[Matt]

I get the concern. However, assuming he's being honest with and about his doctor, there may be a medical concern that is not at risk on the field (for example, with those restrictions, it may be something that is related to inactivity, in which case officiating might help him.)

This is going to be a tough line to toe, because it's going to be difficult to continue as a crew when you don't have confidence in his health, and it's going to be difficult to have confidence in his health without asking for some very personal information. Whether that's a discussion you and/or he are willing to have is the big question.