In-Race Carbohydrate Calculator

Below you'll find an Excel file hosted on this site that contains several different tools/calculators.

-Race Equivalency Chart

-Predicted Range of Marathon Performance under Similar Conditions to Recent Race.

-Continuous Runner Training Paces

-Run/Walk Training Paces

-Continuous Runner Training Paces: Temperature + Dew Point Adjustments

-Run/Walk Training Paces: Temperature + Dew Point Adjustments

You have to "edit" three cells colored in yellow.  For any and all calculators contained in this spreadsheet to work, you must input a recent race distance and time.  Please don't attempt to edit anything other than those three yellow cells.

 

-You can enter a recent distance using the drop-down arrow.

-You can enter a recent race time (make sure it is in the format of Hours: Min Min : Sec Sec)

-And further down the file, you can enter a walking pace (in min/mile format) if you use the run/walk style.

If you'd like to know more about each individual calculator, then scroll below the Excel file for a detailed explanation.

*Please note that at this time the calculator is not mobile friendly.  I apologize for the inconvience.

Below you'll find an Excel file hosted on this site that contains an in-race nutrition calculator

It's important to note that individual responses to in-race nutrition will vary.  This calculator is meant as a general means to figure out carb consumption.  In order to have an accurate picture of in-race nutrition, a runner would need to complete a metabolic efficiency profile.  Ideally, a metabolic efficiency profile would be completed very close to race day to get the most accurate represenation.

You have to "edit" six cells colored in yellow.  For all calculators contained in this spreadsheet to work, you must input information into all six cells.  Please don't attempt to edit anything other than those six yellow cells.

-You can enter your body weight (in pounds).

-Then choose your gender (Male or Female) using the drop-down arrow.

-Then choose an upcoming race distance using the drop-down arrow.

-You can enter a recent distance using the drop-down arrow.

-You can enter a recent race time (make sure it is in the format of Hours: Min Min : Sec Sec)

-And lastly, enter how many grams of carbohydrates you plan to consume per hour during the race (for example, if you consume 100g carbs in 4 hours, that is 25 g of carbs per hour.

Find your estimated finish time for a marathon, or half marathon.

You'll find two sets of data.  One in which a person follows "No Carb Loading Protocol Prior to the Marathon" and one in which a person follows the "Western Australian Carb Loading Protocol" (10.3 g/kg bw carb consumption).  The No Carb Loading calculates based on a 100% glycogen storage estimated value (if you carb load less than 7 g/kg bw, then you are likely in this category).  The WA Carb Loading calculates based on a 190% glycogen storage estimated value (average from the research study).  If you want to know more about the WA protocol see the "Carb Loading" tool.

Then, look at the blue column "Deficit Carbs (g) / hour".  The value that appears in the same row as your "estimated finish time" is the suggested number of carbs that should be consumed per hour during the race.

The purple column "ESTIMATED DISTANCE (in miles) TO HIT WALL WITH NO CARB LOAD OR IN-RACE CONSUMPTION" in the same row as your estimated finish time displays the mile at which you will theoretically run out of glycogen storage and "hit the wall" assuming you come in with normal glycogen storage in your leg muscles.

The orange column "DISTANCE (in miles) TO HIT WALL WITH NO CARB LOAD BUT GLUCOSE CONSUMPTION AT PLANNED RATE" uses your planned carb strategy and displays the mile at which you will theoretically run out of glycogen storage and "hit the wall".

Two "limits" should be noted.  Per Jentjens 2002, when it's "hot" outside (95 F in lab based study), the oxidation of CHO is about 10% less than in cooler temps.  So the recommended limit of in-race carb consumption in a hot race is 50-60 g carbs/ hour.  The maximal intake of carbs per hour is 90g (source has yet to be found, but from memory) when running.  The 90g limit has been marked in black when the advised deficit of carbs exceeds this value.  These have been shown to be irrespective of body weight.

If you'd like to know more about how this calculator was made, then scroll below the Excel file for a detailed explanation.

*Please note that at this time the calculator is not mobile friendly.  I apologize for the inconvenience.

Calculations in this file

Total kcal burned = Body Weight (in kg) * Distance of race (in km)

  *(Humphrey 2013)  This is a general value and a specific value would require physiological testing.

Leg Muscle Mass: Males = Body Weight (in kg) * 21%; Females = Body Weight (in kg) *20%

   *21% and 20% represent averages for males and females respectively with ranges of 14-27% and 18-22% respectively (Rapoport 2010).  Again this illustrates the "average" or generalness of this calculation

CHO Storage in Legs = Leg Muscle Mass * 80

  *(Humphrey 2013)

VO2peak = *formula not shown due to proprietary nature, from Jack Daniels

vVO2 (m/s) = 2.8859+0.0686*(VO2peak-29)

vVO2 (mph) = vVO2 (in m/s) *2.23694

Pace at %VO2peak (in min/mile) = (60/(vVO2 in mph)*(%VO2peak/100))/1440

Marathon Finish Time (Hours:Minutes:Seconds) = ((Pace at %VO2peak * 26.2)/60)/1440

Half Marathon Finish Time (Hours:Minutes:Seconds) = ((Pace at %VO2peak * 26.2)/60)/2880

Average CHO Use = Total kcals burned * ((%VO2peak-5)/100)

  *(Humphrey 2013) 

Subtract CHO Storage in legs = Avg CHO Use - CHO Storage in Legs

Subtract CHO Storage in Liver = Subtract CHO Storage in legs - 100

Deficit Cal/hour = Subtract CHO Storage in Liver / Race Finishing Time

Deficit Carbs (g) / hour = (Deficit Cal/hour) / 4

ESTIMATED DISTANCE (in miles) TO HIT WALL WITH NO CARB LOAD OR IN-RACE CONSUMPTION

    =  (((CHO Storage in Legs / Average CHO Use ) * Race Finish Time) * 60) / Pace at % VO2peak

DISTANCE (in miles) TO HIT WALL WITH NO CARB LOAD BUT GLUCOSE CONSUMPTION AT PLANNED RATE

    = ((((CHO Storage in Legs + ((Planned CHO consump * Race Finish Time) * 4) / Average CHO Use ) * Race Finish Time ) * 60) / Pace at %VO2peak

Sources

Rapoport BI. Metabolic factors limiting performance in marathon runners. PLoS  Comput Biol. 2010 Oct 21;6(10):e1000960. doi: 10.1371/journal.pcbi.1000960. PubMed PMID: 20975938; PubMed Central PMCID: PMC2958805.

 

Humphrey, L. [Hanson's Coaching Services]. (2013, Nov 23). Calculating Caloric Needs for Marathon- Updated 11/22/2013 . [Video File]. https://www.youtube.com/watch?v=TTQt3pjeqKg

Jentjens RLPG, Wagenmakers AJM, Jeukendrup AE: Heat stress increases muscle glycogen use but reduces theoxidation of ingested carbohydrates during exercise. J Appl Physiol 2002, 92:1562–1572.