Are You Overtraining? Two Scientifically Proven Methods to Test Yourself - Method 2: The ABEL Sport Test. Plus: 54 Item Questionnaire + 8 Additional Clues to Identify Overtraining

Theoretically it's already available for everyone. Costs are yet not the only thing you should keep in mind before you buy into Knight Scientific's overtraining analysis system

I've got plenty of positive, skeptic and euphoric feedback in response to last week's first installment of this two-part series on "proven" methods to test for overtraining syndrome (OTS). Before I tackle method number two in today's second installment, I do thus want to briefly remind you that the HRV method is not going to work, when you are chronically overtrained, already. It's also questionable, whether it will be able to identify parasympathetic overtraining syndrome (POTS). The latter is associated with marked decreases, not increases in the ratio of high / low frequency component (Portier. 2001). In people who train intense and with a high volume this effect can even mask the early increase in sympathetic tone and would thus render the HRV method basically useless.

You can learn more about overtraining at the SuppVersity

Heart Rate Variablity (HRV)

ABEL Sports Test + More

Overtraining & Undereating

Calculate your Energy Intake!

There Are No Magic Macros!

Reinvent Your Training!

More alternative tests / indicators of overtraining:

• increased sensitivity of 5HT receptors ➯ early fatigue (Budgett. 2010)
• free testosterone and testosterone/cortisol ratio higher than 30% (Cunha. 2006)
• increasing serum urea and decreased ammonia at rest w/ identical protein intake, indicative of higher gluconeogenesis from protein (Urhausen. 2002)
• low urinary catecholamines, esp. during night and w/ parasympathetic overtraining (Lehmann. 1992) and low ACTH and/or GH response to maximal exercise (~adrenal fatique; cf. Urhausen. 2002)
• inverse ‘iceberg profile’ in Profile of Mood State (POMS) scale (Morgan. 1987) and messed up sleep (Urhausen. 1998)
• decreased glucose & increased fat oxidation during high intensity exercise (Urhausen. 2002)

None of these markers can serve as a sole marker of overtraining. They can however support conclusions you make based on questionnaires, performance data and HRV analyses.

For method number two, so-called ABEL-Sport Test, these interferences between symathetic (~intensity, short(er) term) and parasympathetic (~volume, long(er) term) overtraining shouldn't be a problem. The test is easy, but it's not free. You will after all have to buy a portable luminometer to measure the optical properties of your blog. In other words, the ...

"[...] test does not measure a single biomarker of OTS [overtraining syndrome] but instead utilises hidden information acquired by circulating leucocytes as they patrol the body spotting pathogens, responding to markers of inflammation (cytokines and chemokines) and other changes in the blood that occur after strenuous exercise." (Knight. 2013)

As J Knight, M Wakeman, J Reeves, who have a vested interest in research into their own products, which have been used by elite and amateur athletes in many different fields and were "successfully used" by Skandia Team GB for two years prior to and in the final run up to the Olympics in Beijing in 2008, when Britain’s squad topped the medal table in the Olympic sailing competition, point out, the test is designed to elicit this "hidden information from the cells" (and I should add "hidden information that requires interpretation"!).

The technology relies on the bioluminescent protein Pholasin. It emits light, when it gets in contact with reactive oxygen specimen (ROS). To test the amount of leucocytes in a 5-20µL sample your blood you do thus just have to react it with Pholasin, activate the ROS response of the leukocytes and measure the light response (Roberts. 1985, 1987; Knight. 1999). By superimposing the results on a set of reference sample curve, Knight et al. are then (that's at least the claim) able to identify various responses during training, "indicating if the athlete is heading towards OTS and identifying infections, superimposed on training curves." (Knight. 2013)

With score way beyond 25 (15 is the first signal of OT), it's usually a good idea to take some time off and re-start your training at a saner intensity / volume - irrespective of ABEL or HRV results.

Stay skeptic! Despite the fact that a very similar technology has already been used in the analyses of the effects of foods and cosmetics, there is as of yet no independent comparison of the accuracy of the interpretation of the leukocyte ROS responsible on which Knight et al. base their assessments of the training status.

The word "interpretation" should have made you sit up: Even if the scientists are able to provide a cost-effective solution for individual hobby athletes, it is not guaranteed that the results are actually going to help you control your training load. Before the beneficial real-world effects Knight et al. observed in sailors, footballers and other athletes are confirmed in a well-controlled study by an independent team of researchers, I would thus suggest you rely on the traditional rules of thumb, your personal training experience, the HRV method and the overtraining questionnaire on the right of this "bottom line".

References:

• Budgett, R., Hiscock, N., Arida, R., & Castell, L. M. (2010). The effects of the 5-HT2C agonist m-chlorophenylpiperazine on elite athletes with unexplained underperformance syndrome (overtraining). British journal of sports medicine, 44(4), 280-283. 
• Cunha, G. D. S., Ribeiro, J. L., & Oliveira, A. R. D. (2006). Overtraining: theories, diagnosis and markers. Revista Brasileira de Medicina do Esporte, 12(5), 297-302.
• Knight, J. (1999). Rapid, simple and sensitive blood biocompatibility tests with the light emitting protein Pholasin®. Proceedings of the TechMed/Medical Device Technology Conference. Advanstar Communications UK Ltd, Chester, 3-17.  
• Knight, J., Wakeman, M., & Reeves, J. (2013). Abel-Sport™ Test For Assessing Over Training Syndrome And Detecting Infection. British journal of sports medicine, 47(17), e4-e4.
• Lehmann, M., Gastmann, U., Petersen, K. G., Bachl, N., Seidel, A., Khalaf, A. N., ... & Keul, J. (1992). Training-overtraining: performance, and hormone levels, after a defined increase in training volume versus intensity in experienced middle-and long-distance runners. British journal of sports medicine, 26(4), 233-242.
• Morgan, W. P., Brown, D. R., Raglin, J. S., O'connor, P. J., & Ellickson, K. A. (1987). Psychological monitoring of overtraining and staleness. British Journal of Sports Medicine, 21(3), 107-114.
• Portier H, Louisy F, Laude D, Berthelot M, Guézennec CY (2001). Intense endurance training on heart rate and blood pressure variability in runners. Medicine and science in sports and exercise, 33(7), 1120-1125.
• Roberts, P. A., Knight, J., & Campbell, A. K. (1985). Pholasin®: a new bioluminescent indicator for cell activation. Biochem. Soc. Trans. 1140, 1139-1140. 
• Roberts, P. A., Knight, J., & Campbell, A. K. (1987). Pholasin®: a bioluminescent indicator for detecting activation of single neutrophils. Anal. Biochem. 160, 139-148.
• Urhausen, A., Gabriel, H. H. W., Weiler, B., & Kindermann, W. (1998). Ergometric and psychological findings during overtraining: a long-term follow-up study in endurance athletes. International journal of sports medicine, 19(2), 114-120.
• Urhausen, A., & Kindermann, W. (2002). Diagnosis of overtraining. Sports medicine, 32(2), 95-102.

Colostrum Maintains Testosterone, Cortisol and Heart Rate Recovery, Where Whey Fails - During a Five Day Cycling Event With 10 Highly Trained Male Road Cyclists

Legal gear fresh from the udder? If it works for cyclist, it must be real ;-)

Some of you will probably remember the corresponding installment of "Ask Dr. Andro" from 2011 that dealt with the question whether colostrum and milk products in general are healthy muscle builders, a waste of money or toxic waste (read more). If you do, you will also remember that my review of the literature did support the general benefits of milk proteins, but it did not provide significant evidence that benefits that have been observed in the few existing studies on the ergogenic value of colostrum could not be achieved by whey and/or casein proteins as well. Now, the latest study from the University of Queensland appears to suggest that just this could yet in fact be the case (Shing. 2013) - at least if the outcome measures are the salivary testosterone concentration and modulated autonomic activity over consecutive days of competitive cycling.

10g of whey vs. 10g of cholostrum "isolate"

The scientists from the School of Human Movement Studies recruited 10 highly trained cyclists with an average age of 22.5y and a body weight of ~70kg and put them on two different supplemental protocols

• the control group received consumed 10g whey protein concentrate (“Alacen® 80” Fonterra Co-op Group Limited, Auck- land, New Zealand) per day 
• the colostrum group consumed 10 g Intact® bovine CPC (Numico Research Australia Pty Ltd, South Australia) per day

Neeldess to say, both supplements were isocaloric, packed in identical sachets to and had to be used for the same timespan, which were the 8 weeks prior to and the whole five days of the cycle race that was used as the litmus test for the efficacy of the supplementation regimen.

Colostrum muscle builder or murky allergen (learn more)?

In that it, may be worth adding that the cyclists consumed the in the morning mixed with 50 mL of water and 100 mL of skim milk and that the scientists picked Intact® CPC 3-6, 14 as their colostrum supplement of choice, because the various available products vary largely in their amino acid and protein content. Therefore it appeared sensible to use the same brands that have been used in previous studies, as well. According to Shing et al. Intact® is a standardized, low heat  treated, low fat, low lactose colostrum powder containing 20%  IgG that retains both casein and whey proteins (just as a side note: there was no sponsorship involved in the study, although the brand names may suggests otherwise).

Aside from the objectively measurable saliva responses, the scientists had the participants fill diet and training, as well as illness logs. The latter reflects the hypothesis that the IgG content in the colostrum would strengthen the immune system of the cyclists and should thus result in lowered infection rates. With two vs. four illnesses in the whole study period the differences between the colostrum (2 illnesses) and the whey group were yet statistically not significant.

Figure 1: Change in heart rate recovery (left), salivary testosterone and cortisol levels (right) during the 5-day cycling event (Shing. 2013)

Much contrary to whey group, where the naturally cyclic testosterone rhythm is completely lost and the cortisol rhythm attenuated, both remained intact in the colostrum group. This goes hand in hand with the loss of heart rate variability in the whey control and the increases of the parameter in the colostrum group. Both results in conjunction with the smaller reduction in vigor and the ameliorated change in fatigue in the colostrum group clearly suggest that the cyclists in the whey group were already parasympathetically overtrained, while the stress reducing effects colostrum kept the cyclists in the active arm from falling into the same trap.

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For short time-trials sodium bicarbonate may be the supp of choice (learn more).

Bottom line: The scientists state it in their conclusion "the number of participants in this pilot study was small", too small for my liking, so that it is - as a standalone - simply not enough to prove anything.

The scientists are yet right that "the present data support the potential for bovine CPC supplementation to maintain testosterone concentrations and influence heart rate variability response" in a training regimen that is notorious for its negative impact on the central nervous system and the HPTA. "Support" and "potential" - not more, but not less either.

References:

• Shing CM, Peake JM, Suzuki K, Jenkins DG, Coombes JS. A pilot study: bovine colostrum supplementation and hormonal and autonomic responses to competitive cycling. J Sports Med Phys Fitness. 2013 Oct;53(5):490-501.

Caffeine Works - Study Leaves No Doubt About It! Approx. 400mg of Caffeine Get You Going, Even After 32h Without Sleep - So Why Doesn't It Work for You Anymore?

The answer to post-positioned question in the headline of today's SuppVersity article is not easy to find. Therefore I will start with the facts. Facts, researchers from the University of Sfax present in their latest paper in the peer-reviewed scientific journal Psychology & Behavior; facts that leave little doubt that 5 mg/kg of caffeine could counteract the negative effect of 36 h of total-sleep deprivation on physical and cognitive performances, if your body would still react to stimulus - in other words: If your body still reacted like the bodies of the 13 healthy male habitual caffeine-not-abusing physical education students (age: 21.1 ± 1.1 years; body mass: 77.1 ± 7.2 kg; height: 1.77 ± 0.06 m) who volunteered to participate in the present study, it would get you going - seriously!

The students had exactly the same time schedule at the university from sunrise to sunset under the control of the experimental team. Participants had taken part in various recreational low-intensity physical activities such us walking, jogging, or aerobics in our university.

No time to sleep, do your "cardio" HIIT style instead of steady state for hours

Never Train To Burn Calories!

Tabata = 14.2kcal /min ≠ Fat Loss

30s Intervals + 2:1 Work/Rec.

Making HIIT a Hit Part I/II

Making HIIT a Hit Part II/II

Triple Your Energy Exp.

The participants were prescribed with standard isocaloric meals to consume, with breakfast at 07:30 h, lunch at 12:00 h, and dinner at 20:00 h. Only water was allowed ad libitum between meals. They were requested to maintain their habitual physical activity throughout the experimental period and to avoid strenuous activity before each test session. The overall daily energy intake goal was set at 10.5 MJ (2500 kcal) per capita/day.

Figure 1: Caffeine affects both body temperature and physical performance during sleep deprivation (Souissi. 2014)

During the experimental period, medications, which are expected to affect physical performance, were prohibited, more importantly, though:

"Participants were selected according to their usual consumption of caffeine and on the basis of their answers to the Horne and Ösberg Self-Assessment Questionnaire (Horne. 1979) (i.e., to have a group without “extreme type” (i.e., participants were selected as “neither type”)). This second criterion resulted in a sample of participants who shared the same timing in terms of rising times (06:30 ± 00:30 h) and bedtimes (23:00 ± 00:30 h). Participants reported no sleep disorder, are non-smokers, and do not consume caffeine or any alcoholic beverages."

After four consecutive nights of sleep in the laboratory (sleep adaptation: between 22:30 and 07:00 h), in a randomized order, participants performed four test sessions: after placebo or 5 mg/kg of caffeine ingestion during a baseline night (RN) or a night of 36 h of total sleep deprivation (TSD).

Does this look remotely familiar? If it does, you are already "tolerant".

Is caffeine tolerance even real? Scientists say: Yes! In 1992 Suzette M. Evans and Roland R. Griffiths conducted a study with 32 "healthy subjects with histories of moderate caffeine consumption" who had to abstain from their favorite beverage throughout the study (Evans. 1992). The subjects were stratified into two groups based on several factors including caffeine preference, which was assessed using a caffeine versus placebo choice procedure. Subsequently, subjects received either caffeine (300 mg t.i.d.) or placebo (placebo t.i.d.) for 18 consecutive days, and thereafter were exposed again to a caffeine versus placebo choice procedure. And the result?

"The study documented tolerance development to the subjective effects of caffeine: after chronic dosing, administration of caffeine produced significant subjective effects in the chronic placebo group but not in the chronic caffeine group." The study also provided indirect evidence for tolerance development: during chronic dosing, the chronic caffeine and placebo groups did not differ meaningfully on ratings of mood and subjective effect. That's important, because it means that not all benefits are lost; plus, it explains why you still don't quit drinking your coffee ;-)

During the run-in, participants were synchronized with a nocturnal sleep from 22:30 to 07:00 h. During the TSD-phase, they were not allowed to sleep and were kept awake by passive means such us watching TV.

Figure 2: Caffeine boosts cognitive performance during sleep deprivation (Souissi. 2014)

During each test session, after 10 min of rest in a sitting position, participants ingested the caffeine or the placebo dose; then they had to remain in a sitting position for 60 min. After the 60 min, they performed

• the reaction time, 
• the squat jump (SJ), and 
• the Wingate tests at 18:00 h with 15 min of recovery in-between 

All test sessions took place in similar conditions of temperature and relative humidity (27–28 °C and 63–66%, respectively).  The physical tests were complemented by a simple choice-reaction test and a profile of mood state evaluation - which yielded an impressive reduction of the depression and confusion the subjects felt after the 32h without sleep (see Figure 3)

Figure 3: Results of the profile of mood test w/ & w/out caffeine before and after TSD (Souissi. 2014)

In conjunction with the increase in vigor, decrease in anxiety and fatigue this alone would warrant the use, but not abuse of caffeine after sleepless nights. The latter, i.e. habituation to high doses of caffeine as they are really common in the pre-workout guzzling world of physical culturists, could potentially nullify the results.

So what? To withdraw, or not? In my humble opinion, caffeine junkies like us just have to live with the fact that the psychological and physiolo- gical effects even high doses of caffeine have are negligible. Caffeine or rather coffee is healthy, but it's only healthy if you consume it regularly; and the lack of effects on the central nervous system in the "habitual consumer" will actually protect your nervous and cardiovascular system. So, just stick to whatever you can still get out of caffeine, but do never increase your intake beyond 800mg per day on a chronic basis - if even that does no longer effect you, you've been overtraining + abusing for years.

Bottom line: We all know that caffeine works. At least for those 95% of us who don't belong to the caffeine hypermetabolizer, there is this memory somewhere deep inside our heads. A memory of our first "high dose caffeine, tear down the gym"-experience. It's a memory that's burried deep below memories of years of daily caffeine abuse and the knowledge that the only way to get anywhere close to the caffeine naive state we were in back in the day is withdrawal...

Yeah, I know that's hard to imagine and actually, there is no evidence that would suggest that withdrawal and resensitization would be necessary to get the dozens of health benefits I have written about in the past. In fact, you could rather argue that 400mg+ doses of caffeine are going to have a negative effect on your health, as long as they still 'cause an increase in Central Nervous System (CNS) activity as it was observed in the study at hand. I mean, what would you expect the health consequences of having one of these "high dose caffeine, tear down the gym"-experiences every (other) day? This can hardly be good for your heart and brain, can it?

References:

• Evans, Suzette M., and Roland R. Griffiths. "Caffeine tolerance and choice in humans." Psychopharmacology 108.1-2 (1992): 51-59.
• Horne, John A., and Olov Ostberg. "A self-assessment questionnaire to determine morningness-eveningness in human circadian rhythms." International journal of chronobiology 4.2 (1976): 97. 
• Souissi, Makram  et al."The effects of caffeine ingestion on the reaction time and short-term maximal performance after 36h of sleep deprivation." Physiology & Behavior 131 (2014): 1-6.

Science Round-Up Seconds: A Focus on Intra-/Post Workout Stims, Carbs & Protein and Their Effects on Performance, Hydration, GH, Cortisol, Testosterone & Fatty Acid Oxidation

As mentioned on yesterday's show, small 100kcal packets are as much of a problem as large dinner plates and XXL meals (data based on Coelho do Vale. 2008)

I want to start today's Seconds with a question: How did you like that Carl and I did not rush through the news-lineup as it was the case in previous episodes, but simply took our time to discuss the topics in depth an breadth, yesterday?

Personally, I believe that this is much better than the accumulation of "buzzword" the show had become in the previous weeks due to my "study hunter and gatherer" drive - or, in other words, the mere mass of studies I wanted to pack into the show and Carl's desperate effort to cover them all.

Would you agree? And what other changes / improvements would you like to see in the future? We are open for constructive criticism. You can't improve your game without it.

Let's get to what did not fit into the show, then...

The net result of the spending more time on each and every of the single items, or, to say it in the spirit of yesterday's show, a bit more mindfulness was obviously a much larger amount of Seconds for you to devour today. So, let's not waste any time and get right down to business:

• Is 200mg of caffeine the optimum!?A 2008 study by Beavan et al., which involved 24 professional rugby players who were randomly assigned to receive 0, 200, 400 or 800mg of caffeine 1h before performing a standardized resistance training protocol (Beavan. 2008), found that contrary to what bro-science has been suggesting for years, the ingestion of the high amounts of caffeine (800mg) lead to a profound drop in the testosterone-to-cortisol ratio, while the lower doses of 200mg and 400mg of caffeine only blunted the performance hampering decline of cortisol half-way into the workout, while increasing the testosterone levels by 15%
  Caffeine or pseudoephedrine for performance enhancement? As far as improving you game is concerned, a recent study from the School of Sports Science at the department of Exercise and Health of the University of Western Australia was able to show that you are only wasting your time an money, if you are trying to up your cycling-time trial and thus probably every other HIT performance by ingesting the purported CNS stimulant pseudoephedrine (not to be confused with the "real deal"; cf Spence. 2013).
  
  Contrary to the comparatively low amount of 200mg caffeine, which allowed the 10 well-trained cyclists and triathletes who participated in the study improve their TT times in trial 2 of 3, all of which were performed on th same day, by statistically significant 57s, the ingestion of the WADA banned substance pseudoephedrine at a dosage of 180g would have cost them their license for nothing.

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  Bottom line: Spare yourselves pseudoephedrine and other nasal/sinus decongestant belonging to the the class of phenethylamines and amphetamines (e.g. geranium). Even if others worked (for 1,3-dimethylamine this has never been proven in isolation), the long(er)-term detrimental effects they'll have on your central nervous system really isn't worth it.

• Protein-enhanced Gatorade ain't worth your money -- If you are no ultra-endurance runner or at least marathon runner, you don't need, because you don't benefit intra-workout carbohydrate + electrolyte + protein (CEP) drinks for hydration.
  
  The results of a recent study from the Chinese University of Hong Kong show: A CEP solution containing 42g/L carbohydrate, 21g/L whey protein and 15.3 mmol/L sodium and 2.3 mmol/L potassium does not show "extra benefits for the maintenance of hydration status during 60 min cycling" (Sun. 2013)

• Carbohydrate + protein drinks maximizes GH response to exercise -- Now that you know that it's not worth to guzzle on carbohydrate + electrolyte + protein drinks during a workout for hydration purposes, I guess I should tell you that doing the same (w/out the electrolytes, though), may still provide an athletic / anabolic edge. After all, another recently published study that was conducted at the School of Sport at the Department of Exercise and Health Sciences of the Loughborough University in Leicestershire, U.K (Betts.  2013) shows that the ingestion of a carbohydrate + protein mixture (CHO+PRO: 0.8 g sucrose per kg bod weight per hour + 0.3 g/kg/h whey protein isolate) in the 4h recovery period between two exhaustive treadmill runs at the same intensity augmented the growth hormone response by 60%(!) compared to the ingestion carbohydrate only (0.8 or 1.1g of sucrose /kg per hour).
  

  

  Figure 1: Growth hormone (GH) and cortisol response to 2nd bout of exhaustive treadmill running with either 0.8 or 1.1g of sucrose /kg per hour (CHO, CHO-CHO) or  0.8 g/kg/h sucrose per kg bod weight per hour + 0.3 g/kg/h whey protein isolate (CHO+PRO; cf.

  As the data in figure 1 goes to show you this increase in GH was accompanied by a 23% reduction in cortisol. With both, GH and cortisol being released in response to the depletion of muscle glycogen and impeding low blood glucose levels (Galbo. 1977), you could thus argue that protein (probably by its glucagon promting effects; cf. Claessens. 2008) programs the "anabolic glucose procurement plan".
  

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  Bottom line: Yet another reason for the often touted, yet tried and proven "Bananas + whey" = WIN! And that's not true wrt to the protein anabolic response after a workout, but also in view of the "anabolic" or I should probably say generally more favorable way of glucose procurement during subsequent workouts.

• 

  No, no and no! The ingestion of carbs before a HIIT workout will only increase, not blunt the fatty acid oxidation in the post-workout period.

  Pre-workout carb ingestion does not blunt, but promote fatty acid oxidation after the workout -- In as much as this result may go against common bro-science that you must never consume any carbs before your workout if you are trying to lose body fat, it is actually in line with what I have been preaching before. The beneficial effects of AMPK come with the depletion of ATP and the rise in ADP (~used ATP), not with the constantly depleted ATP stores of a no-carbohydrate + protein only starvation diet. Or put more simply - a constant over-expression of AMPK negates all the benefits of it's cyclic up and down (cf. "The mTOR/AMPK Seesaw"; read more)
  
  While the scientists from the Department of Nutrition & Metabolism at the Faculty of Health and Medical Sciences of the University of Surrey in Guildford, UK, did not observe statistically significant improvements in fatty oxidation due to the small study size (10 healthy untrained females; age 18–22 yr; BMI 22kg/m²), the pronounced decrease in RQ after 8-10x 60 second cycling bouts at 95 % VO2peak separated by 90 seconds recovery at 50 watts in 9 out of 10 participants (see figure 2) does speak itself: "In women, consuming carbohydrate before exercise may potentially be more beneficial for fat oxidation than consuming carbohydrate post-exercise" (Honnor. 2013).
  

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  Bottom line: The results of the study at hand, which stand in line with previous research by Fuchs et al. who presented their research in the Proceedings of the Nutrition Society one year before, re-emphasis the fallacious over-reliance of high fatty oxidation rates during a workout. The max. 60-90min in which you may burn slightly more fat, are simply negligible compared to the much longer post-workout period, where the ingestion of 59 g CHO before a HIIT workout did not blunt but promote fatty acid oxidation.

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Believe it or not, but that's it for today! If you are hungry for more, I suggest you either go to the SuppVersity Facebook Wall or listen to Casual Friday later today... actually, I found Gabriel's name, i.e.  "The Alisa Profumo Show", for the Friday edition of Super Human Radio show quite fitting ;-)

References:

• Beaven CM, Hopkins WG, Hansen KT, Wood MR, Cronin JB, Lowe TE. Dose effect of caffeine on testosterone and cortisol responses to resistance exercise. Int J Sport Nutr Exerc Metab. 2008
  Apr;18(2):131-41.
• Betts JA, Stokes KA, Toone RJ, Williams C. Growth Hormone Responses to Consecutive Exercise Bouts with Ingestion of Carbohydrate plus Protein. Int J Sport Nutr Exerc Metab. 2013 April. 
• Claessens M, Saris WH, van Baak MA. Glucagon and insulin responses after ingestion of different amounts of intact and hydrolysed proteins. Br J Nutr. 2008 Jul;100(1):61-9.
• Coelho do Vale R, Pieters R, Zeelenberg. Flying under the Radar: Perverse Package Size Effects on Consumption Self‐Regulation. Journal of Consumer Research. 2008; 35(3):380-39.
• Fuchs, A. & Young, H. Investigation into gender differences in the effects of feeding around exercise on exercise performance, energy expenditure and substrate utilisation. Proceedings of the Nutrition Society. 2011; 70 (OCE6), E380.
• Galbo H, Richter EA, Hilsted J, Holst JJ, Christensen NJ, Henriksson J. Hormonal regulation during prolonged exercise. Ann N Y Acad Sci. 1977;301:72-80. Review.
• Honnor M, Herdsman M, Collins AL.The effect of food timing on fat oxidation during exercise and resting recovery. Proceedings of the Nutrition Society. 2012; 71 (OCE3), E236 
• Spence A, Sim M, Landers G, Peeling P. A Comparison of Caffeine versus Pseudoephedrine on Cycling Time-Trial Performance. Int J Sport Nutr Exerc Metab. 2013 Apr 9. 
• Sun, F; Li, L; O’Reilly, J; Wong, SH. Effect of carbohydrate-electrolyte-protein solution on hydration. International Journal of Sport Nutrition and Exercise Metabolism. 2013; 23: S1-S15