In gyms, especially in the bodybuilding area, we hear all kinds of training theories. Not only will the most amateurs in the room give us technical advice, but some are also encouraged by "science".
How many times have you heard what are the muscles that are worked in squats? Do we exercise only the gluteus? Or also the quadriceps and hamstrings? Obviously, the squat is a compound exercise that requires the involvement of several muscles, including the rectus abdominis. The greatest force is made by the legs, but it is not a specific exercise to increase your hamstring volume either.
What is the function of the hamstrings in squats?
Some people think that deep squats are specifically for developing the hamstrings, but that's not entirely correct. The function of this muscle is flex the knees and extend the hips, so exercises like the leg curl or the Romanian deadlift They are ideal for the activation and development of the hamstrings.
When we squat, we can't really get the hamstring to have much significant involvement (as little as 20% activation) based on what some studies say. This is because during the concentric phase (raising phase of the squat) we are extending the hip joint, which is actually one of the functions of the hamstrings; however, we are also extending the knee joint, therefore stretching the muscle. Since this is something that happens simultaneously, the hamstrings do not contract too much.
So isn't it real that we feel how our hamstrings work?
Actually, you are confusing hamstrings (biceps femoris) with adductor magnus. They are located in a very similar location, and both are exercising through the squat movement. 
Logically, the hamstrings function as great dynamic stabilizers. In fact, when the knee is bent more than 90º, hamstring tension helps to stabilize the knee, as the forces directed to the quadriceps (dislocation force) on the knee are counteracted.
However, when it comes to bulking up that muscle, the squat alone cannot be used as a tool to build the hamstrings. As we told you before, the leg curl and the Romanian deadlift are two of the best exercises to achieve this goal. Even so, your squats should also be part of the training routine.
Hello;
Although such an article is not without interest, especially for neophytes, the truth is that they cannot be competitors, starting because functional training is more of a concept and as such can be incorporated into many other disciplines, and ending because, as we have said, functional training is part of CrossFit.
Another very different thing is "for what" or "to what" you direct this functional training, because the objective could be functions as different a priori as those of housework or those of a firefighter, with which, although the training could be the same (you never know when someone fixing the house has to jump out the window... and put out a fire in the garden hehe), it seems logical that they would be very different.
However, the joke is very appropriate since, in reality, functional exercise should prepare you for any activity that life demands of you at any time, perhaps even more so for exceptionally demanding situations such as the one mentioned.
Even so, and despite being a sport, and I think this is where many people get a little lost and enter into unnecessary comparisons (although it is true that this article will qualify it later), the pillars of CrossFit and its principles are often forgotten. main objectives, which as will be seen are not at all far from those of a functional training since, in fact and as I said, this is part of the first and have a common goal: to form a more complete and efficient individual from the physical point of view.
Or in the words of the discipline itself:
Greetings.