"Back-to-Back" Swims as Training?

If I'm comfortable doing a 3 mile swim one day and another 3 the next day, am I ready for 6? Yes, you'll be fine. In fact when I did my first 10K in 2010 I found that a 10K is just a longer & slower 5K with a few refreshment stops along the way. However, if you truly race a 5K hard and try to do that for a 10K with no prior 10Ks under your belt, I think you risk blowing up and DNF. In 2010 I swam a 10K on 2 successive days and found the last 2K on the 10K very challenging even though I was swimming slow.

I've noticed that I can race for about 2 hours without feeding and then..... crash; so, for anything longer than that I make sure to have something after 1 - 1.5 hour. Personally, I would do one long swim per week, building up to 10k (or more) before October. You have plenty of time for that. ANother favorite is 100x 100 on a short rest interval.

Why don't you do a long swim every week, or every other week? Just like a build-up for a marathon in running, I've been slowly increasing my mileage on my weekly long swim with a step-back week every third week. I did a build up this spring (over about 4 months) from 4K to 12K as my long swim... sounds like you have plenty of time to get ready before your 10K, you could do it. And unlike with running I find I'm much less "beat up" the day after a long swim than I used to be the day after a long run, so you could actually swim your distance before the big day and have that added confidence.

Here's my question. I'm trying to see which of my training habits from other sports translate well to swim training. Specifically, I also do ultra-distance trail running, and when I am comfortable doing a "50K weekend" (30K Saturday, 20K Sunday) then I know I'm ready for a 50K race. Will the same be roughly true for my swimming? If I'm comfortable doing a 3 mile swim one day and another 3 the next day, am I ready for 6? I think this might apply to ultra-distance swimming, but not to a 10K, or even a 10-mile swim. I agree with the others that you gradually build to a 10K training swim before the race. If I make a list of pros and cons for that, I get all pros and no cons. A 10K training swim doesn't take that long (even for me), so the scheduling should be manageable.

Thanks everyone for the good advice. David I see you're also in the Hudson Valley, where? I live in Hyde Park, NY and will start swimming at Minnewaska soon when the open water swimming starts.

A 10k swim is more like marathon training. Building up your long swim. I agree with this general thought, although I'd say that time-wise a 10K swim is more like a 16-mile run than like a full marathon. It's a distance that you can and should (IMO) work up to completing or exceeding in pre-race workouts, whereas many pretty decent marathoners rarely if ever do long workout runs more than 75-80% of the marathon distance. Having done both, I also will say that a 10K swim is far less traumatic on the body than a 26.2-mile run. Recovering from a 10K swim is easy enough that you can do that distance or more in training, albeit perhaps at a more modest pace than you would in a race, without totally ruining subsequent workouts.

A 10k swim is more like marathon training. Building up your long swim. 10miles or more you need to move closer to something like ultra run training.

I agree with this general thought, although I'd say that time-wise a 10K swim is more like a 16-mile run than like a full marathon. It's a distance that you can and should (IMO) work up to completing or exceeding in pre-race workouts, whereas many pretty decent marathoners rarely if ever do long workout runs more than 75-80% of the marathon distance. Having done both, I also will say that a 10K swim is far less traumatic on the body than a 26.2-mile run. Recovering from a 10K swim is easy enough that you can do that distance or more in training, albeit perhaps at a more modest pace than you would in a race, without totally ruining subsequent workouts. This is my sense of it too; I got to the point that I could do a 10K pool swim continuously week after week (for me I think it was equivalent to more like an 18-22-mile training run in terms of time, but more like a 12-15-miler in terms of stress on the body)... but moving out past that was a little more challenging--12K (7.5 miles) seemed like a torture in the pool. Now that I know I have the endurance for a 10-miler (potentially; I hope that 75% thing works), I'm spending some time getting re-accustomed to swimming in the lake w/o lane lines, clear water, etc.... that's another mental adjustment! Any advice from folks who have trained for a 10-miler?

Any advice from folks who have trained for a 10-miler? We practice associating and dissociating as mental strategies for the race this is the biggest change I and the people I coach work on. kpjoubert.wiki.zoho.com/Associating-and-Dissociating-Practice.html I suggest working on associating skills during the race until you can't take the pain and then go for dissociating to get through the tough spots, or when the internal dialogue goes very negative. Also along with that is nutrition, I use 1.25 cals / lb of body weight per hour in the form of maltodextrin mixed into gatorade to make 600 calorie 24 ounce bottles. Others do it differently, but the necessity of nutrition and the effect it can have on performance is another huge change from 10k to 10 mile.

Thanks everyone. good advice. I just swam 4.1 miles yerserday and felt fine then and now. Will do the 10K distance before my event as you all suggest to get the full feel for the distance.