It's not necessarily the "cross training" (Some seem to think a quick swim, a casual bike, and a fun 10 minute elliptical ride and you'll be a champ!) but rather the ARC Trainer itself. (Cybex used to distribute them but I believe Lifeline owns it now) I have used and trained athletes with the ARC for a decade now, mostly with sprinters and mid distance runners and have been surprised that the buzz isn't louder, as the improvements have been consistent and obvious. I believe that it hasn't caught on big time because of one reason -when used with high intensity, it is gut wrenching and I have had national level mid distance runners compare an ARC interval session (15 thirty second sprints, with a one minute rest between) as harder than any track workout they do. Obviously Valby is doing a longer type of session on it, being a 1500m-10,000m runner, but I can instantly tell she uses it. The power, speed, speed endurance, and pure endurance she shows are enhanced with one or two ARC sessions a week. Also, I have had athletes with a sprained ankle, sore achilles etc. , maintain, if not improve, track, basketball, soccer, football etc. conditioning with the ARC until healed. It also has enabled some ACL surgery athletes to begin some conditioning after two months, enhancing their strength and mental outlook. Obviously the ARC would have to be properly used, (once or twice a week seems best) based on your goals, but it is very challenging, (the adjustable resistance is hard to explain but lactic acid build up is quite immediate!)) is very natural to real running (unlike a bike or eliptical) and it has been very effective for most I have put on it in my small personal training pursuits. I have had sprinters go off of the ARC during the main part of the competitive season, but then go back on it, once or twice a week after season's end, supplementing their regular workouts. If you are on your own with the ARC, go to Quick Start, experiment with your knee height and resistance, and do gradually faster one minute on, one minute off intervals, for 20 minutes. If you are a beginner, check with your Dr. first, as it is quite intense! (Could you set the ARC at a low level of resistance and go for 30 minutes to an hour? Yes. I have seen people doing that at various intensity levels, but have not personally trained anyone in that way. Check with the trainers available, if you want to set the ARC to a preset 'program'.)