Resistance in Training: Earlier or Later?

Before martial arts, I used to be on a swimming team. Aside from endurance and strength training, our coaches would also add resistance-training where we would sprint while wearing t-shirts. The rationale was that if you could swim fast with added resistance, you'd do even better when it was removed. But then I came upon an article about the 1996 Olympics in an old National Geographic magazine, mentioning how the US swimming team used a new training method where swimmers were actually pulled by a mechanism so their muscles would become used to faster speeds. Some claim that this method is far more effective than adding extra drag.So, I was thinking, in martial arts, should “resistance” (uncooperative training partners esp. when practicing throws and locks, more varied attacks when training basic defenses, etc.) outside of sparring/randori/kumite be introduced earlier or later?Now, my main art is aikido. Ideally, aikidoka are supposed to learn first with no-resisting partners to get a feel of a particular technique's flow; and then gradually resistance against the technique, attack variations, etc. should be added. But in practice, a lot of aikidoka simply stop at the non-resisting-partner phase. On the other hand, one of my old instructors, who likes more liveliness in training, introduces resisting techniques as early as possible. This in turn puts off newer students who didn't have the time to get a feel of how a technique is supposed to go.So what do you think?Should resistance be put in early in a martial artists training, or should students be allowed to feel ideal conditions first and then gradually taught how to overcome resistance towards ideal technique?The martial arts is nothing like swimming. It is so much more complicated. it takes decades to become proficient at it. I do believe in teaching students how to deal with non-compliant attackers. However, to start that way early is to expect to lose most students before they begin to learn anything of value. It is hard enough to build confidence and skill. Keep trying to defeat every thing the student does, and you might as well just tell them to quit. I would not ask a first grader to write a 1,000 word report. They would not be able to do it. most would just give up. Those few that did try, would not learn much. They also would certainly not gain any confidence in their ability to get better.Starting to resist a new student to early is like taking them to a bar and pushing them into a fight they are unprepared to handle. I've met a few instructors with this type of mentality. All of them did not have many students. None of them had any students that had good technique or understanding. all they became was brawlers that wore a Gi and a belt..