SEX DIFFERENCES IN THE MUSCLE VOLUME OF THE ILIOPSOAS IN THE ELDERLY / 体力科学

The purpose of this study was to investigate sex differences in the muscle volume (MV) of the iliopsoas, psoas major, and iliacus muscles, normalized by fat free mass (FFM), in the elderly. The subjects were 15 males and 15 females 65 years of age or over. Serial transverse 1.5T magnetic images (10 mm slice) of each subject were taken between the 12^th thoracic vertebrae and the lesser trochanter. FFM was measured with a bioelectrical impedance analyzer. The mean MV of each muscle on the right and left sides were calculated and used for regression analysis of the relationship between MV and FFM.A significant correlation was observed between MV and FFM of the iliacus in both sexes (p<0.01), but not between the MV and FFM of the psoas major. MV normalized by FFM and cross-sectional area (CSA) normalized by FFM^2/3 showed significantly greater values for the psoas major in the males than in the females (p<0.001), but there was no sex difference in the MV or CSA normalized by FFM of the iliacus.These results suggest that elderly males tend to have a greater muscle volume and cross-sectional area of the iliopsoas than elderly females, and that these sex differences are attributable to differences in the psoas major.

Measurement Method of the Masseter Muscle Volume Using 3D Computed Tomography

Since G.N. Hounsfield's clinical use of computed tomography in 1971, digital imaging technique using computers has shown an eye opening progress. Progress has made 3-dimensional understanding of not only facial bones but muscles and other connective tissues possible through 3-dimensional reconstruction of preexisting tomographical images. Also, quantitative analysis of density, distance, volume has become possible, allowing objective analysis of preoperative and postoperative states through imaging. The authors measured the masseter muscle volume of 20 normal individuals and 8 female patients through 3-D reconstructive CT imaging and made a statistical analysis of the measurements. The method used in our study may be applied to the diagnosis of disease causing the change of the facial volume and presurgical design as a useful tool to provide objective information on the evaluation of surgery outcome.

MUSCLE VOLUME AND STRENGTH CHARATERISTICS OF THE ROTATOR CUFF AND DELTOID MUSCLES IN ASYMPTOMATIC BASEBALL PITCHERS / 体力科学

The purpose of this study was to investigate muscle volume (MV) and strength characteristics of the rotator cuff (supraspinatus, infraspinatus, teres minor, and subscapularis) and deltoid muscles in each shoulder of asymptomatic baseball pitchers. Twelve collegiate baseball pitchers (PG) and ten male students (CG) who never played an overhand sports volunteered to participate in this study. Magnetic resonance imaging (Straits II, Hitachi Medico, 1.5 T) was used to measure the MV of rotator cuff and deltoid muscles in both shoulders of each subject. Since the individual muscles were difficult to identify on MRI scans, the infraspinatus and teres minor were analyzed as one infraspinatus muscle. Shoulder abduction (ABD), external rotation (ER), and internal rotation (IR) strengths were measured each side using a hand-held dynamometer (Power Track II, Jtech Medical Industry) . The MV of deltoid muscle was significantly larger value on the dominant side (DOM) than on the non-dominant side (NDOM) in both the PG and CG groups (p<0.05) . However, no significant differences in the MV of the rotator cuff muscles and the measured shoulder strength (ABD, ER, and IR) were observed between both sides in either group. Similarly, no significant differences in the DOM/NDOM ratio of the muscle volume and the measured shoulder strength were observed between the two groups. These results suggest that the rotator cuff muscle volume and strength does not differ in both sides of the PG, and DOM/NDOM ratios of the rotator cuff muscle volume and strength of the PG does not differ in those of the CG.

AGE- AND BENDER RELATED DIFFERENCES IN KNEE EXTENSION TORQUE AND LAG EXTENSION POWER / 体力科学

This study was aimed to investigate the influences of age and gender on isometric muscle torque and explosive muscle power output with reference to muscle volume. A total of 177 healthy subjects of both genders were divided into four groups according to their age and gender : 46 young men (22.0±3.2yrs), 43 young women (22.7±3.3yrs), 46 elderly men (71.2±4.3yrs) and 42 elderly women (72.7±4.5 yrs) . The maximal voluntary isometric knee extension torque of the right leg (hip and knee angle at 90 degrees) and the power of bilateral leg extension in sitting position were mea sured. The ratios of both torque and power to muscle volume, estimated using ultrasonograph measurement, was calculated (torque/MV and power/MV respectively) . Torque was significantly less among the elderly than among the young for both genders, and among women than among the men for both age groups. Significant age-related differences were evident even in terms of torque/ MV, but the corresponding differences between men and women disappeared. On the other hand, power MV showed significant age- and gender-related differences, and the age-related difference was larger than that for torque MV. These results suggest that age- and gender-related differences in power are more noticeable than differences in torque and that these differences are not simply explained by differences in muscle volume.

Architectural properties and specific tension of human knee extensor and flexor muscles based on magnetic resonance imaging / 体力科学

The physiological cross-sectional area (PCSA) of knee extensors (KE) and flexors (KF) was determined using magnetic resonance imaging (MRI) in humans. Twenty two healthy male volunteers were assigned to the subjects and MRI was taken to obtained 41-52 consecutive axial images (slice thickness ; 10 mm, interslice gap ; 0 mm) from right-leg thigh. From these images, anatomical cross-sectional area (ACSA) of KE and KF was determined. Muscle volume was calculated from the summation of each ACSA and the distance between each section. Muscle length was determined as the distance from most proximal to most distal images in which the muscle visible. The PCSA of each muscle was calculated as muscle volume times the cosine of the angle of fiber pinnation divided by fiber length, where published fiber length : muscle length ratio were used to estimate fiber length. The isokinetic knee extension and flexion (angular velocity ; 30, 60, 180, 300, 450 deg/sec) was measured to estimate the muscle force at KE and KF. Specific tension of KE and KF was calculated muscle force deviled by PCSA. The mean muscle volume of KE and KF was 2178, 1141 cm<SUP>3</SUP>. The ratio of KE : KF was 2.6. The mean fiber length in KE was 7-8 cm, and in KF was 6-42 cm. Peak torque during knee extension was significantly higher than knee flexion at all angular velocities. The specific tension of KF was higher than that of KE at all tendon velocities. Moreover, relationships between specific tension and tendon velocity/fiber length, KF was still higher than that of KE. These results suggest that the capacity of tension development differ between KE and KF under the same shortening velocity per unit of sarcomere.

MORPHOLOGICAL CHARACTERISTICS OF TRUNK MUSCLE GROUPS IN JAPANESE FEMALE ELITE JUDO ATHLETES / 体力科学

Using three-dimensional (3 D) imaging, we investigated the morphological characteristics of the M, latissiums dorsi (LD) and M, erector spinae (ES) of the dorsal trunk in judo athletes employing a computer graphics system on magnetic resonance imaging (MRI) . The subjects were five healthy untrained women (HUW) without lower back pain syndrome, and five Japanese female elite judo athletes (EJA) . There was no significant difference in height or weight between the HUW and EJA. Three-dimensional imaging of the LD and ES was reconstructed visually, based on MRI consecutive slice data taken from the first thoracic vertebra to the symphysis pubis along the trunk. Then the volume of the LD and ES was determined using a surface reconstruction algorithm.<BR>The morphological characteristics of the LD in the EJA appeared to indicate enlargment compared with those in the HUW, whereas the characteristics of the ES in both groups were similar. The volume of the LD was significantly different between the HUW (226.6±33.18 m<I>l</I>) and EJA (438.1±107.8 m<I>l</I>), whereas that of the ES showed no difference (HUW; 257.4±78.8 m<I>l</I>, EJA ; 284.0±74.82 m<I>l</I>) . In the EJA, but not in the HUW, there was a significant positive correlation between the volume of the LD and weight, and differences were noted between the two regression slopes. There was also a positive correlation between the volume of the ES and weight in both the HUW and EJA, which showed the same simple linear regression slope. These results suggest that the muscle hypertrophy evident in the LD, but not in the ES, is related to the effects of Judo training.

THREE DIMENSIONAL RECONSTRUCTION OF THIGH MUSCLE GROUPS BY COMPUTER GRAPHICS / 体力科学

The purpose of this study is to develop the non-invesive method for three dimensional analysis of knee extensor and knee flexor muscle groups of the thigh part in human subjects. Our system consisted of magnetic resonance imaging (MRI) to get cross-sectional images of muscle and a computer graphics system which reconstructs three dimensional image of each muscle. The subjects chosen for this study were four healthy male adults, aged from 21 to 30 years. MRI scan was carried out from head of the femur to the upper border of the patella along thigh. Three dimensional (3D) muscular image was reconstructed based on the data from MRI. Referring to the anatomic feature, contour information of knee extensor muscles (KEM) and knee flexor muscles (KFM) was identified on MRI and those muscles were reconstructed to 3 D images using the computer graphics system. This system also provided information on the quantitative volume and cross-sectional area (CSA) of each muscle.<BR>The structure of each muscle of KEM and KFM was displayed by a wireframe model or a surface model on the CRT. It was revealed that 3D muscular images of the surface model using coloring and shadowing were highly effective to understand their shapes and relative location of muscles. CSA and volume of KEM were 86.84±8.38cm<SUP>2</SUP>and 2044.25±168.28cm<SUP>3</SUP> and those of KFM were 38.48±5.90cm<SUP>2</SUP> and 751.95±50.56cm<SUP>3</SUP> respectively.<BR>These results indicate that not only the anatomical information but also the volume and maximum CSAs of KEM and KFM can be measured quantitatively by this method using three dimensional analysis.