Growth-Retarding Effect of "Cardio"-Training is not Prevented by BCAA Supplementation. Endurance-Trained Rats Still -3% Smaller than Age-Mates.

Image 1: Haile Gebrselassie,
probably the greatest distance
runner in history, set 27 world
records; is his sort stature a
result of too much "cardio"
(image by Alexxx86)
Did you ever wonder if Haile Gebrselassie (image 1) is such a great long distance runner, because he is only 5'5" (1.65m, imdb)? Well, after all it could turn out that is is just the other way around - Haile could be only 5'5", because he is a great runner! Rumors have it Gebrselassie ran to school every day as a boy... what? You do not see a relation here, well then you should have a look at the data of a recent rodent study from the Faculty of Pharmaceutical Sciences at the University of Sao Paulo in Brazil (Campos-Ferraz. 2011).

For 5 weeks, Patricia Lopez de Campos-Ferraz and her colleagues, put 32 male Wistar rats (21 days old) on one of four experimental protocols:
  1. 45mg/kg BCAA  + swimming - Sup/Ex
  2. Standard chow + swimming - Ctrl/Ex
  3. 45mg/kg BCAA + sedentary - Sup/Sed
  4. Standard chow + sedentary - Ctrl/Sed
The endurance of the swimming protocol increased by 10 minutes per week - from 20min in the first week to 50 minutes in the fourth and fifth week of the experiment.

Figure 1: Effect of treatment (BCAA + "cardio" or "cardio" only) on cartilage weight, skull-to-tale length and tibia length in adolescent rats (data adapted from Campos-Ferraz. 2011)
As the data in figure 1 goes to show, the "cardio"-induced reduction (-95%, Sup/Ex; -97% Ctrl/Ex) in proteoglycan synthesis is so profound that the +30% higher synthesis rate in the BCAA group could not prevent the statistically significant growth retardations in the sixteen rats of the exercise groups (Sup/Ex + Ctrl/Ex).
Image 2: If the Hulk loves HIIT,
he probably has a healthier
heart than many marathon
runners (image from
Note: I am deliberately using the expression "cardio" here, because ardeous endurance exercises like these, are what the general public thinks heart-healthy exercise should look like. Only a few days ago, Hafstad et al. published a study in the Journal of Applied Physiology (Hafstad. 2011) showing (once again!) that high intensity interval training and not moderate endurance training provides the greatest benefit in terms of increasing aerobic exercise capacity, and cardiac efficiency! While this study was conducted with a rodent model, it corroberates results from human studies such as Ziemann et al. who found that high-intensity interval training performed at a work-to-rest ratio of 1:2 "provided sufficient stimulus to significantly improve markers of anaerobic and aerobic performance in recreationally active college-aged men" (Ziemann. 2011). As long as you do not have existing heart problems, HIIT should be your choice when it comes to training your heart, which is what "cardio"(-vascular training) should be all about, no?
Isn't it ironic, how those poor little critters experienced exactly what the huge group of people who are against strength training for adolescents usually suggest would happen, when kids start to lift weight? I guess, if it was not for the BCAA-induced increases in proteoglycan synthesis and the slight amelioration (-0.5%) of the retarding effect of endurance training on skull-to-tale length, the "anti-strength"-crowd would probably try to blame the effect on the "steroids" (this is how this folks usually refer to all supplements, BCAAs included), the rats received - fortunately, the study design does not allow misinterpretations like that.
Figure 2: Liver and muscle glycogen content in the four groups (data adapted from Campos-Ferraz. 2011)
Before this turns into an "anti-'cardio'-post" I want to mention a few interesting side-findings of the study: While there were no significant differences in muscle weight between the groups, there was a significant effect of BCAA supplementation on food intake in the sedentary group. The rats (all fed ad libitum) who receiving the chow with additional branch-chain-amino acids consumed roughly 7% less food. What I found more surprising, however, was the effect the amino acid supplement had on liver glycogen levels in the trained rats: The small dose [45mg/kg in rats equals ~7.3mg/kg in humans, i.e. ~584mg/day for an 80kg human being] of supplemental BCAAs raised liver glycogen levels by 12.4% (Sup/Sed) and 16.2% (Sup/Ex). The latter finding stands in line with similar elevations in liver glycogen stores after alanine or glutamine, histidine and proline supplementation in Tipton and Wulf (Tipton. 1998) and Aoyama et al. (Aoyama. 1993), respectively and corroborate previous findings by Araujo et al. (Araujo. 2006), who found a 226% increase in liver glycogen in exercised rats supplemented with a significantly higher amount (~1g/day) of BCAAs.
Figure 3: Muscle protein and RNA content in the four groups (data adapted from Campos-Ferraz. 2011)
Finally, while the small dose of branched chain amino acids did suffice to modulate liver (and to a certain degree muscle, cf figure 2) glycogen stores and storage capacity, it failed to result in a higher protein concentration in the trained rats. A finding of which the researchers state that
[t]his is in accordance with another study, in which oral administration of 270mg leucine to rats enhanced phosphorylation of the eu-karyotic initiation factor (eIF) (4F-BP1), but no differences in protein synthesis were found in the liver, which led them to conclude that the translation of mRNA is disjointed from the rates of total protein synthesis but is related to the degree of SK61 phosphorylation (Anthony et al., 2001).
While this may be the case, Campos-Ferraz et al. simply ignore that their "exercise" (I am inclined to say "torture") program was devoid of the most important stimulus of muscle growth, which is muscular overload - what is really surprising is thus not that the rats did not turn into hulk-like muscle-monsters, but rather that the supplemented rats (Sup/Ex) had a statistically non-significant, yet slightly reduced increase in muscle protein content (+3.92mg% vs. +5.52mg%) compared to their exercised peers (Ctrl/Ex) - despite a +23% greater increase in muscle RNA.

Interestingly, we see diametrically opposed effects in the sedentary group, where muscle RNA content is identical, and the BCAA group (Sup/Sed) has a slightly higher muscle protein content (cf. figure 3). So that, after all, we have come full circle to the detrimental effects of arduous "cardio"-training on adolescents ;-)
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