Swedish Physical Activity and Fitness Longitudinal Study

Aging means loss of strength, which can affect the ability to lead an active life and be independent. Physical activity can counteract the loss of strength to some extent, but individual differences are large and the mechanisms are partly unknown. The hypothesis is that changes in the innervation and composition of the muscle may explain the individual differences in strength loss. A group of Swedish men and women have participated in this study of physical performance for almost 50 years, since they were 16 years old. The project will improve the understanding of muscle aging. The findings may help to develop strategies to counteract muscle loss and enable healthy aging and to promote physical activity throughout life

Inclusion criteria: Belonging to the 0.5% of all pupils who entered secondary high school in Sweden in 1974 and attended one of the systematically selected secondary high schools, and was belonging to the systematically selected pupils. Exclusion Criteria: * not being part of the inclusion criteria