ONLINE DRIVERS MEDIA

Green asparagus from the fridge and  from the market are not created equal - at least not when they finally end up on your plate after a short bath in hot water.

You just have to watch one of the consumer report shows on television to hear it: "Frozen veggies are way better than their reputation would suggest." Actually, here in Germany this sentence has been repeated to soften that Ive even heard people say theyd buy the frozen broccoli because it contained "more vitamins and the other good stuff, you know." And you know what? For some veggies like spinach, for example, this may actually be the case. For others, like broccoli or peas, the nutrient status of the frozen and the raw uncooked vegetable appears to be more or less identical (Favell. 1998). But thats something you cannot say for the green asparagus stems, zucchini and green beans in a recent study from the Università degli Studi di Parma in Italy.

I am not an asparagus expert and can still tell that the cell structure of the Transverse  sections boiled (C - from raw | D - from frozen) is profoundly messed up compared to the raw (A) and blanched (B) variety | legend: c = collenchyma; vp = vascular bundle; p = parenchyma; f = fissure.

In the corresponding experiment, the Italian researchers bought Green asparagus stems (Asparagus officinalis L., var. Grande), zucchini (Cucurbita pepo L., va Quine) and green beans (Phaseolus vulgaris L., var. Giamaica) from a local producer and processed them within 24 hours from harvesting. For each of the veggies four samples were prepared: Raw/uncooked  (R), raw/boiled  (B), blanched (BL) and industrially frozen/boiled (FB)

The raw (ten kilograms of each vegetable), blanched (five kilograms of each vegetable) and industrially frozen  samples  (five  kilograms  of  each  vegetable) had been transported were  transported  to  the  University of  Parma laboratories  under  adequate  refrigerated conditions to avoid the exuberant nutrient loss that occurs upon inadequately slow (re-)freezing.
If you "freeze" your veggies in the freezer compartment of your fridge, this will make the cells blast, so that even before they are cooked, and the nutrients flow out. It is generally assume that the latter would not happen, if the veggies are shock-frosted.

Figure 1: Total antioxidant capacity of green asparagus, zucchini and green beans raw, blanched, boiled and frozen and boiled (Paciulli. 2014); as the data tells you frozen veggies with similar  icy grease on them like you see on the right may not really be a better source of antioxidants than fresh veggies from the farmers or even the supermarket.

If we look at the data in Figure 1, though, it would appear that the cells may have "cracked" already so that they are more susceptible to the subsequent heat assault and the frozen + boiled samples end up having consistently lower total antioxidant (Figure 2) and feric acid reducing capacity than their raw + boiled counterparts.

For a similar reason (nutrient retention), the blanched samples have been cooled immediately after blanching in an ice-water bath for 3 min before they have been transported to the laboratories, where their analysis shows that only the Zucchini lost a small, but significant amount of their total antioxidant activity.
References:

• Paciulli, Maria, et al. "Impact of the industrial freezing process on selected vegetables Part I. Structure, texture and antioxidant capacity." Food Research International (2014).

Dont forget that cyclists are not the only group of athletes who can benefit from bicarbonate supplementation. Strength trainees who spend hours in the gym and train at high intensities will also benefit!

I know that most of you are into resistance not endurance training. So, before I even get into the discussion of the experimental procedures and the results of the latest study from the Institute of Sports and Preventive Medicine at the Saarland University in Saarbrücken, Germany, I would like to point you to an older SuppVersity article which indicates that bicarbonate supplementation is able to Up Your Squat (+27%) & Bench Press (+6%) Within 60 Min" (read more).

Now that youve hopefully put away your prejudices against "that endurance supplement", lets get to the previously mentioned study by Florian Egger, Tim Meyer, Ulf Such, and Anne Hecksteden (thanks to Conrad P. Earnest for bringing this to my attention).
To investigate the effects of BICA supplementation on performance during prolonged, high-intensity cycling to exhaustion in well-trained athletes, the scientists from the Saarland University recruited 6 male and 5 female "well-trained" cyclists (mean ± SD: age 24±8 y, BMI 21.3±1.7, VO2peak 67.3±9.8 ml/kg/min - the VO2peak value tells you that they were fit ;-).

In a double-blind, randomized cross-over design, the subjects underwent two stepwise incremental exercise tests and two constant load tests (with two phases) on an electrically braked cycle ergometer (Excalibur Sport, Lode, Groningen, The Netherlands).

Figure 1: Schematic representation of the general design.Time interval between tests is specified in days (d). Data are presented as means ± standard deviation respectively, with minimum (min) and maximum (max) values (Egger. 2014).

As the overview of the study design in Figure 1 tells you, each test type was completed twice. Once after the ingestion of 0.3 g/kg sodium bicarbonate (yes, thats roughly 24g for someone who weighs 80g and should not be consumed too fast, because otherwise it may trigger diarrhea) or a placebo supplement in form of 4 g sodium chloride that was chosen to make sure that any benefits that were observed were due to the natrium, not the bicarbonate content of sodium bicarbonate.
Both the plain salt and the sodium bicarbonate were solved in 0.7 l water. The outcome measures were simple: Only if the subjects were able to pedal significantly longer until they were exhausted in the standardized constant load test, sodium bicarbonate could be considered to have practically relevant performance enhancing effects (maximum performance in the stepwise incremental exercise test, i.e. maximal workload and VO2peak were used as secondary outcomes).

Figure 2: Blood lactate (BLa) concentrations after ingestion (post drink) and during constant load tests (mean ± SD) for the BICA and placebo trials (Egger. 2014)

The other parameters the scientists measured, i.e. the blood lactate [BLa], pH, and bicarbonate concentration, were merely used determine the mechanisms for the potential improvements in exercise performance.

Speaking of auxiliary measures, if you take a look at Figure 2 you will see that the blood pH dropped significantly right after the ingestion of the bicarbonate supplement and remained "low" throughout the trial and afterwards. An observation that does not come unexpected. Previous trials have after all shown that its the ability of bicarbonate to blunt the high-intensity exercise related perturbations in both blood and muscle acid-base that keeps the maximal work rate up and leads to performance increases compared to placebo supplements.
These performance decrements are caused by the accumulation of hydrogen ions (H+) in the myoplasm and their detrimental effects on myofilament interaction, glycolytic flux and sarcoplasmatic reticulum function. As Egger et al. point out

"[t]he ability of the body to prevent or delay these force limiting processes is determined by the capacity of its intrinsic buffering systems, which counteract the accumulation of H+ both inside and outside the cell," (Egger. 2014)

which explains why the benefits of both beta alanine (which increases the intra-cellular buffering capacity) and bicarbonate are most pronounced in athletes competing in high intensity sports.

Figure 3: Time to exhaustion and maximal workload (total) and maximal workload at the individual anaerobic threshold (IAT) during the bicarbonate and placebo trials (Egger. 2014).

Apropos ergogenic effects: I already gave it away in the headline. The consumption of the bicarbonate supplement lead to immediate increases in the time to exhaustion with 49.5 ±11.5 min being the maximum in the bicarbonate and 45.0±9.5 min being the maximum in the placebo condition.

The maximal workload in the stepwise incremental tests (BICA: 341±66 W; placebo: 339±67 W) and workload at IAT (BICA: 234±5.5 W; placebo 233±5.7 W), on the other hand, did not differ significantly.
References:

• Egger F, Meyer T, Such U, Hecksteden A. "Effects of Sodium Bicarbonate on High-Intensity Endurance Performance in Cyclists: A Double-Blind, Randomized Cross-Over Trial". PLoS ONE 9.12 (2014): e114729.
• Hobson, Ruth M., et al. "Effects of ?-alanine supplementation on exercise performance: a meta-analysis." Amino acids 43.1 (2012): 25-37.

The squat may be a power exercise, but trust me, it will also help you to "look good naked"!

I guess it would be hilarious to call the simple insight that cutting the time you rest in-between sets during your squats can turn a regular into a killer workout would be news, right? Well, what about some figures to define "killer" as in one minute rest between sets vs. "regular" as in three minutes rest between sets squats, then? Thats news, right; and we have to thank Nicholas A. Ratamess and his colleagues from the College of New Jersey for these insights.

I mean, huffing and puffing is one thing, but your subjectively perceived level of exhaustion and the very concrete, objectively measured data on the difference in energy expenditure and the contribution of aerobic (fat) and anaerobic (glucose) energy sources during a workout, as they are presented in the paper at hand, are two different animals.
Apropos animal, you dont necessarily have to be a similar "animal" as the 22-year old subjects of the study at hand with their ~8-year training experience to perform the tightly controlled experimental workout, the researchers describe as follows:

"After BL [baseline] measures, each subject performed a warm-up consisting of 3 minutes of stationary cycling and 2–3 lightto-moderate sets (40–60% of 1RM) of the bench press and squat. Respiratory masks were temporarily removed from each subject during the warm-up to allow subjects to consume water one last time before initiating the protocols.

Find out how to optimally train your legs - The SuppVersity EMG Series - Gluteus, Quads & Co | read more

The protocols consisted of performing 5 sets of the bench press and 5 sets of the back squat for up to 10 repetitions using 75% of their predetermined 1RM. The BP group performed the bench press first, whereas the S group performed the back squat first. For all exercises, resistance remained constant while total numbers of repetitions were recorded. Heart rate and oxygen consumption data were collected during the entire protocol. In addition, a linear position transducer (Tendo Sports Machines, Trencin, Slovak Republic) was attached to the bar to measure power and velocity during each completed repetition."

On each of the three occasions the subjects reported to the lap, a different rest interval was used. With 1-, 2-, and 3-minutes of rest in-between sets, the and a standard 2-minute RI was used in between exercises, the study represents more or less what I see trainees do at the gym on a daily basis, as well... ok, the lazy "I just want to be strong"-10-minutes-of-rest-between-sets-fat-ass was not accordingly represented in the study at hand, but lets be honest, how many of the average trainees do actually fall into this category? I mean, if you ask people why they are going to the gym, they will either lie or tell you that they are there to "look better naked".

"Looking good naked" is a valid training goal, folks - so admit to it!

For most people sculpting their body may be only one of the reasons, but in the end, it usually comes down to this and "health" or "fitness", when youre getting honest answers from gym users.

Figure 2: The amount of energy the trainees expended on bench presses and squats was significantly higher with the 1-min rest periods (17% and 36%, for squats; 8% and 18% for bench presses; data based on Ratamess. 2014)

Against that background, the insight that short rest periods lead to significant increases in energy expenditure is highly relevant (Note: The energy expenditure was calculated by multiplying the total VO2 for the session x 5.05kcal/L). Losing fat is after all number one on the "looking good naked" priority list of most trainees and in spite of the fact that you wont lose any fat without dieting, the 36% higher energy expenditure of the 1min vs. 3min rest time workout could make the difference between ordinary and outstanding fat loss results... in spite of the increase in the respiratory exchange ratio, an indicator of an increased anaerobic contribution to the energy expenditure, by the way!

Short rest times + 6 Simple Rules of Reasonable Weight Loss = Succes!

Unfortunately, the myth that "burning fat" during exercise was in any way relevant to your weight / fat loss success is as die hard as it is stupid and flawed.

Especially for the leaner folks out there, "burning fat" is absolutely irrelevant. In fact, the whole HIIT research appears to suggest that short intense, highly glycolytic exercise regimen are more suitable to shed body fat for athletic individuals than arduous multiple-hour workouts in the non-existing (!) "fat burning zone".

The reason I still recommend LISS as a preferable type of cardio training for the advanced trainee with three to four resistance training sessions per week is that all the "high intensity stuff" (dont neglect your strength workouts!) is going to overtax the sympathetic nervous system. The classic light-intensity steady state (LISS) work, on the other hand, offers a welcome parasympathetic stimulus to balance all the intense explosive training youre doing at the gym.
References:

• Ahtianen, Juha P., et al. "Short vs. long rest period between the sets in hypertrophic resistance training: influence on muscle strength, size, and hormonal adaptations in trained men." The Journal of Strength & Conditioning Research 19.3 (2005): 572-582.
• de Salles, Belmiro Freitas, et al. "Rest interval between sets in strength training." Sports Medicine 39.9 (2009): 765-777.
• Ratamess, Nicolas A., et al. "Acute Oxygen Uptake and Resistance Exercise Performance Using Different Rest Interval Lengths: The Influence of Maximal Aerobic Capacity and Exercise Sequence." Journal of Strength & Conditioning Research 28.7 (2014):1875–1888.
• Willardson, Jeffrey M. "A brief review: factors affecting the length of the rest interval between resistance exercise sets." The Journal of Strength & Conditioning Research 20.4 (2006): 978-984. 
• Willardson, Jeffrey M., and Lee N. Burkett. "The effect of different rest intervals between sets on volume components and strength gains." The Journal of Strength & Conditioning Research 22.1 (2008): 146-152.

Do you want to burn some extra fat during your workouts? Ilex can help. But will it also help you lose body fat?

After the nicotine article a week ago, its about time to take a look at less "toxic" fat burners. As the case may be, researchers from the Faculty of Health and Wellbeing at the Sheffield Hallam University have just published a paper about the ability of Yerba Maté (Illex Paraguariensis | YM) to augments fat oxidation and energy expenditure during exercise at various submaximal intensities (Alkhatib. 2014).

Now, as a SuppVersity Reader youre well aware that an "augmentation of fatty acid oxidation during exercise", alone, is not worth your heard earned money. The question to keep in mind, when were going through the results, is thus: Is Ilex Paraguariensis worth using, or is it just worth writing about in a science magazine?
Alright, now that weve set the scene its about time to take a look at the study design. The study followed a double-blind crossover repeated measures experimental design.

The participants were fourteen healthy adults, seven males and seven females [Mean ± SD: age = 20.8 ± 3.4 yr, height = 171.8 ± 10.0 cm, body mass = 70.4 ± 11.3 kg, body mass index (BMI; in kg/m²) = 23.8 + 0.11]. Participants were assigned randomly to each experimental condition within a period of two weeks.

The Coffee³ Advantage Equation: 3 x 250mL Coffee / Day + 2x4 Weeks ? -1kg Body Fat | learn more

Female participants were studied in days 1 to 7 of their menstrual cycle to minimise the influence of cyclical changes in female hormones. All participants were screened prior to the start of the testing in order to determine that they are free from illness and any type of orthopaedic limitation or injury, or chronic disease.

Moreover, none of the subjects consumed ergogenic aids or tons of caffeine regularly (<200 mg/day) - that doesnt mean they never drank more coffee, but they had to abstain from more than 1.5 cups of coffee, tons of energy drinks caffeine containing soft drinks or medications.

A very reasonable request, if you want to measure significant effects from Ilex Paraguariensis which contains 1.5% (according to Alkhatib. 2014) caffeine and roughly 0.12% theobromine (according to Reginatto. 1999).

The tests & supplements

All participants reported to the Physiology Laboratory on two separate occasions following 10 hrs overnight fast, and each testing session (between 07:00am and 10:00am) was separated by at least three days within two weeks period.

During each visit participants ingested either 1000 mg (2× 500 mg capsule) YM or hydroxypropyl methylcellulose placebo empty capsules (PLC). Two capsules with similar coatings of either YM and PLC capsules were placed within an empty water cup and taken in the same way with a 100 ml of water. The YM capsules contained a standardized ground YM leaves (batch number 0422009/2012) with a natural content of approximately 1.5% caffeine (Rio Trading Company, Brighton, United Kingdom).
Immediately following the ingestion of supplement or placebo, participants rested for 60 minutes in a semi-recumbent position in quiet laboratory condition. For the estimation of FAO and CHO at rest and during exercise, breath by breath cardiorespiratory measurements included oxygen uptake ( ) 2 VO , carbon dioxide production, and respiratory exchange ratio (RER), using an online gas analyzer (Metalyzer Cortex 3B, Leipzig, Germany).

The exercise protocol & its consequences

All participants followed the same incremental exercise assessment using an electromagnetically braked cycling ergometer (Schoberer Rad Messtechnik, SRM, Ergo, Julich, Germany). The ergometer was calibrated before use and similar cycling positions were applied in both tests for each participant, which included adjusting the handlebar and saddle height and distance, crank length and toe clip positions during the first visit and re-apply the same position in the following visit.

The cycling protocol consisted of three-minute incremental stages that were initiated at and increased by 0.5 W/kg body mass. Participants cycled at 60–70 rpm throughout the whole test until volitional exhaustion defined as meeting the at least two of 2 peak VO2 termination criteria: RER value > 1.1, heart rate within 10 beats/min of age predicted maximum heart-rate, or achieving levelling-off of VO2 Peak power (P_peak). Similar verbal encouragement was provided to all participants throughout the exercise tests. All tests were followed by a sufficient cool down for at least 20 min, in which participants consumed at least 200 ml of water, and instructed to stay hydrated and consume at least 2 litres of water during the day of the test.
Interestingly, following the 60 min rest after YM ingestion, no significant difference was found for either resting blood lactate contentration (1.4 ± 0.32 vs. 1.5 ± 0.30 mmol/l) or resting respiratory exchange ratio (0.82 ± 0.08 vs. 0.81 ± 0.05) for PLC vs. YM respectively.

In other words: After the workout there were no measurable difference between the active and placebo treatment. The latter cannot be said of the RER during workouts, though.

Figure 1: Significant decreased RER and higher fatty oxidation rates - two sides of the same fat burning coin and evidence that the ingestion of the YM supplement lead to significant increases in fatty oxidation (Alkhatib. 2014)

As you can see in Figure 1 the effects of the Ilex supplements were significant - statistical significant, but also practically relevant? Probably not. The increase in fatty oxidation was after all paid for with an increase in glucose oxidation (see Figure 2).

Figure 2: The glucose usage during workouts decreases, obviously this leads to greater increases in lactate levels, whether its pro-weight loss is questionable, though. If anything it could increase the time to fatigue (Alkhatib. 2014)

The net energy expenditure, the one thing that really counts, was thus identical. For someone who has to get rid of tons of fat in his blood. The increase in RER may be relevant. For someone who is fit and well-trained, its not really important if he or she burns fat or glucose during the workout - why else would HIIT work so well for losing fat - specifically in lean athletic individuals? Well, the answer is easy: It burns glucose and will thus increase GLUT-4 expression insulin sensitivity and, in the end, also fatty oxidation - to replete the depleted energy stores.
References:

• Godfrey, R. J., et al. "A–Z of nutritional supplements: dietary supplements, sports nutrition foods and ergogenic aids for health and performance: Part 45." British journal of sports medicine 47.10 (2013): 659-660.
• Pang, Jisook, Youngshim Choi, and Taesun Park. "Ilex paraguariensis extract ameliorates obesity induced by high-fat diet: Potential role of AMPK in the visceral adipose tissue." Archives of biochemistry and biophysics 476.2 (2008): 178-185.
• Reginatto, Flavio Henrique, et al. "Methylxanthines accumulation in Ilex species-caffeine and theobromine in erva-mate (Ilex paraguariensis) and other Ilex species." Journal of the Brazilian Chemical Society 10.6 (1999): 443-446.

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. Todays 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, shouldnt require large CHO boluses, long duration exercise, on the other hand, is fueled mostly by fat - so why should you supplement with carbohydrates, anyway?
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 wont 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.
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 youve 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.

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; OBrien et al. 2011; OBrien et al. 2013).
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 shouldnt 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.
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.