Lindsay Kos is one of five Boston Marathon entrants testing the Polar RCX5 personal training computer and blogging about it for Boston.com.

By Lindsay Kos, Boston.com Correspondent

These next seven days are all about mental and physical preparation: just dotting the i’s and crossing the t’s on this wild ride of a training cycle. Keep the legs fresh and fluid, get in a bit of extra sleep, and hydrate while fueling with quality foods.

"The hay is in the barn," or so the saying goes.

More importantly, this week is the time to build up the layers comprising your tough mental exterior, the one that’ll slowly wear down on the streets heading to Boston, mile by mile. Start now to visualize your race: the good moments, but more importantly, the bad and ugly ones.

Those times will inevitably hit, and you’ll need a strategy (or several) to pull yourself out and push forward with confidence. After living in a state of ignorant bliss last week, I’m now accepting that this marathon is right around the corner and it’s going to hurt like heck. But if I can push through the doubt and handle the pain, the payoff will be worth every single minute and second of fighting for my sub-3:00 goal.

Last Thursday was a final tuneup workout to get the legs moving at race pace and start to thicken that mental exterior. The workout on tap was a continuous 6 miles: 2 at marathon pace, 2 at half-marathon pace to fatigue the legs a bit and simulate the middle miles of a race, and 2 back at marathon pace.

While our paces were all a bit faster than expected (no surprise for taper week), it was fascinating to see the ebbs and flows of my heart rate as we rolled up and down hills and transitioned from pace to pace. Not surprisingly, the last two miles at marathon pace didn’t feel as comfortable as the first, a sense affirmed by the unarguable stats.

Over the last few weeks of training with the Polar RCX5 and customizing the interface more thanks to Robin’s post, I now have a better sense of my heart rate ranges that correlate with paces and exertion levels. Now, if only it’d hold me back on the starting downhill miles of the marathon….

Thanks for following along on my journey these last few weeks, Boston.com readers, and an even bigger thank you to Matt and the Polar team for allowing me this wonderful and unique opportunity to train with the new Polar RCX5 system. I invite you all to check out my personal blog lindsayruns.com to continue following my training and racing; I certainly can’t wait to analyze everything after I cross the finish line on April 16th, hopefully with a big smile and new PR.