ProPulse® Speed Trainers patented design combines both audible feedback (sound) and dynamic feedback (shifting weight). This combination increases speed, timing, workload, and integrates your entire body when performing basic and advanced exercises. What you place in your hands can resonate throughout your entire body. For example, kettlebells or dumbbells are held in your hands and used to strengthen the upper body, core, and legs. The ProPulse® Speed Trainers use a dynamic return (quickness, force, integration, conditioning) and sound (timing, rhythm, balance and coordination) so you can "hear" and "feel" them working for you and with you.