A couple of years ago I ran my first back-to-back marathons, the Kansas City Marathon on Saturday, and the Des Moines Marathon less than 24 hours later on Sunday. In preparation for the events, I began running back-to-back long runs during the weekends prior. Now, I'm training for my first ultra marathons and I am using this method more than ever. But I've found it to be a very useful tool even when I'm not training for specific extreme endurance challenges.
I actually began running the day after a long run about three years ago. I just found that when I ran 4-5 recovery miles the next day after an 18-22 mile run, my legs just responded better throughout the week. I would always take it slow and even walk a little on the second day. It was really more of a glorified "get some blood flow to the legs" training session than anything. It just helped me not stay "stoved-up" too long after a long run. But I found that as I really extended the mileage on the second day, I became a much stronger runner.
First, running back-to-back long runs teaches my body to run on tired legs. Anyone who's in decent marathon shape can go out there put together a good long run on fresh legs. This past summer, when I was in the best running shape of my life, I could burn through a 20 miler with no trouble at all. But just like everyone else, I'm pretty tuckered out and energy depleted the next day. Getting back out there and completing another run of sizable distance the next day forces me to focus, and paints a more realistic picture of how my body will respond in the late stages of a race.
Also, back-to-backer's force me to manage my pre, post, and during run nutrition effectively. Typically I make sure I recover with a ton of food & fluids after the first day. I try to put as many of the calories back into my body that I lost during the initial run. However, one of the common training techniques for ultra runners is a glycogen depletion run on the second day. Basically, it's simply not recovering from a nutrition standpoint as you typically would after a long run on the first day, and then forcing your body to use more fat stores for the run on the second day. The theory is that it teaches your body how it will respond with little or no remaining glycogen stores late in a race. I've tinkered around with this method a little, but will probably use it a lot more as my ultras draw nearer.
And finally, I've found that back-to-back long runs help me build a mental and physical toughness that I need to compete well in long races. Mentally gearing up twice in the same weekend makes me feel like I've got an edge when I step to the starting line for "simply one long run". But more importantly, it teaches me to fight through little dings, nicks, and aches and pains from the first run. I'm always mindful of true injury and don't run if I feel like there might be serious damage. But usually I loosen up a few miles into the run after I've "toughed out" a few achy initial miles.
Two long runs in one weekend might not be for everyone. I would always recommend starting slow and building up. And they are not really what I'd call a "fun time". In fact, as I sit here writing this, I have the second of two long runs in about 3 hours after running 23 miles yesterday ... and I'm kinda dreading it. But I know if I'm gonna successfully complete my upcoming ultras, I've gotta get the work in. And back-to-back long runs are the cornerstone of my ultra marathon training. So here goes. Have a great week!
(P.S. Just got back from my second long run. I'm dead. But I got in 23 miles on Saturday and 18 and Sunday all without the help of PED's, B12 Injection, Steroids, or Blood Doping. Wow, amazing.)
... be great today!