Inner Thigh Machines Don't Work
Another factor to consider is functional anatomy. What do the inner thigh muscles actually do?
They certainly don’t do the motion that you use on the seated hip adduction machine. Do you know that there isn’t even an official term for movement of the hip in that plane - because it’s unnatural.
The only time that you move your leg like that is when you bring your left leg in when you enter on the driver’s side of the car, and when you pull your right leg out as you exit. That’s about it!
Besides, there are five separate muscles in your inner thigh - each designed to work best when your leg is at different angles.
In the seated hip adductor machine, your leg is positioned in a way that stresses only one of the five adductors - the adductor magnus. The other four muscles are virtually neglected.
The normal, everyday function of the adductors for most people is to pull your thigh back to the neutral position. That is, when your leg moves forward (as in walking), some of these muscles help pull your leg back, and vice versa.
Also, just as important, you use your inner thigh muscles to prevent over-abduction; in other words, you use your adductors to stay balanced whenever you’re on one leg (again, as in walking).
Therefore, the most effective exercises for your inner thighs are those in which you move one leg forward (hip flexion) or backward (hip extension) while standing on one leg (using the adductors as stabilizers).
Direct adductor exercise, however, often has the effect of making the inner thigh muscles adductors discernibly larger - the exact opposite of what most women are trying to accomplish.
Don’t get the impression that seated hip adduction is a complete waste of time; it isn’t. The adductor magnus is a large muscle, therefore the exercise can burn a lot (relatively) of calories.
It just won’t get you the results that you are probably looking for. Be aware of what you are doing and why with this and every exercise that you do.