Your lower abdominal (or abs for short) is the most difficult section of your abdominal region to work out. With that being said, if you are not working on your lower abs, then it would be difficult to develop your full stomach the way you originally had planned.
A mixture of the following work outs would help you develop your lower abs and maintain that toned stomach you’re looking for;
Bent Knee Abdominal Hip Raises: Lay on the floor with your head, torso and buttocks flat on the floor. Your knees should be bent and feet also flat on the floor. Make sure your arms and hands are relaxed by your sides. Use the muscles in your abdomen, lower back and hamstrings to lift your hips and buttocks off the ground. Raise your hips as high as you can, which will make a bridge with your pelvis. Slowly lower your entire body back down to the ground. Repeat. This works the abdominal and lower back muscles, as well as the hamstring and gluteus muscles. This exercise is also good for weight loss.
Ab Flutter Kicks: Lay flat on your back, legs extended. Slowly lift your head and shoulders off the ground as well as lifting up your legs a couple of inches off the ground, your back and buttocks still firmly on the ground. Lift your left leg up higher than the right leg, keeping your right leg still off the ground by a couple of inches. Switch legs so that the right leg is higher than the left, and the left leg is now a couple of inches off the ground. Continue this pattern.
Reverse Crunches: Lay on your back and keep your knees up. Put your hands behind your head (don’t lace your fingers). Keep your heels at a 90 degree angle. Exhale as you lift and bring your chest to your thighs and then stretch back out so your knees are aligned with your hips. You then come back up and repeat the process. Avoid bringing your elbows to your knee caps, allowing for all the work to be done with your core.
Seated Knee Tucks: If you have a sturdy chair, sit with your hands holding the front of the chair for support. Sit towards the front of the chair and lean back with your legs straight out. Bring your feet together and raise them a few inches off the ground.Extend them as far and as high as you can. Return to starting position and repeat. Slowly bring your knees up and in until they are around six to ten inches from your chest. Reverse the motion, then repeat.
Weighted Hand to Leg Ab Crunches: If you have two dumbbells, hold one in each hand. If you don’t own a pair, then anything with a little weight would work, such as filled water bottles or remote controls. Lie flat on a surface with your arms and legs fully extended. Carefully raise your right leg and right arm at the same time. Try keeping your arm and leg straight throughout the movement. Focus the tension on your abs and flex your stomach at the peak position. Repeat with your left leg and arm. Continue this pattern. This exercise targets the lower and middle abdominal muscles and helps to strengthen the general core area.
Every one of these work outs should be improved in slow measures, meaning start off with fewer sets and reps. As you progress and continue these methods over time, you can add on more sets and/or more reps.
Have fun and feel the burn!