Introduction The prevalence of low back pain (LBP) in high-performing athletes varies depending on the type of sports. In previous literature, most attention has been given to sports disciplines with well-known risk factors for LBP such as gymnastics, soccer, rowing and alpine skiing (1). Among athletes who participate in endurance sports LBP seems to be more common in disciplines that specifically load the low back during training and competition such as cross-country skiing (2,3). Studies focusing on cross-country skiers have reported a prevalence of LBP as high as 60% (3,4). We have reported that disc degeneration (DD) after growth spurt may predispose individuals to LBP in later adulthood (5). There is no previous literature on the association between DD and LBP among cross-country skiers.
Methods Study participants were recruited during autumn 2022 among elite cross-country skiers and collegiate athletes that participated in national team camps. Original study group consisted of 72 athletes of which 44 participated in all study points. Study protocol included a 1.5T spinal MRI, a clinical examination and an interview with selected patient-reported outcomes. DD was evaluated visually using the Pfirrmann classification at levels Th11-L5. Grade 3 or higher in Pfirrmann classification was considered to be degenerated. The visual analysis also included assessment of any possible high intensity zones (HIZ) or Modic changes and Schmorl nodes, disc protrusions, bulges and herniations.
Results LBP was reported by 33 (75%) of the skiers. A statistically significant difference was seen in low back numeric rating pain (NRS) scores during the previous week between athletes with and without LBP ( NRS = 2.4 and NRS = 0.4, p = 0.005). No significant difference was seen in the amount of practice hours per year (790 vs. 801, p = 0.75) or in the use of pain medication (15% vs 0%, n = 0.3) between skiers with or without LBP, respectively. None of the athletes without LBP reported modifications from training or pauses in competing, while eleven athletes with LBP reported modifications from training and ten pauses in competing (p = 0.04 and p = 0.04 respectively). Half of the skiers (50%) had at least one disc of grade 3 or higher in the Pfirrmann classification. A statistically significant difference was noticed between those subjects who reported LBP and had at least one disc grade 3 or higher in the Pfirrmann classification compared to subjects who didn´t report LBP (61% vs. 18%, p = 0.03).Modic changes were seen in one, disc bulge in 24, protrusions in ten and disc herniations in two subjects. Schmorl nodes were seen in five and high-intensity zones in 8 subjects.
Discussion The most important findings in our study were the high prevalence of self-reported LBP and a statistically significant difference in the prevalence of at least one degenerated disc in the Pfirrmann classification between skiers who reported LBP compared to those who didn´t. Every third skier reporting LBP had been forced to significantly modify their training and competing at some point during their career due to LBP.