A hack squat machine is a device designed to simulate the movement of the hack squat — a free weight exercise that targets the muscles of the lower body. The machine itself is a large steel frame equipped with a sliding back and head rest. Lifters rest within the frame and flex and extend the knee joints to move the platform along a single plane of motion. Like all squats, a hack squat works the quadriceps, hamstrings, adductors, abductors, and gluteus muscles, while employing the core muscles and calves as synergists. Hack squats have several advantages over conventional squats, including ease of execution and increased lifting capacity.
The original free weight hack squat was made popular around the turn of the 20th century by wrestler George Hackenschmidt. The exercise is a motion similar to standard squats, but involves holding the barbell behind the legs rather than resting it on the shoulders. Keeping the center of gravity low removes the need to balance the weight on the shoulders, making it possible to lift more weight than would be achievable using a typical squat position. The posture required for this movement may be bio-mechanically awkward for some individuals, making the hack squat machine a safer and more easily performed option.
A hack squat machine, like the free weight movement, facilitates heavier lifting by removing the issues of balance and stabilization. The fixed plane of motion inherent in the exercise enforces correct form, while also reducing risk of injury and allowing the exercise to be performed without the assistance of a spotter. Additionally, a hack squat machine may be less intimidating to use than free weights, making it an excellent choice for novice lifters.
To perform a hack squat, the participant rests in the machine with the head and shoulders in the restraint device. The feet should be shoulder-width apart and angled in a slightly toe-out orientation on the platform. One or two handles are usually positioned at hand-level. To begin the squat, the platform must be raised slightly to free the handles, which are then used to disengage the locking mechanism. This frees the weight for movement and allows the exercise to begin.
Just as with a standard squat, a hack squat machine requires the lifter to bend at the knees until the legs reach an approximately 90° angle. Deeper squats will focus more emphasis on the quadriceps, but care must be taken to ensure proper form. As the knees flex, the kneecaps should not move further forward than the toes. Once at the bottom of the movement, the lifter exhales forcefully while activating the thigh muscles and returning to a standing position.
A number of devices exist to make squats more accessible to all fitness participants. The hack squat machine is often confused with a smith machine, which is a specialized squat rack with a built-in spotting device. Leg press machines also function on a similar principle as a hack squat machine, but involve resting on the back and pressing upward with the feet. Heavy squats, such as those performed on a hack squat machine, will not only activate the leg muscles, but also stimulate the production of growth hormone. As a result, all the muscles of the body benefit from hack squats.