Old Injury Rears It's Ugly Head...
In desperate need of some MOJO guys 
I posted this in the macro thread for RnP's advice but also wanted to post over here to get seperate advice from my teammates who may have been down this road in the past and can help me out of my "funk". Thanks ahead of time....
Currently in week 2 of the Jan OS after a 6 week run focused block. Just towards the end of the run focus block I was beginning to feel an old injury coming back in the way of a medial stress fx in my lower left tibia. This injury was from a little over 2 yrs ago and really hasn't bothered me since. With the increase in intensity (at least compared to my earlier training plans outside of da haus) with EN and current body weight I feel the intensity may be a little too much for my body to handle structurally for the time being. This really sucks, because I feel that after the testing that I am where I need to be for training load and my legs (muscularly) and CV fitness are handling the load well, but structurally I'm breaking down in that one area with the run workouts. I know that as I progress and my weight gets down to where it should be the niggling goes away, I just haven't hit that happy medium yet (although week one of the OS I was down 5 lbs 
For the last 2 weeks of the run focus and over the holidays before the start of the JOS I switched out of the dry land running and backfilled with intensity focused pool running which I have had great success with maintaining run fitness in the past. Coming into the JOS, I was again pain free and began the JOS as such. My run testing was only approximately 30 seconds off of my best 5K time all of last season and this test was done on the treddie and not in a race situation.
As of yesterday's run which was only a Z1 35' run, the injury was beginning to show itself again by the end of the session. I am a very diligent icer when these things happen and did so after last nights workout and woke up virtually pain free, but I know that continuing down this path that once I step out on the run again I could inevitably be running into a bad place. Now, I know that IMLP is still a ways off, and is my biggest goal for the year as this is my first IM. I know that adjustments now (painful as they may be psychologically) will allow me to still have a very successful race as the injury is not a full blown stress fx, just a potential precursor to such, as I have been down this road before and know what a niggling pain is vs. the sharp intense pain of the full blown injury. Currently, my bike workouts are right on point and are causing me no structural pain in this area, so I do not believe any changes need to be made with this part of my plan.
So how should I proceed with the run workouts prescribed in the remainder of my OS plan? Should I split out my bike and run plans such that I follow the OSINT plan for bike and OSBEG plan for running? I am very comfortable with kicking my ass in the pool with run workouts, but should I replace all my runs for the time being or only specific ones? I have seen the aqua running plan in the WIKI and like the workouts listed there, but do we have a transition guide to pepper back in the dry land runs slowly to get me back up to speed?
Again, I'm just in the early niggling pain stages of this injury and would rather use good judgement now than to put myself in a bad place later. For me it is wicked hard to step back when everything else is running so smoothly, but one has to learn to listen to their bodies - even if you don't like what it is saying to you...
Any and all suggestions are greatly appreciated 
Comments
I started the Nov OS with an injury and did the beginner plan. At 8 weeks I switched to int for the bike wko and stayed at beginner for the run. My injury continues to improve using this strategy, despite run and bike fitness reaching (subjectively) 12 month highs.
I presume you have researched and attended to any underlying cause of your shin splint/stress fracture problem i.e shoes etc?
A little pain here and there during a workout that persists for a day or three and doesn't get worse or persist at rest is a niggle. Anything more is an injury. I think you are right to modify now and prevent your niggle from becoming an injury.
FWIW I have been down a smilar road before (more than once, unfortunately). In my experiences once I need to ice something or take medication it is an injury which will not get better without time off. Training through the pain with icing etc usually lands me in an extended layoff. Therefore, over the past couple of years I have decidied to stop NSAIDS AND icing . In my opinion if something hurts enough for these measures it is an injury that requires rest and healing, and this is especially true when your event is still several months away.
See my comments below
Should I split out my bike and run plans such that I follow the OSINT plan for bike and OSBEG plan for running?
You could do that, as Satisha mentions above, but there is still intensity in those workouts and it sounds like you need to stay off of it until it heals.
I am very comfortable with kicking my ass in the pool with run workouts, but should I replace all my runs for the time being or only specific ones?
I would say yes to this one, then when you have no pain, I would try a run workout, but only 15minutes of it on the treadmill or outside and the remainder of that run in the pool. I would do that for one week. If you get no pain, I would go up to 20min on road remainder in pool, adding 5 minutes per week until you up to an hour of Z1-2 and then I would try to add in the intensity, but by little chunks. I would not jump into a plan mid plan. I would go back to the start of that plan for the run workouts. Does this make sense?
I have seen the aqua running plan in the WIKI and like the workouts listed there, but do we have a transition guide to pepper back in the dry land runs slowly to get me back up to speed?
See my comments above. I had tendinitis last year and had to water run for 5 weeks. Once I had no swelling or pain, I did the above. I was able to run my half marathon in my HIM and it has stayed away since.
Thanks for the advice thus far...
SO! After all that back story, here's what I've learned:
#1 - This team is amazing and you will have TONS of support and mojo. See here when I panicked before IMNYC: http://tinyurl.com/9wwcjhq
I posted this pre-broken foot, but after the foot happened (conveniently 4 weeks before IMNYC), I LIVED on the elliptical. I ran only ONE time in those four weeks - about 3 miles of a 5:1 run:walk plan - the week before the race. I made it through the IM marathon with a solid run-walk plan (which I would've done anyway b/c that course was a hilly b*tch). Luckily I wasn't planning on winning my AG that day anyway. ;-) Luckily, you have TONS of time before IMLP to get this figured out, which brings me to...
#2 - Make it your JOB to figure out why this is happening again - like Chris and Satish said... Is it a tight or weak calf? Weak abductors/glutes that are throwing off the kinetic chain? How is your cadence? Are you heel striking? Addressing the symptom with ice and modified training is one thing, but getting to the bottom of it will save you a world of pain in the future. A gait analysis is worth its weight in gold and is an investment in your future training/racing self. Totally worth it if you haven't done it.
FWIW, I put myself in the OSBEG plan to ramp up slowly and avoid re-injury. I know how frustrating it is to be forced into the pool for water running when things are going so well, but you absolutely made the right decision for the time-being. Keep us all posted!
after IMFL, took 2 weeks of ez stuff before I jumped into my first ever Run Block.
Went great, good starting vdot, TP intervals were very sustainable. The LAST week called for some Target 5k Pace intervals that I got greedy on and I popped my calf.
For the 3rd OS in a row.
Within days, a 'shin splint' with swelling shows up. Post Tibialis Tendonitis vs Calf Strain vs Fascia Prob vs Stress Fx....whatever, they're all on the Minimal Treatment & No Impact Allowed Plan. Thus MEGA biking, more than usual January swimming and CRAPloads of Deep Water Running with the aquajogger belt (hi intensity laps and long & steady intervals)
From experience, I know that this will take about 2-4 weeks for me to recover, if I stay off of it now. If I keep 'testing' it once a week, I'll be adding weeks to the recovery time. Despite knowing this, I've already done it one time
too much in common here to bore everyone else with. if you want to chat about it, pm me your number and I'll give ya a call.
I don't know if I gave any mojo, just wanted you to know that you are not alone. IM looming and clock is ticking. We can't think about that. Take care of what we can take care of today, only today. We'll be back running in plenty of time.
I will PR this IM mary, mark my words.