Fitness is about recovery, and not getting injured while trying ,to attain a solid Vo2 max threshold. Ive found the best way of doing this is Horizontal.
your idea of doing cardio horizontal is masturbating laying on your back... yeah i finally get your horizontal workout
Seeing as your talking about a pro boxing, (assuming 10 or 12 rounds), i think those statements are just wrong. I believe a 12 round fight is a predominatly aerobic event that requires a very high anaerobic threshold/system as well. Also, there are plenty of boxers who run 5 or more miles, and have execellent physiques. Running 5 miles doesn't nessicarily mean your body will use muscle mass as fuel. This sounds more sensible... You just need to ensure you work/build both energy systems in your training. People do it in different ways. Eg: long distance runs for aerobic, interval bag/pad work for anaerobic. Also remember, as pros train for a fight, they would periodize their training to the fight date. Long distance to start, to work that aerobic base, and then as it gets closer to the fight, switch to alot of intervals/spirnts etc to lift recovery rate and anerobic systems.
You wont be able to get on it fast enougth. Funnily enougth, Ive just got hold of the Physiolgy results on it conducted by Sheffield Hallam sports science department. Working at 140 HR the body produces 35% more lactic, than running or Treadmill. While working at Vo2 max it produces 22% less lactic, this is without impact, interesting yes.
