Thread imbalance

[Tuvas]

I have a program running several threads. One of them must be done
every (Specified time, usually 1 second). The whole point to having a
thread is do this. However, I've noticed the following. When there is
another part of the program that is active, this thread slips into
disuse, ei, it's only ran about once every 4-5 seconds, or perhaps it
waits for a lul in the computing process. How can I ensure that this
does not happen? This thread uses little processing power, so it could
be set to a high priority, if there is a way to do this. Thanks!