Low HR Training


Effect of uphill running on MAF pace and aerobic metabolism (Read 452 times)


    Hello everyone, I am a longtime lurker, but I had an interesting question/observation which I was hoping to get some input on with regard to uphill running. 


    I started following the MAF program loosely about a year ago, and had some moderate success with it until a recent bout with injuries.  I am now fully recovered and getting back into the swing of things training-wise.  I am 31, and I have been trying to keep my heart rate at 145 or below starting back. 


    As an experiment, I have been doing one or two extended runs each week of an hour or more at an 8.5% incline on the treadmill, keeping my MAF heartrate at 145 or below, as I hypothesized that this could potentially accelerate my progress coming back.  Granted, I am running a lot slower than on a flat surface (~14:30 miles on incline), but I can tell that my effort/breathing level feels the same as running on the flat (and obviously my heartrate is the same). 


    However, in doing these extended uphill runs, I have observed some interesting phenomena.  First, towards the end of the run, my legs tend to burn, even though I am keeping my heartrate low.  Second, after the run, my legs feel depleted, similar to how they used to feel pre-MAF when I did hard long runs which depleted my glycogen stores.  Keep in mind, these same effects do not happen to me at all when running on flat surfaces, even on extended long runs.


    With regard to the legs burning, my first inclination is that I am accumulating lactic acid; however, I feel like I am able to keep going at that pace.  Therefore, I don't think I am crossing my lactate threshold.  However, this still concerns me, as it shows that I may be going anaerobic even though I am running at what would usually an aerobic heart rate on flat ground.  My second inclination is that I am hitting a point of glycogen depletion; however, I am not experiencing any "wall" or drop in pace which would normally be characteristic of such a physiological occurrence.


    Based on this experience, is it possible that for extended uphill running, the fuel mix is pushed more away from fat metabolism to glycogen burning while running uphill (even when keeping the same heartrate as running on the flat)?  If this is the case, what would be the implications for training?  Would this mean that you have to adjust your heartrate to a lower rate (possibly MAF -10 or MAF -15) on an extended uphill?  I am thinking of getting an aerobic metabolism test to explore this further, but I first wanted to get everybody's input on whether this is something you have experienced, or whether I am completely nuts?

      Hey Griff,


      Welcome to the club of the unlurked.


      My first reaction to 8.5% was "wow, that's steep." That's quite an incline to be running on for that long. 


      Your legs burning does indicate some lactic acid build-up, even though you HR is still at MAF, and way below lactate threshold. RUnning at that incline at that heart rate most likely uses predominantly slow twitch fibers in the beginning, but you are most likely exhausting them quickly (as compared to a 2 hour run at 1% incline), and then recruiting fast twitch fibers to compensate. This is what will happen on very long runs on courses that are a bit more varied with longer sections of flat and downhill, and only encountering a hill that steep on occasion.---your body will recruit fast twitchers at some point--the Type 2 A intermediate ones first. These can be trained to be more aerobic, and is one of the benefits of long runs. These will burn more sugar than fat as a rule, though. You can also think of these fibers as the ones that begin to be recruited as you go above MAF, and which cause the spike on a graph that measures sugar/fat burning as intensity increases. This deflection point at the bottom of the spike is what defines your MAF. 


      Besides all that, your body is telling you "burn" and "exhaustion" at the end of these runs. I can't tell you how this plan will play out, but I recommend doing regular MAF tests. The burn is similar to the burn you feel during speedwork. This might have a positive effect in the short term, but eventually plateau and reverse. Follow your MAF tests. Dr. Phil has written about the short term vs. long term in this type of anaerobic

      approach (speedwork). I've also seen that after a lengthy race season, MAF will tend to regress---a sign that it's time to rest and do some pure aerobic base work for awhile.


      Also,  if you start to experience calf or achilles problems, back off. Those are some pretty long, steep hills! I've always brought in hills gradually on the TM, and have kept hills to 4% and .3 of a mile max. Usually only one per mile.


      I'm not sure this helps you. I wish you the best. Stay in touch with your MAF tests and aerobic speed, resting heart rate, and the signals from your body---you can't go wrong.


      --JImmy Cool


      p.s. THis 8.5%  incline is not unlike lifting a heavy weight slowly, keeping heart rate down, but getting a burn after 5 reps. Anaerobic.

        (...) but I first wanted to get everybody's input on whether this is something you have experienced, or whether I am completely nuts?



        well that's interesting. I've had trouble with burning muscles on hills but most if that was in the past (well I still have to figure out the perfect warmup for uphill race). I find the following things help avoid the burn:


        - more thorough warm up (still experimenting but it seems that a few quick sprints up the hill help)

        - faster pace, paradoxically makes the burn go away

        - if faster pace is not an option (as you are strict with MAF'ing), then change running style temporarily: if you were going with your calves mainly, then load the quadriceps instead by lifting knee up more (or vice versa, if it's the quads burning)

        - strength training. I have not actually done strength training outside running but I find that the burn heavily depends on the the muscle's strength. I did runs that you could call strength training (controlled sprints twice a week, hard downhill running, and just getting used to hills in general, especially with trail running, that strengthens you sooner!).


        after all the above, I'm now at a point where I can run up 10% hills at low enough HR without feeling them at all in my legs. longer 15% hills are still slightly a challenge but am working on it. Smile


        I am not sure if it's to do with fat burning or glycogen burning, or whatever. it's something to do with muscle strength itself. it's quite telling that you don't experience a wall, either.