Bash causes high CPU

I'm monitoring the status of my MacBook Pro using iStat, and every hour (or so) my CPU usage shoots up to 100%.

When I view my Acitvity Monitor, there is not one process that appears to be have a very high CPU, even though iStat shows my CPU usage go up to 100% (and the noise of the fan begins).

However, I have found that the process called "bash" is always either top or 2nd to the top of the list of CPU usage, even though itself is around 8-10%.

I have tried shutting down a number of the processes and they have no effect on the 100% CPU usage, except for "bash". When I Force Quit bash, the CPU usage drops off back to a very low value immediately.

As such, I was wondering what may be causing "bash" to cause 100% CPU usage, and how I may resolve this.

Many thanks!

D.