I stumbled across an argument on my Twitter timeline the other day with one side making statements about perceived problems in American soccer, and the other side asking for scientific evidence to back up these claims.
Scientific journal articles, or studies pulled from Pub Med seem to be appearing more frequently, about why this style of coaching is better, or that these types of drills are ineffective, etc. Someone who has articulated the role of science in coaching far more eloquently than I have is Charles Poliquin, an Olympic strength coach. I recommend these articles: 1, 2, and 3. Most of his main points apply to soccer as well.
For example, science is about controlling for all variables, and changing only one. Is that relevant to coaching in soccer? Will the conclusions drawn from the study transfer broadly? Of course not. A certain exercise performed with 8 year olds will not necessarily transfer to 14 year olds. Or from boys to girls. Or even between different groups of 8 year olds!
There is also the matter of language. Maybe the findings of one study conflict with another study in another language that you aren't even aware of. Or, perhaps the studies conflict on their findings precisely BECAUSE they are in another language, and cultural differences in the subjects had an impact. Kieran Smith believes that because of the way their respective teachers behave in classrooms, Spanish players are most responsive to and comfortable with a more direct, command-style of coaching than English players.
Then there are all of the topics that haven't been covered in scientific research...
While it's certainly a useful tool to be able to read and understand these studies, in my opinion, the best way to improve as a coach is to study and learn from the best coaches, not the best scientists.