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Whey or casein hydrolysate - or rather no protein - what to use in your intra-workout beverage for endurance?

Last week, waredownloadsoft reader Oscar Qiu asked me which protein supplements I would suggest he'd buy. My answer was simple: "Get a cheap whey protein and if you want to spend extra money, add some micellar casein. Dose it at a ratio of 20:10 whey:casein post-workout (learn why) and, if you feel you're not getting enough protein on a daily basis, optionally, take them at a ratio of 10:20 whey:casein right before bed" (learn more about pre-bed casein).

Now, I am not going to revise this basic supplementation advice I gave based on the results of a recent study from the University of the Witwatersrand (Oosthuyse. 2015), but it may still be worth considering that other protein sources like whey-hydrolysate (learn more) or, as in this case, casein-hydrolysate may have certain context-specific benefits over the aforementioned "staple proteins".
In said study, Oosthuyse et al. tried to find the "protein most suitable for ingestion during endurance exercise" (Oosthuyse . 2015). To this ends, the researchers compared the effects of co-ingesting either

• 15 g/h whey-hydrolysate with (whey-CHO) or without carbohydrates (whey-PLA) or
• 15 g/h casein-hydrolysate with (casein-CHO) or without carbohydrates (casein-PLA).

In conjunction with the placebo, only, and the carbohydrate, only, trials there are six trials, i.e. placebo, placebo+whey, placebo+casein, the 63g/h fructose: maltodextrin (0.8:1) that made up the CHO content of the test beverages, alone, and in conjunction with either whey or casein-hydrolysates.

Table 1 + 2: Dietary records (mean ± SD) for 2 days preceding the day of each experimental trial (left); composition of the experimental beverages consumed during the trials (right | Oosthuyse. 2015).

Practically speaking this meant that 2h after the last meal (postprandial), 8 male cyclists ingested either: carbohydrate-only, carbohydrate-whey-hydrolysate, carbohydrate-casein-hydrolysate or placebo-water in a crossover, double-blind design during 2 h of exercise at 60 %Wmax followed by a 16-km time trial.
Data were evaluated by magnitude-based inferential statistics and revealed only non-significant effects on carbohydrate oxidation, measured from 13CO2 breath enrichment, by either of the two protein hydrolysate in isolation (data not shown),

Figure 1: What really counts are the performance improvements (left) and potential gastrointestinal side effects during (right, c), yet not so much right after the time-trial (right, b | Oosthuyse. 2015).

This changed, when the carbohydrates came into play: While the increased carbohydrate availability obviously lead to increases in glucose oxidation in all trials, these increases were substantially decreased (98% very likely decrease) when the carbohdrate drink was co-ingested with casein-hydrolysate (mean ±SD, 242 ±44; 258±47; 277 ±33g for carbohydrate-casein, carbohydrate-whey and carbohydrate-only, respectively). As it was to be expected, this decrease in carbohydrate oxidation during exercise had to be compensated by increases in fat oxidation - in this case a 93% likely increase from 83 ±27 and 73 in the whey-carbohydrate and carbohydrate-only to 92 ±14 g in the casein-hydrolysate group.

Figure 2:  Hydro whey and hydro casein have only slightly different amino acid makeups - *indicates essential amino acids (Oosthuyse. 2015).

Now, some people who are still believing in the long-overcome theory of exercise-induced fat loss may speculate that the increased fatty oxidation in the casein group would indicate that the co-ingestion of casein-hydrolysate would increase exercise-induced fat loss. You, as a waredownloadsoft reader know that the assumption that increased intra-workout fat oxidation would equal increased fat loss is total bogus. Accordingly, you will appreciate that the addition of casein to the intra-workout equation did have additional, practically relevant benefits: It lead to a significantly faster time trial ( − 3.6%; 90 % CI: ±3.2%) performances compared to placebo-water (95 % likely benefit).

Ok, now that you've hopefully memorized that you can safely ignore the non-existent fat-loss benefits of increased fat oxidation during exercise (assuming it is just to compensate a reduced CHO oxidation, as in this case), you must be careful not to jump to the similarly unwarranted conclusion that the time-trail times in Figure 1 would indicate that you or the (endurance) athletes you may be coaching should exchange all their "Gatorades" and other CHO-based intra-workout beverages for pure casein-hydrolysates.
References:

• Bassini-Cameron, Adriana, et al. "Glutamine protects against increases in blood ammonia in football players in an exercise intensity-dependent way." British journal of sports medicine 42.4 (2008): 260-266.
• Breen, Leigh, Kevin D. Tipton, and Asker E. Jeukendrup. "No effect of carbohydrate-protein on cycling performance and indices of recovery." Med Sci Sports Exerc 42.6 (2010): 1140-1148.
• Cermak, Naomi M., et al. "Muscle metabolism during exercise with carbohydrate or protein-carbohydrate ingestion." Medicine and science in sports and exercise 41.12 (2009): 2158-2164.
• Hobson, Ruth, and Lewis James. "The addition of whey protein to a carbohydrate–electrolyte drink does not influence post-exercise rehydration." Journal of sports sciences 33.1 (2015): 77-84.
• Koopman, René, et al. "Combined ingestion of protein and carbohydrate improves protein balance during ultra-endurance exercise." American Journal of Physiology-Endocrinology and Metabolism 287.4 (2004): E712-E720.
• Korach-Andre, Marion, et al. "Differential metabolic fate of the carbon skeleton and amino-N of [13C] alanine and [15N] alanine ingested during prolonged exercise." Journal of Applied Physiology 93.2 (2002): 499-504.
• Oosthuyse, T., M. Carstens, and A. M. Millen. "Whey or Casein Hydrolysate with Carbohydrate for Metabolism and Performance in Cycling." International journal of sports medicine (2015).
• Saunders, Michael J., Mark D. Kane, and M. Kent Todd. "Effects of a carbohydrate-protein beverage on cycling endurance and muscle damage." MEDICINE AND SCIENCE IN SPORTS AND EXERCISE. 36.7 (2004): 1233-1238.
• Saunders, Michael J., Nicholas D. Luden, and Jeffrey E. Herrick. "Consumption of an oral carbohydrate-protein gel improves cycling endurance and prevents postexercise muscle damage." The Journal of Strength & Conditioning Research 21.3 (2007): 678-684.
• Saunders, Michael J., et al. "Carbohydrate and protein hydrolysate coingestion's improvement of late-exercise time-trial performance." International journal of sport nutrition 19.2 (2009): 136.
• Seifert, John, Joseph Harmon, and Patty DeClercq. "Protein added to a sports drink improves fluid retention." International journal of sport nutrition and exercise metabolism 16.4 (2006): 420.
• Skillen, Rebecca A., et al. "Effects of an amino acid-carbohydrate drink on exercise performance after consecutive-day exercise bouts." International journal of sport nutrition 18.5 (2008): 473.

While this picture shows loaded cardio in its most beautiful form, the study investigated loaded cardio on the treadmill and compared it (for questionable reasons) to non-loaded cardio on a stationary bike and guess what: Both burn the same amount of muscle - NET: Zero!

Carrying a (heavy) load during cardio? Sounds dumb? Well, that's however, how the real world looks like. Not just soldiers who are carrying armor and a heavy backpack in the field, but also hikers will attest to the fact that doing "cardio" with a weight on your shoulders or elsewhere is more natural than running around in the park with your mobile and ear-plugs as the only load you're carrying on top of your ultra-light runners clothing.

With that being said, it is actually quite astonishing that Stefan M. Pasiakos and colleagues from the Military Nutrition Division at the US Army Research Institute of Environmental Medicine in Natick are the first to take a look at the muscle anabolic and catabolic effects of regular (unloaded) and loaded cardio training in 40 free-living healthy, physically fit (peak oxygen uptake, VO2peak 40/60 mL/ kg/ min), adults (37 males and 3 females), normal weight men and women between the ages of 18–39 years.
In said study, the volunteers were then randomly assigned to one of four experimental groups, each
of whom performed a single 90 min exercise bout.

• Two groups performed CE and the other two performed LC. 
• One of each of the exercise groups received EAA drinks to consume during exercise, and the other groups received control (CON) drinks. 

To determine the effects on skeletal muscle, the subjects' individual muscle protein synthesism (MPS) was assessed during exercise and recovery and whole protein turnover was determined in recovery only. What may be a bit surprising in this context is the fact that a resting MPS measure was not included in the study. The authors, however, have a good argument to neglect this, when they say that (a) the MPS responses to endurance-type exercise (i.e.,as they relate to resting MPS) are well established and that (b) their ...

"[...] intent was not to determine temporal changes in MPS within an exercise mode (with or without EAA), but to examine MPS responses between LC and CE during exercise and recovery independently" (Pasiakos. 2015).

Another thing that was just like in any other study, though, was the standardization of diet and physical activity, the scientists describe as follows:

"Volunteers completed 3 d diet and activity records at baseline, and similar to our previous work (Pasiakos. 2011), these records were used to individually prescribe 7 d lead-in diets to maintain body weight and to limit the potential confounding effect of diet on outcome measures. Compliance was confirmed by 24 h dietary recalls conducted every two days during the lead-in phase (Food Processor SQL1, version 10, ESHA Research, Salem, OR) (Table 1). Volunteers were also instructed to maintain activity levels reported at baseline for the first five days of the lead-in phase. All resistive and endurance-type activity was prohibited 48 h before data collection to minimize any potential residual effects of previous exercise on protein turnover" (Pasiakos. 2015).

The actual news is however not the dietary standardization what you are (rightly) interested in is probably the exercise protocol which is - and I will get to that in the bottom line - not ideal: While the LC, i.e. the load carriage training, was performed by walking on a treadmill while wearing a weighted vest equivalent to 30% of baseline body mass, the CE, i.e. the control endurance exercise, was non-weight bearing and performed on a cycle ergometer (Lode, BV, Netherlands), of which the scientists say that they used it to "allow for comparisons with our previous studies" (Pasiakos. 2015).

Illustration 1: Graphical overview of the study design (Pasiakos. 2015) | EAA = 10g of EAAs, CON = non-nutritious control drink; LC = load carrying cardio on a treadmill, CE = control endurance exercise on a stationary bike.

What's unquestionable a strength of the study, though, was the fact that the baseline VO2peak and associated heart rates at maximal and submaximal levels were used to establish target exercise intensities for the LC and CE trials. In addition, speed and grade for LC and power (watts) for CE were adjusted to match the absolute exercise intensity (intended oxygen uptake was 2.4 L /m) and
to elicit a similar energy cost (intended energy expenditure was 1050 kcal /90 min) between
LC and CE. Lastly, ...

"[m]atching the intensity and energy cost was done to isolate the effects of the possible differences in mechanical force and contractile properties of LC and CE from the relative intensity and energy cost of the exercise bout [and a] familiarization trial was conducted to ensure the accuracy of the exercise prescription and the ability of the volunteer to complete the prescribed exercise bout" (Pasiakos. 2015).

As previously alluded to, the intra-workout beverage the subjects consumed was either a high EAA drink (10 g EAA: 0.7 g histidine, 0.7 g isoleucine, 3.6 g leucine, 1.2 g lysine, 0.3 g methionine, 1.4 g phenylalanine, 1.0 g threonine, and 1 g valine) or an identically looking placebo drink (non-nutritive).

Figure 1: Overview of protein fluxes (synthesis vs. breakdown and oxidation) and subsequent net protein balance in the four treatment groups, i.e. loaded and control cardio with and with out EAA (Pasiakos. 2015)

Interestingly enough, the latter, i.e. the 10 grams of EAA drink that was consumed in four small doses (i.e., 350 mg of phenylalanine and 900 mg of leucine per serving), over 90 min to minimize "any isotopic dilution that may have occurred if the EAA drink was consumed as a bolus" (Pasiakos. 2015) was the only treatment that made a difference to the protein flux parameters illustrated in Figure 1. In that it is worth mentioning the tthe difference in protein oxidation alone does not fully explain the conservation of skeletal muscle protein even if we assume that all the amino acids that were oxidized during the EAA supplementation trial came from the EAA supplement. This is curious in view of the lack of effect of BCAAs on exercise (learn more) induced protein breakdown and points with a finger to other EAAs as potential motors of this effect.

Figure 1: Protein synthesis. Mixed-muscle (A), myofibrillar (B), and sarcoplasmic (C) muscle protein synthesis (MPS) during exercise and mixed-muscle (D), myofibrillar (E), and sarcoplasmic (F) MPS in recovery from a 90 min, metabolically matched load carriage (LC) or conventional endurance (CE) exercise bout, with and without (control, CON) essential amino acid (EAA) supplementation. Data are mean ± SD, n = 10 per group. †Mode main effect; LC different than CE, P < 0.05. *Drink main effect; EAA different than CON, P < 0.05 (Pasiakos. 2015).

The fact that the loading didn't make a difference in either direction, i.e. that it did neither increase nor decrease the breakdown or synthesis of muscle protein may be surprising, but it's not the only result worth mentioning before we evaluate the results in the bottom line. In addition, it should be noted:

1. The EAA-mediated decrease in muscle breakdown was complemented by both enhanced mixed-muscle and sarcoplasmic MPS during exercise.
2. During the recovery phase, the mixed muscle and sarcoplasmic protein synthesis in response to loaded cardio training were higher than they were in the control group.

Of these results, finding #2 is of most interest as it puts the alleged uselessness of loaded cardio into perspectives. Muscles do after all grow during rest and if the muscle protein synthesis during the recovery phase is increased compared to the control non-loaded exercise this clearly suggests that loaded endurance exercise is more anabolic than non-loaded endurance exercise.
References:

• Pasiakos, Stefan M., et al. "Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis." The American journal of clinical nutrition 94.3 (2011): 809-818.
• Pasiakos SM, McClung HL, Margolis LM, Murphy NE, Lin GG, Hydren JR, et al. "Human Muscle Protein Synthetic Responses during Weight-Bearing and Non-Weight-Bearing Exercise: A Comparative Study of Exercise Modes and Recovery Nutrition." PLoS ONE 10.10 (2015): Online only.