How do you work in 'tune up' races to your training schedule? (Read 481 times)

Seems like running 'tune up' races before you run a marathon is often recommended. Makes sense - it gives you a chance to gauge your fitness, to get a better idea what a good marathon pace will be for you, and to get in some good times while you're in good shape, so as to not 'waste' all that training on just a single race (the marathon). My question is: I've got my training schedule all set up which I try to follow religiously. How do I work a race or two into that? For example, my routine now is to take Fri off, run Sat a middle distance (10 mi), and then a long run Sun (~20). If I decide I'd like to run a 10K on Sat, what is the best way to adjust the schedule? Does it just 'replace' my easy 10 mi run? Seems like it wouldn't be a good idea to run 20 mi the next day! Do I rest that day, and basically end up with 24 fewer miles than planned? Seems like a steep price to pay (in miles) to run a 'tune up' race. Is there a better way?

Same as mikey here. Last weekend I ran a 15k race on Saturday and then 17 mile long run the next day. Took and extra mile or two to get the kinks out - but it was the best long run I've ever had in terms of time/pace/distance and how I felt afterwards. I've run five races during my marathon training so far and just use them to replace other runs.