While the thigh may seem like a very specific body area, it actually comprises many separate muscles. The most popular thigh muscle categories are the quadriceps and the hamstrings, although these can be further divided into many other specific muscles.
Because the femur, or thigh bone, is connected to the hip with a ball-and-socket joint, the thigh muscles can move the thigh in all directions. Therefore, a good thigh workout has to work all 360⁰ of the thigh musculature. The good news is that most thigh movements draw on an assortment of muscles at once, so in fact, one does not have to do dozens of movements to work the thigh as a whole.
While most thigh exercises target the quadriceps (front thigh), hamstrings (back thigh), outer thigh, and inner thigh independently, diagrams of the thigh musculature show that the muscles themselves do not always fit these specific categories.
If you are working one part of your thigh, you are probably to some extent working the whole thigh, especially if you are doing postural/flexibility exercise that involves holding your leg extended straight. (Pilates involves many such moves.)
The most common way to work the quadriceps in the gym is an apparatus that allows you to push back against resistance with your legs. The most common way to work the hamstrings in the gym is an apparatus that allows you to sit and pull your lower legs from extended position to seated position. Non-equipment ways to work the same muscles are: For quads, crouch and extend as if throwing a basketball; for hamstrings, stand up straight and lift your lower legs out behind you—one at a time.
A gym may also offer equipment for the inner and outer thighs: For the inner, the apparatus forces you to squeeze thighs together against resistance; for the outer, the apparatus forces you draw your thighs apart against resistance.
Untoned inner thighs are a common cause of body-conscious embarrassment, especially for women. Fortunately, there are more intricately targeting exercises for these muscles. The inner thigh muscles are adductors, that is, muscles that pull the limb towards center. The outer thigh muscles are abductors—they pull or lift the limb away from center.
Abduction movements are somewhat more commonplace, and so the adductor muscles are relatively neglected. Fox News Lifestyle lists some moves to give the adductors some attention. One is the “sumo squat,” which is essentially a squat with an intentional contraction of the thighs and glutes to come back to standing.
Another is the “glute bridge with squeeze,” in which you lie down with a medicine ball or other squeezable object between your knees and lift back up until back and thighs form a straight line and lower legs are vertical; all the while, the inner thighs and glutes are squeezing. More examples and details appear on the cited webpage (Fetters 2017).
Sitting with your legs in a V-position and pulling your torso forward is an effective way to stretch your thighs at the end of a workout, as is standing up straight and holding your feet one at a time in your hand behind you. A common perk of thigh exercise is bonus glute exercise, since these two large muscle groups are intimately connected—it is actually difficult to use one without involving the other.
Fetters, K. Aleisha. 7 June 2017. “Five inner-thigh exercises your legs are missing.” Fox News Lifestyle. (Accessed 8 August 2017). < http://www.foxnews.com/lifestyle/2017/06/07/5-inner-thigh-exercises-your-legs-are-missing.html>.