Two groups will be examined for veryfing the morfology and the function of neck muscles.~The profesional group composed by spanish acrobatic skydivers and a general group composed by general physically active population(GPAP). Both groups are matched at known confounder outcomes such as: physical activity level, age, sex, body weight and history of neck pain. Frequency matching will be carried out, subjects will be matched on known confounders.
An observational cohort study, following the Strengthening the Reporting of Observational Studies in Epidemiology(STROBE) guidelines.~Two groups will be examined, a group composed by spanish acrobatic skydivers and a control group composed by general physically active population(GPAP).