Nagios interval_length and check_interval

I am getting a little confused with Nagios timers.

Whilst testing, I set a failure that was not picked up for around 5 minutes. I am not much more than pings and http checks and I really want to step up the timers.

I have seen the main interval_length by default is set to 60 and I set this to 10, along with changing check_interval on a single object to 1 (nothing on inheritance).

What I don't get is that clicking on the host itself seems to show that the difference between Last Check Time and Next Scheduled Active Check is 30 seconds, along with the Last Update happening once every 10 seconds.

I am just not sure what is going on here!

Can anyone recommend the correct way for going about doing a ping every 10 seconds or any other way to achieve much lower times between checks?

Edit - found check_result_reaper_frequency=10 in the nagios.cfg file and now understand why the last update is every 10 seconds... Still puzzled about the delay between actual checks, so, leaving question open.