The Hack Squat

Many bodybuilders use the hack squat as a replacement for the squat. However, they are not identical exercises since the hack squat stresses the knee (and the quadriceps close to the knee) to a much greater extent than in the free weight squat. How you execute the hack squat in relation to your physical abilities also determines how effective the muscular development will be and if the exercise is safe to the joints involved. Strict form is essential for safety in this exercise.

EXECUTION

• Position yourself on the hack squat machine with the feet on the uppermost portion of the platform and your shoulders under the resistance pads as you face away from the apparatus. On some machines you must squat slightly to get under the resistance pads. When you do this be sure that you do not round the back.
• Be sure your feet are forward of the body when positioned and flush against the platform.
• When ready, inhale slightly more than usual and hold your breath as you lower the body.
• Lower until your thighs are approximately level with the floor, at which time there should be a right angle in the knee and in the hip joints.
• For greater hip extension muscle involvement, go slightly below the thigh level position but only if you still maintain the normal curvature of the spine and the feet remain flush against the platform.
• Do not stop in the bottom position and reverse directions by forcefully straightening the legs via hip and knee joint extension.
• Be sure that the feet remain flush against the platform and that the spine retains its normal curvature.
• As you pass the sticking point or the most difficult portion of the up phase, begin to exhale and complete the exhalation when you are in an erect standing position.
• Pause momentarily and then repeat for the necessary repetitions.

MAJOR MUSCLES INVOLVED

The major muscles involved in the hack squat are the quadriceps, located on the anterior thigh. This includes the vastus lateralis, vastus medialis, vastus intermedius and the rectus femoris. The vastus lateralis is a large muscle located half way down the outside of the thigh and is attached to almost the entire length of the femur. The vastus medialis is located on the medial (inner) side of the thigh, somewhat lower than the lateralis and is partially covered by the rectus femoris. The vastus intermedius lies between the vastus medialis and lateralis and beneath the rectus femoris. It is difficult to visually see this muscle separate from the medialis and many times the two are continuous for part of their length. The rectus femoris, which crosses both the hip and knee joints, is a large muscle positioned straight down the front of the thigh. These four muscles converge at the lower end and join into the patella bone and surrounding ligaments. The patella, however, is a free-floating bone which attaches to the tibia bone of the shine via the patella ligament. In addition to protecting the knee joint, the patella also serves to give better leverage to the knee joint extensor muscle pull. If you go to the thigh level or below level position in the hack squat, other major muscles are involved: the gluteus maximus and hamstrings. The gluteus maximus is a very large, fleshy muscle at the back of the hip. The hamstring muscle is composed of three muscles: biceps femoris, semitendinosus and semimembranosus. The biceps femoris is the largest muscle of the hamstring group and is located on the lateral (outer) side of the posterior thigh. The semitendinosus and semimembranosus run from the hip joint to the shin. Because their tendon of insertion is on the medial (inner) side of the knee joint, they are known as the medial hamstrings.

MUSCLE AND JOINT ACTIONS

In the knee there is knee joint extension in which the thigh moves away from the shin. In the hips there is hip joint extension in which the thighs move from a parallel or below parallel position to the vertical position to bring the pelvic girdle in line with the legs and upper body. The spinal muscles remain under isometric contraction to retain the normal curvature of the spine during both the descent and ascent. SPORTS USES: Bodybuilders need knee and hip actions to develop and define the anterior thigh, buttocks and hamstring muscles. Without hip and knee joint extension it would be impossible to lift weights off the floor. These actions are also needed in the deadlift and squat events in powerlifting and in the snatch and clean and jerk in weightlifting. In addition, knee and hip joint extension and the muscles involved are essential in performing many skills. This includes jumping (height or distance), all forms of running, kicking balls and kicking in the martial arts, skipping, leaping and pulling and pushing with the lower body. Thus the sequential and combined knee and hip joint actions are needed in sports such as the high jump, basketball, volleyball, long jump, soccer, diving, track, football, baseball, soccer and basketball.

COMMENTS

1) The hack squat can be an extremely effective and safe exercise to develop the quads (especially the vastus medialis and lateralis) or it can be a highly dangerous exercise. The positive or negative benefits depend upon how well you execute the exercise. For example, one of the key elements in relation to exercise safety is to be sure that you have a 90-degree angle in the knee and hip joints when in the bottom position. To ensure having these angles, it is important that your feet are placed thigh length in front of the trunk. If your feet are close or under the body and your thigh length is approximately 14 inches, not only will you have difficulty in maintaining the whole foot in contact with the platform, but your knees will go well in front of the feet. As a result, the pressure in the knees can be highly dangerous. In addition, the ligaments which maintain knee stability become stretched beyond their normal limits. The only exceptions to this potential danger are bodybuilders and athletes who have exceptional flexibility in the hip, knee and ankle joints–much greater than the flexibility of 90% of their athletic peers. When the feet are placed sufficiently in front of the body so that the shin is vertical and the thigh is horizontal to form a 90-degree angle in the bottom position, the exercise will always be very safe. In this case there is no excessive flexion of the knee joint, the ligaments do not become over-stretched and the pressure within the knee joint does not approach dangerous limits.

2) Think of the hack squat as a wall squat, a common exercise used by skiers. In the wall squat your back remains flush against the wall while the feet are placed out in front so that when you lower the body to the thigh level position you assume and hold a phantom chair position. At this time there is a 90-degree angle in both the knee and hip joints.

3) Another factor in making the hack squat safe (as in the free weight squat) is maintaining the normal curvature of the spine throughout the entire execution. Since the trunk stays directly under the resistance pads throughout execution, the possibilities for rounding the lumbar curve are not as great as in the free weight squat. The potential for danger, however, increases as the thighs approach the level or slightly below level position. For example, tight hamstrings or weak erector spinae muscles make it possible for the pelvis to rotate backwards as you reach thigh level or below, creating a round lumbar spine. This is a weak position of the spine which, in turn, allows for excessive compaction and compression forces on the discs, which can cause spinal injury. The possibilities for rounding the spine are increased greatly if the feet are kept close to the body.

4) Because of the more forward position of the feet, greater stress is placed on the quadriceps close to the knee. For even greater stress, the feet should be placed closer together. Because of the different emphasis, the hack squat is a good addition to various leg exercises for greater development of the quadriceps.

5) To involve the hip joint extensors (gluteus maximus and hamstrings) it is necessary that you go at least to the level or slightly below level thigh position. In so doing, you must still maintain the normal curvature in the lumbar spine. Keep in mind that the more you lower the body the greater is the hip joint flexion and the greater the tendency to round the lower back. Be sure that this does not occur as you do the exercise. In addition, going below the thigh level position requires even greater strength of the quadriceps. Thus build up the necessary strength and flexibility gradually so that you can go below parallel effectively and safely.

6) As with all squatting exercises, it is important that you have a strong mid-section to maintain the proper curvature of the spine throughout the execution. Although there is no forward inclination of the trunk, as occurs in the free weight squat, the pressure that builds up on the spine can still be quite great, especially when the weights that you use are quite high. Thus it is important that the muscles of the spine, especially the erector spinae in the lumbar section, be strong. To strengthen these muscles you should do back raises, back with a twist and reverse back raises. Keep in mind that it is the erector spinae that maintains the normal position of the spine. However, if you have excessive hyperextension (swayback) of the lumbar spine, then you should also do additional abdominal exercises to rotate the pelvis backward to regain the normal curvature. In this case you should do more sit-ups, reverse sit-ups and the pelvic tilt.

7) To assist in maintaining an erect trunk during execution of the hack squat, it is necessary to hold your breath during the down and up phases. If you exhale during any of these phases, especially near the bottom position, the intra-abdominal and intra-thoracic pressure will decrease greatly. As a result, your ability to maintain a rigid spine will be impaired. In addition, breath holding increases your strength by up to 20%. Thus it plays a very important role in helping you maintain safety in the exercise, as well as being able to use more weight.

8) During execution you should maintain the head in proper alignment with the trunk. To help do this it is important that your vision be focused perpendicular to your body or to the angle of incline of the machine. If you look down toward the feet, there will be a tendency to contract the abdominals and round the spine, which is definitely not called for. If you instead do the reverse and look up at the ceiling, there is a stronger tendency to contract the erector spinae, which may place the lower back into excessive lordosis (arching) which can also be injurious to the spine when the forces become sufficiently great. Thus focus your vision directly in front in relation to the angle of incline of the machine to help maintain a good spinal alignment.