Charles Polquin had a protocol to find out when your body was starting to become over trained.
Before beginning the hard training, every day when you first wake up, take your heart rate, try to stay still, don't get up and go to the bathroom,
then take your heart rate, just do it as soon as your mind is not foggy. Write down the number. Do this for 7 days in a row, figure out the average heart rate
and write this down in your training log. After you start training hard, take your heart rate every 2 weeks or so, upon waking. If this new heart rate
is 5 beats or more then your pre-hard training heart rate, you are starting to over train, time to back off
What I have noticed is most guys can train hard for 5 weeks, then they need to take it more easy, for 3 weeks, then their ready for another 5 weeks, of hard training
You might want to check out some of Louie Simsion's and the west side barbell club info. About periodization. If your into powerlifting.