The effect of muscle and tendon hardness after acute exercise -Analysis on ultrasound Real-time Tissue Elastography- / 体力科学

The purpose of this study was to evaluate the change of the hardness of the gastrocnemius muscle (GM) and the Achilles tendon (AT) using Real-time Tissue Elastography (RTE) before and after acute exercise. Nine healthy young male without any exercising custom performed a total of 100 reps. of one-leg heel-rise exercise and the hardness of the gastrocnemius muscle and the Achilles tendon before and after the exercise was examined in comparison. The strain ratio (SR) was even measured in comparison to a reference material. The result indicated that the SR of the GM significantly increased immediately, 15min, 30min and 24h after the exercise, whereas the SR of the AT significantly increased just immediately and 15min after the exercise. In summary, the hardness of GM and AT increased after exercise. These findings suggest that RTE is a useful technique for assessing specific hardness of muscles and tendon, More RTE measurements of various parts of the body and the examination of the relationship between injury and RTE are required for the conditioning of muscles and tendons.

DEVELOPMENT OF THE PREDICTION SYSTEM FOR THE ONSET OF THROWING SHOULDER INJURY ∼WITH LOGISTIC REGRESSION ANALYSIS∼ / 体力科学

The purpose of this study is to identify the risk factors which affect the consecutive onset of throwing shoulder injury of a collegiate baseball team, and to calculate regression formula which could predict the future onset.Prospective study. The subjects are 69 asymptomatic collegiate baseball players. We executed medical checkups and investigated who got throwing shoulder injury during this year. We did logistic regression analysis with the medical checkup findings and the data of the onset and found out the factors which significantly affected the onset. We also calculated Odds ratio of these factors and regression formula which predict the probability of the onset of throwing shoulder injury and evaluated the validity of regression model.52%(36/69 cases) of the players suffered throwing shoulder injury during this year. Among the medical checkup findings of asymptomatic phase, pitcher and catcher, past history of throwing shoulder injury, abnormality of scapula-humeral rhythm, heel-buttock distance were thought to be the risk factors which were near-related to the onset of throwing shoulder injury. We calculated regression formula using the medical checkup findings of asymptomatic phase and we could predict the onset of throwing shoulder injury with 82.5% accuracy.In order to prevent this injury, the method used in this study could be useful for field players to predict the onset of throwing shoulder injury.

UPPER EXTREMITY MUSCLE ACTIVITIES AND STRENGTHS IN OVERHEAD THROWER DURING ECCENTRIC MUSCLE ACTION / 体力科学

PURPOSE : To determine the patterns of electromyographic (EMG) responses and torques of upper extremity muscles in overhead throwers during maximal, eccentric muscle action for shoulder flexion (Flex_Ecc), abduction (Abd_Ecc) and diagonal activities (Dia_Ecc) with full glenohumeral internal rotation, at 60, 120, and 180°/s on the dynamometer.METHODS : Seven asymptomatic subjects (7 men, 4 women) who participate in overhead sports at least three days a week volunteered to participate in this study. Subjects were randomly performed with the test procedure which consisted of at least 5 grade maximal-effort repetitions on the three different testing conditions, at 60, 120, and 180°/s on the dynamometer, while we assessed muscle activation of the anterior deltoid (AD), middle deltoid (MD), posterior deltoid (PD), upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and biceps brachii (BB) muscles by surface electromyography. EMG data was expressed as a percentage of maximum voluntary isometric contraction (%MVIC) that was obtained from the highest root mean square (RMS, 50 ms) of each muscle and was normalized and averaged.RESULT : AD muscle elicited lower muscle activity during Dia_Ecc than Flex_Ecc and Abd_Ecc (P＜0.05) while the MD, PD, UT, MT, and LT muscles elicited overall greater muscle activities during Dia_Ecc. MD and MT muscle activities were significantly greater for the faster speed than for the slower speed as 60°/s during Abd_Ecc (P＜0.05). Peak torque generated greater muscle strength for Dia_Ecc than Flex_Ecc and Abd_Ecc, and it was significantly greater for the faster speed than slower speed during Dia_Ecc (P＜0.05).CONCLUSION : Posterior upper extremity muscle activities and peak torque values were found to be dependent on eccentric muscle action for diagonal shoulder activity at the faster speed. This study provided evidence that isokinetic eccentric muscle strength testing of the posterior upper extremity muscle was effective to develop of a proper program for overhead sports athletes require forceful stability during deceleration phase.

FRONTAL-PLANE KNEE DISPLACEMENT INDEX AS A SCREENING TOOL FOR RISK OF ANTERIOR CRUCIATE LIGAMENT INJURY / 体力科学

The aim of this study is to examine the potential of the two-dimensional posture evaluation method as a screening tool for detecting the high-risk population for anterior cruciate ligament injury.Eleven healthy adults participated in this study. They jumped from a 31 cm-high box and landed on their dominant leg. Three-dimensional knee flexion/extension, knee valgus/varus and hip adduction/abduction angle during single-legged landing were calculated. At the same time, the Frontal-plane Knee Displacement index (FKD)-the knee joint position relative to the line between the hip and ankle joint-was measured.FKD reflects the time variation of three-dimensional knee valgus and hip adduction angle very well.Our results suggest that FKD has potential as a screening tool particularly for movement occurring primarily in the frontal-plane.

EFFECT OF ACUTE RESISTANCE EXERCISE ON BONE METABOLISM DURING MENSTRUAL CYCLE / 体力科学

[Objective] The aim of this investigation was to evaluate bone metabolism responses to acute resistance exercise during the menstrual cycle. [Methods] Subjects were young healthy sedentary women (n=7) with regular menstrual cycles. The subjects performed acute resistance exercise in each phase (follicular and luteal) of the menstrual cycle. Bone metabolism markers (bone formation marker BAP and bone resorption marker ICTP), bone metabolism related hormones (parathyroid hormone, calcitonin, calcium and inorganic phosphorus) and lactate were determined. Blood samples were collected before (Pre) and immediately following the exercise (Post), 1 hour (P1h) and 24 hours (P24h) after the exercise. [Results] BAP significantly increased at Post compared with Pre both in the follicular and luteal phases (p<0.05), but significantly decreased at P1h and P24h in the luteal phase. ICTP significantly increased at Post in the follicular phase (p<0.05) and significantly decreased at P1h and P24h in the luteal phase. The bone metabolism responses in the luteal phase moved to low-bone turnover at P1h and P24h. [Conclusion] The bone metabolism response to acute resistance exercise was different between menstrual phases. These results suggest that bone metabolism is influenced by the menstrual cycle.

THE EFFECTS OF ICING AFTER EXERCISE ON JUMPER'S KNEE / 体力科学

The purpose of this study was to investigate the pathologic changes of jumper's knee before and after jumping and effects of icing after jumping. Sixteen healthy college students and sixteen collegiate volleyball players with jumper's knee were divided into two groups by eight, without icing group and with icing group after jumping exercise. Without icing groups rested for 20 minutes, while with icing groups were treated with ice for 20 minutes after eighty times of jumping. Signal to noise ratio (SNR) and sectional area of patellar tendon with Magnetic Resonance Imaging and the tenderness of patellar tendon with visual analog scale were measured before and after exercise, following with or without icing and 24 and 48 hours later from the treatment. In jumper's knee group, significant increase was found in the SNR, sectional area of patellar tendon, and tenderness of patellar tendon after exercise compared to before exercise. In addition, in jumper's knee with icing group, significant decrease was found in the SNR, sectional area of patellar tendon after icing and 24 and 48 hours after icing, and the tenderness of patellar tendon after icing compared to after exercise. These results suggested that icing was an effective treatment for jumper's knee after exercise.

GENDER DIFFERENCES OF LOWER EXTREMITY KINEMATICS DURING SINGLE LEG LANDING / 体力科学

The higher anterior cruciate ligament (ACL) injury rate of females is one of the most sever athletic-related problems today. The purpose of this study is to compare the lower extremity kinematics between male and female during single leg landing.Six male and four female healthy subjects participated in this study. They jumped from a 32 cm high box and landed with the dominant leg. The landing action was filmed with three video cameras. The knee flexion, knee valgus/varus, and hip adduction/abduction angle and angle velocity were calculated.In female subjects, the knee flexion angle and hip adduction angle were greater compared to males. Also, the knee valgus velocity and hip adduction velocity were higher in females.Our results suggest that knee valgus kinematics may be related to hip adduction. It is important to evaluate hip kinematics when considering knee kinematics to prevent knee ligament injuries.

THE RELATIONSHIPS BETWEEN SHOULDER'S FUNCTION AND DAMAGE FOR HANDBALL PLAYERS / 体力科学

[Objective] The purpose of this study is to examine the relationships between shoulder's function and damage for handball players. Subjects were nine female handball players with dominant shoulder pain.[Methods] Clinical diagnosis was done from the medical doctor's opinion and MRI. Then, the shoulder joint movement was measured with X rays.[Results] Most of them had admitted a lot the impingement syndrome and the subacromial bursitis. The trunk rotation angle at zero-positions was significantly larger in the symptomatic shoulder (dominant shoulder) than in the asymptomatic shoulder (nondominant shoulder). That is, it was obvious that the damage of the shoulder changed tilting angle of scapula medially.[Conclusion] It is reported that the damage of the shoulder causes abnormality to the “scapulohumeral rhythm” by the previous research. But, these results, suggested to need to understand not only “scapulohumeral rhythm” but also movement to the position of the scapula, when the shoulder joint function was observed for the handball player mainly composed of throwing motion.

COLLAGEN AND GLUCOSAMINE HYDRATE SUPPLEMENTATION IMPROVE THE JOINT MARKERS IN HUMANS / 体力科学

The present study was designed to examine the positive impact of collagen and glucosamine hydrate supplementation on joint markers, matrix metalloproteinase-3 (MMP-3), tissue inhibitor of metalloproteinases-1 (TIMP-1) and keratane sulfate (KS) . Thirteen healthy fun-runners supplemented collagen and glucosamine hydrate for 30 days. Blood samples were collected on days 0, 15 and 30. The test-drink supplement, however, significantly decreased MMP-3 and KS on days 15 and 30. These results suggest that the supplementation of collagen and glucosamine hydrate may prevent injury and inflammation of joint cartilages and be useful for joint conditions.

JUMPER'S TIBIA ASSESSED ALONG 64 DIRECTIONS CENTERING CENTER OF GRAVITY OF THE BONE BY pQCT / 体力科学

Side to side difference in tennis players' mid-radius and cross-sectional study on mid-tibia of jumpers and sedentary controls suggest that the improvement of mechanical properties of cortical bone in response to long-term exercise is related to geometric adaptation and not to volumetric bone mineral density. In the present study, geometric and mechanical properties of right tibia were estimated along 64 directions centering center of gravity of the bone on cross-sectional peripheral quantitative computed tomography (pQCT) images. The tibias of 17 jumpers (7 females, 10 males) and 15 controls (8 females, 7males), aged 18-23, were scanned at mid site using pQCT. Periosteal and endocortical radius were larger, cortical thickness was thicker, and mechanical properties (moment of inertia of area and strength strain index) were greater in jumpers compared to those of controls. The differences in cortical thickness between the two groups were dependent on direction of measurement. Defined a direction from tibia's center of gravity to fibula's as 0°, difference in the cortical thickness between jumpers and controls was the greatest at around 240°. Along this direction, differences in mechanical properties were also the most significant, suggesting that the site-specific adaptation of bone to long-term exercise is due to geographical relation of bone to muscle.

EFFECT OF POSITION AND CHANGE OF ANGLE ON ACTIVITY OF SHOULDER MUSCLES DURING SCAPULAR PLANE ABDUCTION / 体力科学

The purpose of this study is to identify the effect of position (full can, empty can) and change of angle on the activity of shoulder muscles during scapular plane abduction ; and also to examine its application to exercises used for rehabilitation of shoulder muscles. Seven healthy subjects (23.4±1.4 yr) with normal shoulder function performed scapular plane abduction with external rotation (full can) and scapular plane abduction with internal rotation (empty can) . An electromyogram was recorded with a fine wire intramuscular electrode at the supraspinatus, deltoid anterior, middle, posterior and trapezius upper with bipolar surface. The EMG activity (RMS) of each muscle was normalized by the highest EMG activity (100%RMS) during a maximum manual muscle test for each muscle (%RMS) . The %RMS of each muscle remarkably increased with a change of the angle for empty can, whereas it showed a slight increase with a change of the angle for full can. This finding suggests that the position of full can and empty can in scapular plane abduction affects the function of shoulder muscles. In addition, full can exercise is recommended in order to improve function of the supraspinatus and the muscular activity balance between the supraspinatus and the deltoid. Empty can exercise is applied to sport-specific exercise for rehabilitation of shoulder muscles.

A GENU VARUM EFFECTS ON EACH LOWER EXTREMITY MUSCLE ACTIVITY DURING LEGPRESS EXERCISE / 体力科学

[Purpose] A leg press generally included in a weight training program to develop the quadriceps. However little is known about the mechanism of the load in lower extremity by the different knee alignment. The purpose of this study is to compare the muscle activity in the different knee align ment during leg press exercise. [Methods] Four normal knee and Five gene varum performed the leg press using three stance of narrow, medium and wide stance with the load of 75%/1 RM. Surface EMG date were collected (1000Hz) from vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF), adductor longus (AL), biceps lemons (HF), tibialis anterior (TA), gastrocnemius (GAS), soleus (SQL) . Integrated EMG (iEMG) values were calculated for each muscle during each rep. A video camera recorded the performing form during leg press from the frontal plane. [Results and Discussion] As the leg press was to strengthen of the thigh muscle, VM, VL and RF of both groups worked strongly. However SQL of genu varum worked as strong as the level of activity of the thigh, iEMG of the SQL showed low value significantly by using wide stance. When the genu varum group performed maximal knee flexion using the narrow, their ankle was valuus on the video screen. This result may become cause of SQL higher activity during leg press. From this we can derive the argument that it will be necessary to take that stance into consideration when athletes who are genu varum performs leg press.

Electromyographic Activity of Shoulder Muscle at Different Positions During External Rotation / 体力科学

Electromyographic activity of the shoulder muscle at 20 and 90°abduction (20 Abd, 90 Abd) during external rotation was investigated in seven healthy men with no history of injury or instability of the shoulder joint.<BR>Electromyography (EMG) was recorded using intramuscular fine-wire electrodes inserted into the M. Supraspinatus, M. Infraspinatus and M. Teres minor, and with bipolar surface electrodes on the middle and posterior parts of M. Deltoid anti the upper and middle parts of M. Trapezius. To compare activity in different muscles, the integrated EMG (iEMG ) activity of each muscle was normalized.<BR>M. Infraspinatus and M. Teres minor showed significantly higher activity at both the 20 Abd and 90Abd compared with the middle and posterior parts of M. Deltoid and upper parts of M. Trapezius. M. Supraspinatus, the middle and posterior parts of M. Deltoid, and upper and middle parts of M. Trapezius all showed a difference in activity level between the two positions.<BR>These findings suggest that when M. Infraspinatus and M. Teres minor contribute to external rotation as a stabilizer and prime mover, consecutively, M. Supraspinatus, the middle and posterior parts of M. Deltoid, and upper and middle parts of M. Trapezius function according to the positions. Moreover, the activity of the upper and middle parts of M. Trapezius in 90Abd should influence stabilization, adduction and upward rotation of the scapula. Therefore, we conclude that the external rotation position is closely related to shoulder muscle activity and coordination.

Effect of Icing Treatment on Muscle Reaction Time and Functional Performance of a Sprained Ankle / 体力科学

[Objective] The purpose of this study was to determine whether icing treatment has an effect on muscle reaction time and functional performance of a sprained ankle. [Methods] Subjects were six persons (healthy group) and six persons who had an acute ankle sprain (patient group) . Anterior talar translation and talar tilt of the six patient group were evaluated by the stress X-ray measure. Ice treatment was applied for 20 minutes. [Results] The following points were clarified : 1) Reaction times of peroneus longus (PL) and peroneus brevis (PB) for the sprained ankle group (SA) were significantly longer than those for the non-sprained ankle group (NA) (p<0.05) . Length of time of standing on one leg with closed eyes for SA was significantly shorter than for NA (p<0.05) . 2) After icing treatment, reaction time of PL for SA tended to be shorter. Furthermore, PB significantly decreased after icing treatment (p<0.05) . Side-steps for SA were significantly increased after icing treatment (p<0.05) . 3) Reaction times of PL and PB for NA significantly increased after icing treatment (p<0.05) . Standing on one leg with closed eyes for NA significantly decreased after icing treatment (p<0.05) . [Conclusion] It was shown that icing treatment of a sprained ankle leads to a shorter muscle reaction time and an increase in the number of side-steps. Therefore, it was concluded that icing treatment of a sprained ankle might be able to improve incapacitated neuromuscular function and functional performance by acute trauma.

EFFECT OF ACUPUNCTURE STIMULATION ON DELAYED ONSET MUSCLE SORENESS PRODUCED BY ECCENTRIC EXERCISE / 体力科学

Delayed Onset Muscle Soreness (DOMS) is characterized by a sensation of discomfort that usually develops 24-48 hours after unaccustomed exercise, with muscle swelling and stiffness that usually results in a reduced range of movement. Muscle weakness is often seen. It may be surmised that DOMS is a problem that affects all athletes.<BR>We examined six male subjects to determine the effect of acupuncture stimulation on DOMS, which was induced experimentally in both legs using a heel raising exercise. Acupuncture stimulation has long been used in the treatment of pain, but there is insufficient proof of its efficacy. A problem acupuncture research has had to face is the concept of a control group. To deal with this, we used non-invasive acupuncture stimulation, which would allow the simulation of the acupuncture procedure without penetrating the skin. The leg that would receive actual acupuncture stimulation and the leg that would receive non-invasive stimulation after the induction of DOMS were determined by randomization.<BR>The muscle stiffness, ankle range of movement, maximal voluntary contraction, one-legged vertical jump, muscle tenderness, pain on muscle stretching, pain on muscle contraction, ankle mobility and subjective muscle strain were measured as indices of stimulation efficacy. Pain on muscle stretching was significantly less (p<0.05) at 48 hours after exercise for the side stimulated by acupuncture as compared with the side stimulated non-invasively. The other indices did not differ significantly between the side stimulated using acupuncture stimulation and the side stimulated non invasively. These results suggest that the early relief of DOMS can be achieved by acupuncture stimulation.

Electromyographic analysis of shoulder muscles during shoulder external rotation with reference to load magnitude / 体力科学

Electromyographic muscle activities of the shoulder muscles during shoulder external rotation with reference to load magnitude were studied in 8 healthy male subjects without history of shoulder injuries. In addition, we discussed the relationship between rotator cuff muscles and superficial muscles. The subjects performed shoulder external rotation from 60°internal rotation to 45° external rotation at 20° of shoulder abduction and 20° of flexion. A Cybex dynamometer used to prescribe angle and velocity of the shoulder movement. At the same time, intramuscular wire electrodes were inserted into the supraspinous, infraspinous and teres minor muscles, and then surface electrodes were placed over the posterior deltoid and middle trapezius muscles. The load magnitude ranged 2-18 Nm and the angle velocity was set at 15 deg/sec. The rotator cuff muscles became significantly to be activated from 2 Nm (the supraspinous and infraspinous m.) and from 4-5 Nm (the teres minor m.) compared with the muscle activity during non-load. The superficial muscles became significantly to be activated from 4-7 Nm (the posterior deltoid m.) and from 3-6 Nm (the middle trapezius m.) compared with the muscle activity during non-load. Within the load range (18 Nm 46.8% MVC), %iEMG of the rotator cuff muscles was always larger than that of the superficial muscles. Therefore, we concluded that the contribution of the rotator cuff muscles was larger than that of the superficial muscles up to 3-4 Nm, and activities of the superficial muscles increased gradually from 3-4 Nm during shoulder external rotation.

CHANGES IN BONE METABOLISM MARKERS ASSOCIATED WITH LONG-DISTANCE RUNNING / 体力科学

To investigate the influence of long-distance running on bone metabolism, we measured bone metabolism markers in eight healthy young men before and 4 months after the start of training program of 10 km running. Measurements were then taken the day before a marathon race, immediately after, and 1 day, 2 days and 5 days after.<BR>As a result of exercise, the levels of serum osteocalcin (OC), a bone formation marker, and urinary deoxypyridinolin (D-Pyr), a bone resorption marker, decreased significantly. After the marathon race, the OC level decreased further corresponding to an increase of hydrocortisone right after the race. However, from the day following the race, the OC level showed a slight increase. D-Pyr showed an increasing tendency immediately after the race, and the levels of OC and D-Pyr increased significantly 5 days after the race.<BR>Bone formation and resorption decreased as a result of light, low-frequency endurance exercise. However, both of them increased after intense physical stress. From this result, it is suggested that the intensity and frequency of exercise affect bone metabolism differently, even though the type of exercise load is similar.

Changes in bone mineral density during sexual maturation in male and female rats: correlation with serum IGF-1, IGFBP-3, osteocalcin and sex steroids / 体力科学

Bone (tibia, femur, and lumbar spine) and blood samples were obtained from 100 (50 males and 50 females) Wistar-Imamichi rats in groups aged 3, 5, 7, 9, 12, 15 and 20 weeks old to investigate the changes in bone mass during puberty in relation to insulin-like growth factor 1 (IGF-1), IGF binding protein (IGFBP) -3, osteocalcin (OC) and sex steroids in normal rats.<BR>Sharp increases in BMD (bone mineral density) in the tibia, femur and lumbar appeared earlier in female than in male rats, and the BMD in females tended to be higher than in males between 5 and 9 weeks old. After 9 weeks old, BMD in males was higher than that in females, as BMD in males continued to increase whereas that in females tended to remain in a steady state after this stage. This sex-related difference in changes in BMD pattern is probably related to the serum concentrations of IGF-1, IGFBP-3, testosterone, and 17β-estradiol with maturation. In males, marked increases in serum IGF-1 and IGFBP-3 concentrations appeared earlier than that in serum testosterone level. IGF-1 and testosterone peaked at 9 weeks of age, and thereafter remarked in a steady state, whereas IGFBP-3 reached a peak at 7 weeks of age, and then declined gradually. In females, the changes in patterns of serum 17β-estradiol, IGF-1, and IGFBP-3 levels were very similar. The levels increased gradually from 3-5 weeks old, peaked at 9 weeks, and then decreased slowly thereafter. In contrast, serum OC concentrations remain relatively high from 3 to 9 and from 3 to 7 weeks old in males and females, respectively, although OC in both sexes declined gradually with aging.<BR>These observations suggest that BMD development occurs earlier in female than in male rats. This sex-related difference in changes in the BMD pattern may result from the earlier onset of puberty in females, and from the sex-specific differences in concentrations of IGF-1, IGFBP-3 and sex steroids with maturation.

The process of bone response to running training in female growing rats / 体力科学

Physical activity in the growing period has been shown to be effective for increasing bone mass because immature bones are more sensitive than mature adult bones to the stimulation with mechanical stress. However, bone growth is not uniform and changes markedly at puberty. Therefore, the response of bone to exercise may differ according to the growth process. The purpose of the present study was to investigate the process of the bone response to running training, and the relationship between the bone response and serum insulin-like growth factor-I (IGF-I) and IGF binding protein-3 (IGFBP-3) levels in female rats. Thirty-three female Wistar-Imamichi rats 4 weeks of age were divided randomly into control (CON) and running training (RUN) groups for 6 and 12 weeks. Training consisted of running on a flatbed treadmill at 30 m/min for 60 min/day, 5 days/week. The bone mineral content (BMC) and bone mineral density (BMD) in the whole and five parts of the tibia were measured by a dual-energy X-ray absorptiometer (DXA) . Simultaneously, we measured serum concentrations of IGF-I, IGFBP-3, osteocalcin and 17β-estradiol. The whole tibial BMD was significantly higher in the RUN groups than in the age-matched CON groups. When BMD was analyzed at five different studied parts within the same tibia, the increase of BMD. was noted in the proximal and distal cancellous bone in the 6-week RUN group, and in the diaphysial, cortical bone, in the 12-week RUN group. Serum concentrations of osteocalcin, a marker of bone formation, were not altered by training, whereas they decreased with aging. Serum IGF-I levels in the training groups were not changed, but IGFBP-3 levels were increased significantly only in 6-week RUN rats. As a complex between IGFBP-3 and IGF-I may be more improve than free IGF-I in the bone formation, the high levels of IGFBP-3 in the 6-week RUN group may induce an increase in the activity of IGF-I. There was a significant positive relationship between serum IGF-I concentration and BMD of the whole tibia in the 6-week study, and between the IGFBP-3 level and BMD in both the 6 and 12-week studies.<BR>In conclusion, 1) the process of the skeletal response to running training is site-specific within the same bone, and 2) the increment of the IGFBP-3 level with training in the growth period may reflect the increment of tibial BMD through training.

Effects of running training in immature and mature periods on bone formation in rats / 体力科学

The purpose of this study was to investigate the effects of running training on bone formation in rats in relation to the age training started. The first experimental period was set from 6 to 12 weeks (wks) old and the second from 12 to 19 wks old. Sixty-four Wistar strain 6-wk-old male rats were initially divided into a non-exercise (N) and an exercise (E) group. At 12 wks old, each group was subdivided into two groups, providing four groups: non-exercise·non-exercise (NN), non-exercise·exercise (NE), exercise·non-exercise (EN) and exercise·exercise (EE) . Exercise consisted of treadmill running at a speed of 30 m/min, 60 mm day, 5 days wk. The animals were sacrificed before the experiment (6 wks old), post-first experiment (12wks old) and postexperiment (19 wks old), the bilateral tibiae were removed and their lengths, bone mineral content (BMC), bone mineral density (BMD) and bone histomorphometric parameters were measured. The tibial length was significantly shorter in 12-wk-old E than N rats and in 19-wk-old EE than NN. At 19 wks old, the total tibial BMD values were significantly higher in EE than NN, and the BMD values of the proximal and distal tibiae, where the cancellous bone was the main component, had increased markedly, whereas no differences between the diaphyseal BMD of each group were noted. Bone histomorphometry at 12 wks old, considered the immature period, showed that the osteoid surfaces and labeled surfaces tended to be increased by running training, but the bone volume was unchanged. In contrast, at 19 wks old, considered the early mature period, the osteoid surfaces showed a tendency to decrease and labeled surfaces to increase and consequently the bone volume increased albeit not significantly. These results suggest that: 1) running training started in immature rats represses longitudinal tibial growth, 2) the cancellous bone is more sensitive then the cortical bone to this type of training and 3) training of early mature rats increases bone volume by increasing the efficiency of osteoid calcification.