From 2007-2013, my “heavy” leg day exercises were done with the smith and leg press machines. I worked hard and lifted heavy. But all I got was big, shapeless legs. I was jealous of other women’s legs. That was frustrating. So I started researching football off-season training. Football players are built, so why not find out how they train? That was a smart move. I learned that they do real squats with a squat rack, and that they stray from leg presses and other machines for exercise.
Free weight exercises, AKA compound exercises, rank higher in effectiveness than isolation exercises, as compound movements train the targeted muscle(s) as well as surrounding muscles. Athletes need to be strong in all directions, such is why isolation exercises (machine-aided exercises) are not often used in their training.
The use of machines is good for people who have injuries, and people who have built a good overall physique and only wish to perfect a specific muscle group (BTW: this can create muscle imbalances and lead to injury).
In late 2013, I got off my machine dependence. And, even though, I cannot lift as heavy as I did with the aid of a smith or leg press machine, my legs look better than ever before.
So ladies, get off of the machines and use free weights!