"Couldn't this impair the adaptation to exercise?" This question cannot be answered based on an acute response study, but with the acute increases in exercise performance (Cooper test, see Figure 2) and in spite of the significant reductions in CK and LDH (see Figure 2), which are usually interpreted as markers of muscle damage, this appears generally unlikely - yet not impossible.

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Figure 2: Copper test (test of physical fitness | more) performance and creatine kinase (CK | more) and lactate dehydro- genase (LDH) levels after the 12-minute Cooper test before and after 7-days of supplementing with ~21g/d of 100% cacao powder (Gonzlez-Garrido. 2015).

On the other hand, it is important to note that only the increased Cooper test performance (Figure 2), but none of the other markers has at least a non-significant predictive value with respect to the possible long-term effects on exercise performance - an effect that will have to be tested in future longer-term studies. A conclusion that would go beyond the scientists' statement that they "have shown the potential that cocoa consumption has on endurance performance and its role in recovery from muscle damage in athletes" (Gonzlez-Garrido. 2015) would thus be unwarranted... as unwarranted as any speculations about the underlying mechanisms: yes, it is likely that the high polyphenol content of 100% cacao is what does the trick, but to prove that we'd need a low polyphenol chocolate control we don't have. If you want to benefit, though, I highly suggest to pick a 100% cacao powder with a low degree of processing