I'm finally finalising my book on the science behind fighting techniques.
One chapter in that book is on throws and takedowns. Despite the common meaning of the terms provided by the Oxford Dictionary, it appears the martial arts has managed to confuse the meaning of the terms as applied to marital arts techniques.
I provide a biomechancially based classification for all techniques that are designed to cause a person to fall to the ground. It's based on the biomechanics of balance and stability. A person is stable if their centre of gravity (CoG) is located over their base of support (BoS) and balanced if they possess control of their CoG with respect to their BoS.
It was interesting reviewing the literature on the throws and takedowns of various martial arts. Books dedicated to throws and takedowns of various martial arts did not distinguish between the two, and in fact often only referred to throws.
Judo, according to Kano's classification of Judo techniques, does not teach takedowns.
A throw is a technique were forces are applied to cause both of the opponent's feet to leave the ground. The biomechancial target of the applied forces is the opponent's BoS.
A takedown is a techniques were forces are applied to cause an opponent's CoG to fall outside of their BoS and a balance recovery is prevented. Takedowns can be subclassified as 'one-legged' or 'two-legged' (for want of a better description) takedowns. The biomechancial target for one-legged takedowns is a person's foot in contact with a support surface. For instance, a foot sweep is a one-legged takedown.
The biomechanical target of a two-legged takedown is an opponent's CoG. Forces are applied to cause an opponent's CoG to fall outside of their BoS and a balance recovery is prevented. A hiki-otoshi (elbow drop) is an example of a two-legged takedown.
Irimi-nage and Mukae-daoshi are good examples of the confusion held within the martial arts over this issue. Irimi-nage is 'entering throw' taught by aikido.
Mukae-daoshi is 'meeting takedown' taught by Yoseikan Budo/Aikido and Jan de Jong.
Using Kano's division of judo techniques (kuzushi, tsukuri, kake), the same kuzushi and tsukuri result in different kake depending on the direction of the applied forces in the kake phase. The same unbalancing and positioning results in a throw or takedown depending on the direction of the applied forces in the execution phase of the technique.
The irimi-nage/entering throw is in fact a takedown while the mukae-daoshi/meeting takdown is in fact a throw. What that also means is that the latter is entirely dependent on the momentum generated during the kuzushi phase of the technique.
It also means that the applied forces for a throw are upward whilst the applied forces for a takedown are downward. A biomechanical understanding of these techniques enables a student to know what to look for in learning and training these techniques as does the instructor. It makes better students of students and better instructors of instructors.