Post-Workout Chlorogenic Acid / Caffeine Supplementation - For Good or For Worse? Plus: Glycogen Synthesis & Why A Post-Workout May Be a Better Idea Than You'd Think

"Done,... where is my post-workout coffee?" - Post workout caffeine / chlorogenic acid - good or bad idea?

I know it's kind of late to post an article like this months after the ISSN conference, but I recently hit on an overview of the poster presentations and noticed that I did actually miss a couple of interesting studies. Don't worry, I won't be addressing a couple of them in the weeks to come in some detail.

Not all are really news-worthy, but aside from today's item on caffeine and chlorogenic acid, there were also posters on nutrient timing, different forms of protein, commercially available supplements and other stuff that's all classic "SuppVersity fodder"?
Caffeine and chlorogenic acid? Right, that sounds like green coffee bean extract, but in the case of Jason R Beam et al.'s study, we are dealing with an artificial stack of

• 5mg/kg body weight of caffeine plus 75 g of dextrose (CAF), 
• 5 mg/kg body weight of chlorogenic acid plus 75 g of dextrose (CGA), or 
• 5 mg/body weight of dextrose plus 75 g dextrose (PLA)

the 10 moderately to highly trained study participants consumed after 30-minutes of  high intensity cycling at 60% of peak power output (~90% HR max).

Figure 1:

As you can see in Figure 1, we do see quite extra-ordinary effects of the administration of both caffeine and chlorogenic acid on post-workout glucose metabolism. The changes in the area under the cure (2h AUC) do yet overestimate the real-world difference between the glucose curves (not shown), which have a slightly higher spike immediately after the ingestion.

"Ok, no caffeine after a workout - right!?"

In the case of caffeine that was to be expected, it has after all been shown to decrease the insulin-induced glucose uptake (Graham. 2001). The fact that the glycemic response was - within the statistically probable margins - still identical, is simply the result that the stimulation of glucose uptake and hepatic, as well as muscular glucose storage is not really necessary as long at the glycogen stores are low. Accordingly, a 2004 study by Battram et al. was unable to show any effect of caffeine ingestion on proglycogen and macroglycogen resynthesis after a workout (Battram. 2004).

Figure 2: Skeletal muscle glycogen content (mmol/kg dw) immediately after exercise 0. 1, 4h after cycling to volitional fatigue (70% Vo2Peak) w/ or w/out coingestion of 8mg/kg BW (+ 1g/kg glucose) after the workout - left; corresponding levels of pCAMK and p-Akt (arbitrary units) 1h and 4h after the workout, right (Pederson. 2009).

As you can see in Figure 2 the net amount of glucose that ends up in the musculature after exhaustive (if you don't deplete the stores this effect won't be there) exercise was in fact favorably affected by the congestion of 8mg/kg caffeine and 1g/kg glucose in with caffeine in the 7 endurance-trained cyclists and triathletes in a study by Pedersen et al. from 2009. The exact underlying mechanisms of this beneficial effects, as well as dose response relationships do yet still have to be determined, but Pederson et al. speculate that it may a result of the increased activation of p-AKT:

You think you've heard about p-Akt before, but are not sure where? Well, chances are it was here at the SuppVersity, yet probably in a different context, i.e. as part of the Intermittent Thoughts on Building Muscle | read more

"The increase [in p-AKT] tended to be higher after the ingestion of caffeine with CHO after both 1 and4hof recovery, but failed to reach statistical significance. Akt seems to regulate glucose uptake by phosphorylating and inhibiting the Rab-GTPase-activating protein AS160. Thus it is tempting to speculate on the role of Akt in glucose transport given that the Akt substrate AS160 has been identified as an important regulator of GLUT4 traffic.

We have recently shown that AS160 is phosphorylated in human skeletal muscle after endurance exercise with concomitant phosphorylation of Akt (7), providing correlative evidence to suggest AS160 is an exercise-responsive protein with a role in glucose uptake." (Pederson. 2009)

If we discard potential negative effects of the caffeine-induced CNS activation on post-exercise nervous system recovery, and take into account that the elevated glucose + insulin AUC Beam observed in the experiments for his dissertation and ISSN conference poster are negligible, the preliminary bottom line for post-workout caffeine intake would be: "If glycogen resynthesis is what you are looking for, do it!"

"What about the effects of chlorogenic acid. Shouldn't the exact opposite happen?"

Now that we've searched for explanations of the effects of caffeine on post-workout glycemia we are still left with the astonishing increase in the two-hour glucose area under the curve, i.e. total glycemia, Beam observed in the glucose + chlorogenic arm of his study.

Figure 3: Insulin (AUC) for each subject during the placebo, caffeine, and chlorogenic acid trials (Beam. 2013)

If you take a closer look at the data to the right, you won't get a mechanistic explanation of the underyling reasons, but you will at least get an idea of what statistical significance means and why we are talking about it in almost every study analysis, even if it does not equate physiological significance.

In this particular case the 2 outliers, subject 1 and subject 6 do not simply "ruin" the statistical significance, they are actually the (almost) only reason that insulin response is not virtually identical to the placebo trial.

As far as potential negative consequences of the post-workout consumption of cholorgenic acid goes, you do thus not have to be worried, whether it is actually a good idea to use a supplement that's meant to increase the activity of AMPK in a phase, when the latter is already maximized, is however questionable. In the best case, the additional benefits will be minimal, in the worst case it  CGA will ruin the glucose repartitioning effects of the workout by increasing AMPK and thus glucose uptake in the fat cells (Alonso-Castro. 2008).
References:

• Alonso-Castro, A. J., Miranda-Torres, A. C., González-Chávez, M. M., & Salazar-Olivo, L. A. (2008). Cecropia obtusifolia Bertol and its active compound, chlorogenic acid, stimulate 2-NBD glucose uptake in both insulin-sensitive and insulin-resistant 3T3 adipocytes. Journal of ethnopharmacology, 120(3), 458-464. 
• Beam, J. (2013). The effect of post-exercise caffeine and chlorogenic acid supplementation on blood glucose disposal and insulin sensitivity.
• Battram, D. S., Shearer, J., Robinson, D., & Graham, T. E. (2004). Caffeine ingestion does not impede the resynthesis of proglycogen and macroglycogen after prolonged exercise and carbohydrate supplementation in humans. Journal of Applied Physiology, 96(3), 943-950.
• Pedersen, D. J., Lessard, S. J., Coffey, V. G., Churchley, E. G., Wootton, A. M., Ng, T., ... & Hawley, J. A. (2008). High rates of muscle glycogen resynthesis after exhaustive exercise when carbohydrate is coingested with caffeine. Journal of Applied Physiology, 105(1), 7-13.