2022 Volume 22 Issue 1 Pages 25-31
Recently, there has been much debate in the baseball community about limiting the number of pitches thrown by each pitcher in Niigata Prefecture, Japan. Based on this concept, a rule was adapter prior to the 2020 season that each pitcher must have thrown less than 100 pitches. We hypothesized that the pitches per each pitcher would decrease, and the number of pitchers thrown in a game would increase in 2020 season compared in 2019 season. In the present study, we investigated the number of games played by each pitcher, the number of pitches thrown by each pitcher in a game, and the type of games in 2019 and 2020 season to compare the burden on the pitcher before and after the rule was applied. There was no significant difference in the number of pitches per each pitcher in a game between both seasons. In addition, according to the data in complete games, the average number of pitches thrown per pitcher did not exceed 100 pitches in both official and practice games in both seasons, while the average number of pitches were over 100 pitches in both season in games except the complete games in which there was no significant difference. In conclusion, the number of pitches by each pitcher did not decrease sufficiently to be affected by the rule change. In the future, the relationship between number of pitches and disability will need to be clarified, and number of pitches will need to be discussed further.
Recently, there has been much debate in the baseball community about limiting the number of pitches allowed per pitcher. In the junior and high school age groups, there is a lot of discussion about 100 pitches or less per game. This limit is applicable across various age groups. In November 2019, the Japan High School Baseball Federation received a proposal from the “Meeting of Experts on Pitching Injury Prevention” (hereinafter referred to as the “Meeting of Experts”), where it was decided that the maximum number of pitches allowed per week for a pitcher in an official game would be 500 [1]. This pitch limit has been applied not only in national tournaments, but also in regional tournaments, after the cancellation of the 92nd National Invitational High School Baseball Tournament (which was scheduled to start on March 11, 2020) but was cancelled to prevent the spread of the novel coronavirus infection. In addition, the Meeting of Expert’s report mentioned the need for applying the limited pitches rule to elementary and junior high school players, aside from only high school players.
Regarding the pitch limit for junior high school pitchers, the Japan Rubber Baseball Association changed the original provision allowing “7 innings per day to prevent injuries to the elbow and shoulders” to “100 pitches per day and 350 pitches per week,” and implemented this provision for competitions occurring after March 2020 [2]. Since 2020, all official games involving elementary school players also apply the rule of “up to 70 pitches per day” to prevent elbow and shoulder injuries [3]. These provisions are said to be behind the proposals by Okuni et al (2005) [4]. of the Japanese Society of Clinical Sports Medicine, where the “number of full-strength pitches should have up to 50 pitches per day and 200 pitches per week, including games, in elementary school players. In junior high school players, the count should be up to 70 pitches per day and 350 pitches per week, whereas for high school students, the pitch counts should be up to 100 pitches per day and 500 pitches per week. Players should not pitch in two or more games per day” [4].
Previous research on shoulder and elbow injuries of baseball pitchers have reported that injuries are more common in pitchers and catchers who play an average of 10 or more games per month, compared to outfield players [5]. The national questionnaire on elementary and junior high school baseball players, carried out by the Japanese Orthopedic Association and Bone and Joint Japan with the help of the Baseball Federation of Japan, clarified the fact that teenage baseball players are being overextended and that it is important to elucidate the relationship between the pitch count, number of games pitched, and injuries of baseball pitchers across all age groups going forth [5]. It is also necessary to reflect the findings obtained through such studies, to use the limited pitches rule for all age groups. This will create an environment where promising players can continue to play baseball for longer periods, without the burden of sustaining injuries.
A previous study on teenage baseball players conducted a questionnaire investigation on pitch count, to elucidate how the number of games played per year and the number of full-strength pitches per day are associated with the onset of elbow pain [6]. In teenage baseball players, the incidence of elbow pain was found to be significantly higher when the number of pitches thrown was more than 50 per day and 200 per week. A previous study on high school baseball pitchers has also aggregated the number of pitches and innings played during games until the end of the season annually, using a questionnaire investigation [7]. The results also revealed that the most common areas of pain among high school students are the elbow, shoulder, and lower back, in that order. However, neither reports concerned junior high school players. There is also an investigation that is conducted annually based on self-reporting by players, but it would be difficult to ascertain the accurate number of pitches per game while relying on their memory. The Japan Rubber Baseball Association is trying to protect junior high school pitchers from disabilities with the limited pitches rule. When considering pitch limits, it is difficult to discern the actual issues that occur if the study does not consider practice games, rather than using only official game records. The junior high school age group is in a period of developmental spurt and is prone to significant changes in physical balance. It is necessary to understand the actual situation of junior high school baseball pitchers and to study the relationship between pitching disorders and pitch counts.
Under such circumstances, Use et al. (2021) conducted a survey to ascertain the actual number of pitchers and pitches in official and practice games played by junior high school pitchers during season 2019, prior to the introduction of the limited pitches rule [8]. This survey reported that the average number of pitchers per official game was significantly lower than those in practice games, and that the average number of pitches per game exceed 100, regardless of whether they are practice or official games.
However, all such data and foreseeable issues were recorded before the introduction of the limited pitches rule. The pitch limit, which was scheduled for introduction from the first half of 2020, was only introduced on a full-scale from the second half of 2020, due to the cancellation of numerous games due to the impact of the novel coronavirus infection. First, it would be necessary to study how the number of pitchers, pitches, and the percentage of complete games changed after introduction of the limited pitches rule. We hypothesized that the pitches per each pitcher would decrease, and the number of pitchers thrown in a game would increase in 2020 season compared in 2019 season. And we need to consider whether the limited pitches rule is helping to prevent shoulder and elbow injuries in teen pitchers.
Therefore, with the help of the Niigata Junior High School Sports Federation’s Rubber Baseball Specialist Department, we investigated the number of pitchers and pitches in practice and official games played by junior high school pitchers in the second half of 2020 and compared the results to those of 2019.
1. Target and survey period
The target schools were rubber baseball clubs affiliated to the Niigata Junior High School Sports Federation. In addition to 216 schools belonging to the Junior High School Sports Federation, Niigata Prefecture has 17 club teams for hardball and 3 club teams for softball. The 17 club teams for hardball and the 3 club teams for softball are not included in the survey in this report. The survey period spanned 2 years, from 2019 to 2020. In addition, the analysis was carried out by dividing the year into two periods, namely Term 1 (from March to July) and Term 2 (from July to November). In junior high school baseball, Year 3 students retired from club activities after the tournament in July. Thereafter, teams are primarily composed of Year 1 and 2 students and players change positions, which is why the year was split into two groups. In this respect, this study is not a longitudinal study of the same players for two consecutive years. The period from December to February was not part of the survey period because no games were played during that time. Even though the aim had been to compare statistics between Term 1 and 2 of 2019 (before application of the limited pitches rule) against Term 1 and 2 of 2020 (after application of the rule), many practice games and all official games during Term 1 of 2020 were cancelled, due to the impact of the novel coronavirus infection. Therefore, we compared the data from Term 2 of 2019 against the data from Term 2 of 2020 for final results in this survey.
Before consenting, the guardians of players and the advisor in each school were briefed that this survey could help prevent injuries in junior high school baseball players, and that care will be taken not to identify individuals when presenting the results of this study. Cooperation was optional, and subjects could discontinue participation based on their own decision.
This study was conducted with the approval of the Niigata University of Health and Welfare Ethics Committee (Approval No.: 18515-201124).
2. Survey items and method
The survey items were as follows: the name of the junior high school, number of games played, game dates, number of pitchers on the team, pitch count of each active pitcher, and the type of game (i.e., practice or official game). The advisor in each school aggregated the survey items for each game played, based on the scorebook. These were reported by email to the authors, both at the end of Term 1 and 2. After this, the authors aggregated the data from each school. The advisors who aggregated the survey items based on the scorebook data were officially appointed as the advisors to the rubber baseball club by each school, having understood the explanations on the purpose and significance of this survey provided during the meeting of the Niigata Junior High School Sports Federation’s Rubber Baseball Specialist Department, and each agreed to cooperate.
3. Statistical processing
The two-sample Kolmogorov-Smirnov test was used to compare the average number of pitchers per game and average pitch count, for both practice and official games. Fisher’s exact test was used to compare the percentage of complete games in official and practice games. The level of statistical significance was set to 5%.
We requested the cooperation of 216 prefectural schools and their rubber baseball clubs affiliated with the Niigata Junior High School Sports Federation. We then obtained responses from 147 schools in Term 1 and 151 schools in Term 2 of 2019. The response rate was 68.0% in Term 1 and 69.9% in Term 2. Of these responses, 12 schools in Term 1 and 23 schools in Term 2 were left out of the analysis for the 2019 statistics because they were unable to keep a score book due to the lack of members, and thus could not ascertain the pitch counts. As two schools in Term 1 had formed joint teams and had no pitchers in their own teams, there were no opportunities for pitching. In addition, 4 schools in Term 2 had suspended activities due to the lack of members. Therefore, they were not playing any games. We analyzed the 133 schools in Term 1 and 124 schools in Term 2, which excluded the aforementioned schools. In 2020, we received responses from 127 schools in Term 2, and as such, the response rate was 58.8%. Of these responses, 2 schools were left out of the analysis because they were unable to keep a score book, due to lack of members. Thus, they could not ascertain the pitch counts. The remaining 125 schools for Term 2 were analyzed.
Table 1 shows the number of games, average number of pitchers per game, average number of pitches per game, number of complete games, percentage of complete games, average number of pitches pitched by pitchers playing complete games, maximum number of pitches (per pitcher), minimum number of pitches (per pitcher)in Term 2 of 2019 and 2020.
There was no significant difference between the two seasons, in terms of the average number of pitchers per official game and per practice game. There were also no significant differences between the seasons, in terms of the average number of pitches per game. There were no significant differences in the percentage of complete games between the official and practice games in 2019 and 2020. Furthermore, there was no significant difference between the two seasons in terms of the average number of pitches for complete games per pitcher.
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In the present study, we investigated the number of games played by each pitcher, the number of pitches thrown by each pitcher in a game, and the type of games in 2019 and 2020 season to compare the burden on the pitcher before and after the rule was applied. There was no significant difference in the number of pitches per each pitcher in a game between both seasons. In addition, according to the data in complete games, the average number of pitches thrown per pitcher did not exceed 100 pitches in both official and practice games in both seasons, while the average number of pitches were over 100 pitches in both season in games except the complete games in which there was no significant difference.
1. Average number of pitchers and pitches per game
According to this survey, the average number of pitches per game exceeded 100 in official and practice games, both in 2019 and 2020. This demonstrates that under the regulation established by the Japan Rubber Baseball Association to maintain “less than 100 pitches per day,” multiple pitchers would have to be used in each game. However, according to the data limited to complete games, the average number of pitches did not exceed 100 in both official and practice games for season 2019 and 2020. This demonstrates that many pitchers manage complete games even under the limited pitches rule of “less than 100 pitches per day,” which came into effect in 2020.
There was no significant difference between the two seasons, in terms of the average number of pitchers per game for official and practice games. In general, practice games provide players with the opportunity to participate, monitor their growth, and discover ways to improve. We hypothesized that when the limited pitches rule was introduced, each advisor would try to train multiple pitchers and the average number of pitchers per game would increase. This did not occur. This may be because current coaches have to train all pitchers, or the lack of players with the skill level and fitness to be tasked with pitching, even when coaches intend to train pitchers, given the declining birth rate and diminishing athlete population. When investigating pitch counts in future, we must deduce whether the average number of pitchers per game in official and practice games has increased. Increasing the average number of pitches is an outcome of introducing the limited pitches rule. In parallel with the introduction of this rule, instructors and reputed training coaches should hold training sessions and baseball classes to expand the population of baseball players and help create an environment in which multiple pitchers can pitch in a single game.
2. Complete games in junior high school baseball
The percentage of complete games played in junior high school baseball was significantly higher in official games than practice games, in both the 2019 and 2020 seasons. However, the average number of pitches per pitchers for complete games did not exceed 100, in both official and practice games of 2019 and 2020. This shows that many pitchers would pitch complete games even under the limited pitches rule. However, it is unclear whether pitching injuries occur in these instances. If so, it may be necessary to reconsider the rule set by the Japan Rubber Baseball Association to maintain “less than 100 pitches per day.” In teenage baseball players, the incidence of elbow pain has been shown to be significantly higher when the number of pitches thrown per day exceeds 50 [6]. In a fact-finding survey of more than 10,000 junior high school baseball players, it was reported that about 50% of them experienced pain in their elbows and shoulders [9]. However, the cause of its occurrence has not been identified. In the U.S., despite recommendations regarding the number of pitches thrown, there have been reports of an increase in pitching disorders among young baseball players [10]. In general, the factors that cause pitching disorders include physical functional factors, problems with the pitching motion, and problems with the number of pitches thrown [11]. First of all, we must investigate in the future whether throwing 100 pitches a day increases the risk of disability in junior high school pitchers who have no physical function problems and no problems with their throwing motion. Currently, we are also conducting a “disability survey” in parallel with this study.
On the other hand, factors other than pitch count that contribute to the occurrence of disability would also need to be identified. In adolescents, whose skills are immature, the throwing motion is less reproducible and the risk of injury is higher regardless of the number of throws [12]. In order to protect such players from disabilities, it is necessary to find rules to limit the number of pitches according to their physical functions and pitching movements.
However, this study cannot clarify whether or not the impact of the pitching restriction rule was observed nationwide. In addition, since the spread of the rule and changes in the mindset of instructors may have been small in the years immediately following the introduction of the rule, it will be necessary to continue and expand the scope of this study. Furthermore, the number of individual pitches per game and per week will need to be investigated in the future. In addition, it would be necessary to examine the prevention of pitching disorders from a perspective that has not yet been verified, such as the relationship between bone density and disorders.
In this study, we investigated the number of pitches and pitchers for practice and official games played by junior high school baseball pitchers in Niigata Prefecture over a two-year period. We compared this data before and after introduction of the limited pitches rule, which allowed for “less than 100 pitches per day.” The results showed no significant difference between 2019 and 2020, in terms of the average number of pitchers and pitches per game, percentage of complete games, and average number of pitchers per pitcher playing a complete game. In the future, the relationship between number of pitches and disability will need to be clarified, and number of pitches will need to be discussed further.
This study was funded by the Grants-in-Aid for Young Scientist: “An attempt to train university baseball players and instructors using VR technology” (Research Director: Ryoichi Use, Niigata University of Health and Welfare Ethics Committee, Case No.: 20K14099). We would like to extend our deepest gratitude to the teachers at the Niigata Junior High School Baseball Association who assisted with this study.
There are no conflicts of interest to declare.
