|Pre-, Post and Intra-workout supplements are a multi-million dollar business. But are the products at least half as effective as the shiny advertisements claim?|
A study from the Department of Public Health at the Aarhus University and a study that raises the question, whether its results are indicate that eccentric training is potent enough to maximize the protein anabolic response to an extend that the additional provision of dietary protein will not lead to further increases in markers of protein synthesis.
Before we draw any conclusions, I guess we should first take a look at what Stine Klejs Rahbek and her colleagues actually did: To investigate the effects of leucine-rich whey protein hydrolysate and carbohydrate (WPH+CHO) versus isocaloric carbohydrate (CHO) supplementation on the Akt-mTOR and the AktFOXO signaling axis, during recovery from muscle-damaging exercise and to evaluate whether their hypothesis that WPH+CHO would accentuate signaling for protein synthesis and attenuate signaling for protein degradation, compared to isocaloric CHO, the researchers recruited twenty-four young healthy recreationally active men who had not participated in systematic resistance training or eccentric dominated activities for lower extremity muscles within 6 months prior to inclusion in the study.
The study itself was conducted in a double blinded, isocaloric placebo-controlled fashion in regards to dietary supplementation. Following inclusion, subjects were randomly allocated into either
- a whey protein hydrolysate+carbohydrate group (WPH+CHO, n = 12) or
- isocaloric carbohydrate placebo group (CHO, n = 12)
|Figure 1: Timeline of interventions and measurements on the four study days are shown. A muscle biopsy was sampled 14 days prior to the exercise trial (i.e. to establish basal level). The protocol for days 1 and 2 was identical (Rahbeck. 2015).|
"On days 1 and 2 (24 and 48 h following exercise, respectively), the subjects were instructed to ingest three supplements at absolute time points similar to day 0, with the fist drink always ingested after the functional tests and biopsy sampling. Biopsy sampling from both the ECC and the CON leg on days 1 and 2 were performed under conditions similar to the pre-exercise biopsy, i.e., the subjects fasted overnight and rested in the supine position for 45 min prior to biopsy sampling. The biopsy sampling on days 1 and 2 was timed to correspond to 24 and 48 h following exercise termination. Assessments on indices of muscle damage (muscle force, muscle soreness and plasma muscle creatine kinase) were repeated at 24, 48, 72, 96, and 168 h after overnight fasting." (Rahbeck. 2015)All Subjects were instructed to refrain from physical activity such as exercise, stair case walking and other types of strenuous activity in the hours/ days between post-exercise assessments of indices of muscle damage to ensure that all measured effects made actually reflected the effects of the exercise + supplementation intervention.
|Figure 2: Effects of eccentric training + supplementation on markers of protein anabolism (left, green) and catabolism (right, red) as measured in the trained leg (Rahbeck. 2015).|
|Eccentric training impairs glucose sensitivity in healthy men (Asp. 1995).|
Don't freak out about the Rahbeck study, take a look at the latest studies leucine science!
Instead of freaking out that your protein supplements may be useless, you may thus rather discard this study as interesting, but inconclusive and take a closer look at the latest evidence that leucine, when consumed in excess and isolation could have side effects you may want to avoid.
- Leucine + endurance exercise - no perfect match? In their latest study, scientist from the São Paulo University were able to show that "leucine supplementation did not potentiate the effects of endurance training on protein turnover, and it also reduced its positive effects on glucose homeostasis" (Costa Junior. 2015) - in rodents.
In view of the fact that the interactions between endurance exercise, leucine supplementation and glucose metabolism have not previously been studies, the scientists analyzed the effects of endurance exercise training plus leucine supplementation on protein turnover and glucose homeostasis in healthy mice.
Reason to panic? No, the effects are not pronounced enough. In view of the fact that the benefits of isolated leucine supplementation and "spiking" other supplements with extra leucine are totally overblown, anyway. This may be the final straw that brakes the leucine guzzling camel's neck for those of you who's primary goal is to use exercise to improve their glucose tolerance.
- Leucine an "anti-pump", "anti-heart health" supplement? While they are a bit removed from human in vivo studies, the claims made by Yang et al. in their latest paper in Amino Acids are a bit frightening.
Based on the observation that increased concentrations of l-leucine in the plasma occur in obese humans and other animals with vascular dysfunction, the scientists argue that the unique inhibitory effect of leucine on NO synthesis from l-arginine in endothelial cells may be part of why the increase in serum BCAA that's brought about by a failure to metabolize the branch-chained amino acids in the obese could negatively modulate cardiovascular homeostasis in insulin resistance.
Figure 4: This is how leucine messes with NO synthesis. It increases the production of glutamine:fructose- 6-phosphate aminotransferase (GFAT) which then shuts down NO synthesis (Yang. 2015).
"Such means may include dietary supplementation with either α-ketoglutarate to enhance the catabolism of l-leucine in the small intestine and other tissues or with N-ethyll-glutamine to inhibit GFAT activity in endothelial cells" (Yang. 2015).If the scientists (reasonable) assumptions are accurate, anything that prevents the leucine-induced activation of GFAT, be it nutritional supplements or pharmaceutical drugs, may in fact contribute to improved cardiovascular function by enhancing vascular NO synthesis. For the average trainee that's not really relevant, but if you look at the composition of contemporary N.O. boosters this revelation may explain why the "old" NO Xplode with arginine, caffeine & co worked significantly better than its BCAA-laden successors.
- Asp, Sven, Jens R. Daugaard, and Erik A. Richter. "Eccentric exercise decreases glucose transporter GLUT4 protein in human skeletal muscle." The Journal of physiology 482.Pt 3 (1995): 705-712.
- Costa Junior, et al. "Leucine supplementation does not affect protein turnover and impairs the benefiial effects of endurance training on glucose homeostasis in healthy mice." Amino Acids (2015): Ahead of Print.
- Kirwan, J. P., et al. "Eccentric exercise induces transient insulin resistance in healthy individuals." J Appl Physiol 72.6 (1992): 2197-202.
- Rahbek, Stine Klejs, et al. "No differential effects of divergent isocaloric supplements on signaling for muscle protein turnover during recovery from muscle-damaging eccentric exercise." Amino Acids (2015): 1-12.
- Yang, Ying, et al. "l-Leucine and NO-mediated cardiovascular function." Amino acids (2015): 1-13.