Hi Mark,

I've never heard of BSXInsight.  Sounds awesome if it's even close to accurate.  In my opinion, if you truly know your real lactate threshold, that is much better than following an equation.  Having said that, MAF training for racing I've found to be really great for building an aerobic base.  Remember that even elite marathoners run a vast majority of their miles at easy pace/ low HR.  Even Maffetone concedes that once you've built a solid base that some speed work is in order.    Knowing your threshold will be great for the speed work you do in training and especially while racing.

I'll attempt to answer some of your questions but I will caution you that I'm a newbie runner.

"I recently purchased a BSX insight and found my LT1 hr to be 141 (substantially higher than the 121 I have been training at).  I plan to to do an October 1 marathon.  I am not sure I could handle running regularly at 141 without getting over trained."  -- If you're trying to prevent overtraining, then you've come to the right place!  Just out of curiosity, what does LT1 refer to?  Is that basically your 60 minute threshold?  Assuming it is, then if it were me I would probably stick to running most of miles in the 120 bpm range whether I'm doing speed work that week or not.  No one can run at their threshold all of the time.

"Do you recommend that I spend some time at the faster hr and recover at the lower rate?"   -- I would absolutely recommend that.  With your heavy mileage and your 10 minute mile pace at 120 bpm, you have a pretty solid base.  I'd make sure at least 70-80% of my time was spent at or below MAF and the rest at or faster than target marathon pace (preferably at the end of the long run).  Perhaps BSXInsight can estimate approximate marathon pace for you?

"Should I base my marathon pace off of the pace at 141?"  -- That depends what LT1 is.  Most often threshold is referred to your maximum possible effort that can be maintained for 60 minutes.  If that's true, you will bonk in the marathon very early at 141 bpm.  Marathon pace, like everything else, seems to be a function of your maximum heart rate so that would imply your maximum heart rate is very low.  I know it can drift down a bit with age but I wouldn't trust the 220 formula as it's highly individual.  For what it's worth, there is a great thread on the LetsRun forums relating max HR to marathon pace.  Here is the link:  http://www.letsrun.com/forum/flat_read.php?thread=1185107

A couple of closing comments.  You sound super fit.  That's a really fast pace at that HR.  Wow.  Also, I wouldn't get discouraged by a slow MAF pace.  The beauty of MAF is forcing you to run easy miles which trains your body to burn fat for fuel efficiently.  If you have a higher max HR like I do, you will find your MAF paces to be very slow but this doesn't matter.  For example, my race paces (including marathon pace) are significantly faster than my MAF pace.  One other point, I would suggest starting to practice eating on the long runs.  I did exactly what you did (no food or water before or during runs for months) and ended up with awful GI problems in my last marathon.

Hope this helps!

Hi,

Thanks for the reply.  My LT1 is 141, this is the upper limit of running aerobically.  My LT2 threshold hr is 158....is the rate I should only be able to sustain for an hour....

 

i will I'll probably resume a course le Saturday group runs and try whatever sport drink they are using.  I went early in the summer and was he last runner....very early in MAF training...

 

Thanks for he encouragement.  I'm delighted that at age 59 I can run this many miles and feel great,  I do wonder though, after a 20+ mile long run when  my Garmin tells me I need a 16 hour recovery!

 

Marl

Ok, that makes sense.  There is a pretty good way to predict marathon pace on a flat if you know your functional threshold pace.  You have everything you need to know right now to calculate it.  Here is how to calculate it:

1. Step 1 is to find functional threshold pace (FTP).  Since you know your LT2 threshold is 158, you can go to a track, warm up for 15 to 20 minutes and then run as close to 158 bpm as possible for a few miles or so. Your average pace at 158 bpm is your current FTP.  You can repeat this test every 4 to 6 weeks as it will likely improve with good MAF training.  Be sure to get a new value for LT2 heart rate each time first.  Also, if you use Training Peaks, they calculate and update your FTP for you.  
2. Calculate Marathon Pace.  Use the following equation:  Pace = FTP*(minutes_racing / 60)^0.06.  As you change the variable that I call "minutes_racing", Pace is very close to what you can sustain for however many minutes you chose.  The limits that this equation is valid for a typical runner conditioned to run the marathon is between about 2 minutes and 225 minutes so you can likely predict race time finishes for the 5K,10K, half marathon, marathon and any distance in between.  I put this equation into Excel and plot the entire range in a handy graph.  For example, if you input your FTP that you found from step 1 and 210 minutes into "minutes_racing" and Pace ends being calculated at 8:00 then you are reasonably sure that you are capable of running a 3:30 time at 8:00 pace.  You do have to find the point where pace intersects distance and time but that's pretty easy to do by inspection.  

Remember that this will give you the pace you are capable of on a flat.  You will have to adjust for hills and other factors.  But at least you will be armed with the knowledge of what pace you can maintain for just about any period of time.