It requires joint actions at the hips, knees, ankles, shoulders, and elbows to work together as a unit generating explosive force. Isolating on single joint actions might work for body builders to improve their appearance, but athletes need to concentrate on activities involving multiple joint actions to improve performance. Your strength and conditioning program should improve functional strength with exercises and drills approximating these skills. In strength training, only free weights allow movement in three dimensions simultaneously. This makes the transfer of strength and power easier to merge with the development of sport skills.
Machines limit the development of sport skills.
For example, when you use free weights, the muscles regulate and coordinate the movement pattern of the resistance, while machines use lever arms, guide rods, and pulleys to dictate the path of the movement. An additional benefit from free weights is help preventing major joint injuries. For example, squatting using free weights requires the back and stomach muscles to stabilize the torso isometrically. This allows the legs and hips to work with the back and stomach muscles as a unit to perform the lift. The adjustable board on the hip sled substitutes as the stabilizer restricting movement and isolating muscle contractions to the hips and legs.