Are you Ignoring the Law of Progressive Overload
 

The most important law in training is that of progressive over - load. That means that in order to get bigger and stronger you need to add weight to the bar or do more reps with the same weight. And you need to consistently strive to beat your previous performances

You absolutely cannot waste your time using light weights if you want to get jacked. It will never work.
You MUST progressively overload the mus - cle by forcing it to do more work over time.
The guys you see in the gym that are using the same weights as they were last year, or even last month, are the guys whose physiques never change.
They always look the same because they always use the same weights.
If you squat 135 for five reps today you had damn sure better be doing that for at least eight reps a month from now, or doing 140-145 pounds for five reps. One of the two, or both, have to be going up or you body will never adapt and grow.
Why would it if you don’t give it any good reason to?

i like to use partials for this type of training..