Keto Marathons Logo

Marathon 1: Penrith, NSW


The Marathons Begin!

The mood was at an all-time high as I was ready to embark on my first-ever marathon. The forecast was sunshine all day, and at 10°C, it was a comfortably fresh start. However, having strained my calf muscle two weeks ago, this was the first run since then, so I was a little nervous that it would blow out on me again.

The strategy was to try and maintain a heart rate at 140 bpm for the entire 42.2 km. In my training runs, I’ve been able to maintain roughly 7 min/km at this heart rate. However, things didn’t go as planned today. From the outset, my heart rate took off, and I adjusted to simply try and keep it in the mid-150s.

I thoroughly enjoyed commencing the challenge, and the first 15 km went by very quickly. The first 10 km completed the loop around the Sydney Regatta Centre, and then I began the picturesque circuit around the Nepean River.

My heart rate started to climb as I approached the halfway 21 km mark, but everything still felt pretty good. A huge thank you to my support crew who greeted me with water, a few laughs, and some action shots as I completed each river loop.

The double-loop course allowed me to stop briefly to recharge with some salt water and a bit of fresh water too. It was getting hot, and hydration was absolutely required.

The entire run was completed without listening to any music or podcasts. My nervousness about a potential injury meant that I was on high alert and continually performing some ‘self diagnostics’.

It was at the 30 km mark that things began to get difficult. My right knee started to scream at me, and I quickly realized that pushing to maintain a running pace was not a smart move. Given I only had 10 km to go, I dropped it back to a brisk walk, which meant I’d be traveling about a minute or so slower each km. Forfeiting 10 minutes off my 5-6 hour time seemed a very smart trade. The brisk walking did the trick, and the knee pain subsided, although I’d attempt a trot every now and again just to recalibrate, but the pain returned each and every time.

Pace per km


It was at the 30km mark that the temperature shot up from 26C to over 32C in less than 10 minutes. The additional heat really added another degree of difficulty for the final 10km to the finish line.

The final 4 km was a tough one mentally as it involved returning from the river loop and completing a final effort beyond the scheduled finish line requiring me to double back. Tomorrow I’ll change the course slightly to make it a mentally easier finish.

Active Pace

Energy levels remained high for the entire run, but I’d be lying if I didn’t say I was very glad to see the 42.2 km mark arrive. Whilst my muscles felt totally fine, it was my knees and joints that were really sore by the end. The thought of doing it all again didn’t carry the same level of excitement as this morning! Having a large fat fuel tank is one thing, but there is a lot of additional stress on the body caused by so many repeated movements.

Marathon 1 Statistics

All done! I finished my first-ever marathon in 5 hours 40 minutes (average pace 8 min/km).

Heart Rate

The goal was to maintain my heart rate in under 140 bpm (zone 2) however I spent the vast majority of the time well over 150 (zone 3). I was thus working a bit harder than i would have liked.

Continuous Blood Glucose

My blood glucose was very stable at 5.2 for the entire run. My body will have been creating glucose at a sufficient rate to offset the glucose utilised throughout the day. I didn’t get any of the blood sugar dips I’d observed during my training runs. That may be due to the warmer weather as each training run was done at 4 am in 4-9°C temps.

The shaded area on the chart below indicates the normal range for blood glucose.

24 Hour CGM

Blood Ketones

Prior to my marathon my blood ketone level was at 0.1 mmol/L. Any ketone reading above zero indicates that my body is creating ketone bodies and is thus in a state of ketosis. This level is consistent with my daily ketones over the previous couple of weeks in which ketones fluctuated between 0.1-0.4 mmol/L. Testing immediately after the first marathon saw my ketones rise up to 0.8 mmol/L and then remain at that level for the rest of the day.


My final meal was at 7 pm last night, and the 5-day fast has commenced! It will be only salt and water for the next 5 days until after my final marathon on Sunday. I’m sure everyone will ask, so here is the last meal…


Sleep was pretty poor last night as the excitement of starting the marathons really got to me. I felt like a 6-year-old boy the night before his birthday. Needless to say, I was awake from around 4 am and tried my best to get some rest until 6am.

My sleep statistics indicate a restless night and sub optimal REM sleep.

Morning Testing

Testing was done at 6am as planned, and the results were as follows:

  • Ketones: 0.1
  • Glucose: 6.0
  • Weight: 75.5 kg
  • Mood: 9/10
  • Hunger: 0/10

Post Marathon

Post-run involved a massage to the legs and lower back followed by a very long Epsom salt bath. Recovering for tomorrow is the number one priority. After preparing dinner for the kids (and a salt water drink for me), the day was done. The reality of doing it all again tomorrow is daunting but let’s check that again in the morning.

Tomorrow’s strategy will be to take it much slower. Target will be a genuine max 140 heart rate, and I expect the pace will be around the 8.30/9 min/km mark. I need to give my knees a chance to recover, and a change of shoes might alleviate some of the pain. I expected some unknown challenges to manifest, and here they are! Warm-up marathon done and only 169 km to go.

Related Posts