Wachi M1,2, Kida N2, Noguchi S1,2, Hyodo Y1, Kanazawa N1, Yamamoto T1, Nomura T2
1Kanazawa Orthopaedic & Sports Medicine Clinic, Shiga, Japan, 2Kyoto Institute of Technology, Kyoto, Japan
Background: The trunk muscles play an important role in the achievement of high sports performance. Therefore, previous studies have reported that specific hypertrophy in trunk muscles are observed in athletes associated with various sports. Of those, a series of by Sanchis-Moysi et al. determined that the rectus abdominis, obliques and transversus abdominis (TrA) muscle in tennis players could be characterized by asymmetrical hypertrophy. Similarly, Hides et al. determined the asymmetry of the multifidus lumborum in cricket players. On the other hand, it has been revealed that asymmetric sporting athletes with low back pain exist greater bilateral asymmetry in the trunk muscles. Although one previous studies have shown that high school baseball players already experience low back pain, many of these reports concern elite athletes, such as college and professional players.Therefore, we hypothesized that asymmetry of trunk muscles already occurs in baseball batters at high school age before adolescence.
Purpose: The objective of this study was to compare the development and asymmetry in trunk muscles between adult and youth baseball batters.
Methods: Forty adult baseball batters and 40 high youth baseball batters participated in this study. However, pitchers and those who had orthopedic diseases, including low back pain, were excluded. Muscle thickness was measured using a B-mode ultrasound device and 7.5Hz linear probe. Thicknesses of the upper rectus abdominis, central rectus abdominis, lower rectus abdominis, external abdominal oblique, internal abdominal oblique (IO), TrA, and multifidus lumborum muscles were measured. The differences in mean muscle thickness of the right and left trunk muscle was calculated. Furthermore, in order to exclude the influence of weight between youth and adult baseball batters, the values corrected by 1/3 power of the body weight was used to calculate the development rate of the trunk muscle.
Results: All muscle thicknesses were significantly larger in adult baseball batters than in youth baseball batters (P 0.001). Moreover, when the difference in muscle thickness was adjusted using body weight, significant differences in all muscles remained. In particular, the difference between the groups was the greatest in the IO (28.7 ± 28.8%) and TrA (29.9 ± 29.5%), as compared to other muscles. Furthermore, muscle thicknesses of the IO and TrA on the batting side were significantly greater in adult baseball batters (P 0.001). In contrast, this difference was not observed in youth baseball batters.
Conclusion(s): The trunk muscles of adult baseball batters are significantly larger than those of youth baseball batters; in particular, significant development was observed in IO and TrA. Furthermore, in adult baseball batters, IO and TrA on the non-dominant side were significantly larger, and bilateral asymmetry occurred. By contrast, in youth baseball batters, such asymmetry was not observed. This specific hypertrophy in the trunk muscle occurs at period of adolescence, and such characteristics may be related to the occurrence of bilateral asymmetry.
Implications: The asymmetry of IO and TrA may contribute to improvement of baseball technique.
Keywords: Ultrasonography, Abdominal oblique muscles, Sports performance
Funding acknowledgements: none
Purpose: The objective of this study was to compare the development and asymmetry in trunk muscles between adult and youth baseball batters.
Methods: Forty adult baseball batters and 40 high youth baseball batters participated in this study. However, pitchers and those who had orthopedic diseases, including low back pain, were excluded. Muscle thickness was measured using a B-mode ultrasound device and 7.5Hz linear probe. Thicknesses of the upper rectus abdominis, central rectus abdominis, lower rectus abdominis, external abdominal oblique, internal abdominal oblique (IO), TrA, and multifidus lumborum muscles were measured. The differences in mean muscle thickness of the right and left trunk muscle was calculated. Furthermore, in order to exclude the influence of weight between youth and adult baseball batters, the values corrected by 1/3 power of the body weight was used to calculate the development rate of the trunk muscle.
Results: All muscle thicknesses were significantly larger in adult baseball batters than in youth baseball batters (P 0.001). Moreover, when the difference in muscle thickness was adjusted using body weight, significant differences in all muscles remained. In particular, the difference between the groups was the greatest in the IO (28.7 ± 28.8%) and TrA (29.9 ± 29.5%), as compared to other muscles. Furthermore, muscle thicknesses of the IO and TrA on the batting side were significantly greater in adult baseball batters (P 0.001). In contrast, this difference was not observed in youth baseball batters.
Conclusion(s): The trunk muscles of adult baseball batters are significantly larger than those of youth baseball batters; in particular, significant development was observed in IO and TrA. Furthermore, in adult baseball batters, IO and TrA on the non-dominant side were significantly larger, and bilateral asymmetry occurred. By contrast, in youth baseball batters, such asymmetry was not observed. This specific hypertrophy in the trunk muscle occurs at period of adolescence, and such characteristics may be related to the occurrence of bilateral asymmetry.
Implications: The asymmetry of IO and TrA may contribute to improvement of baseball technique.
Keywords: Ultrasonography, Abdominal oblique muscles, Sports performance
Funding acknowledgements: none
Topic: Sport & sports injuries; Musculoskeletal: spine
Ethics approval required: Yes
Institution: Ritsumeikan University
Ethics committee: the Institutional Review Board of Ritsumeikan University
Ethics number: IRB-2013-015
All authors, affiliations and abstracts have been published as submitted.
