Training for endurance has been part and parcel of who I am since I care to remember. I have competed in various different endurance events over the last 25 years. Starting off in schools cross country races so many years ago, has led me on an educational and experimental journey. The transition from an ordinary healthy western diet to a low carbohydrate high fat (lchf) diet is part of that journey.
I, like many skeptics thought I couldn’t sustain myself with such an approach. Normally, regular weekly miles at 50 – 70 miles per week required copious amounts of pasta, rice, potatoes, bagels, etc. Then there was the recovery drinks….
Heart Rate Zones
Before beginning lchf I had been training modestly at about 20-30 miles per week at various heart rate zones. I had determined my lactate threshold from a VO2 max test I had done previously. I also did some calculations based on the principles set out in Friel & Byrns’, “Going Long“. Based on this information my zones look like this:
From this information I was able to work out different heart rate zones for different training intensities.
Note my aerobic intensity correlated to between 130-150. This is a zone I would become very familiar with.
I had completed the Dublin City Marathon in 2013, running from 55- 75 miles per week using these intensities. My training was based around my long run with tempo runs, intervals (1 mile repeats), and easy runs making up the remainder. My long runs started out at 15 miles and topped out at 22 mile. Most of these long runs were ran at my long run intensity (138-156) with the last 6-11 mile at the high end of my marathon race pace (155-163). Tempos were ran at lactate threshold pace as part of a medium long run, and ranged from 5-9 mile at tempo. Intervals were ran at the high end of lactate threshold pace. This training plan delivered a 3.02.30 marathon with an average mile split of 6.58 minutes per mile.
My lchf training began as a 3-4 mile run 3 times weekly at my aerobic max (135-145). I progressed frequency until I got to 6 days a week, before increasing mileage. Note all my runs were in my aerobic zone only. There were no tempos, intervals or marathon pace runs.
We know from previous articles, we predominately burn fat when in our aerobic zone. Therefore the reason behind only using this training zone, was to encourage my body to burn fat for fuel. This will allow me to recover better, run longer and require no additional food while running. The more time I spent at the top end of this zone, the better my body was able to utilize fat for fuel and the faster I ran.
I did monthly 5 mile time trials to see if there was any improvements. I was progressing so quickly that there was no need for the monthly tests. I was getting faster on a weekly basis over longer distances. The average pace that I could hold for 5 miles, was extending to 8, 10, 12 miles etc. The improvements shocked me, so much so, that after 5 months I have gone from 5 miles with an average heart rate of 144 at 8.15 per mile to 17 miles at an average heart rate of 144 at 6.48 per mile. The only increases from week to week were mileage and frequency.
I then took it one step further to see if this training method had any negative effects when I ran above my aerobic threshold and delved into my anaerobic zone. I ran a 20 mile race a few week ago at an average heart rate of 159 (way above my 145-150 aerobic zone). My average mile split was 6.37 minutes per mile. During this race I ate only a 1/4 of a banana at mile 12 and drank only water. This has proved to me that not only has lchf in conjunction with aerobic only training, improved both my aerobic and anaerobic endurance.