The official U.S. army fitness training handbook

A soldier's level of physical fitness has a direct impact on his combat readiness. The many battles in which American troops have fought underscore the important role physical fitness plays on the battlefield. The renewed nationwide interest in fitness has been accompanied by many research studies on the effects of regular participation in sound physical fitness programs. The overwhelming conclusion is that such programs enhance a person's quality of life, improve productivity, and bring about positive physical and mental changes. Not only are physically fit soldiers essential to the Army, they are also more likely to lead enjoyable, productive lives.
This manual is primarily concerned with issues relating directly to the development and maintenance of the five components of physical fitness:

ØCardiorespiratory (CR) endurance--the efficiency with which the body delivers oxygen and nutrients needed for muscular activity and transports waste products from the cells.
ØMuscular strength--the greatest amount of force a muscle or muscle group can exert in a single effort.
ØMuscular endurance--the ability of a muscle or muscle group to perform repeated movements with a submaximal force for extended periods of time.
ØFlexibility--the ability to move the joints (for example, elbow or knee) or any group of joints through an entire, normal range of motion.
ØBody composition--the amount of body fat a soldier has in comparison to his total body mass.

U.S. ARMY FITNESS TRAINING HANDBOOK is an outstanding resource for anyone interested in improving mental health, physical health, and general well-being