Track Ball Soft Strength this high performance jump rope adds JC9796 this high performance jump rope adds intensity to training and builds endurance and forearm muscles Spine cradling massage toolAlleviate back and neck soreness and reduce your chance of recurring painAlso work on both sides of your bicep quadricep or calf muscle for an efficient massageErgonomically designed to access the muscles surrounding the spine and respect the integrity of its anatomy by avoiding direct contact with bonesLets you perform self myofascial release (SMR) to stimulate the stretch reflex in muscles and break up soft tissue adhesions (fascia) responsible for tension and stiffness