I have a question for some of the physiogeeks around here.
For the past couple months I've been training at a boxing gym. There are quite a few female boxers there who are very serious about the sport and pretty much train all day every day. They all have amazingly muscular bodies, sort of like slightly stockier, less sculpted off-season figure competitors. This seems contrary to most of the advice I've seen about muscle building. That is, they all eat in a caloric deficit (to make weight class).
They train for hours and hours every day, pretty much always keeping their heart rate up, and always training the same muscle groups daily without allowing time for recovery. Everything is light weight/high rep (though they do reach failure). They do a ton of cardio. Yet, they're ripped. Is there an explanation for this?