
This is true but the weight was 1,500lb for crying out loud. Pulling that kind of weight is going to tax my body and my limit strength to a Maximum, also tightening my body as much as I can. When you use momentum we are not doing isolation exercises. We are not going for perfect form and trying to work the muscle. We are trying to move the heaviest weight we can and to do this we need to use all of our body's resources to accomplish the lift.
There is a difference between hitting the muscle and really isolating it and trying your best to pick up an insane amount of weight. I'm here to tell you that you cannot perform a Squat or Dead lift with a maximum weight going perfectly slow and strict to work the muscle. You will never defeat your best max by using the isolation principle.
To go up in weight and have a personal best you must use some body momentum and as long as you are trying to max out then why not use all your body's resources that you have been blessed with. When you are ready to do some triceps pushdowns or dumbbell curls then by all means incorporate the Isolation principle and work the muscle to the best of your ability.
Just remember there is a difference between working the muscle and moving the heaviest weight you can.