I have suffered from chronic foot and calf cramping for years. Anything can trigger it, but certainly times when I use all my foot and calf muscles--such as social dancing, skiing, or lots of walking--make it worse, especially at night. Since starting on this product three weeks ago, I've been virtually cramp free. It feels like a miracle. Before when I would go skiing, I knew I would pay that night, even with magnesium supplements. The last two times I've taken 4 tabs right before skiing and 4 tabs right after and...NO CRAMPING! I cannot recommend this product enough, and it's rare that I recommend anything.