An older article I wrote for a European Triathlon Magazine, but worth the read. Not only for those of you as a reminder – but for many of you new to my coaching and consulting.
Endurance racing comes down to a simple ingredient called carbohydrates. Yes – carbs, those evil calories that the rest of the world seems to hate – we need desperately in endurance events to fuel our brains and allow us to push our effort in many sections of any endurance race.
We all know we have plenty of fat in our body to run 100s of miles, cycling 100s of miles and swim…well, that’s different – but you get the point. But as many of you have heard me say – we only have about 20 miles of running in us based off the carbs stored in our liver and muscles. That’s apporx. 2000 cals. Figure most ‘endurance events’ are more than 8-10 hrs, and those require a minimum of 7000-8000 cals.
Now throw in this annoying fact that you have also heard me say: we can only absorb max 350 cals per hour in carbs. Most of the time its way less than that…closer to 250 cals per hour. Yet – as many of you have seen on your power meters or garmin watches, that your burn rate on endurance races is way higher – like 600-1000 cals per hour! Simple math shows you that we are running at a deficit of about 300-600 cals PER HOUR! Now, most of you know from testing, that if the pace is relatively slow, or if you have developed a good fat burning engine, one where you can hold about 80% of T2 (LT, AeT) without activating your anaerobic energy system, then you COULD get half your energy from stored fat, half from carbs…So – doing that math again, its brings us quite close to equal balanced energy BURN and energy FUEL needed. Even sum game that allows for steady pace/effort/output for quite a long time! This can be trained very effectively by developing a fantastic aerobic energy system.
Mess around with this balance too much and things get complicated. Surges in effort, standing while pushing over a roller, running uphill too hard, swimming too fast for a bit, anything where the HR/effort jumps quickly, then Carbs become the dominant fuel, and because of ancient adrenal system functions, this causes your fat burning ability to slow way down for…..hours! Even if you slow down, or dial back the HR dramatically, because of the adrenal response, the body will not return to ‘par’ for a while. (Have you ever ridden harder in a group ride, seeing watts way higher than you ever train…and feel really good? And want to just keep riding like that – and you can??! That is all carb pushing through you – and a few hrs later you are dozing off on the couch….instead of running a marathon…)
As you can see – your harder effort too early in the day – in ANY endurance event (over 5 hrs) means that your fuel source will run out. Your harder effort comes at the cost of burning through those carbs way too quickly without being able to replace/replenish them. By going too hard – even for shorter periods only – you are shutting down your fat burning as a fuel source…and that means at some point in your later stages of your event, the deficit of output to input will be too big…and you are walking, hiking, stopping or slowing down considerably.
Keep this in mind when racing your endurance event in the future. Can you go faster? Sure. But at some point your run out of fuel, literally…and you slow down. Instead, as many of you have also heard me say/preach: go as FAST as you can, using the LEAST amount of energy…Energy being burn rate of fuel…