Gave the Blu-ray disc of ST III a spin last night. The supplementaries have an index section related to the ships. One index (Excelsior)
said that transwarp caused unhealthy side-effects for the crew.
Is this fanwank or where did this idea come from? I can't remember. Sounds like this was the end of transwarp, though I prefer the idea that the bumpers added onto the Enterprise-B
contained technology to countermand such unhealthy effects.