Mid Run Fueling
This entry provides an introduction for fueling while running. It looks at the objectives, constraints and proposes some approaches. It focuses on fueling in liquid or solid form, not Hydration.
1 Objectives for Fueling
- Carbohydrate for the brain. Without sufficient blood sugar, mental functioning degrades. This can impact mood, creating depression, or cognitive reasoning, which impairs judgment. In some cases it can reduce motor skills, making trail running harder.
- Carbohydrate for muscle function. Muscles require both carbohydrate and fat to function, but it is the carbohydrate that is normally the limiting factor. Authorities estimate most people have about 2,000 Calories of stored carbohydrate (Glycogen).
- Protein to protect muscles. Consuming Protein has been shown to protect the muscles from damage during exercise and to improve recovery. Protein and carbohydrate together have also been shown to improve endurance more than carbohydrate alone.
- Fat for muscle function. The human body contains more stored fat than needed for even extreme endurance runs. However, I suspect that our bodies have a limited rate at which body fat can be burned, so consuming fat may be beneficial.
- Intensity. The biggest influence on fueling is the running intensity. Digesting fuel requires blood, oxygen and energy.
- Running at very high intensity may prevent any digestion or absorption, even of water. If fuel is consumed before running at this intensity may result in nausea or vomiting. Luckily, this pace generally does not require any fueling during the run, as the duration is short. The specific pace will vary from person to person, but would typically be mile to 10k race pace.
- Running at mid intensity generally allows for the consumption of simple carbohydrates or simple carbohydrate/Protein mix. This fuel will offset the limited carbohydrate stores in the body. Again, specific paces depend on the individual, but are likely to be half marathon to 50K pace for most people.
- Running at low intensity often allows the digestion of complex food. The longer duration of lower intensity running can require a mixture of carbohydrate, Protein and fat. This tends to occur at ultramarathon distances.
- Heat. Higher temperatures make digestion harder, possibly because the blood is drawn to the surface of the skin for cooling. Nausea on hot runs is more common than cooler conditions.
- Individuality. Some runners have the ability to digest a wide range of foods, where others struggle. It is important to learn what works for you.
- Circumstance. What can be digested seems to sometimes vary without any obvious cause. What works on one run can sometimes not work on another similar run. I suspect this may be due to the initial state of the body, such as the level of sodium stored, or what has been eaten over the previous few days.
3 Suggested Fueling
- For runs of an hour or less, most runners do not require fueling. In hot conditions, some water may help. Follow Nutrient Timing post-run.
- For runs of one to four hours, try simple carbohydrates or a carbohydrate/Protein mix.
- Sports drinks can work well, but different drinks work for different people. I get on well with Gatorade (it's cheap), but other people have digestive distress from it. If Gatorade does not work, try a drink with less sugar and more Maltodextrin. An example would be Hammer Heed. The problem with sports drink is that on races you have few options, and the drinks are often mixed inconsistently. On marathons, it's common to get dilute, colored water most of the time, and occasionally a cup of overly concentrated syrup.
- Adding Protein to carbohydrate can be done by simply adding Whey Protein to your favorite drink, or buying a premixed formula like Accelerade.
- Gel packs are a great source of portable fuel. Most are concentrated glucose polymers which are easy to digest, but personal preferences for different gels vary a lot. I get on well with most gels, though I prefer Gu or Accel. I find Gu is the easiest to digest of the gels I've tried, and Accel provides added Protein. The only gel I dislike is Cliff Shots, which are made with brown rice syrup that is bitter and does not settle as well as other gels. Also see How to eat a Gel and When to eat Energy Gels in the Marathon.
- For runs longer than four hours, try solid food. I would suggest starting with simpler solid fuels such as candy (M&Ms are a personal favorite) or crackers. See Fueling in an Ultra for more details.
- I find that for even 100+ mile runs, that Fellrnr's Go Juice is all I need, but I am running these distances at a higher intensity than many runners.
4 Applying the Suggestions
I can't emphasize enough the need to work out what works for you as an individual. Here is a protocol for experimentation.
- Try a fuel on a short run at target race pace. If it doesn't work on a short run, it is unlikely to work at longer distances.
- Next, try on a longer run, ideally when running at or near your target race pace. For long runs for marathon training, doing the last few miles at race pace is a good proving time for fuel.
- Finally, try the fuel on a race and see how it works. It is best to avoid a fuel when racing that you've not tried before. However, few of us train at the ultra distances we race at, so it is hard to experiment in training for this type of race. In that situation, go with what appeals at the time, but be cautious.
- Carry a Portable Pharmacy with Gas-X and anti-acids, as sometimes things go wrong.