Most traditional martial arts training methods are build around forms practice, or "kata;" prearranged sequences of movements.
Ellis Amdur, a well known martial arts writer attempts to explain the benefits of forms training with regards to a specific practice, called iai in Japanese, in an article of The Aikido Journal. I've excerpted some of the article below. If you click on the title of this post, you'll be directed to the complete piece. Please pay a visit.
Some practitioners of modern martial arts deride kata training, claiming that an adherence to form is inherently weak. They claim that one trains stereotyped responses by rote and repetition, thereby rendering oneself unable to respond with freedom to an unpredictable, random attack. On the other hand, one’s freedom is limited by one’s neurological organization — stereotypical patterns of action and reaction entrained through another type of kata training — the repetitive, habitual patterns of movement one arrives at simply by living. Proper kata training is, in fact, a means of teaching one’s nervous system new patterns of response. Without sufficient repetition — ideally, mindful aware repetition - the nervous system will not develop new interconnections to coordinate new patterns of response. It is, paradoxically, through limitation and delineation, that one is able to approach freedom.
There is no doubt that kata are limiting in one sense, but concentration and limitation also cause the creation of skills that would otherwise never even develop. For example, the hook would probably never have occurred to anyone, had cross-hip throws, which were a devastating counter to crude roundhouse punches, not been eliminated from boxing. Similarly, an upright posture, which gave impetus to the development of the so many of the sophisticated throws of judo, far superior to the cruder throws of older jujutsu systems, was in part, a product of Kano Jigoro’s ideals for the moral/physical education of the sport’s practitioners.
In comparison to many other cultures’ fighting traditions, solo training is not emphasized in Japanese martial arts. Chinese martial arts are an exemplar of the latter. I’ve recently become passionately re-involved with xingyi, training about two hours a day minimum. Xingyi, which literally means “form directed by the will” is, very definitely, a neurological retraining system. The most important method of practice of xingyi is solo practice. (It is true that, at higher levels, partner practice and later, sparring is considered essential, but even so, the solo form is considered the primary). I find that the incessant mindful repetition of the same movements has begun to change my “instinctive” response to unrehearsed or random opposition, i.e., sparring.
This then leads me to contemplate iai, that rather peculiar practice of isolating out a single aspect of sword play — unsheathing and resheathing the weapon, and making it either a specialized study within a ryu, or a complete study in-and-of itself. In the oldest ryu, iai was an auxiliary training method. But why was it even included in the curriculum? Many other sword-bearing cultures have never made such practice a part of their training.
Typically, iai is described as a training method to deal with surprise attack, night infiltration, or fighting in a crouch in low-ceiling rooms, etc. This is surely part of the truth, but iai served an even more important purpose. First of all, it’s a damn sight more interesting solo practice than suburi, both for its practical utility and complexity — thus, the solo practitioner had a means of maintaining interest in long periods of practice, as well as doing an activity more complex than suburi, and less contrived than practicing “one-half” of a kata against an imaginary opponent. Furthermore, it was the equivalent of a gun-safety course. There, in the preparation for the forms and the forms themselves, is the equivalent of gun cleaning, checking your load, weapon awareness and retention, etc. It was so essential that it was included in most early bujutsu, and in many systems, its absence was considered such a lack that it was later added.
Like many activities, its practice became its own reward, and iai eventually became iaido, a specialized training that, through its limitation, led to the same kind of advanced sophisticated techniques that similar limitation engendered in the aforementioned judo and boxing. It is true that such specialization only occurs in peacetime. Sophistication is a luxury. Some koryu scholars and practitioners deride more modern specialized disciplines as a manifestataion of degeneration. But how fortunate a society that has enough peacetime that its members can afford the time to create sports or disciplines of self-study out of purely pragmatic fighting methods.