Workrave suggests frequents micro-breaks of 30 seconds by default. If one wants to take no more than 30 seconds, the possibilities are limited. Just standing up and sitting back already take a fair share of that time, leaving little time to do anything else.

One might therefore wonder if standing up during the micro-break is necessary. Is Workrave requesting a break from sitting at the computer, or just a break from computer usage? Effectively, this poses the question of how "break" is defined.
Workrave requests to relax for a few seconds, but "relaxing" is vague. The need for greater precision is evidenced by the frequently asked question "Could you implement support for reading the screen during a break?".

It may not be necessary to change the micro-break dialog, but something like a link, a manual entry or tooltip should be added.

As for what the definition should be, I am not an ergonomist. It's not clear whether Workrave authors had one in mind, as the following FAQ answer suggests:
"It is very hard to give proper guidelines here. My best advice is to play around and see what works for you. Which settings "feel right". Basically, that's how Workrave's defaults evolve."
http://www.workrave.org/documentation/faq/#what-are-good-values-for-the-micropause-restbreak-and-daily-limit-timers

It would indeed be logical for people with different issues to take different breaks, but what if a user is strictly using Workrave for preventive purposes? If there is no answer to that, or if we don't have one, saying so would already be an improvement.