Concurrent training is the idea that you can train for two separate/non-matching goals at the same time, such as maximal strength and body composition, or in this case endurance training/maximal strength.
You see, my girlfriend Kelsi has been running every day of 2013 thus far. So far this year she's logged about 150 miles or so and her mileage will continue to go up as she trains for some races she has coming up. She's been weight training this entire time, and we've been keeping her programming simple. She get's to choose her own exercises every day as long as she fulfills some specific movement patterns (i.e. unilateral horizontal row, uni-lateral knee dominant, etc). You would think that with this recipe she would be losing strength every day, but that's not the case.
Just yesterday she pulled a PR of 225 for two singles, and smoked them. Her strength continues to go up as she continues to run more and more.
The secret here is not in any of her programming, but in her recovery. Kelsi does a great job of getting as much sleep as her schedule will allow (she's a trainer, so her alarm often goes off at 4:30 a.m.) and eating as much as she physically can. She has discovered that PB&J's make her feel great for her runs and allow her to pack a bunch of calories into a small meal. She eats cleanly as often as possible, but when she's low on calories anything goes.
The great job she's doing eating is evident in the fact that she's only lost two pounds since she started running every day. Her caloric expenditure is huge, so I was nervous about her losing a ton of weight.
As I'm writing this, Boston is finishing up getting about 30" of snow and Kelsi just finished a three mile run...in the blizzard. Let this be a lesson that you can do just about anything if you're willing to put in the hard work necessary.
Keep up the great work, Kels!!!
Have a great day, and go lift some heavy shit!