In this age of high-tech equipment, this black/green 4 lb. GoFit GF-MB4 Medicine Ball is very simplistic, yet incredibly effective in training the whole body through a complete range of motion. Medicine balls build core trunk strength and joint integrity. Medicine Ball training is designed to strengthen these areas and allows you to more fully access your muscle strength. You also become more resistant to injuries. The medicine ball provides resistance through a full range of motion to abdominal exercises. This means you will be able to keep the abdominal muscles fully loaded with resistance through all planes of movement. By keeping your abdominals fully loaded through a full range of motion, you will develop your abdominals in a much faster period of time. * Before beginning any weight loss or exercise program, you should consult with your physician. 4 Lbs. Rubber Medicine Ball With Pebble Grip Surface to Tighten & Tone. Black/Green, Rubber. Includes Brook Benten Training Manual. GoFit. net Medicine ball in black and green provides fitness benefits for building core trunk strength.