This is a lower ab, leg workout that I have been doing a lot lately. These 4 exercises work a number of muscles but also target the lower abdominals (aka rectus abdominis) in particular.
As well as your lower abs, these movements also improve the strength and mobility of your hips and lower back, which is great for anyone who spends much of their day sitting at a desk.
Read more about why you should Not Ignore Your Core