Muscle groups and their corresponding functions
The external oblique muscles serve as the cover of the sides of the abdomen. In addition, it helps in the rotation of the trunk and the spine. Serving as further support to the abdominal wall, theinternal oblique muscles are located beneath the external oblique muscles; thus, they also serve as cover of the abdomen at its sides.
The internal oblique muscles help in forced respiration, and aid in raising the pressure inside the abdominal cavity. They also rotate and turn the trunk with assistance from other muscles. More importantly, they serve to counteract the actions of the diaphragm, resulting in coordinated fashion of regulating the volume of the chest cavity.
The transverse abdominis is the muscle in the side and front of the abdomen. It lies underneath the internal oblique muscles; therefore, it follows that it is the deepest muscle in the front and side of the abdomen. Its main function is to compress the ribs and the abdominal organs. In addition, it stabilizes the thorax and the pelvis. It plays a great role when a pregnant woman delivers her child, by pushing the child through and out in the pelvic canal.
Probably unknown to you, there is a back portion of the abdomen, and one of the most prominent muscles in this region is the latissimus dorsi. It is responsible for extending, adducting, and rotating the arms—aside from covering the abdomen at the back.
Strengthening exercises for the abdominals using the body weight
Crunches (Modified sit-ups)
Lie flat on the floor in a supine position, with knees bent and your hands placed over your chest. Slowly raise your head and your shoulders around six inches off the floor. Remain as it is for two seconds then return to the starting point.Exhale as you sit up and inhale as you come down. Do two to three sets of 10 to 20 crunches daily. These exercises are intended and good for your rectus abdominis.
Lie flat on the floor in a supine position, with knees bent and your feet flat on the floor. Place your arms at your side and with the palms down.Keeping your knees still bent, bring your legs up followed by lifting your pelvis towards the chest. Exhale as you gradually lift your pelvis. You can do two to three sets of 10. This exercise is intended for the transverse abdominis muscle.
Lie flat on the floor in supine position, with your knees bent and your feet flat on the floor. Simultaneously tighten your butt muscles and your abdominals while raising your pelvis fromthe floor. While raising your pelvis, press your lower back towards the floor. Hold contracted muscles for three to ten seconds while exhaling. You can do this for three to five times.
Calf muscles 
The gastrocnemius muscle is found at the back portion of the lower leg, andit runs overits entire length. It is connected at the back of the knee and to the heel.When this muscle contracts, your lower leg is pulled towards the upper leg, causing bending at your knees. More importantly, this muscle plays an active role when you walk.
The other component of the calf muscles is the soleus. It is located at the back of the lower leg, in close proximity with thegastrocnemius. It is primarily used to push the ground when you walk. In addition, it is very important in dancing and running. To prevent you from falling forward, the soleus will contract to pull your feet against the ground, maintaining your upright posture.
(To be continued)
- Glover B, Shepherd J, Glover SF. Strengthening. In: The Runner’s Handbook. 2nd revised ed. New York: Penguin Books USA Inc.; 1996:578-597.