The decision to use the 20 per cent threshold continues to be controversial because the potential fitness effects of this amount of admixture are unknown, and the threshold used will influence the decision to list by determining the number of populations classified as part of the native taxon (Haig & Allendorf 2006). (rsbl.royalsocietypublishing.org)
«This time we have gone one step further by evaluating the intensity of soccer training as well as the health and fitness effects of soccer for untrained elderly men with little experience of soccer.» (sciencedaily.com)
As a skeptic and a scientist, I tend to think that this fitness effect is not just about breast milk but probably intertwined with other factors. (scienceofmom.com)