For any IM vets who have done marathons as well. I know this is kind of a crazy question, but what are the time delta’s between straight marathon times and IM marathon times? I know that if you have major physical trouble such as massive upper or lower GI trouble that the whole conversation is moot. However if one is feeling reasonably “OK” I wonder what the difference would be.
For example. If a person is capable of running a 3:18-3:20 on fresh legs, given the exact same kind of training. Is a 3:45 a possibility (barring major illness)? Any opinions from the IM veteran contingent?
I think it has everything to do with how good a cyclist you are. I know that before I got strong on the bike, I would get outrun by people in tri’s that I could smoke in stand-alone running races. Also, I think how much IM experience you have has something to do with it.
I’m assuming this is your first IM… I’d say it’s possible but unlikely. I can run a sub-3 marathon, and I did 3:50 in my first IM marathon(and that was with only one minute of walking).
I don’t know that any rule of thumb really applies. I have heard that 30-45 minutes may be a rough guide. Of course, that gap is probably closer for the top guys. My marathon times are very close to yours and in 12 IMs I’d say 45 min is about right for me…that is the ones where I didn’t blow up:-)
I’ve heard +20% for the IM marathon - but I think most people run slower on IM’s. Personal records: 2.50 fresh legs & 3.16 IM. (But I think the 3.16 is a better performance.)
I have a friend who swears by 1min/mile difference, but I think it varies from person to person. His best marathon is 3:00 and he has run a 3:26 in IMHawaii, so I guess the math works for him (he is somewhat exceptional). I have ended up more like 1:15min/mile, maybe a little more. My opinion is that the more comfortable you are as a runner in an IM is dependent on your overall strength and fitness on the bike. I know a local athlete who is a 2:36 marathoner who has yet to crack 5 hours in an IM run. His cycling is his undoing. Everybody is different, but I venture to guess that if you are sufficiently trained, 1:00min/mile is exceptional, 1:15-1:30/mile difference more reasonable. How about looking into the comparison between your IM vs. 1/2IM run? My last 3 IM runs vs last 3 1/2 IM runs the IM came out to about 2x the difference of the 1/2 (1/2 = :40s/mile slower that 1/2 marathon pace; IM = 1:20/mile slower than marathon pace). I checked with a couple of training partners and they seem to all fall in the same proportion. If you never did an IM this may still be a good standard to work from, perhaps a little more practical than just using a running race time. Hope this helps. BTY here is the math, because I am not a math major I could make a mistake:
now all you need is a 1/2 marathon time, a 1/2IM split, and you can compare the difference, multiply by 2 and add to your marathon race pace and you have a number…I’m home sick from work, lots of time to kill.
I know anytime someone asks a question, they hate to hear “it depends” - but it does. I agree a lot with one post - it depends upon your cycling strength. A stronger cyclist is going to be a lot less fatigued come time for the run. Also, related to this, the bike course matters - the harder/hillier/more wind on the bike course, the less fdresh the lags are going to be for the run.
Despite this, I will give you my gut feeling (and this is assuming you are comparing apples to apples i.e. the marathon course and the IM marathon course share common profile, conditions, etc.). For your first IM take your fastest marathon time run within the past 2 years and add between 50 minutes and 1 hour 10 minutes. I did a 2:55 marathon in late 2000 and in 2001 did a 4 flat at IM Florida. Now, in a subsequent IM, the body has adapted a bit, the triathlete has learned a lot, and the delta should be less. I did a 3:00 in 2002 and at IM Canada did a 3:27. I credit a lot of that to stronger cycling skills, but also to learning pacing better for the IM. If you want to compare p.r.s to p.r.s - the delta for me is 38 minutes (2:49 / 3:27).
Oh one other method you may want to consider is using 1/2 Ironman times. Again, there is no “rule” or “science” but estimates based upon past results. I find that if you take what you consider to be your “good/solid” 1/2 IM run time (not necessarily your best) and double it, and add about 10 minutes you can be in the ball park. This method is right on to the minute for one of my IM’s and pretty close for others.
For my first IM, I looked towards my most painful, dissappointing marathon which was around 4:30. I figured that was indicative of what I could do when fatigued. My actual IM run was 4:45. Probably because during the marathon I started faster and blew up after the 1/2 way point. The IM run was pretty consistent as I was just tired and not really hurting.
I also considered my good marathon times which are around 3:40. Adding an hour to that yields nearly the same result.