Free-weight training includes the use of dumbbells, kettlebells, weight plates, barbells, cable machines, medicine balls, sandbags, sleds, prowlers, ropes and any other object which increases the loading your body is required to overcome. Some free-weight exercises (such as dumbbell overhead pressing) can help you achieve the strength requirements for bodyweight movements (such as a cartwheel or handstand). The reverse can also be true in that bodyweight movements can help you achieve the strength requirements for free-weight exercises. Free-weight exercises can also be used for sports rehabilitation (such as single arm pulling and pushing with the cable machine to strengthen the shoulders) and to assist the main lifts (such as pull-throughs to strengthen the hamstrings for a deadlift). I find that free-weight training is an essential component to a comprehensive and effective training program.