The inchworm exercise is a movement where the hands and feet work together in incremental fashion, resembling the crawling movement of an inchworm. It's an excellent exercise to tone the core muscles. Because it forces resistance of movement, it's also an ideal exercise to develop stability.
The inchworm is performed by starting in a standing position, bent at the waist, with the tips of the fingers pressing on the floor for support. The knees should be slightly bent. The hands are then moved forward until the body is in a plank position, as in the beginning of a push-up. The feet are then moved up slowly to the starting position, and the process is repeated six to ten times. However, proper form is more important than the number of repetitions when it comes to toning the core muscles.
The inchworm is a very functional exercise. No equipment is necessary, and it doesn't put strain on the back like sit-ups and crunches. It can be used as a warm-up or cool-down exercise before or after more strenuous weight work. It is important, however, to maintain the best form possible, bracing the core muscles and adjusting by bending the knees if the hamstrings are too tight.