To Spit or to Swallow - That is the Question! Carbohydrate Mouthrinse May Be Better Than Water, Yet Still Not an Option for Performance Oriented Athletes

Image 1: "You need carbs to fuel your workouts!" You know the whole litany... what may be news to you is that scientists are speculating that "intra workout carbs" do not necessarily have to be ingested to do their ergogenic magic.

Those of you, who already "friended" me on Facebook and are following what is going on on the SuppVersity Facebook page (just want to remind you that Facebook has now an option that allows you to be informed, whenever something new is posted), will probably remember the discussion revolving around "carbohydrate mouthrinsing" and whether or not it may be even more beneficial to spit and not to drink your Gatorade... now, all the health benefits of low-carbohydrate (when I am talking "low" I am not talking of Atkins type <80g) diets aside, it does seem pretty counter-intuitive that just swishing one of those carbohydrate-laden electrolyte drinks in between your teeth for a few seconds, to then spit it out again could actually have any merit. Yet, science, or I should say a handful of studies, do suggest otherwise.

As part of their recently published study into the effects of carbohydrate mouthrinsing on exercise capacity in the pre- and postprandial state (Fares. 2011), Elie-J. M. Fares and Bengt Kayser have compiled a list of the 8 hitherto published peer-reviewed papers on that subject. And if you just went by the column "increased perfomance", "yes or no", it appears like it was an established fact that carbohydrate mouthrinsing was highly ergogenic. After all, six out of the eight studies are marked with the tag "increased performance".

Figure 1: Performance increases and standard deviations of the respective measures from studies on the advantage of carbohydrate vs. artificially sweetened or plain water mouthrinse (data calculated based on summary in table 2 of (Fares. 2011)

If we do yet have a look at the quantity of those performance increases and the individual standard deviations (I compiled the respective data for you in figure 1), things begin to look less conclusive. I mean, there is obviously a standard deviation for both arms of each study and there also is a mean improvement (or decrease in performance), but if the "performance increment" is smaller than the standard deviation, for all but one study, this does make me feel uncomfortable with the statement that I would see "scientific evidence", let alone "conclusive scientific evidence" in support of carbohydrate mouth-rinses.

Mouthrinse vs. placebo = minimal (if any advantage), but what about vs. ingestion?

Regardless of what you think about the real world significance of an average performance increase of 1% (calculated based on the data from figure 1), for the small fraction of athletes for whom these minimal performance increases would actually count, i.e. high intensity endurance athletes, like time-trial Tour de France cyclists, the "control", or I should say the "benchmark" should not be plain or sweetened water, but rather one of these crab-, ah... pardon me, carb-loaden sugary electrolyte drinks these athletes are habitually consuming. I was thusly happy to see that Catherine Moss, a student of Sports and Exercise Sciences at the Massey University in Auckland, New Zealand has recently conducted an experiment for her thesis that has much more practical relevance for the high achieving athletes (Moss. 2011).

Table 1: Composition of the placebo and CHO supplement in the Moss study (adopted from Moss. 2011)

In a randomized, counter-balanced, double-blind study, Moss had eight recreationally trained cyclists perform a time trial (with a predetermined amount of work) in the course of which the cyclists ingested or rinsed (swirling 0.33ml/kg body weight of the solution for 8s) with either a placebo solution or a carbohydrate drink, whenever another 12.5% of the total work was done. In that it is worth mentioning that the composition of the CHO solutions differed for the one that was meant to be ingested and the one that was intended to be swished. With the former containing 7.5% and the latter 15% carbs, Moss mimicked solutions that had been used "successfully" previous studies. I do yet no idea, why the placebo did not contain electrolytes, as this could obviously have made a difference at least in the ingestion trials... I guess this is what distinguishes a thesis like this from a study that is worth being published in a peer-reviewed journal ;-)

Figure 2: Mean power output (in Watts) at different time points during time trial (data adapted from Moss. 2011).

As the performance data in figure 2 goes to show, only the ingestion of the carbohydrate led to significant improvements in mean power output, specifically at the later stages of the time trial. This "breakdown" may be explained by the "glycogen reduction exercise protocol" all participants had conducted the day before the time trial. So that after a "low carbohydrate" dinner, the participants were supposed to be glycogen depleted when they performed the time-trial on the subsequent morning.

Figure 3: Total time (in s) during time trial (data adapted from Moss. 2011).

In a way this is an unfair advantage, for the carb ingestion, which accordingly elicited way better time trial times. It does yet not lessen the significance of data on carbohydrate vs. water mouth rinse, which shows pretty conclusively that in a glycogen depleted state both forms of mouthrinsing (plain water or a 15% carbohydrate solution) are equally ineffective, when it comes to actual performance increases.

Figure 4: Pleasure / displeasure feeling during time trial (data adapted from Moss. 2011).

If you do however look at the pleasure/displeasure feeling scale data in figure 4, I would speculate that in a non-glycogen depleted state the carbohydrate-rinsers would have performed significantly better... I mean, without gas in the tank a car won't work even if it "wanted". In view of the fact that the carbohydrate ingestion group did yet pedal at a higher intensity, this would warrant further investigation.

Figure 5: Respiratory exchange ratio (higher values = higher carbohydrate oxidation) during time trial (data adapted from Moss. 2011).

That being said, there was what I consider an interesting effect of carbohydrate rinsing on the respiratory exchange ratio (remember higher values = higher carb oxidation), which would suggest that the theory Fares and Kayser propose (Fares. 2011), according to which the activation of sweetness taste receptors cells (T1R2 and T1R3) in the mouth would explain the previously cited performance "increases" in other studies, may have its merits. What else than the sensation of incoming carbs could explain that the cyclists burned more carbs in the carb mouthrinse compared to the placebo mouthrinse trial (cf. figure 5) - and that in the absence of significant differences in blood glucose or insulin levels?

Spit it or suck it? What's right for you?

While we do not know whether it would make sense to mouthrinse in a glycogen repleted state (yeah, I know +1% ;-), for any athlete interested in maximal performance, simply ingesting his carb + electrolyte drink would certainly be the best option. The (intermittendly) fasting dieter, who wants to maximize his fatty acid oxidation in the course of say his "morning cardio", on the other hand, would be best off with a non-carby electrolyte drink that helps him avoid dehydration and does not compromise (even if the effect is minimal) fatty acid oxidation... what? You want to know who would  benefit from spitting his carbs out? Well, at least based on the current data, mostly the cleaning contractors of your local gym - after all, they would have to work overtime (and be paid overtime) to clean up the mess ;-)

Intermittent Thoughts on Intermittent Fasting - Programing Success: Building Muscle Begins With Losing Body Fat.

Image 1: Arnold does the "double bicep" + vacuums. If you want to look like a bodybuilder, muscle alone is not enough.

First, I want to thank Jahed, Pablo, RF, Angimal, Garrett and Rudolf for their patience. After all, it has been two weeks now since you have submitted your (meta-)goals, which were all more related to building muscle and increasing performance, then to losing body fat, which was the topic the last installment of the Intermittent Thoughts dealt with. Yet although, at first sight, both topics have little (to nothing) to do with each other, there are are at least three important factors by which a reduction in body fat is very well related to increased muscularity and skeletal muscle hypertrophy. Let's get back to the "Peter Griffin" type of chubby person from the last installment, for a few seconds. Imagine "Peter" has packed on, say 10lbs of lean muscle and now stands in front of you, does the "double bicep" and vacuums, just like Arnold does in image 1... what? Why are you laughing?

Do you want muscles? Or do you want to look muscular?

Now, obviously the first intersection of bodyfat and muscularity (in a broader sense) relates to the question whether or not your body fat level is low enough for any increases in skeletal muscle mass to be visible. I mean +10lbs on the ripped frame of a 202lbs (now 212lbs) bodybuilder look absolutely freekish. On our Peter Griffin, a gain of 10lbs of lean muscle tissue will probably go completely unrecognized - this also puts "chubby" beginners at risk of neglecting the strength training component of their exercise regimen, because, from a mere "cosmetic" stand point, each gram of body fat they drop will make a significant difference in terms of the way they look. Building muscle beneath the thick layers of adipose tissue, on the other hand, initially appears to have little value... but remember: looks are deceptive, and I hope that my elaborations in the last installment made it quite clear "building a bigger metabolic engine" and not starving the latter away on a low-calorie diet, is the cornerstone of maintainable reductions in body fat levels.

Figure 1: Where are you on the fat/muscle mass (FFMI = weight/height[in m]²) continuum? *indicates age-group 20-29 in the NHANES dataset (data based on data from Hattori. 1999; Picket. 2005; CDC, NHANES data from 2010)

Interestingly enough, being lean, or, I should say, the metabolic and endocrine consequences of being lean actually have way more profound implications on "building muscle", than the mere advantage of the immediate visibility of the newly acquired lean body tissue. On "the boards" (meaning bulletin boards like bodybuilding.com, anabolicminds, etc.) it is a recurrent topic whether you should "bulk" (people there interpret that mainly as "eat to gain" and often as "overeat to gain") or "cut" (meaning lose fat) first. And while the answer obviously depends on where you are starting from, it stands out of question that the average American male (aged 27-62) who gets fatter and fatter every year and currently has a body fat percentage of 24.9% (Rohrmann. 2011) would be ill-advised to even think about the word "bulking".

Image 2: Just to put the 24.9% body fat of the average American male into perspective. The average bodyfat percentage of a sekitori sumo wrestler is 28.6%
(Hattori. 1999)!

Please note, that the "no bulk with high body fat percentage" rule does also apply to the female physical culturists out there. The reason that I am mainly addressing the male faction of my readership here, is that women are not so stupid to think, they would have to down 2-3 portions of "weight gainers" (these products are exactly what they are called, they will make you gain weight, not muscle) and 4-5 protein shakes in addition to a hypo-caloric (junkfood-)diet in order to build a muscular physique, anyways. Things would be different, though if the physique of a sekitori sumo wrestler (one of the higher ranked sumos, cf. image 2), is what you are aspiring. In that case you can start "bulking" with weight gainers and all the other "high class" products the industry has to offer... I mean the average sekitori sumo has 109kg of lean muscle tissue hidden somwhere beyond the 45.4kg of fat he is carrying around the dohyo.

If you want to "program success" and your "motivational elevator pitch" from part one of this part of the Intermittent Thoughts Series contains sentences like "look like a cover model." (Garrett; November 14, 2011 3:05 AM) or "[building] a stronger body, bodyfat below 8%" (RF, November 7, 2011 12:22 PM) or my favorite one which obviously nobody was dared to say, yet 90% of the Men's Health readers probably have on their minds "build muscle just to look good at the beach / impress the ladies", it is imperative that you lose your love handles first! Not to (just) to be able to see the gains you are making, but to set yourself up for optimal lean muscle gains (in essence, this is also related to the assumption Jahed Momand's assumption made in his "motivational elevator pitch" that leaning out prior to building his maximal clean and jerk and snatch to compete at 85kg probably is the smartest way to go, after all a low body fat percentage is obligatory if you want to be competitive in the lower weight classes).

The endocrine advantage of low(er) body fat percentages

The first and often overlooked advantage of a decent degree of leanness (cf. "active American", figure 1) is a hormonal one. According to the findings of the latest (published) NHANES data (National Health and Nutrition Examination Survey III; Rohrmann. 2011) there is a direct correlation between body-fatness as measured by BMI, waist circumference and body fat levels, on the one hand, and total and free testosterone and estrogen levels and their binding globulin SHBG:

Total and free testosterone and sex hormone binding globulin concentrations decreased, whereas total and free estradiol increased with increasing BMI, waist circumference, and percent body fat (all p trend < 0.05). 

Further statistical analysis of the data reveals that a body fat increase of one-quartile (e.g. from the lower 1/4 of the study population to the next fatter quartile) goes hand in hand with a decreases in sex hormones into the next lower quartile (e.g. from the highest into the next lower quartile). A sample calculation for a 50 year old white non-smoker revealed that for each 5.2cm increase in body waist circumference or +2.7% increase in body fat, the free testosterone level decreased by 2%. With an increase of "only" +3.7cm or +1.8% in waist circumference or body-fatness, respectively you can however bump up your estrogen levels by 2%.

Figure 2: Relative free testosterone and free estradiol levels in men from the NHANES study; data expressed relative to serum levels of "lean" men with <84.9cm ~ 33.4" waist circumference; values above the bars are the differences between relative testosterone vs. estradiol levels compared to "lean" men (calculated based on Rohrmann. 2011)

In view of the differential response of androgenic and estrogenic free (i.e. "active") hormones to changes in body-fatness (cf. figure 2), it is no wonder that we see a characteristic and in terms of lean muscle gains highly unfavorable pattern in the "fatter" quartiles of the study population, with maximal  free estradiol levels (1.08pg/ml; +30% vs. min) and minimal free testosterone levels (0.097ng/ml; -13% vs. max) in the "fattest" quartile of the study population (I deliberately selected waist circumference over "body fat levels" which were measured by bio-impedence, as my body fat marker of choice). Even if you as a SuppVersity reader should by now be aware that testosterone alone does not "build muscle", its highly facilitative effect on exercise induced increases in lean body tissue is significantly blunted by the fat-induced reduction in free testosterone and the (by the way fat promoting) increase in free estradiol in "chubby" men.

The endocrine factor: By leaning out first you set the hormonal scene (a higher testosterone to estrogen ratio) for optimal lean muscle gains.

The metabolic advantage of lower body fat levels

While testosterone and estrogen levels obviously figure large in the orchestrate that determines whether the nutrients you ingest (remember no one of you eats "calories") end up being stored as body fat, used as "fuel" or building block for lean muscle tissue, insulin, the "most anabolic agent in the world" (a quote from steroids.com; obviously a very questionable statement), may play an even greater role, when it comes to building muscle, not fat. Those of you have have listened to Dr. Layne Norton's and Dr. Connelly's dissertations on the largely misunderstood role of insulin in relation to the protein synthetic response to exercise, as well as its highly undesirable effects on fat storage during the last episodes of BodyRX Radio, will be aware that the often touted idea that "insulin is the most anabolic agent in the world" applies, above all else, to adipose tissue.

Image 3: "Insulin the most anabolic agent in the world"!? Correct, if we are talking about fat,  not muscle tissue ;-)

While "broscience" and the producers of sugary "weight gainers" and "post-workout recovery formulas" still maintain the myth of the "muscle building insulin spike" the (post-workout) ingestion of large amounts of fast-acting carbohydrates would provide, a recent study from Stuart Phillips lab at McMasters University into the purported benefits of the "insulin spike" produced by the co-ingesting 50g of carbohydrates with your 25g of whey protein post-workout found neither an increase in muscle protein synthesis, nor decreases in muscle protein breakdown, which are often cited as another benefit of increased insulin levels (Staples. 2011). More specifically, the additional +1,250% (!) increase in insulin (over +400% with whey alone) did not have any additional effect on protein synthesis, or, in other words: With insulin some (here 5x above fasted baseline) appears to be good, more, on the other hand is not only not better, it is in fact worse.

That being said, the improvements in insulin sensitivity which go hand in hand with reductions in body fat levels (increases in leptin sensitivity, reductions in inflammation, etc.) will decrease your basal, as well as your postprandial insulin levels, because your body will simply need less of the storage hormone to get the job done. This, in turn, will allow you to fuel your workouts with appropriate (not exorbitant) amounts of carbohydrates without running the risk of storing additional body fat. This is particularly true, in view of the fact that the "type of insulin sensitivity" you acquire when you selectively lose body fat (not muscle) favors the storage of blood sugar as muscle glycogen over its conversion to triglycerides and subsequent storage in adipose tissue (note that the latter happens both in obese and insulin resistant, as well as in "reduced obese" individuals, who have lost a lot of body mass, not fat, on prolonged calorie restricted diets).

The metabolic factor: By reducing your body fat levels first (leaning out vs. just losing weight) you decrease the risk that (superfluous) carbohydrates (and other nutrients) get stored as body fat.

The anti-livelong-obesity advantage of lower body fat levels

Image 4: There are two ways to get fat, adipose tissue hypertrophy and adipose tissue hyperplasia. While you obviously want to avoid both, only the latter is potentially irreversible (Otto. 2005).

The third and maybe most far-reaching  advantage of lowering your body fat level before bulking up is actually related to the leeway you have in terms of the unavoidable fat gain that is part of every "bulk" no matter how "clean" it may be (see also red box below). It should be obvious that just as the myonuclei in your skeletal muscle have a limited capacity to "grow" (also to hypertrophy, i.e. to simply increase their size /we will discuss the three pathways of muscle growth in one of the upcoming installments in more detail), your fat cells can only store a finite amount of lipids before they begin to "burst from the seams" (some scientists even believe that this is part of what triggers the detrimental inflammatory cascade in obese individuals). When that is about to happen, the only way your body can protect itself from suffocating in glucose and triglycerides that can neither be burned as fuel nor stored in the bristling adipocytes is to generate new fat cells (adipocyte hyperplasia).

My definition of a clean bulk: You may now be shocked to hear that even a "clean bulk" will necessarily also increase the amount of body fat you are carrying. That, and this is a very important point, does yet not mean that your body fat % must necessarily increase. A "clean bulk" by (my) definition is a bulk where you add more muscle than fat tissue to your frame. Now, even if you you were an absolute zero in math, you should recognize that this implies that your body fat percentage would actually drop, although your overall body fat levels may increase. Keep that in mind, whenever you are trying to gain muscle. Your goal should never be to cut fat (reduce overall fat mass) and build muscle (increase lean muscle tissue) at the same time - if you try that you program stagnancy, not progress!
Now, the unfortunate truth is that it is pretty easy to "empty" those cells again (you can do this in weeks), yet uncertain on which time-scales (if at all) and by which means (other than surgery) you can get rid of newly acquired adipocytes ever again.

An infant usually has about 5 to 6 billion fat cells, the number of which naturally increases during early childhood and puberty, so that the average healthy adult ends up with 25 to 30 billion fat cells. If those 30 billion adipocytes are already filled up when you start bulking, chances are that your body feels compelled to increase its storage capacity, so that - in the worse case - you end up with the roughly 75 billion fat cells, the typical overweight adult is carrying around on his "chubby" frame. If you still insist that you are not "big" enough and continue to eat whatever you can grab, the number of fat cells can increase up to 250, even 300 billion... it stands to reason that even when you emptied all of those, you would still be "fat".

The anti-obesity factor: By leaning out first, you reduce the risk of a (potentially irreversible) increase in adipocyte number that may set you up for lifelong weight problems.

An intermittent conclusion on the first step of programming skeletal muscle hypertophy

Image 5: After a handful of unsuccesful bulking efforts, SuppVersity Student Duong Nguyen eventually made it right - he leaned out first. If you are interested in his subsequent bulk, check out his blog!

As you may notice, I (once again) went off on a tangent. I hope you don't mind that you have not yet learned about effective ways measure your progress, about how to improve your gains by setting realistic, but challenging goals and about the often-overlooked impact the mind-muscle will (not could!) have on the real world outcomes of your efforts in the gym, in this installment of the Intermittent Thoughts.

But hey! For (hopefully) a minority of you the "time to bulk" may not have come anyways ;-) So, if you have not achieved a degree of leanness comparable to that of the "average active American" (cf. figure 1), I suggest you re-read last week's installment on setting yourself up for body-fat loss and thusly take appropriate measures to increase the effectiveness of your first or next "bulk" and decrease the propensity of doing permanent "aesthetic" or even metabolic damage.

As for the rest of you, I would hope that you could at least gain a few new insights into the challenges your not so lean friends are facing when they are trying to gain muscle without adding another inch to their waistlines.

VPX Pre- & Post-Workout Nutrition Gets "Sponsored" Scientific Approval: +4% Lean Mass, -6% Body Fat, +13% Upper and +21% Lower Body Strength in 29 Days

Image 1: Supplemental double-whammy. VPX' now
"scientifically proven" pre- & postworkout products

This is one of those cases, where I cannot decide whether I should applaud VPX or just shake my head... the scientist in me says: "Hey, you know how that is - with a research grant from the government cutting edge science is impossible, especially if you want to investigate something as 'profane' as building muscle". The cynic skeptic, on the other hand, whispers: "Come on, what results would you expect, if the study was financed by the producer of the supplement under scrutiny?" I guess I will applaud skeptically and exercise special caution in my analysis of the latest study from the Department of Health and Performance at Baylor University (Willoughby. 2011).

As in previous studies (Willoughby. 2007; Willoughby. 2009), Darryn S. Willoughby and his colleagues availed themselves of a buckload of VPX supplements and recruited 19 previously recreationally active, yet untrained (*) men with an average age of 22.8 +/-4.67 years, a height of 179.5 +/-6.38 cm and a total body mass of 79.1 +/-16.13 kg for another study into the effects of two supplements, which are supposed to "advance you to the next level of fitness" (VPX. 2011). Strength and body composition (body fat measured reliably by DEXA, not body-impedance), venous blood sampling and muscle biopsies were performed on day 0 and day 29 of the 4-week study period, in the course of which the participants underwent a standardized resistance training protocol (upper-/lower-body split, 4x à week), which mirrored the one that had been used in Willoughby. 2009 already (*).

Figure 1: Illustration of the training regimen (based on Willoughby. 2011)

The bodybuilding-type beginner 2x split training regimen is unquestionably a huge plus of the study (cf. figure 1). Performed twice a weak, this is what real world training would look like and so that it stands out of question that the results of the study will translate into practice - at least for everyone who has not touched a dumbbell more than thrice a week within the last 12 and abstained from all sorts of performance enhancing supplements and drugs within the last 3 months (*).

The NO Shotgun approach to protein NO SyntheSize??? 

Figure 2: Ingredient profiles of
No Shotgun and No SyntheSize

More important than the identical training regimen was yet obviously the supplementation protocol, to which the participants were assigned in a double-blind randomization process (on a side note: "double-blind" means that not only the subjects, but the scientists, as well, did not know which participants received the placebo and which ones the VPX products). While half of the subjects consumed a maltodextrose placebo (27g pre, 27g post workout), the subjects in the "NOSS" group consumed the same amount of NO Shotgun and NO SyntheSize as their pre- and posworkout supplement, respectively. Now, as the names imply, both supplements are intended to increase nitric oxide production and protein synthesis, yet with a focus on the former in NO Shotgun that is loaden with arginine and a heap of stimulants and a focus on the latter in NO SyntheSize, the composition of which is pretty similar (cf. figure 2), yet without the "Redline Energy & Meltdown Fat Burning Technology" ;-)

Although there were no specifically dietary guidelines, the research did at least collect some nutritional data based on a 4-day questionnaire all participants had to answer at the beginning and end of the study. While there was a slight reduction in the total caloric intake in the carb group (interestingly mainly from carbohydates), neither the intra-group changes, nor the inter-group differences reached statistical significance.

More muscle, less fat! Trainee, what more can you ask for?

That there were no differences is yet something you cannot say of the changes in body composition the study participants underwent in the course of this 28-day intervention.

Figure 3: Relative changes (compared to baseline) in body composition after 16 strength training sessions in 28 days with either 54g of maltodextrin or 27g of NO Shotgun and 27g NO Synthesize pre- and postworkout (Willoughby. 2011)

As a passing view of the relative changes (compared to baseline) in figure 3 show, the NOSS group (receiving NO Shotgun prior and NO SyntheSize post workout) registered significantly more pronounced elevations in fat free mass (p<.023 indicates that the chances that this was sheer coincidence are 23%) and - contrary to the carbohydrate group - lost -6% of their body fat, while the carb eaters added another 2% of adipose tissue to their love-handles.

Figure 4: Changes in upper and lower body strength (in kg/kg body weight during bench press and leg press at 1RM) after 16 strength training sessions in 28 days with either 54g of maltodextrin or 27g of NO Shotgun and 27g of NO Synthesize pre- and postworkout (Willoughby. 2011)

Interestingly, the lean mass increase went hand in hand with likewise (statistically) significantly greater (p-values see figure 4) increases in both upper (+13% vs. +1%) and lower (+21% vs. +11%) strength in the subjects in the NO Shotgun + NO SyntheSize groups.

* you may have wondered what all the asterisks in the previous paragraphs meant... well, they indicate specificities in the study design detractors may call "precautions that ensure that the VPX supplements are sitting pretty" ... I mean the exact same supplementation protocol performed on a bunch of veteran bodybuilders would probably not have elicited any measurable effects on body composition - keep that in mind when you interpret the results.

Now, it obviously should not surprise you that the protein (and leucine) loaden and creatine, beta-alanine spiked workout supplements outperform simple sugar water. It is thus more interesting to take another look at the data from the 2009 "NO Shotgun only"-study, Willoughby et al. have done (Willoughby. 2009). On the exact same training protocol, yet with only 27g of NO Shotgun or placebo 30min preworkout, the participants lost less body fat (-1.21%), but gained the exact same ~4% of lean mass and comparable increases in bench press and leg press 1RM (+8.82% and +18.4%, respectively).

Scientifically proven ingredients make scientifically proven products

I leave it up to you whether or not the results of this study will influence your next supplement purchase - after all, even the VPX guys will be aware that their supplements are not so unique that intelligent people like you would not be able to identify the key ingredients in their products (EAAs, hydrolized protein, creatine, beta alanine, some workout-boosting stimulants, etc.) and realize that there are way more than those two products which would probably have produced identically (within statistical margins) results, if, and here we've come full circle, if their respective manufacturers had the money and the balls to do scientific studies on their products.

Pre-Workout Nutrition & Supplementation for Athletes - What Works, What Doesn't Work | Perfect Timing, Fast or Slow Carbs, Glucose & Fructose, Fats, Protein & More

For sedentary, video-game and smartphone addicted youths, it's they're the gateway drug.. ah, I mean drink to insulin therapy for full-blown diabetes. For athletes CHO + caffeine containing drinks can be very useful.

As Michael J. Ormsbee and his colleagues point out in their latest review, "[e]ndurance athletes rarely compete in the fasted state, as this may compromise fuel stores." The means by which means endurance athletes (and anyone who is about to embark on a long(er) workout) should (pre-)fuel their workouts is yet still debated.

Some swear by whole foods, others stick to special carbohydrate mixes, others again combine carbohydrates and protein and many simply grab the next best energy drink or supplement with an allegedly "science-based" formula. What is optimal, however, isn't just determined by the amount of energy it delivers. It's also influenced by the metabolic effects of the preworkout meal.

Learn more about carbohydrates at the SuppVersity!

Intra-Workout CHO 101

Spit or Swallow Your Carbs?

Peri-Workout Supp Update

PWO CHO or PRO Supplementation?

194 Bananas in 3 Weeks - Healthy!

The Fructose Scam: An Update!

Having a ton of fat, but no carbohydrates, for example, could steer an athletes metabolism away from carbohydrate and toward fat metabolism. For a sprinter this would be a disaster, for an endurance athlete, on the other hand, it could have certain benefits.

When I look at the tabular overview of the studies, Ormsbee et al. reviewed in their latest paper, there is yet another factor that appears to have an even greater impact on the benefits of pre-workout meals / supplementation and that's timing! In the discussion of their results, the South African researchers write.

Figure 1: Drop in glucose in well-trained cyclist on the onset of 30min cycling exercise after ingestion of 75g glucose or fructose or placebo (Koivisto. 1981)

"The timing of CHO intake influences its metabolic effects. Indeed, insulin and blood glucose elevations are positively correlated with CHO meal proximity to exercise (Moseley. 2003). Studies in which CHO is consumed 1–4 h prior to exercise often report glucose and insulin levels declining to near-basal levels prior to exercise (Coyle. 1985; Kotsiopoulou. 2002; Chen. 2009).

Alternatively, when subjects consume CHO ≤60 min before exercise, insulin and blood glucose levels are reported to be elevated immediately prior to exercise (Koivisto. 1981; Chryssanthopoulos. 1994; Febbraio. 2000a,b)." (Ormsbee. 2014)

What both the 1-4h prior and the <60 min pre-exercise approach have in common is that they trigger an initial drop in blood glucose at the onset of the exercise period. Interestingly, the latter is more pronounced for shorter time-spans between the ingestion of the meal / nutrient supplement and the workout.

If we go by the general trend in the studies,Ormsbee et al. reviewed, it appears as if you'd better leave 60min between your last meal and your workout if you want to benefit.

Take home message T as in "timing": If you belong to the unfortunate few percent of people who bunk at the beginning of their workouts don't eat in the 1h-pre time.window. Other ways to at least reduce the drop in blood glucose are: (1) use fruits / fructose instead of glucose and (2) skip the pre-workout meal altogether ;-)

In general, it's not necessary to consume "slow" carbs. Chen et al. for example observed performance increases with high, but not with low GI carbs ingested 2h before a workout (Chen. 2009); what Ormsbee et al. don't mention in their overview, tough, is that this worked only, because the subjects supplemented 2h before and during the workout.

In view of the aforementioned problem with reductions in blood glucose it should be obvious that consuming high glycemic index (high GI) carbohydrates before a race may not be ideal.

Figure 2: When they are ingested 30 min before an endurance exercise bouts, slow digesting carbohydrates (LGI) from muesli have no advantage over fast digesting carbs (HGI) from instant mashed potatoes [please not that this study also shows that it doesn't have to be Gatorade or other sugar water]; on the contrary, the lactate levels after the workout were lower and the total work was higher (albeit not significantly) in the HGI trial (Febbraio. 2000a)

The experimental evidence, on the other hand, shows that when the high GI meal (instant mashed potatoes) is consumed 30 minutes before the workout, there are no negative effects on the exercise performance of 8 trained men who cycled at 70% peak oxygen uptake for 120 min followed by a 30-min performance cycle (see Figure 2).

Fat burning machines train low and compete high!?

Similarly, the evidence for the usefulness of high fat feeding immediately before a competition isn't there (Ormsbee. 2014). Rather than that many endurance athletes who follow a lowe(er) carbohydrate diet, "train low" and "compete high" - in this case "high" and "low" don't refer to the altitude, thought, but indicate training with a low carbohydrate intake and increasing the carbohydrate intake shortly before a competition. Some experts see this critically, though. Louise M. Burke, for example, writes:

"More recently, it has been suggested that athletes should train with low carbohydrate stores but restore fuel availability for competition (‘‘train low, compete high’’), based on observations that the intracellular signaling pathways underpinning adaptations to training are enhanced when exercise is undertaken with low glycogen stores. The present literature is limited to studies of ‘‘twice a day’’ training (low glycogen for the second session) or withholding carbohydrate intake during training sessions. Despite increasing the muscle adaptive response and reducing the reliance on carbohydrate utilization during exercise, there is no clear evidence that these strategies enhance exercise performance. Further studies on dietary periodization strategies, especially those mimicking real-life athletic practices, are needed." (Burke. 2010; my emphasis)

In an article in the Journal of Sports Sciences Burke wrote with John A. Hawley, Stephen H. S. Wong & Asker E. Jeukendrup, the authors accordingly classify the "train low, compete high"-principle as principle with "equivocal evidence" (Burke. 2011).

But what about fat adapation and keto-athletes? Obviously Burke's position stands in contrast to papers by Volek, Noakes and Phinney who have recently repeated their conviction that "the shift to fatty acids and ketones as primary fuels when dietary carbohydrate is restricted could be of benefit for some athletes" (Volek. 2014), even though they still cannot provide the scientific evidence that would turn the "could" in the previously cited sentence into a "can".

More recent research again suggests that we may not even be dealing with an "either or" problem, here. In fact, an experiment Murakamiet al. conducted only recently would suggest:

Could using fat and carbs, instead of fat or carbs increase performance even more?

The scientist from the Fukuoka University examined the performance effect of consuming either: (1) a high-fat meal 4 h pre-exercise + a placebo jelly 3 min before exercise (HFM + P); (2) a high-fat meal 4 h pre-exercise + maltodextrin jelly 3 min before exercise (HFM+ M); or (3) a high-CHO meal 4 h pre-exercise + placebo jelly 3 min before exercise (HCM + P).

The study was conducted after the subjects, eight  male collegiate long-distance athletes, who engaged in physical training almost every day, had consumed an isocaloric, high-CHO diet for three days (2562 ± 19 kcal). The isocaloric test meals (1007 ± 21 kcal) were consumed 4 h before a standardized exercise test consisting of 80 min submaximal runing on a treadmill at each runner’s pre-determined lactate threshold (LT) speed.

Post-workout muscle glycogen resynthesis with glucose or glucose + fructose (Casey. 2000)

What's the right starch for you? Unless you plan to work out for less than 20 minutes, you should prefer slow digesting modified starches (resistant starches) like WM-HDP over fast-digesting ones like Vitargo(R) in your pre-workout nutrition. When it comes to intra-workout nutrition, though, A mix of both fast and slow digesting carbs can yield additional benefits. The same holds true for post-workout supplementation, where the isocaloric replacement of up to 50% of the glucose with fructose can make the tons of sugar easier to handle for your stomach (Casey. 2000), and the addition of 0.4g/kg of fast digesting protein to 0.8g/kg carbohydrates can significantly increase the glycogen resynthesis after workouts (van Loon. 2000).

The endurance component was immediately followed by a time trial to exhaustion (TTE), where the HFM + M group were able to run 8% (8 minutes) longer than their peers in the HFM + P  and the 10% longer than the HCM + P group. As Ormsbee et al. highlight in their review:

"This suggests that CHO feeding subsequent to a HFM pre-exercise and three days of a proper CHO loading protocol can elicit an enhancement in the endurance performance of well-trained runners.[...] however, Murakami and colleagues did not include a HCM + M group, which raises questions about whether the HFM + M group performed longer primarily due to HFM [i.e. due to the extra fat] or rather as a result of the increased caloric consumption of maltodextrin immediately pre-exercise." (Ormsbee. 2014)

It appears likely that this methodological issue renders the study results more or less worthless, because previous studies have found more or less unequivocally that fat and fat & carbohydrate supplements don't increase the exercise performance of endurance athletes:

• 

  Figure 3: Next to changes in substrate oxidation (CHO ￬ | FAT ￪) the blunted growth hormone response was the only sign. difference Whitley et al. found when they compared a high carbohydrate to a high fat meal (Whitley. 1998)

  Whitley et al. (1998) who couldn't find a performance increase w/ 50g of carbohydrates, 14g protein and 80g fat during 90 min cycling 70% VO2max and a 10 km TT
• Okano, G., et al. (1996) who didn't find performance increases in response to the ingestion of a 30% carbohydrate, 61% fat and 9% protein meal 4h before an exercise test that consisted of cycling at 65% of the maximal oxygen consumption for the first 120 min of exercise, followed by an increased dose of 80 % V0_max,
• Rowlands et al. (2002) who found no benefits of consuming a high fat meal before a 50-km time trial, and
• Paul, et al. (2003) who found that even dosed at 1.3g/kg body weight a high fat meal has no effect on timetrial performance of 8 trained men.

Overall, the combination of fat and carbohydrates or the use of fat instead of carbohydrates does therefore appear similarly futile. What is important, though, is that having fats in your preworkout meal is not going to decrease your workout performance significantly. Moreover, it remains to be seen, whether the results differ in "fat adapted" athletes in future studies.

Caffeine & protein, the bodybuilder's darlings

Both caffeine and protein have been shown to be useful for endurance athletes, but only the former, i.e. caffeine supplements will lead to significant performance increases.

"Regardless of an athlete’s genetic disposition, a dose of 3–6 mg of caffeine/kg of body weight has been shown to enhance performance in most individuals, with no further benefit from higher doses." (Ormsbee. 2014)

For the latter, i.e. protein, the latest review clearly states that the contemporary evidence shows that

"[...] when carbohydrate supplementation was delivered at optimal rates during or after exercise, protein supplements provided no further ergogenic effect, regardless of the performance metric used." (McLellan. 2014)

What protein supplements can do, though, is to speed up the glycogen resynthesis and glycogen hypersaturation after workouts (Morifuji. 20045) and contribute and "enhance skeletal muscle remodelling and stimulate adaptations that promote an endurance phenotype" (Moore. 2014).

 Post-Workout Glycogen Repletion - The Role of Protein, Leucine, Phenylalanine and Insulin. Plus: Protein & Carbs How Much do You Actually Need After a Workout? Learn more about PWO supplements

Bottom line: Last week I've concluded that there is currently no alternative to carbohydrates, when it comes to intra-workout supplementation on long(er) duration endurance races. This week, the conclusion I will borrow from Ormsbee et al is not much different: "Consuming a CHO-rich meal [>0.8g/kg body weight] in the hours prior to endurance exercise appears to benefit performance."

The use of high fat supplements or additional fat in a pre-workout meal, on the other hand has no significant scientific backup that would suggest that it does anything, but shift the substrate metabolism from high glucose to medium glucose & medium fat oxidation. Protein and caffeine, on the other hand can help. Yet only caffeine (0.3-0.6mg/kg) is something that will have immediate performance enhancing effects, when it's consumed before a workout. Protein, on the other hand, should be consumed in the post-workout phase instead  | Comment on Facebook!

Ah, and yes: (A) You can use bananas, mashed potatoes and other whole foods instead of sugar drinks. And (B) These suggestions are also valid for strength trainees, who like their workouts (1) intense, (2) long (>35 minutes) and (3) with only 60s of rest between sets. If you are one of the "let's take a break" guys who spends 2h in the gym doing ten sets of bench presses and a lot of talking, you better spare yourself the carbohydrate load before the workout.

References:

• Burke, L. M. "Fueling strategies to optimize performance: training high or training low?." Scandinavian journal of medicine & science in sports 20.s2 (2010): 48-58.
• Burke, Louise M., et al. "Carbohydrates for training and competition." Journal of Sports Sciences 29.sup1 (2011): S17-S27.
• Casey, Anna, et al. "Effect of carbohydrate ingestion on glycogen resynthesis in human liver and skeletal muscle, measured by 13C MRS." American Journal of Physiology-Endocrinology And Metabolism 278.1 (2000): E65-E75.
• Chen, Y. J., et al. "Effects of glycemic index meal and CHO-electrolyte drink on cytokine response and run performance in endurance athletes." Journal of Science and Medicine in Sport 12.6 (2009): 697-703. 
• Coyle, Edward F., et al. "Substrate usage during prolonged exercise following a preexercise meal." J Appl Physiol 59.2 (1985): 429-33.
• Chryssanthopoulos, C., L. C. Hennessy, and C. Williams. "The influence of pre-exercise glucose ingestion on endurance running capacity." British journal of sports medicine 28.2 (1994): 105-109.
• Febbraio, Mark A., et al. "Effects of carbohydrate ingestion before and during exercise on glucose kinetics and performance." Journal of Applied Physiology 89.6 (2000a): 2220-2226.
• Febbraio, Mark A., et al. "Preexercise carbohydrate ingestion, glucose kinetics, and muscle glycogen use: effect of the glycemic index." Journal of Applied Physiology 89.5 (2000b): 1845-1851.
• Kotsiopoulou, Christina, and Veronica Vleck. "The effect of a high carbohydrate meal on endurance running capacity." International journal of sport nutrition and exercise metabolism 12 (2002): 157-171.
• Koivisto, Veikko A., Sirkka-Lisa Karonen, and Esko A. Nikkila. "Carbohydrate ingestion before exercise: comparison of glucose, fructose, and sweet placebo." J Appl Physiol 51.4 (1981): 783-787. 
• McLellan, Tom M., Stefan M. Pasiakos, and Harris R. Lieberman. "Effects of Protein in Combination with Carbohydrate Supplements on Acute or Repeat Endurance Exercise Performance: A Systematic Review." Sports Medicine 44.4 (2014): 535-550.
• Moseley, Luke, Graeme I. Lancaster, and Asker E. Jeukendrup. "Effects of timing of pre-exercise ingestion of carbohydrate on subsequent metabolism and cycling performance." European journal of applied physiology 88.4-5 (2003): 453-458.
• Moore, Daniel R., et al. "Beyond muscle hypertrophy: why dietary protein is important for endurance athletes 1." Applied Physiology, Nutrition, and Metabolism 39.999 (2014): 1-11.
• Morifuji, Masashi, et al. "Dietary whey protein increases liver and skeletal muscle glycogen levels in exercise-trained rats." British journal of nutrition 93.04 (2005): 439-445.
• Murakami, Ikuma, et al. "Significant effect of a pre-exercise high-fat meal after a 3-day high-carbohydrate diet on endurance performance." Nutrients 4.7 (2012): 625-637.
• Okano, G., et al. "Effect of 4h preexercise high carbohydrate and high fat meal ingestion on endurance performance and metabolism." International journal of sports medicine 17.07 (1996): 530-534.
• Ormsbee, Michael J., Christopher W. Bach, and Daniel A. Baur. "Pre-Exercise Nutrition: The Role of Macronutrients, Modified Starches and Supplements on Metabolism and Endurance Performance." Nutrients 6.5 (2014): 1782-1808.
• Paul, David, et al. "No effect of pre-exercise meal on substrate metabolism and time trial performance during intense endurance exercise." International journal of sport nutrition and exercise metabolism 13 (2003): 489-503.
• Rowlands, David S., and Will G. Hopkins. "Effect of high-fat, high-carbohydrate, and high-protein meals on metabolism and performance during endurance cycling." International journal of sport nutrition and exercise metabolism 12 (2002): 318-335.
• van Loon, Luc JC, et al. "Maximizing postexercise muscle glycogen synthesis: carbohydrate supplementation and the application of amino acid or protein hydrolysate mixtures." The American journal of clinical nutrition 72.1 (2000): 106-111.
• Volek, Jeff S., Timothy Noakes, and Stephen D. Phinney. "Rethinking fat as a fuel for endurance exercise." European journal of sport science ahead-of-print (2014): 1-8. 
• Whitley, Helena A., et al. "Metabolic and performance responses during endurance exercise after high-fat and high-carbohydrate meals." Journal of Applied Physiology 85.2 (1998): 418-424.

Carbohydrate Supplementation During Workouts - Who Benefits? How Much and Which Type(s) of CHO are Best?

Compared to liquid beverages, gels have the advantage of causing lower GI stress, when significant quantities of CHOs are consumed during exercise. Bars, can be held in the cheek pouch and chewed during critical phases of a race.

The headline gives it away. Today's SuppVersity article is a brief review of the (mostly sponsored) literature on Gatora.... ah, I mean carbohydrate supplementation during exercise. The headline also implies that the usefulness and efficacy of carbohydrate supplements depends on exercise duration and the type of exercise.

As a seasoned student of the SuppVersity you will know that certain paradox involved with regard to the duration / type of exercise. Short exercise durations, for example, shouldn't require large CHO boluses, long duration exercise, on the other hand, is fueled mostly by fat - so why should you supplement with carbohydrates, anyway?

Want to improve your exercise performance? Try sodium bicarbonate, as well!

The Hazards of Acidosis

Build Bigger Legs W/ Bicarbonate

HIIT it Hard W/ NaCHO3

BA + Bicarb are Synergists

Bicarb Buffers Creatine

Creatine + Baking Soda = 2x Win!

I promise to answer this and other questions in the following paragraphs, but before I do so, I would like to point out that there is as of now no evidence that the much-praised "fat adaptation" increases the exercise performance to an "Olympia" level. Carbohydrate supplements, on the other hand, are still part of the regular supplementation regimen for the 99% of the top athletes.

That being said, the human physiology dictates that the use of carbohydrate supplements during aerobic workouts that last less than 60 minutes is useless, because muscle glycogen is generally not limiting to performance when exercise durations are less than ~60 minutes.

It should not work for short duration exercise, but it still does

Interestingly, 16 out of 23 studies, Trent Stellingwerff and Gregory R. Cox from the Canadian Sport Institute-Pacific and the Australian Institute of Sport reviewed for their recent paper in Applied Physiology have found that carbohydrate supplementation and/or oral (mouth) exposure to carbohydrate can improve performance of tasks less than 1 hour in duration:

You won't fully deplete your muscular glyocogen levels
during short duration resistance training (Haff. 2003)

"In 2004 a seminal paper was published showing that a carbohydrate mouth-wash (swirling 25ml of a 6% CHO beverage (only ~1.5g of CHO in 25ml [6.4% maltodextrin solution (CHO)]) around in the mouth for ~10 sec, every 7.5min) significantly improved time trial (TT) performance [in seven male and two female endurance cyclists] by ~3% (Carter et al. 2004a)." (Stellingwerff & Cox. 2014)

This effect of CHO mouth-washing to improve performance in events from 30-60min has now been replicated in several other performance studies (10 of 13 studies) using both cycling and running interventions and with both sweet (sucrose) and non-sweet (maltodextrin) caloric CHO sources,as compared to 5 non-caloric artificial sweetener placebo trials showing no performance enhancing effects.

Figure 1: Hard to believe, but true - In 2010 Pottier et al. observed that CHO mouth-rinsing, but not CHO ingestion increases the 1h high intensity time-trial performance in trained subjects.

 "All these findings have been mechanistically supported with a functional magnetic resonance brain imaging study showing that CHO mouth-washing from both sweet tasting glucose and non-sweet maltodextrin can stimulate the brain areas of the insula/frontal operculum, orbitofrontal cortex and striatum, which are involved with brain centers responsible for reward and motor control (Chambers et al. 2009). Interestingly, if the mouth (oral receptors) and GI tract is by-passed by CHO infusion straight into the blood stream then 1h cycling TT performance was unaltered as compared to no CHO supplementation (Carter et al. 2004b)." (Stellingwerff & Cox. 2014)

Studies evaluating the effects on perceived exertion (Fares et al. 2011) found similar benefits all of which support the idea that the effect does not occur in the musculature, but rather in the head.

So what do you do to benefit during short-duration (<60) minute workouts? To benefit during short duration exercise exercise (<1h) ~1.5g of high GI carbohydrates (30g/h total = max) consumed or used as a mouth-wash in servings of 25ml for 5 to 10 sec every 8 to 10 min of exercise will do the trick. Since it can be difficult to actually drink / mouth-wash with CHO during critical phases of the race, Stellingwerff and Cox suggest "placing a sports confectionary in the cheek cavity" as a more practical option for some athletes.

It should be obvious that the physiological, or rater intra-muscular benefits of carbohydrate supplements increases with the exercise duration.

CHO supplementation during exercise that lasts 60 minutes or longer

In view of the fact that it is 100% logical and well established by studies by Coyle et al. (Coyle 1992a; Coyle 1992b) that the intake of carbohydrate (glucose alone, and glucose + fructose blends) can significantly improve prolonged endurance capacity and performance (>60min of exercise (Jeukendrup 2010)).

Figure 2: Overview of the performance increases in the 50 studies Stellingwerff & Cox reviewed (2014)

Against that background I will not bother you with another overview of the results, but focus on the efficacy of different carbohydrate supplementation strategies and types of carbohydrate supplements for exercise durations beyond the "magical" hour.

Glucose + fructose - the combination advantage

As a SuppVersity reader you've previously heard about the benefits of combining glucose and fructose in your intra-workout beverage. It is thus only logical that most commercially available formulas are mixtures  glucose + fructose (GLU:FRU) or maltodextrin + fructose - so-called "multi-transportable CHOs". The advantage of using both glucose and fructose is that the carbohydrates will be absorbed via SGLT1 and GLUT5 intestinal transporters.

Comparison of single vs. mutliple CHO sources (CHO, carbohydrate; FRU, fruc- tose; GLU, glucose; Perf, performance; P, placebo; TT, time-trial; TTE, time to exhaustion; Signif, Significant; SUC, sucrose; Stellingwerff & Cox. 2014)

Fructose + glucose mixtures excel, but it takes carbohydrate intake rates of more than 60g/h for the advantages to reach statistical significance. Why? Well, less than 60g/h don't overload the regular glucose transporters in the gut, and the advantage of having both SHLT1 and GLUT5 intestinal transport becomes irrelevant. Several studies have now shown that high intake rates (>70g/h) of GLU:FRU blendsduring moderate intensity, prolonged (>2h) exercise, results in ~8% improvement in endurance performance over both a  1h  TT  (Currell  and  Jeukendrup  2008)  and  over  100km  of  cycling  (Triplett,  Doyle  et  al.  2010) compared to glucose alone, and 19.5% versus water (see Table 1). Another research group has shown  further increases in performance with GLU:FRU blends over multiple sprints  after an endurance pre-load (O'Brien and Rowlands 2011; O'Brien, Stannard et al. 2013).

Specifically during long(er) duration exercise, when the carbohydrate consumption can exceed 60g/h there is a significant performance increase with multi- vs. single source carbohydrate supplements (Stellingwerff & Cox. 2014)

An advantage that has been scientifically established among others by Jeukendrup et al. (2010) who found that this pattern of CHO ingestion results in ~20 to 50% higher CHO oxidation rates compared to the ingestion of a drink that contains nothing but glucose or maltodextrin.


Now an increase in carbohydrate oxidation alone does not sound like something you would aim for as an endurance athlete. In practice, increases in carbohydrate oxidation have yet been shown to increase the performance during prolonged exercise bouts compared to isocaloric glucose-only beverages. (Currell et al. 2008; Triplett et al. 2010; O'Brien et al. 2011; O'Brien et al. 2013).

So how much does it take during long(er) 1-2h+ exercise: You've already learned that glucose + fructose mixtures should be preferred to carbohydrate supplements with only one type of CHO. While 30-60g/h, which is the amount of carbohydrates that is currently suggested by the American College of Sport Medicine (ACSM 2000; Sawka, Burke et al. 2007) appears to be be enough for exercise durations ranging from 60-120 minutes, recent evidence suggests that hard exercise bouts which last longer than 2h require up tp 90g/h or carbohydrate solutions with a CHO content of >8%.

Needless to say that there is still research to be done with respect to individual influencing variables of carbohydrate requirements. The currently available evidence, for example, is largely based on results from runners and cyclists. Two other factors / issues that come to mind are...

• the dose-response relationship, which appears to be capped at 75g/h - at least according to a large-scale multi-center study by Smith et al. (Smith. 2013) who found that their subjects, endurance trained cyclists or triathletes experienced significant performance increases, with increasing amounts of carbohydrates (0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 and 120g of CHO/h) during a 2h constant load ride.
  
  

  

  Figure 3: Mean log time to complete time trial (natural) as function of CHO treatment condition with fitted quadratic curve (with 95% CI of mean curves). Differences 100 represent percent change in performance. The quadratic function relating CHO ingestion rate to time complete time trial for 43% (95% CI = 11%–75%,P= 0.059) of the variation in mean performance score (Smith. 2013)

  The CHO given was a 1:1:1 glucose:maltodextrin:fructose blend. Results indicated incremental performance improvements of 1.0%, 2.0%, 3.0%, 4.0%, and 4.7% at 9, 19, 31, 48, and 78g CHO/h, respectively, with diminishing performance enhancement seen at CHO levels >78g/h.
  
  The optimal amount for performance (+4.7%) was 78g/h, with a range of 68 to 88g/h. However, even at 10g/h, a 1.0% increase in performance was observed, showing even a small amount of carbohydrate has the potential to positively impact performance. 
• the optimal mix of glucose, dextrose, fructose, maltodextrin or other "special" carbohydrates  - needless to say that waxy maize, hydroxypropyl distarches (learn more) or the expensive fast absorbing highly insulinogenic patented carbohydrate source Vitargo come to mind, when we are talking about finding the optimal mix of different carbohydrate sources - a mix, by the way, of which you can safely assume that it will differ according to the physiological demands of the workout and the exercise duration.
  
  One thing we shouldn't forget, though, is that next to optimal performance, optimal GI tolerance, i.e. the absence of bloating, diarrhea & co would be an important criteria the "optimal" carbohydrate blend would have to meet.

• 

  Figure 4: CHO suppl. ameliorates  testosterone reductions in 800m runners (de Sousa. 2010)

  the impact of carbohydrate supplementation on hormonal changes during and in response exercise - several human studies suggest that CHO supplementation attenuates the suppression of the hypothalamic-pituitary-gonadal axis and the rise in stress hormones during periods of intense training; a recent rodent study shows that the provision of carbohydrate supple- ments can prevent / reverse exercise-associated menstrual dysfunction (de Sousa. 2010; Zhao. 2014)

I guess, I could come up with additional research gabs, but in the end, a list of "gaps" is not exactly useful for you. Much in contrast to a conclusion, which I am about to formulate in the bottom line, now.

Bottom line: As of now it looks as if the recommendations I made in the light(er) blue boxes for short (<1h), long (1-2h) and ultra-long (>2g) workouts are the best we have.

For the majority of resistance trainees, intra-workout carbohydrate supplementation is at best facilitative. The repletion of the depleted glycogen stores after your workouts, however, is necessary | learn more about glycogen repletion

What I find particularly interesting is that for shorter duration exercise situations (<1h) and high(er) exercise intensity, similar benefits can be achieved with swallowing vs.  outh-washing with only 30g/h of liquid CHO sources. Performance increases in the 2.6% ± 3.3% range may not sound earth-shattering, but if you were running for an hour, your competitor who made sure to bring a carb bottle would be 83s faster than you are - that's 83s which could make the difference between first and last place.

For longer duration exercise, the studies, Stellingwerff and Cox reviewed in the previously cited article yielded an intermediate improvement of 4.9%±4.9% with significantly higher values in studies investigation long(er) + higher intensity exercise. The notion that carbohydrate supplements were useless and the various position statements of sporting bodies all over the world just a concession to the sponsoring money of the industry is thus unwarranted | Comment on Facebook!

References:

• Carter,  J.,  Jeukendrup,  A.E.,  Mundel,  T.,  and  Jones,  D.A.  (2003).  Carbohydrate  supplementation  improves moderate and high-intensity exercise in the heat. Pflügers Archiv : European journal of physiology446: 211-9.
• Carter, J.M., Jeukendrup, A.E., and Jones, D.A. (2004a). The effect of carbohydrate mouth rinse on 1-h cycle time trial performance. Medicine and science in sports and exercise36: 2107-11.
• Carter, J.M., Jeukendrup, A.E.,  Mann, C.H., and  Jones, D.A. (2004b). The effect of glucose infusion on glucose kinetics during a 1-h time trial. Medicine and science in sports and exercise36: 1543-50. 
• Chambers,  E.S.,  Bridge,  M.W.,  and  Jones,  D.A.  (2009). Carbohydrate  sensing  in  the  human  mouth:  effects  on exercise performance and brain activity. The Journal of physiology587: 1779-94. 
• de Sousa, Maysa Vieira, et al. (2010). Effects of carbohydrate supplementation on competitive runners undergoing overload training followed by a session of intermittent exercise." European journal of applied physiology 109.3: 507-516.
• Fares, E.J. and Kayser, B. (2011). Carbohydrate mouthrinse effects on exercise capacity in pre- and postprandial States. J Nutr Metab2011: 385962.   
• Pottier, Andries, et al. (2010). Mouth rinse but not ingestion of a carbohydrate solution improves 1‐h cycle time trial performance" Scandinavian journal of medicine & science in sports 20.1: 105-111.
• Sawka,  M.N.,  Burke,  L.M.,  Eichner,  E.R.,  Maughan,  R.J.,  Montain,  S.J.,  and  Stachenfeld,  N.S. (2007).  American College of Sports Medicine position stand. Exerciseand fluid replacement. Medicine and science in sports and exercise39: 377-90.
• Smith, JohnEric W., et al. (2013). Curvilinear dose-response relationship of carbohydrate (0-120 g/h) and performance." Med Sci Sports Exerc 45.2: 336-341. 
• Stellingwerff, T., & Cox, G. R. (2014). Systematic Review: Carbohydrate Supplementation on Exercise Performance or Capacity of Varying Durations. Applied Physiology, Nutrition, and Metabolism (2014). Ahead of Print. 
• Zhao, Can, et al. (2014). Effects of carbohydrate supplements on exercise-induced menstrual dysfunction and ovarian subcellular structural changes in rats." Journal of Sport and Health Science 3.3: 189-195.