A pair of dumbbells is the most basic and simple tool for body strengthening. Karatedo practitioners should have a pair at home, so that they can use them for training whenever they want. It is particularly helpful for those who are relatively weak and seldom do exercises.
Dumbbells with suitable weights are important to training. In general, if we use heavy dumbbells for training, our slow contraction muscle fibres (SCMF) will be built up and our bodies will be muscular. It is because SCMF are larger than fast contraction muscle fibres (FCMF). However SCMF contract slower than FCMF, therefore our body movement will be relatively clumsy. Karatedo demands speedy techniques and swift body movement, therefore it is not suitable for us to use heavy dumbbells for training. On the other hand, we cannot train up useful muscle strength when dumbbells are too light. A suitable dumbbell should weigh about 1/10 of our body weight.
There is a wide variety of training methods with dumbbells. We can do arm-curls, lifting and pushing exercises to strengthen our arms, and also Dachi-standing and squatting exercises to strengthen our stances and legs. However our attention should be drawn to the fact that punching with dumbbells cannot improve our punching.