ive noticed that some of the top guys in ironman do appear to be quite muscular. does carrying around that muscle fatigue them much at all? or do people think it is neccessary. also interested in it from my own perspective as ive done a fair amout of weights over last 8 years…so just wondering if this is all built from weights or is more of their ‘natural’ body shape.
I don’t know if I’m the best guy to answer this but while you wait for a good answer, you can read mine 
I don’t think the top pro’s say “I need bigger muscles to go faster”. I think it’s more likely that they say “I need to go faster”
I believe that their muscles are a product of their training to go faster. They may believe they need to be stronger to go faster, and train to be stronger, but I don’t think they specifically train to get bigger per se. I think their muscles get bigger because they train to get stronger/faster. I don’t think they train to get bigger, and hope that makes them faster.
I’m a fat little bastard. I don’t train to get slimmer, I train to get faster. This is very lucky because even though I’ve been doing tri’s for 11 years now, and done 4 IM, I’ve managed to get faster just about every year (I’m at my fastest right now) and I’m heavier than I’ve ever been. I raced my first IM in '95, age 34 and weighed about 75kg I did 14:21 on a very easy course (Esprit Tri in Montreal). Recently I did IMNZ at 85kg (that’s 22lbs heavier!) at age 43 and managed 13:04 on a much tougher course on a much harder day.
I don’t care how fat I get (within reason,given the health drawbacks of excessive weight) as long as I can keep getting faster at tri’s.
TriDork
At the rate I’m going, I expect to be 100kg (220lbs) by the time I’m 55 and win my first IM!!!