<P> Before the industrial revolution, fitness was defined as the capacity to carry out the day's activities without undue fatigue . However, with automation and changes in lifestyles physical fitness is now considered a measure of the body's ability to function efficiently and effectively in work and leisure activities, to be healthy, to resist hypokinetic diseases, and to meet emergency situations . </P> <P> Fitness is defined as the quality or state of being fit . Around 1950, perhaps consistent with the Industrial Revolution and the treatise of World War II, the term "fitness" increased in western vernacular by a factor of ten . The modern definition of fitness describes either a person or machine's ability to perform a specific function or a holistic definition of human adaptability to cope with various situations . This has led to an interrelation of human fitness and attractiveness which has mobilized global fitness and fitness equipment industries . Regarding specific function, fitness is attributed to persons who possess significant aerobic or anaerobic ability, i.e. strength or endurance . A well - rounded fitness program will improve a person in all aspects of fitness, rather than one, such as only cardio / respiratory endurance or only weight training . </P> <P> A comprehensive fitness program tailored to an individual typically focuses on one or more specific skills, and on age - or health - related needs such as bone health . Many sources also cite mental, social and emotional health as an important part of overall fitness . This is often presented in textbooks as a triangle made up of three points, which represent physical, emotional, and mental fitness . Physical fitness can also prevent or treat many chronic health conditions brought on by unhealthy lifestyle or aging . Working out can also help some people sleep better and possibly alleviate some mood disorders in certain individuals . </P> <P> Developing research has demonstrated that many of the benefits of exercise are mediated through the role of skeletal muscle as an endocrine organ . That is, contracting muscles release multiple substances known as myokines which promote the growth of new tissue, tissue repair, and various anti-inflammatory functions, which in turn reduce the risk of developing various inflammatory diseases . </P>

Name two of the five alternative principles of fitness