Why Hojo Undo, Part 4. Ishi Sashi vs. Dumbells
There are two things to address when comparing dumbbells to ishi sashi, there is the equipment differences themselves and the exercises they are used for. The equipment difference is pretty straight forward. With a dumbbell the weight is centered around the handle and thus around your hand. This allows you to handle the most amount of weight. With an ishi sashi the weight is centered a few inches away from your hand meaning that the weight you feel is magnified by a small lever arm. This means that with an ishi sashi the limiting factor will always be your wrist strength.
This leads nicely into the exercises. Dumbbells are used to train the prime movers, the large muscles of the body. That is why there is so much overlap with barbell training and also why dumbbells come in so many different sizes. Obviously the weight you use for bench press is going to be a lot more than the one you use for bicep curl.
For ishi sashi the main purpose is to train the main limiting factor, wrist strength. All ishi sashi exercises involve controlling the ishi sashi while keeping the wrist from bending. This is fantastically beneficial for keeping a straight wrist while punching, and equally useful for maintaining strength during grabbing techniques. Traditionally ishi sashi come in relatively few weight denominations with around 10lb or 4.5kg being the most common. You simply don't need more weight to strengthen the small joint of the wrist. In fact, it is better to keep the weight low. Low weight prevents injury, allows for more precise control, and lets you do more reps which is better for this kind of strength. For specific exercises check outwww.modernhojoundo.com/index.php/videos.
Dumbbells are so named because they developed from equipment designed to help people train for ringing church bells. Medieval church bells required a lot of strength to ring loudly so people had to train for the job, and since the village didn't want to hear them doing so at all hours they trained with bells that couldn't actually ring, ie dumb bells.
Ishi sashi means stone padlock. The original ishi sashi were fitted handle out next to a door. A board was then slotted through the gap and the door was locked.