One of the more annoying, yet common myths in the fitness world is that you can "spot train" muscles. Not only is it not possible, it shows how highly uneducated some people are with exercising, yet these people keep "educating" people on how to train. Under education is a huge problem in our industry, and spot training is the perfect example of that lack of knowledge.
Targeting the "Lower" Abs or the "tear drop" in the Quads, are two of my favorite that people will try over and over to spot train.
Let's break down the "lower" Abs myth. Your rectus abdominis is your "6 pack" muscle that everyone in the world of exercise tries to achieve. First off it should be called an 8 pack, but that's a blog for a different time. Second, the musculature is all connected making it impossible to work the lower portion of the abs without contracting the entire muscle.
I know, I know, what you are going to tell me is that when you do roman chair knees tucks that you feel your lower abs just burning the good post exercise burn. Well, yes you will feel a burn, but it's actually not your abs. It's a muscle known as your Psoas, which is a muscle in the hip flexor group. That is the muscle you feel being worked. Planks, sit ups, rollouts, HIIT training, and a healthy diet is the best way to achieve that "6-pack".
Now lets look at the "tear drop" muscle of the leg. It's the muscle just above the knee cap known as the "Vastus Lateralis" and when in shape, it looks good! We've all seen athletes with great looking Quad muscles, hockey and football players lead the pack, but, heck Serena Williams has better Quads then most men do. The way to get this muscle to "pop" is just like any other muscle. Cardio, Strength and diet. You have to work on your legs! Full range of motion leg exercises. I've seen people do half squats, reduced range of motion split squats, leaning forward with a bar on your back, etc to try and spot train this muscle. Unless you are coming off of an injury you should always go through an exercises full ROM (range of motion) to get the most bang for your buck. You'll recruit more muscle fibers for the lift, bringing more blood to the muscle, hence, bringing more nutrients for repair to the muscle, hence, making it bigger, stronger, leaner, quicker!