This is a linkpost for http://squirrelinhell.blogspot.com/2017/08/the-unyoga-manifesto.html
Not directly related to rationality, but this approach should help with exercise akrasia (the post is about yoga, but generalizes to other forms of exercise), and that's always on topic.
Doing yoga improved my rationality skills. If I were rewriting optimal exercise I'd add a section titled Retraining your Broken CNS.