at the back | ✔️ | |
| The only real predictor of success is success itself – results should ultimately determine ranking and therefore race pen | – | – |
| Riders need to understand why they are placed in a certain pen | ✔️ |
As you can see, Category Enforcement has delivered some real improvements. By taking a range of efforts in across different durations, and considering all Zwift activities, it is now very difficult to fool the system – either deliberately or simply due to a lack of races.
However, there are many issues still to overcome. Long term we know that Zwift are working on a results-based system, but I understand that is still in the design phase so could be some time away. Hopefully that is a ranking system that updates based on how you perform against those around you.
In the meantime, there are some quick wins that could elevate the Category Enforcement system to the next level.
Zwift Racer Score
I recently came across this research paper which uses a formula to create a ‘compound score’ for a rider’s capability. This score is, in effect, a combination of w/kg and raw watts, to better predict performance versus either w/kg or raw watts alone.
Zwift could use the same formula to create a ‘Racer Score’ which would then be used to determine your category. This removes a number of issues related to communicating w/kg, and better groups riders on ability as demonstrated by the paper. The Critical Power calculation introduced by Category Enforcement would still be the key input to this formula, which is actually very simple:
Example calculation for a rider with a CP of 310w and a weight of 73kg:
Zwift Racer Score = 310 x (310/73) = 1316
Customisable Pen Boundaries
The Racer Score approach certainly improves matters, but ultimately with a fixed category system, race experiences will be very consistent. That’s great if you are always at the front of the field, but for a bottom B or bottom C the experience is really not enjoyable or motivating.
By allowing race organisers to determine how the pens are split (choosing upper Racer Scores for each pen) sometime riders will be at the front of a field and sometimes at the back. This approach is also critical for a future ranking system to ensure variety to keep rankings fair and accurate.
Communicate Racer Score
The calculated Racer Score should be communicated on both ZwiftPower and your Zwift profile. A rider needs to know the result of the calculation so they can understand why they are placed in a certain pen. Simply show the racer their Score! If a racer is inclined to work out their calculated Critical Power, of course they can do this by reversing the formula using their weight in kg.
This will also avoid any confusion with the existing ZwiftPower categories, which still use w/kg boundaries. Medium-term there would be no real reason to keep the Zwift Power categories.
That’s it! 3 simple (in my mind at least!) changes that would massively improve category enforcement.
Questions or Comments?
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