Muscle imbalances make you more susceptible to muscle strains and injury, while balanced muscles can make you stronger and more athletic. Muscle imbalances can occur from past injuries, using poor technique or poor posture. Abdominals may show imbalance between the right and left side or between the upper and lower abs. Having weak abdominals compared to hip flexors or upper- or lower-body development can lead to poor posture, which can create further problems.
If you feel you have an imbalance between the right and left side of your abdominals, see how long you can hold a side plank on each side. You should be in a straight line from your head to feet with your elbow directly under your shoulder and your neck in line with your spine. If one side is much stronger than the other, give extra attention to the weaker side. Target the obliques using wood chops, where you perform twice as many from the weaker side as the stronger side until your muscles become balanced. Perform wood chops holding a medicine ball, dumbbell or cable handle as resistance as you swing it at an angle across the front of your body. Trunk twists, where you twist your upper body and shoulders from one side to the other, are also good for developing the obliques.
Often the upper abs appear more defined than the lower abs. In most cases, this is because more fat is stored on the lower abdominal wall, and you will have to reduce your overall body fat percentage to allow the lower abs to drop fat and look as well developed as the upper abs. If the problem is more than body fat, ensure that you are maintaining correct form when performing crunches and leg lifts. Keep your abs contracted throughout the exercises. Do not jerk your head off the floor or tuck your chin into your chest during crunches. Keep your head and shoulders pressed against the floor and do not let your back arch during leg lifts.
Muscle imbalance can exist between abdominals and strong hip flexors, which bring the legs and trunk toward each other. If situps cause your lower back to arch and create pain in the lower back, you need to strengthen the abdominals. Good exercises are side planks, side plank raises and oblique crunches. Side plank raises start from the side plank position then lower the hip until it almost touches the floor before returning to the start. Oblique crunches move the elbow toward the opposite knee without using the neck and keeping the lower back on the floor. Work gradually on weaker muscles to create muscle balance without straining. Good posture goes a long way to preventing muscle imbalance between the abdominals and other areas.
Isolation exercises can contribute to muscle imbalance, so rather than focusing just on building up weaker muscles, perform compound movements. Compound movements that use lots of muscles help by making different muscles work together in the way that nature designed the body for functional activities. Opt for exercises such as bicycle crunches, anti-rotation exercises and even squats, which mimic daily movement and help train your whole body to work as a unit.