Tuesday, January 15, 2013

Long Run Fueling: In Marathon Training

How we fuel during our long runs is an important aspect in our marathon training that can have a significant impact on our performance on race day.   Fueling, for the purpose of this blog, is what fluids, solids or gels we consume during our run. 
I arrived at my methodology for fueling like I do most everything in my training philosophy, through a combination of understanding the science and physiology behind it, and real world experience of how it works and feels in the actual application of it.
In MPR training programs we have 3 types of long runs:  easy pace long runs, steady state long runs, and fast finish long runs.   First let me tell you how I recommend handling fueling on each of these long runs, and then I’ll tell you why and how it all works together to enhance our race day performance.
Easy Pace Long Run:  As the name suggests these are long runs done at an easy, conversational pace.  During these long runs I recommend not consuming any calories, instead consume water only (ideally 3-6 oz. every 20-25 minutes), with electrolyte replacement tablets/capsules optional during some (but not all) of the water stations.  I definitely recommend including at least some electrolytes in the warmer weather. 
Steady State Long Run:  These are long runs done at a pace roughly mid-way between easy pace and aerobic threshold pace (usually 5-10% slower than AT).  On these runs I recommend practicing fueling as you would in a race.  3-6 oz. (2-3 swallows) of watered down sports drink every 20-25 minutes, and a higher calorie drink/gel/solid once every 40-60 minutes.
Fast Finish Long Run:  These are long runs in which the first 70-80% are done at an easy pace and the last 20-30% are done at or close to aerobic threshold pace.   On these runs I recommend taking water only during the easy pace portion of the run, and then just before accelerating to AT pace switch over to sports drink/gels/solids as you would in a race for the fast section of the run.
Ok, so how do these recommendations help prepare us for race day.
On the easy pace long runs without calories, we are significantly depleting our glycogen supplies (our body’s preferred source), which cause us to have a burn a higher percentage of alternative fuel (fat mainly), the longer we run.  This has 2 desired effects, our body responds to this glycogen depletion by increasing the amount of glycogen it stores in the future.  Additionally, it helps the body become more efficient at (or at least more use to) burning higher percentages of fat for energy when it needs to.  So on these easy runs, we are building up our glycogen storage tanks, and improving our efficiency in low glycogen situations, both critical for race day performance in the marathon.  We don’t take in calories on these runs for 2 reasons: the intake of calories during the run tends to mute the body’s response to glycogen depletion, causing it not to increase the storage as significantly; and with a consistent intake in glycogen/calories, the body burns less fat as a fuel source, reducing our body’s chance to learn to operate more efficiently at higher fat burn rates.  But we do take in water on easy pace long runs to get the body use to absorbing fluids on a regular basis while running. 
Note: Be careful on these easy paced long runs with no calories, we want to deplete our glycogen supplies significantly but we never want to actually bonk in training.
On steady state long runs we practice our race day fueling routines.  We do this because we need to get our body use to and efficient at partially replacing its glycogen and fluid loss while on the run as that is what we will require of it on race day.  Our steady state long runs are a near perfect place to practice this because the paces we are running at are only moderately (5-10%) slower than race pace, allowing our body’s to learn to handle fueling at quicker paces.
Our fast finish long runs then become a combination of fueling strategies.  We take in water only (electrolytes optional) during the easy pace section of the run to enhance the depletion of our glycogen supplies, which allows us to practice running at race pace (or near it) in the fast finish section in a somewhat depleted state, while practicing our race day fueling at race pace during that section of the run. 
So now you can probably see how all of this begins to come together to help us out on race day.  We go into the race with a larger glycogen storage tank from our work on our easy pace long runs, and we are adept at partially replacing some of our fluids and glycogen during the race through our work on our steady state and fast finish long runs.  This combination a bigger storage tank and ability to partially replace energy puts us in the best possible position for having the most glycogen to utilize in the race.  The more glycogen we have to utilize, the higher burn rates we can maintain, which equals the faster the pace we can run at in the race.  When we combine that with other aspects of our training which improves our efficiency (calorie usage) at race pace, we have the makings for a best possible race day performance.
For marathon runners who are in a training cycle focused on a shorter distance (10k-HM), I still utilize these fueling strategies on our long runs, so that when they transition into a marathon focused cycle later on they are already comfortable with these strategies and their body more advanced in its associated adaptations.
It is also important to note that it is critical to refuel quickly after long runs of all types.  The better and quicker (to some extent) we refuel after our long runs the quicker our bodies will recover from the run.  Significant fluids and calories need to be ingested within the first 30-45 minutes after a long run and it’s recommended to have a balanced meal, if possible, within the first 2 hours after a long run. 
Before long runs, I recommend in-taking some moderate amount of calories, usually 45 minutes or more before the start of the run.  If doing your long run first thing in the morning, this may mean something light when you first wake-up.   


  1. This is great information. I have found a real benefit in my running since adapting a water only strategy on easy runs under 16-17 miles It has made a big difference when racing or doing higher intensity long run work.

  2. This is very helpful. I think in practice I was doing some variation of this but it would help if I fine-tuned it. Knowing the science behind it helps to emphasize the importance of it.

  3. I have bookmarked or printed many of your posts. Thank you for sharing your wisdom and strategies, as well as the logic behind them.