Leg Raises machine

Crunch machines usually use extra resistance in the form of selectorized weight stacks or plate loading, and are often performed for moderate to high reps, like 8-12 reps per set or higher , as part of the ab-focused portion of a workout.

Like situps, crunches help you build muscle. But unlike situps, they work only the abdominal muscles. This intense muscle isolation makes them a popular exercise for people trying to get six-pack abs . This also makes them ideal for strengthening your core, which includes your lower back muscles and obliques.

Dr. Laskowski: The abdominal crunch is one of the most common exercises used to train the abdominal muscles . The abdominal crunch targets the abdominal muscles, which are part of your core muscle group. The stronger your core muscles, the easier it is to do most physical activities and sports.

According to the study, researchers found that most of the claims made by ab machine manufacturers are greatly exaggerated and that the devices worked no better to stimulate muscle activity than good old-fashioned crunches or sit-ups . But despite the surrounding hype, ab machines may not be without certain value.