jimmyb -  This is awesome!  Thanks for posting this and your feedback.  Curious, what was your level of aerobic fitness when you did the test?  Was it before a training cycle?  Would it be helpful to re-do the test throughout a training cycle to see if/how it changes?

SD_BlackHills - I'm with you on the 30 minute test - longer than 5K but shorter than 10K.  I really don't like 5K's, so I would dread having to do this test.  However, if I ever tried Friel, I'm sure I could suck it up and do it.

 

jimmyb -  This is awesome!  Thanks for posting this and your feedback.  Curious, what was your level of aerobic fitness when you did the test?  Was it before a training cycle?  Would it be helpful to re-do the test throughout a training cycle to see if/how it changes?

 

SD_BlackHills - I'm with you on the 30 minute test - longer than 5K but shorter than 10K.  I really don't like 5K's, so I would dread having to do this test.  However, if I ever tried Friel, I'm sure I could suck it up and do it.

Hey Bert-o,

I was not very fit at the time. My age was 48. 180-48=132 bpm. My MAF in the test was 142 bpm. The fat/sugar ratio plateau extended from 130-142bpm. I like to call that my MAF range.  The 180-formula fell into that range, but wasn't exact with the deflection point, even with 5 beats added, but was exact in terms of getting it in the range.

I figure the same thing is happening anywhere in that HR range. Whether I'm running at 130 or 142, it's the same fat/sugar ratio. I do believe my MAF is about the same now at age 56, based on breathing. I find that 130 bpm, working at the lower end of the MAF range for most of my aerobic work, is just as good as working at 142. Less stress as well. When and if I find another guy to test me (need the RQ info)---the one that tested me came to the house, and no longer does it---I might try it again to see what's up.

I once tried to buy the software and equipment, but they wouldn't sell it to me---I don't remember the reason....I wasn't qualified somehow. I wanted to be able to experiment with it for a few reasons. I've had a question that I've never been able to find the answer for:

 If I run at the same intensity for let's say two hours or more, does my sugar/fat burning ratio remain the same even though my heart rate rises?

For example, if I establish a pace at MAF for 30 minutes and I'm burning 62%fat/38% sugar, then maintain that pace for another 90+ minutes, my heart rate will probably rise 10-25 beats depending on the temperature and fitness. If my fat-sugar ratio remains the same, am I not still running at MAF in terms of fibers,  and aerobic vs. anaerobic energy systems?  If so, is it only important to establish a pace at MAF then hold that pace regardless of HR drift.

I was hoping to figure that out myself. Along with keeping track a few times a year to see if the MAF changed at all at different levels of fitness.  I figured if I could get the software for a thousand dollars, I'd save money in the long run. Hopefully, an app will come along for the layman to do this cheaply.

I've always had this enjoyment in experimenting, stats and data collecting with the running. I wish that Dr. Phil would have taken it further in terms of scientific study (beyond the strong anecdotal evidence), laying it out just exactly what is happening in terms of muscle fibers, energy usage, and heart rate. Why is there a plateau that defines the deflection point that is MAF? Why is there a leveling off of Fat/sugar burning for an approximate 10 bpm spread (in my case) before the quick rise in sugar burning? I understand that the rise is due to the recruitment of type 2 sugar-burning fibers, but don't understand the plateau.  I don't understand the plateaus in HR that happen when I do a treadmill test during which  intensity increases incrementally.

I keep searching for the answers, but  can't find any. Perhaps, as a runner, it's not really important.  In terms of keeping it simple, it really all comes down to whether or not I'm improving at the same aerobic HR, and am feeling good at the same time--staying healthy.

jimmyb - Interesting you were not very fit during the test.  I've read that proper training (endurance) will help create more fat burning enzymes in your body, so based on that I (would guess) that you should push that 62% / 38% fat / sugar burning ratio higher in the HR range, which is why I was curious about retesting through training.  Too bad that guy no longer does the tests anymore.

SD_Blackhillls - I agree it would be nice if there were an affordable product out there to test yourself.  That data is incredibly insightful.

I just finished my first 50K race.  I used HR to help guide my pace and effort, although I didn't follow through with my plan very well.  It didn't matter because I had a successful day.  You can read my race report -> HERE  But here's a summary of my HR data from the race.  The Avg pace and HR are for each race segment (not cumulative).

You can see a bit of HR drift during 21-30K segment, but then I slowed down and my HR went down a bit.  I attribute this more to do with mechanical issues (stiffening hamstring).  But even aerobically, 5+ hours of continuous running is a long time.  My fat to sugar burning ratio must be pretty good though.  I really never felt like I was running out of energy and didn't really consume very many calories during the race (probably about 700 calories in gels, gatorade, a coke, and beer).  If / when I do more races in the ultra distance, I won't use HR as a guidance.... it's more of a mechanical and mental test than an aerobic one.