FUEL: July 2012

Fueling to Last.....

the importance of nutrition in endurance events

Before you head out on a long road trip, you likely check at least a few essentials.  Tire pressure? Check.  Oil level? Check.  Full tank? Check.  Before you consider an endurance event, are you checking the essentials?  And do you know what you are looking for?

Fueling for a long ride or run (half-marathon, marathon, triathlon and century ride) is not the same as a standard workout.  While much of it is individual in preference and tolerance, these 3 principles remain important for all. 

First and foremost, hydrate.  The water you drink even 2 days before a long run is a critical piece to successful fueling.  Replacing fluid along the way is also important, so plan to carry water or to stop at the water tables as needed.  The correct "volume" is a hotly debated topic and depends greatly on your personal sweat rate, expected pace, and fitness level.  Most studies and experts on the subject suggest 12-24 ounces of fluid replacement per hour is a good place to start, however an argument can be made for both more AND less than that range.  If the temperature is 70° or higher, choosing sports drinks will also replenish electrolytes and help prevent hyponatremia (dangerously low sodium levels) caused by excessive sweat loss.

Second, carbo-loading.  This is a term the seasoned endurance athlete is familiar with.  The process of filling the muscles’ glycogen stores by consumption of carbohydrate rich foods in order to maximize the body’s energy reserves is not a new concept.  Carbo-loading is generally done for long (as in ultra-endurance events lasting >3 hours) race day and not commonly for training runs. Good fuel choices include pasta, oatmeal, cereal.  Fruits and vegetables can be a good source as well, however we often recommend people be very careful with fiber consumption prior to racing (many of our athletes for example significantly reduce fiber consumption prior to racing due to the potential of gastric discomfort).  Ideally the choices should be lower in fat as you get near race day as the emphasis is on glycogen (sugar) storage.  Studies confirm that a glycogen-depleted athlete is at higher risk for fatigue, injury and decreased performance (sometimes referred to as "bonking" or "hitting the wall").

Fueling for endurance races has gotten more attention lately.  Some strategies have become rather complex as athletes continue to push their limits.  We asked one of our fueling experts, dietician Eileen Chroback, how implementing the glycemic index strategy would work in endurance training.  Eileen recommends a low glycemic index snack or meal prior to exercise to provide a slower, sustained-release supply of glucose to fuel activity and a high glycemic index snack post exercise to provide a more rapid re-fueling effect for recovery.  However, Eileen points out that, “the primary issues must be addressed first in the amount of carbohydrate and the timing of fuel intake.  What often ends up being the more crucial issue for an endurance athlete regarding pre-exercise fueling is the inclusion of carbohydrate-rich sources that their gastrointestinal tract will handle, and not cause gastrointestinal distress or the need for the toilet, potentially interfering with training or the event. Low-glycemic index items tend to be higher in fiber, gas-producing compounds, and fats that can affect bowel issues.  So, it's very important for an athlete to individualize his choices, and include foods he or she know and tolerates, rather than stressing-out about exact glycemic index score.”

And third, don’t try anything new on race day.    Whether seasoned racer or newbie at the starting line, you’ve likely heard some of this before.  Don’t try new shoes, new socks or ANY new gear… this should include your fuel as well.  If you haven't trained with it, and it's not critical, it's likely best to avoid it.  Unless you're got an Iron-gut, trying fuels (whether liquid, or gel or solid, or supplemental) during your training runs or rides is by far the best strategy.  The further in advance you figure out what you need to eat and what you can (and can't) reliably digest the better.  This is the time to learn your body-specific fueling needs so that on race day you are ready to rock it.  Or, as we like to say “rocket”! 


Written by Amy Weller, PT, DPT, GCS.  Amy is a Partner and Director of Clinical services with Pro-Activity.