Keeping feet together, open your knees to a 45-degree angle. Squeeze your abs and lift your hips off the floor and roll them towards your chest. Pause and slowly lowering your hips back to the starting position.
Read moreWhat does a crunch improve?
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.
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