For a rock-hard midsection, increase the resistance and range of your ab exercises
Do one set of exercise 1 and then rest for 30 seconds. Then do one set of exercise 2 and rest for another 30 seconds before repeating the pair of exercises two more times. Do the whole workout three times a week for four weeks, resting for at least a day between workouts.
Swiss Ball Jackknife A
Time: 40-50 seconds
Get into a press-up position with the tops of your feet resting on a Swiss ball, so that your body forms a straight line from toes to shoulders.
Swiss Ball Jackknife B
Time: 40 -50 seconds
Keeping your back straight, contract your abs and roll the ball in towards you as far as you can. Do as many reps as possible in 40-50 seconds but keep the motion steady and constant.
Straight-Arm Weighted Crunch A
Time: 40-50 seconds
Lie on your back on a Swiss ball holding a medicine ball or dumb-bell in your hands, which should be extended behind your head in a straight line.
Straight-Arm Weighted Crunch B
Time: 40-50 seconds
Contract your abs and crunch your torso upwards. Do as many reps as possible in 40-50 seconds but keep the motion steady and constant.