I took a look at a 3-hour long bike ride (Exercise Intensity on Low Carb) last month. I did the ride at a average heart rate of 138 bpm.
I took a longer ride later that same week and I have the data from that ride. How does the data from the ride compare to my recent thoughts on Heart Rate Training (HRT)? I did push myself as hard as I could on the ride. What I am interested in is the question in reverse. That is, if I push hard and long what was my heart rate?
From the HRT data and my own VO2max testing I know that my aerobic (fat fueled) zone is at a heart rate of 112-122 bpm. That means that at a higher heart rate (level of exertion) I am burning down my glycogen stores. (That is a problem if you are Low Carb.) After this long ride my blood sugar was pretty low (in the 50’s). Clearly from my blood sugar, I burned through my glycogen stores.
Here’s the trip I took along the Great Allegheny Passage Trail. I took the trip with my 14-year old son. I think I almost killed him. The GPS and heart rate data dropped out a couple of times along the way but here’s the map.
It was a long ride at almost 4 hours of riding. My speed at 8.8 mph was really slow. Here’s the details of the ride.
The data showed my average heart rate at 125 bpm. Hard to tell exactly where it was but here’s the graph that the program recorded. This was clearly an endurance event. The green line is approximately my MAF heart rate of 112-122 bpm. It is pretty close to the average of 125 bpm on the ride. The fact that there was activity above the line indicates that some portion of that activity was fueled by carbohydrates (glycogen stores).
Fat Oxidation Rates
That’s a total of 227 minutes and 1398 calories. This is a fat oxidation rate of 0.68 g/min (assuming all of the activity was fat fueled – which is wasn’t). That is very close to the rate noted here (Nutrition. 2004 Jul-Aug;20(7-8):716-727. Optimizing fat oxidation through exercise and diet. Achten J, Jeukendrup AE.).
With increasing exercise intensities, the fat oxidation rate increased to a maximum of 0.60 ± 0.07 g/min at 64 ± 4% VO2max (range 42-84), which corresponds to 74 ± 3% HRmax (range 54-92).
I want to repeat a long endurance ride with my heart rate limited at 112-122 bpm and see how my performance turns out.