I'm in no way a fitness expert (ask Marty on these forums about my amazing lack of upper body strength
) but I can relate my experiences. I've recently started exercising and doing some light weight
training. For me the exercises that have given me the most obvious benefit in my aikido practice have been: running for endurance, crunches for really tucking in on those rolls, squats for gettin' up off the floor, and deadlifts seem to give me a feeling of greater stability in my trunk overall.
I'm sure the other exercises I do help also but it feels like these ones in particular have given almost immediate benefit...especially the crunches and squats.