**1. Introduction**

Competitive alpine skiing is a popular ye<sup>t</sup> high-risk sport. At all competition levels, health problems are frequent [1–7]. In particular, lower back has been reported to be one of the most affected body regions for overuse complaints [8]. Adolescent competitive alpine skiers are also known to suffer from relatively high rates of radiographic abnormalities in the thoracolumbar spine [9]. Specifically, degenerative disc changes were observed to be more prevalent in adolescent competitive alpine skiers than in age-matched controls [10]. Moreover, a recent study found such disc degenerations (particularly disc dehydration and disc protrusion) to be significantly more prevalent in symptomatic than in asymptomatic athletes [11]. However, little is known about the prevalence

of lower back complaints in adolescent skiers with respect to severity (i.e., intensity and disability). Additionally, the role of discipline preference is widely unexplored as of yet.

The link between lower back pain and physical activity has been described as a U-shaped relationship, whereas increased risk was found for both sedentary subjects and those practicing strenuous physical activities [12]. According to this association, athletes may be considered a high-risk population, mainly due to the training and competition loads they are subjected to. Moreover, as a result of their musculoskeletal and spinal immaturity and excessive height growth, adolescent athletes are especially vulnerable [11,13].

From a biomechanical perspective, the following factors may contribute to overloading of the lower back structures in alpine ski racing [14]: (a) repetitive and heavy mechanical loads, particularly when accompanied by insufficient recovery between the training sessions [15]; (b) unphysiological postures (i.e., frontal bending, lateral bending, and torsion), associated with high ground reaction forces (up to 2.89 times the body weight) [16]; and (c) excessive exposure to low-frequency whole-body vibrations [17–20]. Since all of these factors are typical characteristics of alpine skiing-specific sports exposure, studying the relations between training attributes and lower back complaints is of superior importance.

Therefore, the aims of this study were: (1) to describe the demographics, sports exposure, and other sports- or warm-up-related practices of adolescent competitive alpine skiers; (2) to assess the prevalence of lower back complaints in this specific cohort with respect to sex, category, and discipline preference; (3) to explore their lower back complaints severity (i.e., intensity and disability); and (4) to investigate the potential relations with training attributes.

#### **2. Materials and Methods**

#### *2.1. Study Design and Setting*

This study was designed as a cross-sectional observation and was based on a structured and customized questionnaire package. Data were collected in the participants' sport clubs facilities at the end of the competition season. Questionnaires were spread physically. A member of the research team introduced the questionnaires to the participants, explaining all the questionnaire items and scales. Subsequently, the participants filled the questionnaires independently and individually.

#### *2.2. Participants and Recruitment*

Participants were included if they were members of ski clubs associated with the FISI (Italian Winter Sports Federation) Veneto region section and competed in the categories under 16 (U-16) and under 18 (U-18) years old. There were no study exclusions. All the ski clubs associated with the FISI Veneto region were contacted and invited to take part in the study. Finally, 188 adolescent competitive alpine skiers (110 males and 78 females) volunteered for the purpose of the current study; 128 belonged to the category U-16 and 60 to the U-18. The entire study sample represented about 70% of all U-16 and U-18 competitive alpine skiers affiliated to the FISI clubs in that region. The Ethics Committee of the Department of Biomedical Sciences of the University of Padua approved the study (HEC-DSB/02-19). Prior to the study, all the participants and their parents or legal representatives provided written informed consent. The participants did not receive any reward for their participation in the study.

#### *2.3. Assessment Methods and Parameters*

The questionnaire package comprised four parts: (1) questions on participants' demographics, sports exposure (years of sports participation, number of competitions/season, number of skiing days/season, number of athletic preparation days/season) and other sports- or warm-up-related practices; (2) the Nordic Musculoskeletal Questionnaire (NMQ), Italian version [21,22]; (3) specific questions on how their skiing discipline (e.g., Slalom—SL; Giant Slalom—GS; Super-G—SG; or Downhill (DH)) was related to the occurrence of lower back complaints; (4) the Graded Chronic Pain Scale (GCPS), Italian version [23,24].

The NMQ aimed on investigating the time prevalence of musculoskeletal complaints in the lower back during the last 12 months and 7 days, respectively, as well as on whether these complaints resulted in any restrictions while carrying out normal activities or whether they required medical attention or not. Questionnaire completion was supported by a body map displaying the pain area. The GCPS was used to grade the severity of the lower back complaints. The underlying methodology consists of seven questions related to pain intensity items and disability items with respect to the 6 months preceding the questionnaire. Answers were provided on a scale from 0 (e.g., "no pain" or "no interference/change") to 10 (e.g., "pain as bad it could be" or "unable to carry on any activity/extreme change") [23]. Based on these scale points, as well as on a specific scoring system, the Characteristic Pain Intensity (0–100), Disability Score (0–100), and Disability Points (0–3) were calculated and, subsequently, were assigned to five severity grades, as described in Von Kor ff et al. [23]: Grade 0 (pain-free); Grade I (low disability—low intensity); Grade II (low disability, high intensity); Grade III (high disability, moderately limiting); and Grade IV (high disability—severely limiting).

#### *2.4. Statistical Analysis*

Participant demographics, sports exposure, and training/competition/other sports practices were expressed as the mean ± SD and percentage proportions, respectively. NMQ-related measures and GCPS-based classifications were expressed as the absolute number and percentage of participants affected. The GCPS scores were described as the mean ± SD. All the measures were presented for the entire sample and the subgroups based on sex (female and male) and competition category (U-16 and U-18). Prevalence was additionally described with respect to the discipline to which they were perceived as being attributable. Pearson's Chi-squared tests were used to assess the potential sex and category di fferences in measures with percentage proportions at *p* < 0.05. Independent sample *t*-tests were used to evaluate the sex and category di fferences in interval scaled measures at *p* < 0.05. Pearson's correlation analysis was performed on GCPS items and scores, as well as on the relationship between GCPS scores, years of sports participation, number of competitions/season, number of skiing days/season, and number of athletic preparation days/season. For any correlation analysis, statistical significance was set at *p* ≤ 0.05.
