**4. Discussion**

The main findings of this study were: (1) as many as 80.3% of all participating adolescent skiers su ffered from lower back complaints during the last 12 months (50.0% during the last 7 days; 28.2% with restrictions in normal activities; and 27.7% requiring medical attention); (2) 50.7% of the participants reported their lower back complaints being attributable to SL, and 26.0% to GS; (3) despite the fact that the majority of the participants experienced lower back complaints of a low intensity/low disability (Grade I, 57.4%), a considerable portion su ffered from a high intensity/low disability complaints (Grade II, 21.8%); (4) there were small ye<sup>t</sup> significant correlations between the Characteristic Pain Intensity and the training attributes "years of sports participation", "number of competitions/season", and "number of skiing days/season".

#### *4.1. Prevalence of Lower Back Complaints with Respect to Sex, Category and Discipline Preference*

The current study found relatively high rates of lower back complaints in adolescent competitive alpine skiers. Indeed, 50.0% and 80.3% of the participants displayed lower back complaints in the last 7 days and 12 months, respectively. These values are considerably higher than those was previously reported for other populations. For example, a 12 months lower back pain prevalence of between 49.8% and 65.0% was observed in previous studies in elite athletes of di fferent sports [25–27]. A 7 days lower back pain prevalence between 19.4% and 25.3% was reported for endurance athletes [25]. Previous works found a 12 months lower back complaints prevalence ranging from 20.5% to 57.0% in non-athletic adolescents [25,28,29], while a 7 days lower back complaints prevalence of about 20.0% was reported for young non-athletes [25].

The higher prevalence of lower back complaints observed in the present study compared to other athletic (and non-athletic) adolescents suggests that competitive alpine skiers are especially prone for lower back complaints. Indeed, in the sport of alpine ski racing, repetitive and heavy mechanical loads, high ground reaction forces, and the exposure to low-frequency whole-body vibrations have

been shown to adversely affect the spinal structures while skiing [14,16,17]. Moreover, in young skiers, the immaturity of the musculoskeletal system may exacerbate the damage experienced by the spine during the practice of this sport [13].

Despite these plausible sports-related adverse loading patterns, only a few studies, however, have investigated the occurrence of lower back complaints in competitive alpine skiers. Moreover, due to focusing on a different age group and reporting other time prevalence measures or absolute injury rates, most of them are not directly comparable to the results of the current study [3,4,6,8,11]. The only study directly comparable to our investigation reported similar magnitudes of current low back pain (67.0%) in ski high school athletes aged 15–19 years [30].

Noteworthy, in our study, a higher 7 days lower back complaints prevalence was observed in females with respect to males (60.3% vs. 42.7%). These results are in agreemen<sup>t</sup> with previous works and, on the one hand, may be explained by a different pain threshold and symptom perception between males and females [31,32]. On the other hand, this sex difference may also be explained by the different anatomical characteristics of the female body (e.g., greater spine flexibility), as well as the different pubertal growth and hormonal states [33,34].

Furthermore, our study revealed that, during the 12 months prior to data collection, 28.2% of the participants were restricted in carrying out normal daily life activities, while 27.2% needed to see a physician. This latter percentage is similar to the magnitudes found in previous studies (range between 24.0 and 33.0%) including large cohorts of children and adolescents [35,36].

Interestingly, we found different skiing disciplines to have different perceived impacts on lower back complaints. Indeed, 50.7% attributed their lower back complaints to SL, while 26.0% reported to have suffered them in connection with GS and 7.3% with SG. None of the participants attributed their lower back complaints to DH. A possible explanation is that, in SL, there are more pronounced and larger ground reaction force peaks (approximately plus 20.0%) after gate passage than in GS [37].

Regarding the prevalence of lower back complaints according to the annual programming period, we found that the prevalence of lower back complaints lasting less than 7 days was 86.0% in the off-season and 33.3% in the competition season. Conversely, the frequency of lower back complaints lasting more than two weeks changed from 3.3% in the off-season to 21.3% in the period of the competition season. This fact may sugges<sup>t</sup> that more severe lower back complaints emerge from skiing rather than from off-snow training [3].

#### *4.2. Severity of Lower Back Complaints with Respect to Intensity and Disability*

Another aim of this work was to study the severity (i.e., pain intensity and disability) of lower back complaints in adolescent competitive alpine skiers. Despite the fact that most of the participants (57.4%) reported low intensity—low disability complaints (Grade I of the GCPS), 21.8% showed high intensity—low disability complaints (Grade II). These findings showed that a considerable part of the participants suffered from a relatively high severity of lower back complaints already at a relatively young age (15–18 y). However, the pain resulted in being of low disability, which is in agreemen<sup>t</sup> with previous studies in adolescent athletes [25,38]. One potential explanation for this finding may be the consideration that the cohort of the current study consisted of relatively young athletes, who may not have suffered from an extensive accumulation of adverse loadings over time yet.

#### *4.3. Relationship between Lower Back Complaints Severity and Training Attributes*

The current study revealed small ye<sup>t</sup> significant correlations between Characteristic Pain Intensity and the training attributes "years of sports participation", "number of competitions/season", and "number of skiing days/season". These findings further support our current understanding of the development of lower back overuse injuries, according to which an accumulation of adverse loadings on the athletes' spine is a key driver for inducing pain [16]. However, the present sample was homogeneous with respect to training attributes, since the participants of our study belonged to ski

clubs of the same region. Therefore, the results of this study may be specific to our cohort and should be interpreted with caution.

## *4.4. Methodological Considerations*

Despite providing valuable new insights into the prevalence and severity of lower back complaints in adolescent competitive alpine skiers, this study has some limitations that one should be aware of. First, the retrospective nature of the NMQ and GCPS methodologies may cause them to suffer from a recall bias. Recent and more severe complaints are more likely to be remembered than older and less severe ones. Second, the background and experience of the participants filling out the questionnaires may influence the outcomes. Third, other potential cofounders for lower back complaints, such as smoking, hours of sleep per night, and psychosocial factors (depression, stress, poor academic performance, poor competitive results, etc.), were not evaluated in this study.
