There is no real climbing in Chatt. You can ride the entire course in aero, if you are average to above average cyclist.

The elevation profile is very misleading. Yes, it says something like ~4k of climbing, but all but 2 hills, you are rolling all the way up on them because they were proceeded by rolling down a hill before that. The 2-3 hills where you are not rolling all the way up, you are probably rolling 75% up on them. It a fast bike course.

The run, on the other hand ... be afraid. Be very afraid :)

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My marathon PR is "under three, high twos. I had a two hour and fifty-something."

Just did Chat at my 1st and I'm an average cyclist with no hills to train with. The hills at Chat were fine. There were 2 longish climbs but that was it.

It was a fast course up and down the hills... The run, not so much :)

Another plug for Chatt... I only went small ring on the second loop this year, because I thought I was over cooking it and was trying to conserve energy. First year I did the course, I never moved the front from the big ring. Yea, it's 4500 or so of climbing, but its FUUUUNNN.

I talked to another athlete on the course that said Boulder is very similar though, other than the starting elevation.

Unfortunately, the momentum from coming off the bridge doesn't carry too far up the hill on Barton during the run though

Both have their for and against reasons.
I raced Boulder in 2015, and Chattanooga in 2014 and 2018 (last weekend).
My take for a newbie.

Boulder // https://www.facebook.com/...ps/1533666713416165/
Less challenging bike ride.
Could be HOT on race day.
Early spring = more indoor training needed.
Rez swim. Might be wetsuit legal and no waves, but rolling start and crowded.
Some of the run is in NO shade.
Altitude becomes an issue in high heat and if you are pushing red line during the race.
Could be 1, 2 or who knows how they will work transition. Point to point usually from start to finish.
IM village is downtown Boulder, but race is at Rez and can be time consuming to go back and forth.
Housing easy to find, but may not be convenient location.
Sort of spectator friendly.

Chattanooga // https://www.facebook.com/groups/154018848532000/
Down river swim unless it gets canceled. First time was this year in 4 races.
Bike course has rolling hills. Couple of big climbs, but short.
Some of the run is in the open with no shade.
Can be HOT, HUMID, or both. Weather will be a crap shoot.
Late year allows for more outdoor riding for training.
Course support is awesome.
1 transition. Finish is by the start. Makes getting gear after much easier.
IM village is right by transition. One stop for pre-race running around.
TONS of shops and restaurants by IM Village and places to stay. You could stay near village and not need a car all week.
Very spectator friendly course.

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Ryan
http://www.SetThePaceTriathlon.com
http://www.TriathlonTrainingDaddy.com
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