I read this article (pdf) (p1, 6, 7) from Hammer Nutrition's Endurance News earlier in the summer. It had an impact on my thinking. You may have heard me mention a few times lately that I'm working on eating less. This is the source of that thinking.
The article argues that most people incorrectly think about replacement when it comes to a fueling strategy. If you're losing 900 calories/hr then you should replace 900 calories/hr, right? If you're losing 3000mg of salt/hr then you should replace 3000mg of salt/hr, right?
Wrong. And wrong.
Your body can't absorb that many calories and that much salt quickly enough. Yes, you can physically swallow those quantities. But your body can't process and absorb them. The result is a bloated stomach.
The stomach is a bottleneck and simply jamming more food into it only makes it more of one.
Instead of thinking about replacement we should be thinking about replenishment. Replenishment means that you focus not on how much you're losing but instead on how much you can absorb.
With this mindset we're guided to take in a good bit less water, food and salt. This keeps things moving smoothly.
Of course, any recommendation needs to be taken with a grain of salt. Every person's body is different, especially when pushed to the extremes.
Check out the article for actionable absorption numbers. But a summary is: -Less than 30 oz water/hr (a large water bottle is ~25oz) -About 250-280 kCal/hr (2-3 gels/hr) -4-6 salt tabs/hr (large athlete)
I've been working with these throughout the summer on my daily workouts. The main thing I've done is to adjust the number of gels I eat. While in the past I'd pound one every 20 minutes, now I'm taking more of a responsive approach. I listen to my body. I wait until my stomach feels empty. And then my eyes will usually cross a bit... or not focus on something quickly. I'm not talking about a bonk... this is much more subtle... I think of it as a pre-bonk. I'll eat a gel and feel better again in minutes. This stretches out the time between gels.
But be careful. I have to work hard to listen to my body. It's taken me years to understand the signals. It took years of bonking to understand what the pre-bonk feels like. While racing I probably won't rely completely on this approach. I'll blend a timeline approach and a listening approach. For example, I'll have an upper limit on time between gels... say 30 minutes. But if I'm feeling empty with 22 min since my last gel, I'll eat one.
Water has been a little trickier because it's so dependent on temperature. Watching my forearms for sweat beads is a good indicator that I'm still sweating. If I drink too much I pee which costs time in a race. If I drink too little my performance suffers. In general I'm drinking a little less these days but still sweating.
Salt is also difficult but the ultrarunning helped me a bunch. On the 50 miler I overloaded the salt. When I barfed at the end it was white and chalky... all sodium... and a great physiological clue. The abundance of sodium shut down my stomach lining and it all just sat there. Since then I've noticed on long workouts that when I overdo the salt I feel a slightly acidic sensation in my throat... almost a pre-barf... or some slight pressure from my stomach in the barfing direction. Again, it's very subtle.
All of these signals took years to understand and gain confidence in. Because while I can now single them out as important, they happen alongside a multitude of other signals. Pains, burns, areas of fatigue, gas build-ups (and releases), pressure points, emotions... while you're racing they all flood in. It takes a lot of bad experiences to understand which ones you need to pay attention to.
I'm certainly not an authority on my body yet... I'm a student of it. But maybe I'm past the first grade?
The 15 Mile Half Marathon