Written by Dr. Dunstan Hadley, during the late 1970s and early 1980s, it covers just about all the information needed by pilots of Hang Gliders (or any aircraft for that matter) on how the human body is affected by flight, motion and the effects of acceleration, changes in atmospheric pressure and among others, wind chill. Even today it is essential for all engaged in air sports from Hang Gliding to powered sport or even professional aviation. A good easy to read book and if you can still find one, buy it and use it.