There are a million and one ways to build leg strength and this is one of the best ways. This exercise was just made for building strength and stamina in the lower body. Not only that but this action also is high calorie expenditure because you are pulling against resistance.
To some extent you are also engaging your core so this really is a beneficial exercise as you can get a lot out of it. A one of those 'maximal' exercises and well worth doing.
The reason I use a resistance band with clients for this exercise is because it is soft around the waist and doesn't cause any discomfort as there is some elasticity.
Why do I incorporate this in workouts? Simply because I can make this movement as easy or as hard as necessary to benefit clients.
How hard my client trains depends on how much restraint I apply to the resistance band. When you are moving forwards against this kind of resistance you really have to drive your legs hard and push forwards with all the strength you have!
So you see, working out does not have to be complicated! As a mobile personal trainer, this is a brilliant training method that can be done almost anywhere!