1. Introduction
Both the time and date of birth can play an important role in people’s lives. In sports competitions, athletes are typically placed in groups according to their time of birth, where the most typical category is annual grouping due to the chronological age [
1]. This means that athletes born between the cut-off dates of January 1st and December 31st in the same calendar year are assigned to the same group. The intention of this grouping is to provide equal and fair competitions by trying to reduce the maturational differences between athletes competing together. However, this annual grouping leads to an almost one-year age difference between athletes born early and those born late in the same year, and this difference in age is referred to as relative age [
2]. The potential differences within a one-year cohort of athletes are well established, and the consequence of this grouping is known as the relative age effect (RAE) [
3,
4].
Relative age effects are found in a lot of contexts, and the effect varies with several variables. One of the factors is body mass, with a more pronounced RAE in sports, where size, strength and weight are advantageous [
5,
6]. Typical sports are ice hockey [
7], rugby [
8], soccer [
9] and basketball [
10]. In sports where weight and size are a disadvantage, the RAE is absent or even reversed, as documented in sports like gymnastics [
6] or ski jumping [
11]. Also, in sports that are largely dependent on technical (motor) skills, the RAE is less likely to be found [
12]. Another variable coupled with the RAE is the performance level, where a high performance level is associated with a more pronounced effect [
1]. Even within one single sport, there seem to be variations in RAE. This can be exemplified in handball and soccer, where RAE can vary according to player position, e.g., certain somatotypes are associated with player positions [
13]. Similar variations are found in alpine skiing, where the effect is identified in speed events but not in technical events [
14]. Gender is also a variable, as it is more pronounced among male athletes compared to female athletes within the same sport [
15]. However, in a review by Smith et al. [
16], it is argued that the effects among female competitors still exist, but they are masked due to smaller groups, less selection pressure, lighter competition level and differences in physical demands.
When growing older, athletes are usually allocated to age categories that contain several increments or years in the same age category, e.g., in junior sports and in Masters sports, the age span varies from 2 to 5 years. In these age bands, the effects of the relative age work over a longer time span, leading to what is known as the constituent year effect (CYE) [
2]. The impact of an athlete’s constituent year increases with the age range in the multi-year age band, meaning that the effect is greater among a 5-year age band than among a two-year age band. A CYE works similarly to RAE in that the effects are more pronounced among children and adolescents in that the youngest athletes in the multi-year age band are more likely to succeed. At a certain age, there will be a shift in the effect, as the effect is found to be inverse among athletes in Masters sport. In studies by Medic et al. [
17] and Medic et al. [
18], the probability of participating in the US championships in masters swimming and track and field was higher if the athletes were in the first and second year and lower if they were in their fourth or fifth year in the five-year age band category. This switch, in effect, can be explained by peak performance normally occurring around 27 years, albeit depending on the sport characteristics [
19].
The advantages of being stronger and heavier than your peers in the same multi-age cohort are reported, especially in sports that require high demands in terms of physical properties [
20]. Thus, it has been argued that the CYE works similarly to RAE, only stronger because the relative age in the cohort works over a longer time period [
21]. Thus, the CYE will work as a magnifying lens on the RAE, as it makes any change or variation more visible. In the paper by Bjerke et al. [
21], who studied junior alpine skiers participating in the Junior World Championship (JWC), it was found that participation varied with age across the 5-year age span. In fact, participation varied almost linearly with age, with significantly fewer younger skiers (17 to 18 years) competing in the JWC compared to older skiers (20 and 21 years). Additionally, in that study, participation varied with the speed of the events: the higher the speed, the older the athletes. The effect of speed varied with gender in that it was evident two years later for male skiers as compared to female skiers. Most importantly, the results from Bjerke et al. [
21] suggest that relative age may not be the important variable for explaining age-related differences in performance since the effect of age is not equal for the different events and also varies with sex. Rather, it seems that the RAE may act as a proxy for relative development, which may explain both the variations in speed and the differences between sexes due to differences in puberty offset. Hence, it would be more correct to replace the term relative age effect with relative development effect.
The purpose of the current study was to further examine the potential relationship between race performance and the age of participants in the alpine skiing Junior World Championships. Not least because Bjerke et al. [
21] did not measure actual performance but used participation as a proxy. The present study aimed to investigate whether that proxy was indeed a good representation of actual performance and, thus, whether the results and conclusions would hold. Based upon the presented considerations, it was hypothesised that (1) the CYE is closely related to the skiers’ performance in that the older the skiers are within the five-year age span, the better their results are. (2) The CYE is more pronounced among male skiers compared to female skiers, and (3) the relationship between CYE and performance is stronger, if not linearly related to speed, in the speed events (Downhill and Super-G).
5. Conclusions
The present study examined whether a constituent year effect is evident among athletes in the Junior World Championship in alpine skiing. A previous study had suggested such an effect based on a proxy variable, but it lacked actual data on performance. The present results show, as was suggested, that older skiers systematically outperform younger skiers across all events. The effect is greater among male skiers but is also found in females. The CYE becomes increasingly stronger with the increasing speed of the events, indicating that age alone may not explain the difference. However, differences in development may also explain this effect. We argue that the CYE is more about differences in development than age. The ability to maintain control at higher speed increases as a result of physical development and experience; therefore, it correlates closely with age. Thus, the CYE is really a proxy for relative development. Consequently, the RAE, which the CYE is a magnified version of, is not a relative age effect but a development effect, and hence would be more correctly termed as the relative development effect (RDE).