There are many kinds of dumbbells to choose from in the gym, generally ranging from 3kg to 20kg. When bodybuilders choose their weight, they should decide according to their own foundation. Beginners should take more than 6- 10KG to ensure that each group can reach 10-20 times, and the number of groups is not less than 4. With the progress of fitness, the weight of dumbbells can be gradually adjusted to achieve better exercise effect.