Improve workout score by using interval range instead of fixed zones

The workout score is amazing as it is not to strict but still gives a nice incentive to execute it correctly.

In some cases there is a calculation error when the set interval ranges do not match with the FTP zones. (mainly vo2max workouts, but sometimes also tempo / sweet spot intervals) When this occurs, the score can be lower than it should be, for example:

FTP of 290 watt

Workout: 5 x 4 minutes at vo2max. Suggested range is 299 watt - 328 watt.

Vo2max zone starts at 307 watt.

In this case, when the vo2max intervals are done within the range, but below the vo2max zone (for example 300 watts), the workout score will be low where it could be perfectly executed.

A solution could be to use the ranges from the workout instead of fixed zones calculated from FTP. These ranges are quite small so this would make the workout score a lot stricter which is maybe an unwanted side effect.

An other option could be to make the workout score zones dynamic, by letting them start at a bottom of a set interval range, in the above case 299 instead of 307.