When Do I Increase My Weights

My 

Weight lifting has become a HUGE part of my fitness journey, and I am still working on as well have improved on my nutrition which is major.  I am fond of my home workouts for reasons I shall share later but my focus is on weight increase.

My workouts are with a trainer, and still at home.  There is a sheet to record weights used and monitor growth and the trainer actually suggests when to increase the weights. I am good in following the trainers because they have more knowledge than I.  However if my current weight use is still challenging I will not increase for reasons of : possible injury and compromising form to get the benefits.  When I am able to lift, lunge or press with weights that are not challenging or I am able to do 3-5 more reps without feeling a challenge then I will increase my weights.

I know by how much well, this depends on what I have at home.  There weights in between the 5 pound increase such as 10 to 12 instead of 15 or 15 to 17 instead of 20 and yes 20 to 22 instead of 25.  Oh yeah I am speaking of dumbbells because I can increase in increments of 2 or 2.5 on the barbels.  For me I have only that 12 on the dumbbells so I have to up my weights by 5 .  Which I do with caution.

Cautious weight increase is important to stay on the journey without injury and to benefit from the challenge of increasing the weights.  To a week of increasing weights and or reps with safety.