Marathon tougher than HIM ??? (Page 2)

Apples and oranges.  Plus, harder how?  Length of recovery time?  Difficulty in executing your fastest time?  Suffering during the race?

Either one can be harder depending on how you define it.

Sure.  A 3:10 Marathon racer should have no problem breaking 5 hours in a HIM.

A 1:48/100 swim, 20.1mph bike, and a 1:35 run with 2 min transitions gets you 4:59:49.  

I don't think it's a stretch to say someone that can run a 3:10 marathon is capable of that

Again, it's not a fair comparison if you're not in comparably good shape for both and are racing both at all-out capacity. 

But if you are, it's very clear from the practices of pro marathoners as well as pro long-distance triathletes, that the marathon is significantly harder on the body. To the point of breaking it if you are truly in shape and pushing it to the max. Point illustrated is that there are NO professional marathoners who will race marathons more than a few times a year, and there are NO pro long course triathletes who even do marathon races at any point in their training, whereas they'll definitely do HIM races as part of their tuneup for IM. You will even see a fair number of pro triathletes doing open half marathons as tune up races for their A race, but you will not see them doing marathons as it is too much of a toll on the body if raced all-out.

This question comes up about once a year, and the answer is always near unanimous.  

This table should give you a good idea of what you may be capable of for an HIM run - assuming the training is there, and you didn't over cook the swim or bike.

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I have trained for a half dozen Marathons and actually run two of then (two I trained for were canceled and some I just never signed up for because life got busy).  Preparing for my first 70.3 I found this thread to be very interesting.  

I did my 70.3 last week end as my first Triathlon I have trained for.    I however did a sprint Triathlon 7 years ago and a duathlon 14 years both with no training. They were both just a fun cross training workout.  When I started training for my 70.3 that I just completed I took it seriously and put together a 4 month training plan that I followed very diligently like I have for all the Marathons I ran.  I feel my preparation for my Marathons and my 70.3 were very equal.  The intensity of my Marathon was a lot higher though.  For a marathon my effort is probably 5% higher on the lactate threshold % than I am at in a 70.3 Triathlon.  For me it is easier to do 5-6 hours at the 5% lower effort than 3-3.5 hours at the higher effort.  

Well...I am 4 days into recovery from the 70.3 and I still have sore calves.  I guess that I shouldn't have pointed my toes to kick on the swim.  I though the bike and run were going to take the biggest toll on me so I focused on them in training and went light on swimming.  Turns out the swim is what caused the most post race time for recovery.  Who'da thunk?

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No, it's not even remotely close to a purely academic argument. 

The pounding of 26.2 miles run as hard as you can is a really big deal. Like super-high injury risk deal, to the point that no professionals in open marathon or triathlon do more than a few "A" races at marathon distance a year where they really go all out. If you go into the marathon thinking you'll both train and race for it with similar risk to training for a HIM, you'll be at significant risk of an injury, whether it be a stress fracture, or bad tendon/ligament strain that sidelines you for weeks if not months. 

The duration of the race is not as big a factor for injury risk. It'll tire you out, and you may be even too tired to keep going, but it won't break you like running fast for too far will. That's another reason why there are no events like the running "Tour De France" where you'd have to run like 10 marathons in a row on 10 consecutive days. The best running pros would not compete - too much risk for career-ending injury in something like that, even if they have the cardio and endurance to do it.