I've got some exciting news to share and I've been doing some serious research digging leading into the Fall racing season. The act of carb loading is not a new topic around here. I've lightly covered the Western Australian Carb Loading Method prior (What do you use for your running fuel? Carbs, yum, yum, yum! My scientific strategy!). In a nutshell, you consume roughly 10.3 grams of carbohydrates for every kilogram body weight (10.3 g carb/kg bw) the day prior to the event. But since then, I've been doing some further digging into the performance benefits, men vs women, and how to practically complete the protocol using Maurten 320 Drink Mix as a possible liquid carb source. I highly recommend practicing one of these methods about 4-6 weeks prior to your event just to make sure you tolerate it (nothing new on race day).
In case you're interested, I've developed two calculators that help you do the math for pre-race carb loading (link) and in-race carb consumption (link). Just be aware that at this time they're not mobile friendly calculators.
But who really is this important for?
-Research has shown that events over 90 minutes are ones that can benefit from a performance standpoint when doing a carb loading strategy.
Hawley JA, Schabort EJ, Noakes TD, Dennis SC. Carbohydrate-loading and exercise performance. An update. Sports Med. 1997 Aug;24(2):73-81. Review. PubMed PMID: 9291549.
Is there a minimum threshold to see significant gains in % increase in glycogen storage and in performance?
-Yes, it appears that minimum threshold is 7 grams carbs/kg bw in males and 8 grams carbs/kg bw in females. If you do a carb loading strategy that is less than either of these values, then the research suggests you will see no statistically significant additional % increase in glycogen storage or increased performance. So if you do less, you'll just replenish your glycogen storage rather than dramatically increasing it.
Sedlock DA. The latest on carbohydrate loading: a practical approach. Curr Sports Med Rep. 2008 Jul-Aug;7(4):209-13. doi: 10.1249/JSR.0b013e31817ef9cb. PubMed PMID: 18607222.
What kind of increase in performance could I expect?
-According to Atkinson et al. 2011, you could increase performance by as much as 0.17 km/hr for every 1 g carb/kg bw at 7 g/kg bw or more. Additionally, it appears it allows you to better maintain pace at the tail end of the race. There are certainly flaws with this paper, but it is supportive to the idea of an increase in performance. By increase in performance, I mean that you can achieve peak performance based on what your data suggests. But it does not mean you're suddenly going to become superman/superwoman and far exceed your performance limit. So what does this mean in real marathon finish times?
Say a person had data to suggest peak marathon performance was a 6:48 min/mile (2:58 marathon). Let's say to achieve that would require 10g/kg bw carb intake. If we use a 0.17km/hr decrease from 10g down to 6g it would suggest the difference in performance would be a 2:58 vs 3:07. So the carb loading strategy would suggest an increase in performance of about 5% for this runner.
Say a person had data to suggest peak marathon performance was an 11:00 min/mile (4:48 marathon). Let's say to achieve that would require 10g/kg bw carb intake. If we use a 0.17km/hr decrease from 10g down to 6g it would suggest the difference in performance would be a 4:48 vs 5:12. So the carb loading strategy would suggest an increase in performance of about 8% for this runner.
Do we know this to be fact? No. But the data would suggest that it is something to consider given the highest correlation in this study was shown to be gender, BMI, training distance 2nd week prior to race, and then pre-race carb loading strategy.
Atkinson G, Taylor CE, Morgan N, Ormond LR, Wallis GA. Pre-race dietary carbohydrate intake can independently influence sub-elite marathon running
performance. Int J Sports Med. 2011 Aug;32(8):611-7. doi: 10.1055/s-0031-1273739. Epub 2011 May 17. PubMed PMID: 21590642.
If I do a one-day protocol (like the Western Australian Method) does it have to occur on the day prior like in the research study?
-A separate research paper (Arnall et al. 2007) has shown that carb loading can allow muscle glycogen to remain significantly elevated for as many as 5 days after the loading period. As long as no exercise at a low effort was greater than 20 min (as was conducted in this study, so you could possibly go longer, but this study did not analyze that specifically) and a 60% carb diet was followed afterwards.
Arnall, D.A., A.G. Nelson, J. Quigley, et al. Supercompensated glycogen loads persist 5 days in resting trained cyclists. Eur. J. Appl. Physiol. 99:251Y256, 2007.
So with that being said, here are some methods to consider.
Western Australian Method (my recommended carb loading strategy)
The Western Australian carbohydrate loading procedure comes from the Fairchild et al. 2002 paper. In the original paper, the authors concluded a 1-day carb loading procedure with 10.3 grams/kilogram body weight of carbohydrates consumed could yield an average gain of 190% of normal glycogen storage. A drawback to the original research was the need for a glycogen depletion (GD) exercise the morning of the carb procedure. The GD exercise was a 5 min warm-up, then 150 seconds of cycling at 130% VO2peak (really really really fast), and then 30 seconds of all-out sprint. Not necessarily a desirable workout to be carried out the day prior to your big race.
Fairchild TJ, Fletcher S, Steele P, Goodman C, Dawson B, Fournier PA. Rapid carbohydrate loading after a short bout of near maximal-intensity exercise. Med Sci Sports Exerc. 2002 Jun;34(6):980-6. PubMed PMID: 12048325.
However, a follow-up research article (Bussau et al. 2002) showed that the GD exercise was unnecessary for the glycogen supercompensation to occur. Additionally, no statistically significant increase was seen in glycogen storage when increasing the WA protocol from 1 day to 3 days. This follow-up article cemented this protocol into a 1 day carb consumption with no need for any intense exercise proceeding the big race. In my mind, a win-win. It's important to note, the subjects of this research were all men who trained about 11 hours per week with a VO2peak of 59 (around a 1:20 half marathon or 2:47 marathon).
Bussau VA, Fairchild TJ, Rao A, Steele P, Fournier PA. Carbohydrate loading in human muscle: an improved 1 day protocol. Eur J Appl Physiol. 2002 Jul;87(3):290-5. Epub 2002 May 28. PubMed PMID: 12111292.
In order to carry out the WA protocol, do the following:
-On the day prior to the event, consume 10.3 grams of carbohydrates per kilogram body weight.
-80% of those carbs should be in liquid form in order to aid in absorption. This is where Maurten Drink Mix 320 comes in (see towards the end of this).
-The protein (g) and fat (g) values are suggested based on a 90% carb, 7.5% protein, and 2.5% fat diet on that single day.
-In theory, you would be able to store 190% of normal glycogen storage.
-In theory, if glycogen depletion were the only limiting factor (it isn't), then using the below calculation would yield the time which is the fastest you could run without taking in any nutrition during the race (in theory). That is not necessarily how fast you can run the event, rather it is meant to show whether the need for in-race nutrition may still be necessary given your goal time. This value is calculated by the following method:
((60/(vV02mph*(((Carb storage (kcal) / Estimated Calories burned (kcal))*100)+5)/100)))*26.2)/1440 = Time to glycogen depletion
Something that may become immediately evident is the sheer amount of carbohydrates and calories needed to carry out the WA method. This may be a significant increase for most females. But as will be noted in the Tarnoplosky and James methods, a significant increase in caloric intake and carb intake (by ratio to body weight) is a critical step to yield glycogen supercompensation in females. But with that being said, this method isn't for everyone. Not everyone wants to attempt to consume several hundred grams of carbohydrates the day prior to the event. So below are a few other options.
Sherman Method
The Sherman method consists of 3 days of a "normal diet" followed by 3 days of a "high carb" diet. The normal diet was 50% carbs (protein and fat not specified) and the high carb diet was 70% carbs (protein and fat not specified). This method does not require a glycogen depletion workout. Instead, it was conducted with the following exercise protocol:
Low intensity pace (73% VO2max) for 90 min on Day 6, 40 min on Day 5, 40 min on Day 4, 20 min on Day 3, 20 min on Day 2, rest on the day prior to the event, and then Day 0 was the event.
Sherman, W.M., D.L. Costill, W.J. Fink, and J.M. Miller. Effect of exercise-diet manipulation on muscle glycogen and its subsequent utilization during performance. Int. J. Sports Med. 2:114Y118, 1981.
Goforth Method
The Goforth Method examined two possible protocols simultaneously. This method was done either with or without a glycogen depletion (GD) exercise. The GD exercise was 90 min at 65% VO2peak followed by 1 min run:1 min rest at 120% VO2peak for five intervals. This was conducted 7 days prior to the event. For the remaining days between the GD exercise and event day, the participants were limited to 20 min at 65% VO2peak per day.
During days 6 through 4 proceeding the event, the participants (men) consumed an 80% carb, 10% protein, and 10% fat diet. This equated to 9 grams of carbs per kilogram body weight in these men. During days 3 through 1 proceeding the event, the men consumed a 56% carbs, 26% protein, and 18% fat diet. This equated to 6.5 grams of carbs per kilogram body weight in these men.
The men who did the GD exercise saw their glycogen storage increase 147%. The men who did not do the GD exercise saw their glycogen storage increase 124%. The theoretical times needed to ensure in-race nutrition would not be necessary can be calculated like above for these two possible methods (with and without GD). It's important to note, these pale in comparison to the WA method which showed a 190% increase in storage in two separate papers.
This method was done with liquid carbs in part. The men consumed 315 g of liquid carbs per day during the 1st phase (80% carb) and 210 g of liquid carbs per day during the second phase (56% carbs). This would be about 44-48% of the total carbs consumed in these men.
Goforth HW Jr, Laurent D, Prusaczyk WK, Schneider KE, Petersen KF, Shulman GI. Effects of depletion exercise and light training on muscle glycogen supercompensation in men. Am J Physiol Endocrinol Metab. 2003 Dec;285(6):E1304-11. Epub 2003 Aug 5. PubMed PMID: 12902321; PubMed Central PMCID: PMC2995524.
Research Based on Women
Tarnopolsky Method
Most of the research conducted to date in the glycogen supercompensation realm has been based on data from men. But several research articles (Tarnopolsky 1995, Walker 2000, Andrews 2003, Nicklas 1989, McLay 2007, and Paul 2001) have shown that men and women do not necessarily react the same to similar carb loading methods. What may indeed matter more than the composition of the diet is the total caloric intake and the total grams of carbohydrates per kilogram body weight.
Tarnopolsky aimed to test just that in the 2001 paper. Men and women consumed one of three diets for five days.
Normal diet (Men was 3000 calories and 6.1 g carb per kilogram body weight and Women was 2000 calories and 5.1 g carb per kg/bw)
High Carb (Men was 3000 calories and 7.9 g carb/kg bw and Women 2000 calories and 6.4 g carb/kg bw)
High Carb/High Calorie (Men was 4000 calories and 10.5 g carb/kg bw and Women 2711 calories and 8.8 g carb/kg bw).
The content of the normal diet was 58% C, 28% P, and 14% F. The High carb and the High Carb/High calorie were 75% C, 15% P, and 10% F. Lastly, the FFM (free fat mass) relative to carb consumption was equivalent in all three diets between genders (6.8 vs 6.6, 8.8 vs 8.3, and 11.7 vs 11.3).
The method also required a glycogen depletion exercise to occur on the 5th day proceeding the event. It was 60 min at 65% VO2peak followed by a 2:1 run to rest at 85% VO2peak. The remaining days were at 65% VO2peak at 60, 45, 30, and 0 min proceeding the event.
The result was men increased glycogen storage by 138% over normal and women by 117%. Not the same, but one of the higher reported values for females at the time. The value shown shows the in-theory marathon time that would not require in-race nutrition.
This study does reinforce that a high carb diet alone (75/15/15) was not enough to make a significant increase in glycogen storage in females, but was able to make a nominal increase in males. Males had a 123% increase whereas females had a 113% increase. This was likely due to the disparity in grams of carbs per kilogram body weight, but as the author posits this would require a significant portion of dietary calories comes from carbs to hit a value near 10 g carbs/kg bw.
To note, the males in this study had at least a 55 VO2peak (average was 63) and the females had at least a 45 VO2peak (average was 53). A 45 VO2peak estimates a HM at 1:40 and M at 3:28, and a 53 VO2peak estimates a HM at 1:27 and M at 3:01. Just to give you an idea as to the test subjects in this study.
Tarnopolsky, M.A., S.A. Atkinson, S.M. Phillips, and J.D. MacDougall. Carbohydrate loading and metabolism during exercise in men and women. J. Appl. Physiol. 78:1360Y1368, 1995.
Walker, J.L., J.F. Heigenhauser, E. Hultman, and L.L. Spriet. Dietary carbohydrate, muscle glycogen content, and endurance performance in well-trained women. J. Appl. Physiol. 88:2151Y2158, 2000.
Andrews, J.L., D.A. Sedlock, M.G. Flynn, et al. Carbohydrate loading and supplementation in endurance-trained women runners. J. Appl. Physiol. 95:584Y590, 2003.
Nicklas, B.J., A.C. Hackney, and R.L. Sharp. The menstrual cycle and exercise: performance, muscle glycogen, and substrate response. Int. J. Sports Med. 10:264Y269, 1989.
McLay, R.T., C.D. Thomson, S.M. Williams, and N.J. Rehrer. Carbohydrate loading and female endurance athletes: effect of menstrual-cycle phase. Int. J. Sport Nutr. Exerc. Metab. 17:189Y205, 2007.
Paul, D.R., S.M. Mulroy, J.A. Horner, et al. Carbohydrate-loading during the follicular phase of the menstrual cycle: effects on muscle glycogen and exercise performance. Int. J. Sport Nutr. Exerc. Metab. 11:430Y441, 2001.
James Method
The James 2001 article represents an important piece to the puzzle. In this study, men and women both consumed about 10 g carbs per kilogram body weight (10.5 g/kg bw in males and 9.9 g/kg bw in females). The participants went through a glycogen depletion exercise of 61% VO2peak for 90 min on day 4 prior to the event. The next three days were spent in the carb loading procedure, but no exercise was done.
Both the males and females were able to significantly increase their glycogen storage to about 182% normal. The females were tested 6 days prior to mensuration and separately 6 days post mensuration. All of these women were on oral contraceptives for at least the last two years and showed no hormonal changes between the two timeframes. This is important to note because according to Marieb et al. 1998 females when not on oral contraceptives showed a greater ability to store additional glycogen during the luteal phase of the menstrual cycle.
Because the males and females showed a similar response when on a similar diet (as expressed as g carbs/kg bw), then it leads me to believe that females may elicit the same response from the Western Australian method as did men. This would eliminate the need for three days (as the James method uses) and the need for a GD exercise (as the James method uses).
James AP, Lorraine M, Cullen D, Goodman C, Dawson B, Palmer TN, Fournier PA. Muscle glycogen supercompensation: absence of a gender-related difference. Eur J Appl Physiol. 2001 Oct;85(6):533-8. PubMed PMID: 11718281.
Marieb, E.N. The reproductive system. In: Human Anatomy and Physiology, E.N. Marieb. Menlo Park, CA: Benjamin/Cummings Science Publishing, 1998, pp. 1056- 1061.
Maurten Drink Mix 320 Advantages as a Liquid Carb Source for Carb Loading
As soon as I became aware of Maurten Drink Mix 320, the real possible avenue of it's use became clear to me. Normally, a carb based liquid product requires a 2 g carb per 1 oz water absorption rate. But Maurten Drink Mix 320 is unique given it is absorbable at 4.6 g carb per 1 oz water. When doing a massive carb loading strategy, this is a HUGE win.
Let's say you follow a 10g/kg bw protocol. Let's say you weigh 75 kilograms. That means you'd need to consume 750 g carb to complete the protocol. If you follow the 80% from liquid source, then that's 600 g carbs. If you did a 2:1 ratio like almost all liquid carb sources require, then you'd need to consume 300oz of water on that day. That's 2.3 gallons of water. It can be done, but man is it tough.
Whereas, let's use Maurten instead. At 4.6 g carb per ounce water, that means 600g carb would need 130 oz water. That's still a ton of water, but it's only 1 gallon comparatively. That's a huge win.
But I couldn't be sure whether this was practical and whether Maurten's product had actually been used for carb loading. Their website didn't have anything beyond in-race nutrition really mentioned. So I reached out to Maurten's Sports Nutritionist whom is partially responsible for the carb loading procedure of some of the top athletes they work with (including the Swedish Marathon Champion). He was nice enough to confirm my ideas on the product as well as confirm they do indeed follow a similar protocol in their elite athletes. As the sports nutritionist pointed out, what's probably most important more than anything when following the protocol is the sheer amount of carbs per kilogram body weight. The liquid source doesn't have to be 80% for it to work. It helps it become a feasible protocol for most. But many of their athletes daily diet is already 7-8 g carb per kilogram body weight and during peak season/high volume can be much higher. So he agreed the 10g/kg bw amount is a good number to try and hit, but that it doesn't have to be solely liquid carbs if you don't want it to be (but from a bulk standpoint can make it easier).
Summary
So the short of it.
If you plan to race longer than 90 min, you'll likely benefit from a carb loading strategy. If you're male, you'll need at least 7 g/kg bw to see a noticeable increase. If you're female, you'll need at least 8 g/kg bw to see a noticeable increase (although based on some of the research I'd argue that male/female are probably the same value if tested head to head for a minimal threshold). For females, this likely means a significant increase in a one time caloric intake. You'll gain some weight (as will males), but the weight gain is offset by the performance gains. The Western Australian Carb Loading Method offers a easy to follow procedure with some major benefits over other methods.
-1 day protocol -Can occur as many as 5 days prior to event -Consume 10 g carb/kg bw -No glycogen depletion workout necessary -Use Maurten Drink Mix 320 to reduce the water burden of a liquid carb sourced strategy
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Follow-up Questions
What about intake during the race? Do slower runners require more carbs, 3 hour marathon versus 5? Or does the slower pace offset the amount being burned per hour?
Great question and one that I don't believe necessarily has a definitive answer.
Atkinson G, Taylor CE, Morgan N, Ormond LR, Wallis GA. Pre-race dietary carbohydrate intake can independently influence sub-elite marathon running
performance. Int J Sports Med. 2011 Aug;32(8):611-7. doi: 10.1055/s-0031-1273739. Epub 2011 May 17. PubMed PMID: 21590642.
This paper also evaluated in-race nutrition vs performance and found no statistically significant relationship. Doesn't mean there isn't one, merely that they didn't find one, but did for pre-race carb.
It's my belief that the need for in-race nutrition depends on one's metabolic efficiency. True for everyone that the faster you run, the more carbs you need to burn. But the crux point is not the same amongst all runners. As a general value, it's
(% VO2max - 5%) = % Carbs burned as energy
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.
But this is merely an average with an unknown STD. So some could be %VO2max = %Carbs and others could be %VO2max - 15% = %Carbs.
From there, the research suggests that the caloric burn rate is more dependent on the distance than the duration.
Humphrey, L. [Hanson's Coaching Services]. (2013, Nov 23). Calculating Caloric Needs for Marathon- Updated 11/22/2013 . [Video File].
So a 250 pound person running a marathon (3 hours or 5 hours) would be the same caloric burn (4800 kcal). The fitness is different between the 3 hour marathoner and 5 hour marathoner, but if both ran at 75% VO2max for the race, then the presumption would be they would require the same number of carbs to make it through the race (assuming same metabolic efficiency as well). So since the amount of carbs would be the same, then that means the rate of consumption would need to be higher for the 3 hour marathon runner.
The 3 hour marathon runner would need 113 g carb per hour. *Note this value is above the noted tolerance limit of in-race carbs of 90g.
The 5 hour marathon runner would need 68 g carb per hour.
But both would need about 340 g carb in total (assuming 100% glycogen storage).
But as you can see there were a lot of "averages" and "assumptions" in those numbers. So the answer to your question is not definitive and "depends" on the circumstances between the runners.
If it's better for the carbs to be liquid, then I think it would follow that it would be better for the non-liquid carbs to NOT be fiber heavy - would you agree? That is, go for the white bread carbs rather than whole wheat. I am thinking this would be the case to speed digestion and uptake into the system.
The research seems mixed on this topic. I think the reasoning for the liquid suggestion is not necessarily the speed of uptake. More so, it's less bulky in general because you expel the liquid quite quickly. Thus, making it easier to tolerate. The drink used in the WA protocol paper was heavy in maltodextrose, but did suggest avoiding vegetables (and other "energy poor" foods). An important consideration is likely trying to stay close to the 90% carbs, 7.5% protein, 2.5% fat. If you aim for 10g carbs/kg bw and yet increase protein and fat beyond 7.5/2.5% respectively, then you'll find yourself inadvertently also increasing calories even further beyond normal caloric intake.
It seems like for almost anyone this would be a significant bump up in food intake for the day. Wouldn't there be concerns about how quickly things would be coming out the other end? As in, possibly causing race-morning GI problems? (And when I say "wouldn't there be concerns", I mean "I have some concerns", ha ha.)
Two thoughts.
-Practice the protocol 4-6 weeks in advance of the actual race. That'll tell you how you specifically react.
-As pointed out by the Arnall paper, you can do the carb loading as many as 5 days in advance and still have a statistically significant increase in glycogen storage.
For me personally, I've done this plan several times the day prior to marathons (not with Maurten though) and never found I had an issue.
Is there any discussion as to whether the recommended intake might be based on ideal body weight vs. actual body weight? For an elite runner, they're likely the same, but for others like myself, there's some disparity.
That's a good discussion. Unfortunately, I don't believe anything I read directly answered that question. However, I think we can take several papers together and come up with a hypothesis. As you point you, most studies are based on elite athletes and therefore it's kind of an unknown whether not the results seen in them is correlative to results seen in normal athletes.
1) Simplistically (Energy = mass * gravity * distance)
Based on this, if one's weight were higher, then they are going to burn more calories over the same distance. If you burn more calories, then it means you need more calories. As long as one's metabolic efficiency is the same (an assumption) between their higher weight and their ideal weight, then it would mean the higher weight version of yourself would need more carbs stored to run the same distance race. So this would suggest a higher intake is necessary for someone who weighs more than ideal weight.
2) The Tarnoplosky paper examined men vs women and FFS (free fat mass, or their mass without their fat taken into consideration). So this would be similar but not the same for correcting between non-ideal weight and ideal weight since the majority of non-ideal weight is usually in the form of fat.
Tarnopolsky, M.A., S.A. Atkinson, S.M. Phillips, and J.D. MacDougall. Carbohydrate loading and metabolism during exercise in men and women. J. Appl. Physiol. 78:1360Y1368, 1995.
When men and women had the same intake based on their FFM, there was a difference between glycogen compensation.
At 11.7 vs 11.3 g/kg FFM - Men (138%) vs Women (117%)
But if you were instead to use g/kg bw without correcting for FFM
At 7.9 vs 8.8 g/kg bw - Men (123%) vs Women (117%)
It's not a perfect system because at the lower end of the carb loading spectrum women may not react the same. But according to the James paper, when fed the same amount of carbs on a per kg bw basis (not corrected for FFM), then the Males and Females had the same increase (182%).
James AP, Lorraine M, Cullen D, Goodman C, Dawson B, Palmer TN, Fournier PA. Muscle glycogen supercompensation: absence of a gender-related difference. Eur J Appl Physiol. 2001 Oct;85(6):533-8. PubMed PMID: 11718281.
So it doesn't directly answer the question of ideal vs non-ideal, but does give us some indication between body mass vs free fat mass.
3) The Atkinson 2011 paper was done in "sub-elite" athletes. The average marathon finishing times was 4:33, and the range was 2:48-7:40. In this study, it was concluded that if a runner consumed greater than 7 g/kg bw carbs then they finished faster than the normal population and suffered less of a fade. When the authors pair matched each of the athletes who took greater than 7 g/kg bw with another runner that took less than 7 g/kg bw but was the statistically not different between age, BMI, training data and previous # of marathons, the >7 g/kg bw group was still statistically faster. This would suggest that even when a person has a non-ideal bw, they are still better off taking more than 7 g carbs/kg bw then less carbs.
So I think the hypothesis to be tested has a sound basis of data to back it up. A non-ideal body weight person would still be suggested to take in the greater than 7 g/kg bw carb loading procedure to elicit the desired glycogen super compensation and performance benefit. To know for sure, we'd have to see a solid research study to directly answer this question.
What would you think the results/problems be for someone who is routinely very low carb (<20 per day)? And also does not routinely consume wheat or sugar? My mind went immediately to cupcakes at WDW prior to the marathon, lol! Not optimal carbs I am sure, lol!
Tough question. I came across only one article that seemed to discuss this topic during my research binge.
Problem with the study is it is based on one athlete, and is a 15-day change in diet from LC (31 g per day, or 0.5 g carb/kg bw) to HC (335 g per day, or 5 g carb/kg bw). So I don't think it answers the question since the carb loading wasn't nearly high enough.
I will say that an important consideration to cupcakes is their high fat content (even though I know you're joking). Ideally, the carb loading be done with a large % of your diet consisting of carbs. The more fat/protein beyond the 90% carb, 7.5% protein, 2.5% fat used in the WA protocol, the more calories you are likely piling on since you're still aiming for the 10 g carbs/kg bw. So more calories means you'll probably feel even fuller and may gain slightly more weight.
As with everyone else, I'd suggest giving it a try mid-training plan to see how you tolerate it. You can find for yourself what level of carbs works best. Technically, you wouldn't even have to practice before a long run if you didn't want to. You're not testing the performance benefits. Merely, whether or not you can tolerate that level of consumption. This way it would have the least impact on your training.
