I get this question most frequently from golfers who want to deconstruct their swings, which is essentially the same task. Until recently, however, there hasn't really been a good answer. But Sony's recently introduced DCR-DVD505 camcorder has a new feature called Smooth Slow Recording, which captures 3 seconds of video at 240fps and plays it back at 60fps. Because tape can't record at variable frame rates, we've only now begun to see products--tapeless models that can record to DVD, SD, hard drives, and so on--that offer this type of flexibility. As far as I can tell, the DVD505 is the only consumer model to offer it; the Panasonic AG-HVX200 is capable as well, but I suspect $6,000 is outside your definition of economical.