EXECUTION
- Sit on an exercise bench in a straddle position, i.e., one leg on each side of the bench. The buttocks should be fairly close to the end of the bench seat with your hands 6-12 inches behind the buttocks grasping the sides of the bench.
- Incline the trunk backward at approximately a 45-60? angle and support your weight on extended arms.
- Raise the legs until they are level to the bench or slightly above. This is the beginning position.
- When you are ready, inhale slightly more than usual and then hold your breath as you bend the legs and bring the knees in toward the chest.
- The head and shoulders may also move slightly toward the legs as you do this, but should remain basically in position throughout the execution.
- When the knees get close to the chest, hold the position momentarily and then exhale and straighten the legs to return to the initial position and then repeat.
WORKOUT TIPS
- For most effective execution, keep the trunk stable and bring the knees as close to the chest as possible. Doing this produces greater shortening and stronger muscular contractions of the abdominal muscles.
- To be sure that you keep the trunk in place as much as possible during execution, keep the arms extended. Do not bend and straighten the arms during execution.
- If there is any raising of the trunk, it should only be the head and shoulders, not the hips. If the hips move up, you will be using the hip flexors to do the work, not the abdominals.
- The hip joint flexor muscles play mainly a stabilizing role in this exercise. They are involved to initiate bringing the knees up and then contract isometrically to hold the leg-hip position as the abdominals rotate the pelvis backward to continue raising the knees toward the chest.
- Be sure that you lean back only to about a 45-60? angle. If you lean all the way back, then you will have greater involvement of the hip flexors, not the abdominals. If you are erect, the ROM will be lessened.
- To make the exercise even more difficult, you can do figure eights. Hold the legs almost straight above the level of the bench and then trace figure eights from side to side.
- If the basic knee-up exercise is too difficult, then you should do the exercise in your bare feet to lessen the resistance. When you can then do the exercise easily for up to 15-20 repetitions, then do the exercise with your shoes on.
Major Muscles Involved
The most involved muscles are the abdominals, mainly the rectus abdominis and the internal and external oblique. The rectus abdominis is a long slender muscle that runs vertically down the abdomen from the lower rib cage to the pubic bone of the pelvis. The upper portion has tendonus strips that run horizontally and provide the divisions usually seen in a ripped midsection. The internal and external oblique muscles cover the front and front sides of the abdomen. The fibers of the external oblique run at a downward angle on both sides of the body to form the letter V when viewed from the front. Directly underneath, the fibers of the internal obliques form an inverted V at the upper end but are more horizontal in the lower abdomen. In the hip joint, the major muscles involved are the psoas, iliacus, rectus femoris and pectineus. The psoas and iliacus combine into a common tendon at the hip joint and are known as the iliopsoas. The iliacus is located deep on the inner side hip bone while the psoas is deep in the lower abdomen and attaches to the lumbar vertebrae. The rectus femoris is one of the quadriceps muscles and is positioned in the center of the thigh running from below the knee joint to above the hip joint. The pectineus is a small muscle that crosses the hip on the inner front side of the hip joint.
Muscle/Joint Actions
In knee-ups, there is spinal flexion which occurs mainly in the waist (lumbar spine). In this movement, the hips rotate backward and the legs move closer to the trunk. In the beginning stages, there is hip flexion with the legs moving toward the hips. This involves the hip flexor muscles which contract concentrically to initiate the bringing-in of the legs but then the hip flexors contract statically to hold the leg-hip angle.
Sports Uses
The knee-ups exercise is most important in fitness competition especially in floor routines when raising the legs and/or body. It also plays a valuable role in bodybuilding for strengthening the abdominals and hip flexors both of which also play an important role in hanging leg raises and other advanced abdominal exercises. In addition, it is an excellent exercise for defining the abdominals. Knee-ups are very important for athletes involved in running, jumping, and kicking when bringing the legs forward and upward and whenever raising the legs in execution of various stunts in fitness competition, on gymnastics apparatus and in dance. This exercise also plays a valuable role when moving the legs in various sports activities such as in swimming, ballet and other forms of dance, the pole vault and high jump. It also plays a valuable role in sports such as soccer, when executing tackling movements, and when executing stepping out actions when cutting.