You may know by now. The 99% of the times that I go out on a bike ride, I ride slow. And I never stop in the middle of the ride for a coffee. I stop at the end.
But there is always an odd 1%. And that happened last Sunday. Not that I went out, rode fast AND stopped for a coffee. I only decided to … ride a little faster.
My friend R is a pretty strong cyclist. He does not have a power meter, nor a heart rate monitor. He just goes on feeling. Old school, but it works pretty well for him and you may argue it’s the best way to do it. I always have hard times trying to explain him why it’s important to ride slow and not to stop on an endurance ride. After a lot of struggles and trial and error, I think he’s getting it now.
But the other weekend I wanted to make him happier. I decided to ride faster. Not like flat-out, but controlled. I decided to take our ride as a short granfondo (it ended up being a 100k ride) and as an opportunity to test my nutrition plan and my sport nutrition products ahead of the season. Not long ago I was also suggested by performance biochemist and Head of the Elite Sport Group Dr. Rob Child to put in a fast ride every now and then and test my nutrition plan a bit more often. So I decided to took that chance.
My latest physiological test with the performance analysis software INSCYD was dated August 18th. From those lactate tests I knew that at a power output of 220-230 watts (well under lactate threshold, but already at a good tempo pace) I would have consumed somewhere between 135 and 155 grams of carbohydrates per hour. And that’s A LOT of carbs, something around 300 and 400 grams of pasta per hour (depending on the brand and type) or 6 bananas per hour! EEK!
My latest INSCYD test from August and the Fat & Carbs combustion curves per power output.
That’s exactly why I do a lot of slow rides at slow pace (FatMax). Firstly, I need to improve the ability of my body to use fat as a source of energy and its ability to spare carbs. And secondly, because no matter how much carbs I eat when I ride at that power output (my max carbs intake per hour would be 90 grams, so well away from my body requirement) that would never be enough to match what I would consume. The bonk would basically be a mathematical certitude.
But because the Sunday one was a ‘bonus ride’ I took it as a test. I planned to get in the max amount of carbs I knew my body would have potentially absorbed per hour (although it’s never this simple either) and targeted 90 grams of carb per hour.
Or, in other terms: almost 4 bananas or 300 grams of pasta per hour. Translated into my sport nutrition plan that equalled to taking with me 4 gels of 50 grams that contained around 50 grams of carbs each (these worked well), two bars of 25 grams of carbs each (they didn’t work well at all) and a solution of maltodextrins for an extra 100 grams of carbs. So 400 grams of carbs ready to go into my mouth for a planned four hour ride (so I even planned an extra 10 grams per hour). Note: I also had porridge for breakfast and pizza the night before, just in case a bad day was around the corner.
Fast forward to the day of the ride, I stayed out in front most of the time and targeted 220-230 watts for my 3-second average. My friend R, after two hours covered on my wheel, tried to push hard at more than 300 watts (I was holding 270 just to stay on his wheel), but I decided not to follow his game. I knew exactly what could I — and could not — hold. And most importantly, I knew why I couldn’t.
Everything went pretty OK until 2 hours 30 mins into the ride. Then a pure pain until 3 hours, when I finally decided to stop targeting 220 watts because no longer possible.
That mix of grinding and spinning lasted a good three hours, where we stopped once for a pee and another time because my friend R couldn’t reach his bar in his pocket. In those three hours I consumed EVERYTHING I had with me except one of the two bars (they really didn’t work). So a blistering 350 grams of carbs per 3 hours, or 116 grams PER HOUR.
Result? Math isn’t an opinion, but a precise science: with still a deficit of more or less 30-40 grams per hour despite my nutrition plan, I couldn’t hold that pace anymore and I bonked! Wohoo!
I knew it was coming because I knew my physiology, and I only limited the damage by eating as much as I could. That is one of the reasons why didn’t bonk spectacularly, and the second one being that my standard slow rides had left me with an OK fat-burning pace.
God bless the slow rides!
