Coach Jay Johnson has once again delivered an outstanding interview in his new podcast, this time with Dr. Trent Stellingwerff, of the Canadian Sport Center – Pacific. Dr. Stellingwerff is an expert in nutritional physiology (or is it physiological nutrition), and an outstanding runner in his own right – while also being married to the 4:05 1500 runner Hillary Stellingwerff.
The topic of this interview is sports nutrition for the marathon, focusing specifically on the marathon itself (not the training cycle). As such, it is a can’t miss for any runner who has suffered the “bonk” (or “hit the wall”) – in other words, anyone who has run a marathon and hopes to do better. Dr. Stellingwerff has not only researched the subject from a scientific approach, but has significant field experience working with endurance athletes in a range of sports, and is an accomplished runner in his own right.
You should really listen to the podcast to get the full science behind the ideas, as it’s always better to know the why’s behind the what’s. To entice you, here are the key points Dr. Stellingwerff made in regards to nutrition for the marathon.
You will run out of glycogen by around mile 18. Your body can store, at most, around 2000 calories of energy in the form of glycogen. No amount of carbo-loading will help you overcome this. And, if you run a marathon in your anaerobic zone, you are burning mostly carbohydrates and cannot utilize fat effectively. This is why the marathon is uniquely challenging – ultras generally remain aerobic (except for the elites), and shorter races aren’t long enough to run out of glycogen.
Target the rule of 15 – 15 g of carbohydrates, 150 mL (5 fl. oz.) of fluids every 15 minutes. Since each gram of carbohydrate delivers four calories, this is 240 calories per hour. Sports drinks typically provided at marathon aid stations contain around 14 grams of carbs per 8 oz. (237 fluid ounces) – this is not a concentrated enough form of carbohydrates and needs supplemented with energy gels.
The maximum fluids the stomach can absorb per hour is 700-800 mL (~25 fl. oz.). This is three cups of water or sports drink (though one must consider the yield of actually getting it down, as well as how full the cups are) per hour. This also combines with the above point to limit the amount of calories per hour you can take in via carbohydrate and electrolyte drinks at~200. This is close to your needs – if you go over the 150 mL per 15 minutes guideline and can “stomach” that well enough.
The best form of carbohydrate is a combination of glucose and fructose. These carbohydrates are taken up by different mechanisms, so when used in combination, they don’t overwhelm a single pathway, as relying only on glucose would. Both Gatorade and Powerade seem to contain such a combination, as, it seems, do most typical energy gels.
Caffeine in the amount of 150-200 mg taken one hour before the race helps to delay the onset of pain and fatigue. This may be best taken via a pill, since the caffeine levels in various forms of coffee can vary significantly (plus, coffee introduced acid which may lead to gastrointestinal upset for some consumers). Caffeine starts having an impact one hour after consumption, and continues to do so for about three hours. A better strategy may be to take half the caffeine before the race and half around 60-90 minutes into the race (depending on your target time), such that the impact of the second one starts to hit just as the first is beginning to fade a bit. I’d discussed the impact of caffeine for runners in a general sense previously; it’s helpful to get this specific advice on how to manage it for racing.
Combining all these concepts above, one can begin to plot a fueling strategy for their race, considering the location of aid stations (often spaced every 1.5 miles – thus the 15 minute timing may be a bit tricky unless you run either a 15-minute or a 30-minute 5K), the type of fuel available (for example, where do gels become available – and do any contain caffeine – and how much?). Due to some of these issues. Dr. Stellingwerff advocates bringing your own fuel belt. This fueling strategy can complement your marathon pacing strategy to fully prepare you mentally for the race.
I had commented in my Towpath Marathon summary that it was the first race in which I didn’t bonk, and it was also the first race in which I didn’t consume any gels. It doesn’t seem that even the excessive availability of sports drinks on the course provided adequate carbohydrates per Dr. Stellingwerff’s formula. Specifically, if I averaged 4 oz. of sports drink every mile, this would have been 36 oz. of fluid per hour – too much to absorb by a significant amount – so I probably didn’t drink that much. If I had been able to stomach that amount, it would have provided the desired 60 mg of carbohydrates per hour, but that seems difficult to believe. Maybe the fact that 90% of workouts, including most of the long runs, were done before breakfast provided some improved glycogen utilization efficiency through enhancing the ability to burn fat.
The other interesting comment made by Dr. Stellingwerff was in response to Coach Johnson’s question seeking one piece of advice for the adult runner. It’s simple – volume is key – you should run as much as time and your body allow. If you aren’t yet bought into the high mileage belief, it’s time to get on board and figure out how to make it work for you.
The podcast is well-worth an hour of your time – especially to hear the killer workout that some of the marathoners Dr. Stellingwerff works with do as a key element of their training (sorry, you’ll have to listen to find out). Coach Jay Johnson’s podcast is quickly becoming must-hear for any serious marathon runner, as this is the second in a row (following on the discussion of ancillary work for runners with Scott Douglas) that provides hard-hitting insights to help with your training and race strategies.