Based on ancient drawing and writings, the origin of the ‘medicine ball’ dates back 2,000 years to Ancient Greece. Spartan warriors would train with animal bladders stuffed with sand. Since then, medicine balls have been used in one form or another to build health, strength, and resistance training. The HeroStrength Slam Ball develops power, strength, and speed. Whether you’re working your triceps, abdomen, or shoulders, HeroStrength has the right product for your exercise needs to increase explosive power for athletes in all sports. The HeroStrength Slam Ball has a tough rubber outer shell filled with a mixture of sand, iron granules, and adjustable air. Able to withstand all your powerful slams while increasing heartbeat and burning many calories.