Reindex during an Insert?

I have a MYSQL database with several large tables (approx 30million records in each)
We received a daily update of approx 50k of records in 2 of these tables.
As you'd imagine over a 3 year period the table is pretty much grinding to a halt.
I'd like to run an update command to reindex the tables and then run it on a rolling basis.

Also, is there a way of doing a reindex after every batch insert?


Thanks in advance.