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 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.

It seems likely to consider that the bone density (BD) of athletes is higher than that of control subjects. But recently, many authors reported lower BD of amenorrheic female athletes, and suggested that strenuous exercise could decrease BD through, probably, endocrinological disorder.
So, we compared BD of second metatarsal in female athletes with irregular menstrual cycle (IM group) or with stress fracture (SF group) to that of normal menstrual athletes (NM group) or those without bony injuries (NF group), by MD/MS method.
MD/MS method, which is the screening method of BD by scanning mid-diaphysis of second metacarpal (or metatarsal) for 3cm by 20times in X-ray films, was developped from microdensitometry whose scanning was only once at the same part of the bone.
BD of IM group was lower than that of NM group, but without significant difference. BD of SF group was significantly lower than that of NF group.
The index of mechanical strength of the bone, “I”, that is area moment of inertia, did not increase in accordance with decrease of BD. We supeculate this as one of the factor of stress fracture in a sense of decreased mechanical strength.

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.

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.

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.

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.

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.

Investigation was made into knee joint problems among tea pickers through a questionnaire. Following this, physical examinations were given and radiography was taken.
Of the male respondents, 18.9% said that they have pains in the knee (s). The corresponding figure for the women was a high as 38.5%. The number of men and women who complained of knee pain increased with age. However, it was not clear whether the incidence of knee pain has any bearing on the number of years they had worked or working hours per day. Rather, it seems to depend on the configuration of the plantation.
Knee pain occurs more frequently in persons working on sloping and hilly lands than those working on flat land. The difference in Q-angle is wider in the hilly area than in the flat land.
X-ray examination of the knee joint of the persons who complained of sensations revealed degenerative changes in the form of the synovial cavity. Changes in the form of the patella were more evident in the persons working on the sloping land than on the flat land.
On the slope, tea pickers have to bend their knees, requring femoral quadriceps and crural triceps to maintain contraction for cours. Thus the level of stress on the kneecaps becomes high.
To prevent knee joint injuries, improvement of footings, mechanization of collecting work, decreases in the frequency of decending and ascending the slop, and having a rest at proper intervals are necessary.
Furthermore, it is necessary to strengthen femoral quadriceps by excercise and control weight.