However, something caught my eye recently in GZ's post of his discussions with Lucho on training, and that was the phrase "utilize fat as fuel". This stood out to me because it fits with my low-carb diet, and I find the physiology behind low-carb eating logical and effective.
I've also been trying to fit that diet into running, an activity that historically has worshipped at the altar of carbohydrates, in the form of carb loading before races, using gels for energy, etc. I found the notion of training the body to use fat as an energy source very interesting.
And of course there's the overall advantage of increasing base conditioning and the ability to maintain a given speed for longer. I'd like to begin pushing that envelope a bit.
So, recently I've spent some time absorbing posts on this topic with more interest.
Wednesday I did my first run in a long time using the Forerunner 405's heart rate monitor. The last time was on La Plata Peak a couple of years ago. I had never really attached actual heart rates to the perceptions I've had at different running speeds until now, but there were some definite correlations between my experience and the concept of maximum aerobic heart rate (MAHR). Observations:
- Using the calculation of 180 minus my age, my MAHR is 131 (+/-5 bpm). I sorted out a final value during the run, and chose 135 because it's right below where I start having to take occasional deep breaths to catch up on air.
- When I felt the need to take a deep breath, I knew I was pushing 140 bpm and getting out of range. Like clockwork. That's good, because it gives me some intuitive measure of heart rate without a monitor.
- On the relatively flat eastern sections of Bluestem and So. Boulder Creek (west of Highway 93) I was at about 7:30 pace downhill and 9:15 uphill at 135 bpm. Taking the average of the two paces, I figure that's about 8:20 on level ground when fresh.
- The center of my target (131-ish) is pretty much what I've typically regarded as my "endurance" pace, because it's sustainable over a long period. That makes perfect sense now.
- Trying to keep a constant heart rate made for really slow uphills, and downhills that were at a faster tempo than I expected.
- I like the fact that this gives running at a slow pace some purpose, rather than just being slow :)
- I also like the fact that it provides a reason to run at a pace that is comfortable and enjoyable. MAHR pace was already my favorite running speed. However, I was running harder uphill and not fast enough on downhill to maintain that HR consistently.
- Apparently MAHR is the pace I tend to run uphill at high altitude. When I wore the HR monitor on La Plata my max was 149 even though I ran a significant amount of it (slowly). I find it fascinating that this number is so close to the number from this evening. Obviously I just dialed back my pace until I was aerobic, based on how I felt, without knowing about MAHR.