Cardarine: Steers muscle fibres towards type I
It is well established that on ketogenic diet, the mechanism for fatty acid oxidation and optimization of such is an end result of increasing the density of Type I muscle fibres by compensatory decrease in type II. These are endurance type fibres that are largely dependant on fatty acid oxidation and not glycolysis/glycogen. For this reason, they are much smaller in size due to mitochondrial protein content and a host of other mechanisms.
Marathon runners have high density/count of type I muscle fibres (upwards of 90% Type I) and are visually smaller and statistically have much lower power output (which is obvious). Bodybuilders and sprinters have on average over 70% Type II (correct me if I'm wrong here).
Cardarine works in a manner that induces genes that would otherwise be induced during a ketogenic diet for the purpose of utilising and optimising fat for fuel.
Conclusion: Cardarine will attenuate potential strength maximus and anaerobic performance over time by reducing Type II fibre types.
source? i don't think you cant find direct literature indicating this but can be formed from gathering the mechanisms involved from an array of studies related to muscle metabolism