A new text for coaches from Routledge Sport Science is now available everywhere, contributors including Bill Sands and John Salmela, titled The Science of Gymnastics.
Several people have told me it’s good.
• energetic, physical and physiological assessment
• training principles
• diet, nutrition and supplementation
• growth and development issues
• kinetics and kinematics
• angular and linear motion
• angular momentum
• stress, anxiety and coping
• motivation and goal setting
• mental skills training for practice and competition
• the psychology of learning and performance.

It’s available in paperback or ebook for $54.95. From that same Routledge link you can preview some pages free. University instructors can request a Complimentary Exam Copy.
