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I traveled to Costa Rica for a week in August, my birthday immediately followed, and then just a couple weeks ago, I sprained my foot walking across a New York City street.

Life is unpredictable, and even though my training plan is cut and dry and right there for the doing, sometimes injury, busy work schedules, family obligations, or pre-planned travels make sticking to the plan nearly impossible.

Instead of getting discouraged, I took the opportunity to figure out what to do and see how to jump right back in after a missed workout or even a week off by turning to Andrew Allden, my coach with Team USA Endurance, the official running U.S. Olympic team for the NYC Marathon, for words of wisdom.

As he says, "Folks often deviate from a plan." So if you're keeping up in general but missing just a couple days, you should be okay. "For example, if you get in three days instead of five, do the hard days only," says Allden, who is also the women's cross country coach at the University of South Carolina.

However, if you go cold turkey for up to a week or two, the impact is obviously going to be different. "If you've missed five days to a week, start with an easy day but return to where you left off pretty quickly," he says. But if you've missed 10 to 14 days, you'll need about a week to return to normal. More time than that is when you need to worry.

And be sure you're not adding fad or experimental-type workouts to your plan, as these can impact your existing training negatively or cause injuries, Allden cautions. You also can't make up for missed training at the last minute. "Once you get inside 14 and certainly 11 days before a marathon, you should be tapering, not trying to make up for long run you missed two months ago," he says. "It takes 10 days for a workout to register in terms of fitness, so anything inside of 10 days adds to fatigue and not fitness." Remember, it's a marathon, not a sprint, and your training should mirror that.

If there's one thing to keep in mind, though, the golden ticket rests in those long runs. "In case of marathons, a long run takes priority," Allden says. Granted, skimping on cross training and shorter, endurance-focused runs will not improve your speed and strength, but if it's a matter of not training or doing the minimum, long runs are what it's all about.

Do you need extra motivation to stick to your plan? "You can maintain fitness during a low or reduced period of training but not improve it," Allden says. So yes, you'll be able to finish if that's where your fitness level currently is, but if you slack off and let other things take priority over your training, you're cheating yourself out of an awesome finish. Sure, injuries are tough to get around, but if it's anything else you're considering, just imagine that feeling as you cross the finish line having been able to run the whole thing-or better yet, PR-and go with your training.