The study population will consist of Finnish elite cross-country skiers between 18 and 35 years of age. Invitation letters will be sent to all skiers who are selected to national teams at season 2022-2023. The study population for the current study will be approximately 100 individuals. Study protocol for the current study will consist of a semi-structured interview, clinical examination, lumbar spine MRI and patient reported outcome measures. All participants will sign an informed consent before commencement of the study. If a participant is younger than 18 years, also his/her caregiver will be asked for a signed consent.~The interview comprised of questions about the athletes training volume and possible LBP without associated trauma. (suspension from training or competition due to LBP, possible contacts to health-care providers).~Body height and weight were self-reported. Leg length inequality was assessed comparing the height of the left and right iliac crests in standing position with straight knees. Wooden blocks of different thickness (with 0.5 cm increment) were used for correction of possible leg length inequality. Symmetry of the back was measured in forward bending using a scoliometer.~From MRI (high field 1.5 T) the signal intensity of the nucleus pulposus will be assessed both qualitatively and quantitatively. The midline T2-weighted images will be independently evaluated visually by three evaluators using a Pfirrmann classification. The quantitative nucleus signal intensities will be assessed by two evaluators using a relative measure comparing the signal intensity of the nucleus pulposus to that of the adjacent cerebrospinal fluid on T2-weighted images.
The investigators will examine the prevalence of low-back pain and disc degeneration among Finnish elite skiers between 16 and 35 years of age and compare these findings with the data collected among healthy volunteers studied between 1994-2021.