Book excerpt: The ability of striated muscle tissue to adapt to changes in activity or in working conditions is extremely high. In some ways it is comparable to the ability of the brain to learn. The interest in muscle adaptation is increasing in relation to the idea that physical fitness helps in the prevention of disease, may counteract the loss of physical performance and generally improves wellbeing. Plasticity is the word used since the late 1970’s to indicate collectively all the processes and mechanisms which form the background of muscle adaptation. This book aims to provide a systematic updating of the available knowledge on molecular and cellular mechanisms, as well as on changes at whole muscle level. The book means to be a guide and a help for people who enter the field as PhD or medical students, but is also a tool for refreshing and updating knowledge for people already active in the field in basic sciences as well as in applied disciplines such as neurology, sports science and rehabilitation.