[Canon]

so how do u know how much is 8 reps??? I mean when ur lifting to 8 reps how do u know when to stop when you do 8 reps...sombody told me that its sum % of you max??

[Teamorbit]

Go by feel bro and log your workouts thats the only way to know. If you train by the % of your max then you have already defeated yourself in what failure is to you.

Example today was chest for me and last week I was able to hit 135 dumbells on the incline 4 times. Today I was only able to hit 130s 4 times failure. Some days you might be stronger.

[monkeybiker]

When you first start you should start with fairly light weights so you can practise the exercise. You then start to increase how much weight you lift.

If your target is to do 3 sets of 8 reps then pick a weight you think that you can do this with. If you do all 3 sets with 8 reps then next workout increase the weight a little.
If you did 2 sets of 8 and then did a set of say 6 but could do no more then stick with this weight for your next workout.