Blocks on the 400m dash

It all depends on what the person running the dash prefers. I personally don't know how to use a block, so I just run it without it.

Blocks are highly recommended when running a 400m. Remember: it's a sprint. You don't see 100m dashers starting without blocks, so there's nothing different about starting blocks for the 400. If you don't know how to use blocks, you should really get some extra help from a coach or someone on the team who has experience. Using blocks will almost always cut down your time in any race.