1. Introduction
The basic military training (BMT) is a 5-week program for prospective cadets summoned to each armed forces’ military academy. It focuses on military knowledge such as cultivation of basic fitness, national ideology, concepts of national security, and drills, which are qualities that cadets must be equipped with. The average age range of prospective cadets that participate in the BMT is 19–22, and they are reasonably similar in body composition to those in the same age group. According to a national status survey, the average body mass index (BMI) of the 19–24 age group, which is the same age group as prospective cadets, demonstrated a rising trend from the early 2000s until recently [
1]. As such, the rise of BMI among those aged 19–24 is related to the social phenomena of rising obesity rates and deteriorating fitness among youths [
2,
3]. Thus, prospective cadets, who are taking their first steps within the military, also have similar physical attributes to average youths in the same age group. In fact, in the case of those who applied for the Naval Academy in 2011, men had similar levels as the average of those in the same age groups, and women had higher levels than the average of those in the same age groups. It has also been reported that the fitness levels shown in fitness tests during the selection process have been gradually becoming lower than in the past [
4].
As if to reflect such a phenomenon, the lifestyle within the academies, which have the goal of training elite defenders of the state, and the BMT program, which is a program for providing the cadets military knowledge, are conducted with the goal of cultivating strong fitness levels by increasing the proportion of time spent in physical training. Additionally, military fitness tests are performed using categories and methods designated by the Korea Ministry of National Defense. From 2010, the existing 1500 m running has been changed to 3000 m running. As such, training contents such as the increase of distance for double march training, and the increase of time spent in physical training, are being reflected in BMT for prospective cadets, officers, and non-commissioned officer candidates. However, due to various causes such as maladjustment to strict communal living, as well as physical and mental exhaustion from intensive education and training, some people give up entering the academies during the summons period. The occurrence of these abandonment, despite Pre-enrollment medical test, mental health-related issues are reported as a major cause of problems constantly during the BMT of the US military [
5,
6]. For the academies that strive to train excellent soldiers, this is a source of great disappointment.
Therefore, alongside the efforts for raising the fitness levels of prospective cadets going through BMT, efforts are needed to manage and mediate changes in their mental states. However, for youths used to a freer lifestyle, five weeks of BMT is quite a long period for them to endure and overcome. Moreover, based on the dual-mode model theory [
7], referring to effects of the intensity of physical exercise on emotional changes, especially for prospective cadets that have lower than average fitness levels, the high intensity training during the summons period is highly likely to induce negative emotions.
Research on the relevance of exercise to various psychological factors such as emotion and mood is being proactively conducted through studies that investigate the relationship of psychological effects with exercise, such as confirming differences in psychological variables that depend on the conditions of physical activity such as obesity and exercise [
8,
9,
10]. In general, physical fitness is closely related to mental health in various populations [
11,
12,
13]. For example, it is important to pay attention to young people throughout low cost strategies for improving mental health. Physical activity is often suggested as one such approach [
14]. And using a retrospective cohort design, showed that midlife physical fitness is associated with a lower risk of later-life depression [
15]. Especially, in military populations, the relation between physical fitness and mental health is notably relevant because of the properties of the army environment, which were requiring than any other occupation [
16].
Particularly, in Yoon’s [
17] research, the psychological states of athletes, rather than of average person or students, were measured periodically, and directions for checking and preventing overtraining were proposed as well. Regarding earlier studies from outside Korea, research has shown that during BMT, groups with higher fitness test records are mentally healthier than groups with lower records [
5,
6]. However, these studies simply examined the differences between groups, and therefore have difficulty in providing more specific explanations. Additionally, due to the differences in social and cultural backgrounds, a substantive approach is needed for domestic research. However, currently there are no related domestic studies.
As the scales that measure emotional states related to exercise, the FS (feeling scale), the SEES (subjective exercise experience scale), and the POMS (profile of mood states) are being utilized variously in the field. Among them, the POMS comprises six factors of tension, depression, anger, fatigue, vigor, and confusion. POMS is a suitable tool often used to identify the mood of an athlete. As a pioneering psychometric tool for overtraining research, the relevance of POMS as a monitoring instrument is emphasized by many studies [
18].
Domestically, it has been used effectively for repeatedly measuring and observing changes in mood states during extreme situations such as in an ultra-marathon [
19], or during restricted situations such as camp training [
20]. Therefore, for this study that is being done on prospective cadets undergoing BMT, POMS seems to be the most appropriate scale for evaluating mood states.
On the other hand, fitness or performance capability focuses mainly on changes or growth depending on the passage of time in the field of kinesiology research. Similarly, the Latent Growth Model analysis method enables observation that considers individual differences in the relevant changes during the same time periods. Like the
t-test and analysis of variance, this method is effective in research that attempts to confirm changes through comparing different groups and making periodical observations. Additionally, a latent growth model considers the initial levels and rate of change, and therefore enables confirmation of variability depending on the period. Furthermore, it has an advantage of verifying various models of hypothesis established by the researcher such as a normal SEM (structural equation model) [
21]. Due to these advantages of LGM (latent growth model), there have been a variety of studies on changes in BMI, physical strength, physical activity and psychological factors [
22,
23,
24,
25,
26].
However, due to difficulty in data collection, domestic use is currently lacking. Therefore, it is thought that an analysis applying a Latent Growth Model is a more effective approach rather than simply analyzing the differences between groups in a study that observes changing states through periodical measurements.
As such, this study’s objectives are to repeatedly examine the fitness levels and mood states of two classes of prospective cadets in identical periods during five weeks of BMT, and then to verify what changes are happening during the period through such longitudinal data. The results derived from the study can later be used as baseline data needed for creating a scientific training program that considers physical and mental levels as well as characteristics of the prospective cadets. It can also be used as a basis for deciding whether the program is applicable to prospective cadets who have deteriorating fitness levels overall. Furthermore, there is academic significance in revealing whether the relationship between exercise and emotion have similar characteristics in terms of military training.
4. Discussion
Existing studies that have examined the fitness and related characteristics of prospective cadets participating in BMT were limited to the goal of examining changes in physical development and fitness levels, and this was done for creating a more effective BMT program. As such, this study was carried out to offer baseline data for creating a more scientific training program for prospective cadets. Having examined the prospective cadets during BMT on their fitness levels per measurement period, changes in mood states, and changes in mood states depending on initial fitness levels, the results can be discussed as follows.
First, having examined the changes in fitness levels following measurement periods, all events showed high improvements in fitness levels. Such results are similar to the existing research results that suggested changes in fitness in the prospective cadets through BMT [
41,
42,
43], confirming that fitness levels dramatically improved. In particular, the change in fitness levels between week one and week three was greater than the change between week three and week five. Additionally, depending on the passage of time, the rate of change for those with high initial fitness levels decreased, whereas the rate of change for those with low initial fitness levels increased. In a study with two classes that showed similar tendencies, this study differentiated itself from existing research by suggesting results from comparing differences in rate of change depending on initial fitness levels.
Next, having examined the changes in mood states per measurement period, it was shown that some negative factors (fatigue and anger) increased at the week three. However, it was confirmed that TMD scores decreased overall without any relevance to initial mood states. Such results are in accordance with Kim et al.’s [
20] research, which examined the changes of mood states in female soccer players following a period of training camp, and Kang and Lee’s [
19] research, which showed changes in mood state profiles of those running in 100 km ultra-marathons. Thus, the study is highly significant in that it yielded identical results to existing research that examined changes in mood state with the same measurement tools after short periods of excessive training. However, unlike changes in fitness levels, it also showed that there was an insignificant correlation between the initial mood state and the rate of change. This implies that the variable of five weeks of dynamic BMT can give rise to various changes depending on individual characteristics. Furthermore, the study is significant in that it dealt with the psychological states of prospective cadets during BMT, which was lacking in domestic research.
Lastly, the effect of initial fitness levels of prospective cadets during BMT on their mood state changes was verified through the Latent Growth Model. Such an approach was conducted under the assumption that the intensity from the BMT program felt by prospective cadets with lower fitness levels would be different. The results confirmed that on average, participants with low fitness levels had lower initial mood states, and that higher fitness levels were correlated with larger changes in mood states. Such results show that the fact that gaps in mood states can happen depending on initial fitness levels must be considered. Moreover, unlike existing studies, this study conducted the verification through a Latent Growth Model, confirming the results that the rate of change in mood state was different depending on initial fitness levels.
Particularly, participants with low initial fitness showed a highly increasing rate of change compared to participants with high initial fitness. This is a result that reflects well the nature of the goal of BMT, which is to prepare the prospective cadets for the lifestyle at the Academy. Additionally, in Shannon’s [
6] research, it was shown that during BMT, the group with higher fitness test scores was mentally healthier than the group with lower fitness test scores. In Crowley et al.’s [
5] research, it was shown that the group with an above average fitness test scores had 60% lower symptoms of depression than the below average group. As such, it was confirmed that the results were shown to be identical to the existing studies with similar contexts. It seems that this study has contributed toward explaining such phenomena by providing more concrete data.
5. Conclusions
The participants selected for this study were prospective cadets undergoing five weeks of BMT after being summoned to the Academy. After analyzing with the Latent Growth Model the effects that fitness levels per measurement period, changes in mood states, and initial fitness levels have on changes in mood state per measurement period, the following conclusions were derived.
First, during BMT, the fitness levels of the prospective cadets increased rapidly, and the rate of change was much larger for those that had lower initial fitness levels than those with higher initial fitness levels. Second, during BMT, the prospective cadets showed a tendency for positive changes in mood states. However, initial mood states and rate of change per measurement period did not show a significant relationship. Third, during BMT, prospective cadets with low initial fitness levels showed negative change tendencies in initial mood states. Those with high initial fitness levels showed a high rate of change for mood states. Furthermore, depending on the initial fitness level, there were large differences for mood states.
Such results show that BMT has positive effects on fitness levels and mood state changes in prospective cadets. Additionally, this implies that the rate of change for mood states differs by initial fitness levels. Therefore, we expect that this study’s results will be used as baseline data that will provide a foundation for creating a more effective BMT program for prospective cadets, preventing the loss of human capital and helping to train prospective cadets with healthier psychological states. Furthermore, this study’s results have been confirmed through analysis via the Latent Growth Model. Therefore, this study is significant because the results have more depth compared to existing research that examined fitness and mood states through simple group comparisons. However, there are limitations in this study in that there was no distinction between classes and genders. This study focuses on psychological changes caused by physical fitness tests among the BMT of prospective cadet. Therefore, it is determined that the psychological changes caused by prospective cadet recognizing the burden of physical fitness tests would be the same. Thus, there is a limitation to the research in that there is no distinction between classes and genders of the prospective cadet. Furthermore, the study participants are likely to be exposed to authoritative situations due to the Characteristics of the participants. Future studies need to take into account the various current situations of participants. As well as that the BMT conducted in another year showed a total difference of four hours for physical training. To examine more specific relationships on effects, later studies must verify fitness levels and changes in mood states through complex models of Latent Growth. Furthermore, it is hoped that there will be a proliferation of studies that consider various psychological and social characteristics together rather than being limited to the physical aspects of prospective cadets.