Long-distance racing makes you slowly. Since MACCA decided to go for the Olympics he had to do quite some adjustments of his way of training. It may sound bizarre to you, but the Ironman distances make you slowly, your reaction time slows down, swimming looks almost lethargic, and running is controlled. On short course swimming is just fast beyond fast. On the bike the guys try to safe energy for the run, because the run takes it all. Plus the crucial difference that drafting gives the race a totally different spin.
For this reason and for the matter of age Chris changed his approach to training. He extended the weekly training rhythm for the sake of recovery, and does more speed work now for stimulating more and other muscle fibers much faster, altering the patterns of neuromuscular recruitment. Boxing is an excellent method to achieve that.