"Isolation machines" vs "Free weights";
I'll get to the reason for using quotes shortly.
I eventually would become injured at some point during weight training. Once I understood the reason for all the injuries; I've been pain free for 20+ years. No matter which muscle I thought to be working out, the pain usually ended up in my lower back, around the waist and hip areas.
I too would look for different approaches to muscle strengthening; "Isolation machines", "Free weights"... I asked similar questions and receive similar responses to which system is best.
In the past, I leaned more towards "Isolation machines" because, for me, they were safer. Well, that is what I thought, even through all those separate injuries.
It took several, but separate, visits to physical therapy sessions, when I realized; I was the cause of the injuries...
The trick is proper form, you know, body positioning. I was working out with 100 lbs. of "Isolation machine" weights prior to learning about proper form. Once I learned how to apply proper form to isolate and focus on a particular muscle, no more injuries, well not during weight training at least. It took awhile to learn how to apply the use of proper technique within a particular sport activity. Remember when I was using 100 lbs to work out? 10 lbs of weight and proper form left me feeling stronger and fit, confident. I am now using more weight. Have to listen to my body to learn when it is safe to move up in the amount of weight to use during a workout.
Concluding with the reason for using quotation marks with "Isolation machines" and "Free weights". What they both have in common, for safe and effective fitness training, is the application or use of proper form; proper muscle isolation.