these are pretty simple exercises for lower abs
1. Lay on your on your back with your legs stretched out on the floor. Put your hands on your sides and rest your head on the floor. Now all you have to do is lift your legs to a 45 degree angle of the ground and then bring them down again, but make sure not to rest your legs on the floor. Repeat this movement for 10 - 15 repetitions and then rest your legs back on the floor.
2. Next, continues from where you left of with the first one. Simply raise put your hands behind your head and lift it up of the ground slightly. Now all you do is bring in your legs to your stomach bending at the knees then kick them out again but do not make your legs touch the floor. Repeat this movement 10 - 15 times, and then we will move on to the third exercise.
3. And finally for the last one, for your lower abs is as follows. Bend your legs at the knees and let both big toes touch, so that your knees are outwards. With your head still in same position from the last exercise, that is slightly off the ground with your hands behind your head for support, rock your legs back and forth using your bum as the pivot point. You should feel it, right where you want it, that is your lower abs.