If you're worried that your team is overworked, then add or remove a small task. Ideally, adding a task should take an hour or so over the course of a week and is large enough that it’s meaningful, but not so large that it forces people to drop other responsibilities.
And removing a task such as canceling a standing meeting or giving the team a week off from filling out the team dashboard.
After the trial period, you can ask your team "What did you do with the extra time?" By their response, you can measure their workload.