Since when do changes in neuronal firing efficiency not constitute a "physiological change?" Curious Neuroscience major here. I'm guessing you're talking in terms of muscle composition, but increases in neuronal efficiency alone can make a TREMENDOUS difference in your athleticism. (insert cliche' "not what you got but how you use it" line here)
You might be interested in a general lifting program Dartmouth Ultimate followed a few years back--it's a general strength program, designed not to be too technical (good for a college ultimate team when some people have no lifting experience), and incorporating some plyos and single-leg work to help prep for ultimate play.
The program is designed to be done in six weeks scaling up the weight as you scale down the reps, with three days a week (likely MWF, though TThS would probably work too) and about an hour-hour and a half to commit to working out, depending on how quickly you work. It also tapers down so that you should be at a relative peak by the end of the program (you can cycle back to the start if you want to).
For the record, we always spread the program over 9 weeks (with practice it was too much to lift three days a week), which fit our pre-season winter training leading up to spring break very nicely. The first year we started this program the A team had no significant injuries in the spring season (which was a big difference from prior years, but sample size skepticism should apply here).
My own impression, having followed the program for at least two seasons and maybe another off-season as well; it's a solid all-around program that will help get you in game shape. It's not going to make you into a stud by itself, and it's not going to kill you either (unless you try to do so to yourself very hard).
I've uploaded the .xls (excel) file here for download:http://drop.io/ultimateprogram
Some exercise descriptions are on the second page (book) of the file.
I'd recommend throwing in some sprinting/conditioning work to go with as others have suggested here (I would recommend against straight "cardio" in favor of good old-fashioned intense interval work in the range of 100-200m, perhaps starting with 400s if you have the willpower and really feel like your endurance is lacking). I don't buy not being able to do a lot for endurance in 6 weeks--people have gotten "in shape" in less time with enough hard work. (Which is, incidentally, the Most Important Thing with training. Do you want it enough?)
Incidentally, I subscribe to the theory that it's less "endurance" and more "recovery" that gives you staying power in ultimate--there's all sorts of breaks on-field, between stoppages from class to your man just chilling in the stack, and you get to rest between points too--train to go hard when you're on, and recover quickly when you're not.