The purpose of this study was to determine the differences in the growth patterns of the external oblique (EO), internal oblique (IO), and transversus abdominis (TrA) muscles in adolescence baseball players. The subjects were 17 elementary school students (ES), 56 junior high school students (JS), and 21 high school students (HS) who played baseball. The EO, IO, and TrA muscle thicknesses were imaged using an ultrasound imaging device and analyzed separately on the dominant and non-dominant sides. Curve regression estimation of the relationship between EO, IO, and TrA and chronological age was used to read inflection points. An analysis of covariance was also performed, using body weight as a covariate for comparison with each of the EO, IO, and TrA grades. The inflection point readings showed that TrA was 11.26 years old (p<0.01, R2=0.45) for the dominant side and 10.10 years old (p<0.01, R2=0.46) for the non-dominant side, earlier than the inflection points of EO and IO. Analysis of covariance showed no significant difference in EO between any of the grades. IO showed significantly higher values for muscle thickness as the grade increased, both on the dominant and non-dominant side. TrA was higher for JS among ES and JS and higher for HS among ES and HS on both the dominant and non-dominant sides. EO may growth with increasing body size, while IO is interpreted to increase with increasing age due to the movement of baseball. TrA may grow earlier than EO and IO.

The purpose of this study was to determine the developmental pattern of swing speed in youth baseball players between 6 and 14 years old. A total of 1213 baseball players performed toss batting. Swing speed was measured with a specialized accelerometer. In addition, 618 of the 1213 players were measured for total fat free mass by using Inbody770. In study1, Regression analysis was performed on the relationship between chronological age or height and swing speed, and the extreme values were calculated. Then, an allometric equation based on height was also used to estimate the relative growth of swing speed and total fat free mass and to compare the difference of relative growth patterns between swing speed and total fat free mass in study2. Swing speed was strongly related to both chronological age and height, with cubic regression for the relationship with chronological age and linear for the relationship with height. The regression equation obtained for chronological age was solved and found that developmental rate was maximal at approximately 10.25 years old. Allometric analysis showed that the developmental pattern of swing speed differed from that of fat free mass, with a temporary decline in developmental rate from 153.6 cm to 160.9 cm. Based on the results of this study, further research in youth baseball players would be expected to identify the factors causing sluggish development of swing speed as well as to develop an exercise program for improving batting ability.

The present study aimed to investigate how the morphological and mechanical properties of Achilles tendon change in adolescent boys. Twenty-nine adolescent boys and 12 male adults participated. Ultrasonography was used to measure Achilles tendon elongation. The transition point, that is, the intersection point of the “Toe” and “Linear” regions was determined from tendon elongation-tendon force relationship, and the stiffness and Young’s modulus of the Achilles tendon were calculated from linear region. The hysteresis was calculated as the ratio of the area within the tendon elongation-tendon force loop to the area beneath the load portion of the curve. The stiffness, Young’s modulus and stress at transition point were greater in adults (544 ± 231 N/mm, 1.6 ± 0.7 GPa, 23 ± 6 MPa) than in adolescents (374 ± 177 N/mm, 1.1 ± 0.7 GPa, 19 ± 10 MPa). However, no differences were observed in the tendon length and the tendon cross-sectional area and stress at transition point between adolescents (174 ± 23 mm, 60 ± 11 mm², 6.1 ± 2.0 %) and adults (180 ± 30 mm, 63 ± 7 mm², 5.5 ± 2.2 %). The hysteresis in adolescents (20 ± 18 %) was greater than that of adults (12 ± 10 %). These results suggest that the morphological properties of Achilles tendon are similar between adolescents and adults, but that mechanical properties are altered with growth to become a stiffer and more spring-like structure.

Objective : The present study examined the effects of the self-management print media intervention on improving quality of life.Methods : The study was designed as an intervention study. We conducted questionnaire research on women (JKOM, Japanese style CSQ) over 40 years old who had knee pain. After program relevance determination, self-management print media intervention and an exercise intervention were implemented. The participants were 63 women (self-management print media intervention), and 80 women (exercise intervention). We examined valiances of pain intensity and activity limitation and pain coping strategies on each intervention using Wilcoxon signed-ranks test.Results : Pain intensity and activity limitation improved in both interventions. On the other hand, pain coping strategies differed. In the self-management print media intervention, the scores of diverting attention, praying or hoping, increasing activity level and increasing pain behavior significantly decreased. For the exercise intervention, a significant decrease was seen in coping, self-statements, catastrophizing, increasing activity level, and increasing pain behavior.Conclusion : The results indicated that the self-management print media intervention had greater effect than the exercise intervention for women with knee pain. As one health assistance measure, this self-management print media intervention should become widely used.

It is well known that extreme repetitive stress on the apophysis without considering the physical characteristics of children induces a growth disorder of the growing skeleton. However, only a few studies have evaluated the indexes of the muscle-tendon complex as a risk factor of apophysitis. The purpose of this study was to investigate the relationship between the elastic properties of the Achilles tendon, physical characteristics, muscle tightness (MT) and general joint laxity score (GLP), and tenderness from typical apophysitis (calcaneal tubercle, tibial tuberosity and iliac spine) in kindergarten and elementary school students. Body and lower leg size, and MT of the calf muscle increased ; while GLP decreased significantly with age. The Elastic index of the Achilles tendon and its standard deviations were greater among 5^th and 6^th graders than among 3^rd and 4^th graders. Point tenderness was more frequent in older age groups (4^th-6^th graders) than in younger age groups (kindergartren-3^rd graders) and was greatest in 4^th graders. When subjects were categorized into groups with and without point tenderness, no significant differences were found between GLP, muscle tightness of gastrocnemius, quadriceps and iliopsoas. However subjects who showed point tenderness had a higher Elastic index (p=0.07). Considering the pathomechanics of apophysitis, repetitive traction of the apophysis by a stiffer muscle-tendon unit lead to injury of the apophysis and growth plate. Tendon properties appear to be more sensitive to the pathomechanics of apophysitis.

The purpose of this study was to investigate semitendinosus muscle (ST) behavior during isometric knee flexions. Healthy male subjects were directed to exert ramp isometric knee flexion up to a maximum of eight knee flexion angles (0, 15, 30, 45, 60, 75, 90, 105 degrees). Displacement of the tendinous intersection (TI) in ST was measured using ultrasonographic images. TI moved proximally 15.8±4.9mm by maximum isometric contraction at 0 degrees, and the displacement of TI was significant at over 30% ramp maximum. Maximum knee flexion torque significantly correlated to displacement of TI at every knee angle, and decreased as the flexion angle increased. These results suggested that TI moved proximally in accordance with flexion torque, and demonstrated the unique behavior of ST, that is, the proximal part concentrically contracted, whereas the distal part eccentrically contracted.

A preparticipation examination for athletes should be performed to prevent severe athletic injury by examining physical characteristics related to various injuries. The general joint laxity test has been included among the check-up items considering as relating factor of joint injury. Authors investigated the relationship between the score of general joint laxity for freshmen examination and the incidence of major joint injury, during the succeeding 5 athletic seasons, in eighty-seven collegiate American football players.
Significant higher scores were observed in athletes affected by shoulder injury, and slightly higher scores in those affected by knee joint injury. But, the scores were similar between athletes with and without elbow or ankle injury.
The degree of laxity was associated with shoulder and knee joint injury in a comparison of incidence of these injuries among tight, medium and lax groups.
Authors concluded that general joint laxity is related to the incidence of shoulder and knee joint injury.

The purpose of this study was to investigate the influence of a shoulder injury on rotator cuff muscle thickness and shoulder muscle strength in baseball players. Based on orthopedic medical checks performed by a doctor for 57 male collegiate baseball players, two groups, the pain-free normal group (NOR group, n=19) and the impingement test positive group (IMP group, n=17) volunteered to participate in the study. Muscle thickness of the supraspinatus, infraspinatus and posterior deltoid muscles was measured bilaterally using a B-mode ultrasound apparatus (SSD-500, Aloka) with a 5-MHz transducer. Isometric shoulder abduction strength was measured bilaterally with a hand-held dynamometer in the sitting position with the arm at 45 degrees abduction, and shoulder external and internal rotation strength were measured bilaterally with an isokinetic dynamometer in the sitting position with the upper arm at 90 degrees abduction.
When the two groups were compared, the NOR group showed significantly greater values on the dominant side than on the non-dominant side for muscle thickness of the posterior deltoid. However, the IMP group showed significantly greater values on the non-dominant side than on the dominant side of muscle thickness of the supraspinatus, the muscle strength with the abduction and external rotation (300 deg/sec) and external internal rotation strength ratio (180 deg/sec) .
Also, the IMP group had a significantly weaker dominant/non-dominant ratio of supraspinatus muscle thickness (p<0.05) and abduction strength than the NOR group (p<0.01) .
These results suggest that baseball players with positive impingement show both a morphological and functional decline in the supraspinatus muscle. The dominant side supraspinatus weakness observed in the IMP group of this study may reflect muscle atrophy and chronic fatigue.

The purpose of this study is to investigate the degenerative change of the cervical spine in American football (AF) players. The subjects were 27 collegiate AF players who had an annual radiological examination of the cervical spine. X-ray films of the lateral view were read by digital scanner and the anterior and posterior height of each spine (C 3-C 6) was measured. The subjects were divided into two groups based on experience of AF in high school (inexperienced and experienced) or the position played (lines and backs) .
Although the anterior height did not change from the first grade to fourth grade, the posterior height of C 4, C 5 and C6 significantly increased (P <0.05) . The experienced group showed a faster increase in the rate of posterior height than the inexperienced group. Also, the backs group showed a faster increase in the rate of posterior height than the lines group. The increased posterior height, which sometimes includes bony spur, results in kyphotic change of cervical alignment and impingement of the cervical nerve root. The faster growth rate in experienced or backs groups suggests that higher mechanical stress to the cervical spine and younger start of AF caused degeneration.

Injury of the anterior cruciate ligament (ACL) occurs frequently in female gymnasts and basketball players. However, there is no effective method for preventing ACL injury. Recently, a fatigue phenomenon of the ligament tissue has been considered to be the main causative factor in ACL injury.
The present study was done to investigate the relationship between knee laxity and general joint looseness in 34 female college basketball players at an orthopedic medical check-up.
Knee laxity was evaluated in terms of the anterior displacement (AD) value measured by a KT-2000 knee ligament arthrometer at 20 lb. General joint looseness was evaluated in terms of the general joint laxity (GL) score including six major joints and the spine.
There was a significant correlation between the AD value and GL score, the correlation coefficients being 0.48 (p<0.01) at the right knee and 0.54 (p<0.01) at the left knee.
The ACL of athletes with a higher AD would always be exposed to higher anterior stress than in athletes with a lower AD, thus possibly leading to a fatigue state. Therefore, we consider that athletes with a high AD are at greater risk of ACL injury. Our results suggest that the easy GL test is an effective screening method for differentiating those with a high AD and a greater risk of ACL injury.