The Effects of Physical Fitness and Competition Experience on the Performance and Health of Athletes

This study aimed to examine the physical fitness of athletes and identify their talents by measuring and evaluating their physical fitness and to review the studies regarding competitive history and health of athletes. Generally, the physical fitness levels of athletes are higher than those of nonathletes. Besides the studies assessing the association between physical fitness and injury, studies aimed to predict performance from physical fitness data exist. Several studies attempting to identify talents using physical fitness tests based on such findings exist. Improving performance by identifying and training talents at early ages is common. However, the optimum age of sports specialization has been reconsidered. Some athletes choose their specialization after trying several sports and training styles. For example, in Japan, junior high school students who play sports regularly tend to quit sports after graduation. This tendency may be partly due to the competitive education in Japan. Delayed sports specialization may improve the mental and physical health of athletes. It has recently been reported that there are some issues in promoting the health of former athletes. In youth sports, intense training may significantly increase the risk of injury. As described above, my review of the findings of the physical fitness of athletes identified several issues related to the accurate evaluation of physical fitness and the performance and health of athletes. Future studies should further determine possible methods to improve the performance and health of athletes and former athletes by analyzing the increasing data volume on the physical fitness of athletes.


Introduction
This study aimed to examine the physical fitness of athletes and identify their talents by measuring and evaluating their physical fitness and to explore physical fitness and competition experience that are closely associated with the performance and health of athletes. In several countries, significant medical and scientific support has been provided to elite athletes, including Olympic athletes. This support has also recently been extended to Paralympic athletes, which is one of the characteristics of this kind of support. Those who provide support take a basic approach of measuring and evaluating various components of physical fitness and feeding back the data to the athletes. Although there are differences depending on the characteristics of the sport, providing feedback on output capability, such as muscle strength, power, and endurance, is often provided to athletes. Defining and measuring the factors of physical fitness and handling physical fitness data is a critical issue in sports science and sportology. The size and complexity of the data have significantly increased. Not only performance but also experiences of athletes during adolescence significantly affect their health. This is a literature review regarding the measurement of athletesʼ physical fitness, competition experiences, and

Performance and physical fitness of athletes
Physical fitness is an essential factor of performance in sports. Several studies on the physical fitness of athletes in various sports have been conducted 1) 2) . Generally, it has been reported that there are differences in physical fitness depending on the competition level. Garstecki et al. 3) compared the physical fitness between Division I and II football players with different competitive levels and found that the physical fitness of Division I athletes is higher than that of Division II athletes. Sell et al. 4) also found that the physical fitness of starting members of a lacrosse team is higher than that of other team members.
Athletes with higher physical fitness can acquire high-level skills and use advanced tactics. Physical fitness is also required to perform intense exercise. Additionally, it is generally known that improved physical fitness leads to injury prevention. Several studies aimed to estimate the performance of athletes from various data on their physical fitness have been conducted 5) 6) . Among these studies, several investigations on sports determining which physical fitness levels of athletes affect performance exist. For example, there are several studies 5) 7) on the physical fitness of athletes in triathlon and kayaking in which the physical ability of athletes has a more significant effect on performance than their nonphysical ability.
On the contrary, competition records in ball games (sports) are neither time-nor distance-based. The ball games (sports) are more significantly influenced by technical factors. However, studies on the physical fitness of athletes in soccer, baseball, basketball, and volleyball have also been conducted 8) 9) . Even in ball games (sports) athletes, there is a certain association between physical fitness and performance. Therefore, the measurement and evaluation of physical fitness can be a very important scientific approach in all sports. It is also significantly common to provide physical fitness training for injury prevention. Several studies in sports medicine examine physical fitness before and after injury, injury prevention, and disease-related results of physical fitness tests 10) 11) .
The other hand, only a few studies that specifically focus on the physical fitness of elite athletes such as Olympic athletes have been conducted. Several elite athletes worldwide receive various types of medical and scientific support. However, it is rare to publish or share the findings in competitive sports in which athletes compete against other athletes or rivals from other countries. Athletes in Japan are provided with medical and scientific support from the Japan Institute of Sports Sciences (JISS). In Japan, there are national training centers that provide Olympic athletes and Paralympic athletes with support to improve performance. Additionally, a characteristic of competitive sports where it is not common to share information with rivals is that there are as many training methods as the number of sports and athletes. In other words, a tailor-made approach is necessary. Each sport has several branches and specialized positions. In modern sports, the required ability and physical fitness levels of athletes often vary significantly depending on the specialized position. Besides the studies in sports medicine and health care, only a few studies on"performance"have been conducted because it is difficult to quantify"performance" .
Comparison of physical fitness between different sports is also an interesting research topic. Each sport requires different physical fitness levels and physiological characteristics, which means important factors of physical fitness vary depending on the sport. The Faculty of Health and Sports Science, Juntendo University has a large quantity of data for the comparison of event characteristics in collegelevel athletes 12) . The above data and event are from the Cumulative Study on Physical Fitness at Juntendo University. This cumulative study on physical fitness was started by Professor Toshiro Azuma, the first dean of the School of Health and Physical Education (Faculty of Health and Sports Science), Juntendo University. The database developed in the study has data ranging from 1973 data on the physical fitness of college students in health and physical education to recent data on the This manuscript was submitted for the Special Issue "Tokyo 2020 Olympic and Paralympic Games, and Sportology", prior to the decision to postpone the Tokyo 2020 Summer Olympics to 2021. physical fitness of college students in health and sports science. The cumulative study on physical fitness is still ongoing. This study aims to clarify not only the secular trends of each type of physical fitness but also the differences in the physical fitness of athletes in each sport. College athletes in competitive sports are special. College athletes in each sport are considered to have the physical fitness levels required for each sport. In other words, athletes with physical fitness levels required for each sport are able continue their sport careers. These are valuable data because the physical fitness of athletes in each sport has been acquired through several hours of practice and training.
As described above, the physical fitness of athletes is a very important basic factor, which is closely associated with performance, training, and injury prevention. The advantage of physical fitness tests is that they can be performed in educational and training settings. Physical fitness tests should also be used for the scientific study of sports. Although it is difficult to study sports from the viewpoint of"performance" , more studies and reports are required to examine this issue.

The physical fitness tests for the identification of sport talents and sports specialization
The previous section reported research on performance and physical fitness of athletes. Athletes have a certain level of experience in their specialized sport. There are two types of professional athletes: (i) those who have played one sport since childhood and (ii) those who started to play professionally at a certain age. It is common to identify and train talents in sport from an early age. Although training is vital for athletes to acquire a high degree of performance, it does not mean that everyone can become an elite athlete simply by training. The performance of athletes has also been studied from the viewpoint of genetics and innate talent. Physical fitness tests are often used to evaluate physical ability and performance levels. These tests are also often used to identify young talents at an early age. A systematic review by Johnston et al. 13) on the identification of talents in sport found that several of the related studies examined the physical characteristics of athletes. The literature review also found that several studies focused on male subjects and athletes aged 10 to 20 years.
A literature review by Rees et al. 14) identified various factors related to talents in sport such as birth date, birthplace, genes, and family support. The review also mentioned the importance of factors related to the anthropometry and physical fitness of athletes. Data on athletes at various levels have been reported for several years to identify talents in sport. Research has also been conducted on a wide range of sports. It has been reported that aerobic capacity, anaerobic endurance, and anaerobic power are particularly important for sports performance. For example, Dodd and Newansʼ 15) literature review of the physiological aspects of soccer found that the research included data on the physical attributes of soccer players and recommended that instructors use a physical fitness test battery.
However, on the contrary, there are a number of issues associated with intensive sports training from a young age. In particular, the win-at-all-costs mentality in several sports is an issue of significant concern. It has long been reported that it takes at least 10,000 hours to master chess 16) . The same principle applies to several fields of sports and exercise. Instructors and parents tend to want children to practice and train as long as possible to improve their physical fitness, skills, and performance as early as possible. This is a more difficult task for instructors in sports where athletes reach their peak performance in their teens. Problems such as corporal punishment and verbal abuse in youth sports have recently been discussed more often in Japan. Similarly, the issue of whether to limit the number of pitches and innings pitched has been recently discussed more often in the baseball.
Recent studies show that conventional sports talent identification and training programs are not always effective 17) . The International Olympic Committee (IOC) has also issued a statement on the training of young athletes 18) . Myer et al.ʼs 19) literature review of sports specialization recommended that parents and educators should let young athletes play various sports depending on their developmental stages to improve their physical performance. The review also showed the importance of integrative neuromuscular training to improve various physical performances and reduce the risk of injury. Jayanthi et al.ʼs 20) literature review of specialization in youth sports from the viewpoint of sports medicine showed that high degree of sports specialization leads to a higher risk of injury and overuse. The review also indicated the importance of playing various sports for mental and physical health.
Lastly, the number of Japanese athletes registered in school by sport is shown in Table-  each sport, mainly during extracurricular activities in school. Certainly, there are several individuals who are not registered in these sports but play sports outside school in private or other organizations. Therefore, although not comprehensive, the table shows the characteristics of sports in Japan and those of athletes in each sport. A key characteristic of youth sports in Japan is a significant decrease in high school athlete population. This tendency is more evident in college and adult populations. The decrease of athlete populations is a problem in terms of performance, healthy exercise habits, and other factors. Although this study did not examine the issue in detail, competitionoriented training in extracurricular activities may be relatively responsible for the abovementioned tendency. It is essential to provide an environment, guidance, and educational activities to allow more young athletes to continue to participate in sports. It is interesting that the degree of decrease in the athlete population varies by sport. Some minor sports have a large player population. Therefore, it is important to consider sports from a wider perspective rather than from a limited perspective. As described above, there are several difficult issues to be addressed regarding talent identification and training methods. Therefore, it may not be easy to determine the solutions to the issues. However, recent studies suggest that it is possible for athletes to reach a competitive level without concentrating on one sport since childhood. The most important task is to create a system that allows more young athletes to continue to participate in sports. Therefore, the health of athletes needs to be put into perspective.

Physical fitness and health of athletes
There have been several studies assessing the association between physical fitness and disease and mortality 24) . Regular moderate exercise is considered to improve physical fitness, reduce the risk of death, and prevent disease 25) . For example, Grøntved et al. 26) reported that muscle strength training, yoga, and stretching, reduce the risk of type 2 diabetes. Hence, what is the health status of athletes with high physical fitness, specifically former athletes? Athletes are generally considered to be healthy and to maintain their physical fitness and health even after retirement. However, some athletes are at health risk. For example, there are several athletes who quit due to injury or burnout resulting from several years of professional training and practice. Intense training from an early age may have a negative impact on athletesʼ mind and body. Do athletes continue to exercise for health after their competitive careers? Several years of professional training that is significantly specialized for competition may not be effective in improving performance but rather impair the health of athletes.
Someya et al. examined the changes in the health and physical fitness of college athletes after graduation. Their study found that former college athletes with low weight gain (BMI > 23 kg/m 2 ) are also at a higher risk of hypertension even if their BMI was normal during the college years 27) . Additionally, there is a study showing that former college athletes with low weight gain (BMI > 22 kg/m 2 ) are also at a higher risk of diabetes mellitus 28) . It has also been reported that individuals with low endurance (i.e., measured by 1,500-m running) at the university have a higher risk of developing diabetes 29) .
Simon et al. 30) reported that the physical fitness levels of former college athletes with the mean age of 53 years were significantly lower than those of nonathletes. Sorenson et al. 31) reported that the amount of exercise in college athletes was significantly higher than that in nonathletes during the college years, but that there was no significant difference in the amount of exercise between former college athletes and nonathletes after graduation. Moreover, a study on the age of sports specialization and health of former athletes in later life has also been conducted 32) . In the long term, even highly competitive athletes should learn to exercise and continue performing in later life to maintain health and wellness.
As mentioned in the previous section, several junior high school athletes do not continue to participate in sports in high school. This tendency is even more pronounced among college students. In particular, several adolescent girls do not exercise regularly even overseas 33) . High school students are required to attend a certain number of physical education classes, whereas college students are not. Although it would be preferable to ensure junior high school students acquire exercise habits and learn about the importance of regular exercise, unfortunately, the prevalence of regular exercise in Japan is low 34) . Schools in Japan may put significant emphasis on competitive training in extracurricular activities. Even in extracurricular activities, guidance and advice for regular exercise is necessary for health in a long-term perspective.
Issues regarding the health of athletes in later life may be associated with exercise habits, overuse, and psychological factors. Several hours of exercise and high physical fitness during professional careers do not guarantee the health of former athletes in later life. Instructors and educators need to teach athletes in competitive training about the importance of health and regular exercise in a long-term perspective.

Conclusion
This study focused on the physical fitness of athletes and referred to the importance of physical fitness tests and talent identification in competitive sports. An essential issue in talent identification in competitive sports is training methods for young athletes. To promote regular exercise in later life, not only competitive training but also health education is required in schools. Recent studies suggest that several former athletes are at health risk and do not exercise regularly.
Although the improvement of performance will continue to be the most important task in the physical fitness of athletes, the maintenance of physical fitness and regular exercise are also required for the health of former athletes. For this reason, the types and number of data to be handled have greatly increased. Nowadays, professionals in all industries use big data and artificial intelligence. To improve performance and maintain and promote health, there will be more opportunities to measure and evaluate physical functions and performance using new methods. More data that are not directly related to physical fitness (e.g., data obtained from wearable devices during everyday practice and training) will also be available. Hence, researchers, students, and experts in sports sciences and sportology require multiple perspectives and additional analytical skills in the future.