Dan Ross (Dross) wrote:
Weight training helps too but the consensus has always seemed to be that bulking up is bad for aikido due to loss of flexibiliy/mobility, so stick to lower weight and higher reps and make sure to stretch and warm up/cool down properly.
It may indeed be 'the consensus'. If so, it is a consensus of ignorance.
First of all, unwanted 'bulking up' is in itself a myth. Ask anyone who has seriously tried to gain strength and mass without the aid of steroids, and they will tell you that ballooning up from lifting weights just doesn't happen. Gaining substantial mass requires very particular, demanding regimen, in terms of diet, intense training, and minimization of endurance activity, for YEARS.
Secondly, there is nothing about gaining strength and muscle mass that inherently leads to reduced flexibility, mobility, or speed of movement. In fact, many weight training exercises can themselves be used to INCREASE flexibility. Supplemental stretching is not even necessarily required, and stretching before lifting or doing anything requiring the expression of strength can actually be counterproductive. ROM in joints can be maintained by merely using it.
Thirdly, if one is interested in mobility, your prescription of distance running and high-rep muscular endurance training is precisely wrong. Doing both of these activities extensively without additional strength, speed, and/or power training will cause adaptations that de-emphasize the size of fast-twitch muscle fibers and the body's neurological ability to recruit them.
Even if the person is overweight, and would like to reduce bodyfat to become more mobile, running and muscular endurance work are mediocre to poor choices. Gaining muscle mass and high intensity interval training are the best choices for long term fat loss.
One study showed that competitive Olympic lifters were on par with world-class sprinters for about 30 yards. As I implied above, if you want to see how slow, stiff, and immobile someone who is all "bulked up" from lifting weights is, check out an NBA game.