The purpose of this study was to investigate bilateral deficit (BLD) of force in submaximal isometric muscle contraction and effect of muscle fatigue on BLD. In Experiment 1, nine male students were subjected to investigate whether BLD occurs in submaximal force generation. They were asked to generate maximal force of the elbow flexors with their right, left, and right and left arms simultaneously. They also performed submaximal force generation at 30% and 60% of MVC in a way similar to that for the maximal force generation. The magnitude of BLD was compared between maximal and submaximal conditions by Bilateral Index: BI=100× (Bilateral Right and Left force/Unilateral Right force + Unilateral Left force) - 100. The mean values of BI during maximal. 30%, and 60% force generations were -9.4, -10.6, and -7.4, respectively, and there was no signi-ficant difference between conditions. This suggests that BLD occurs similarly regardless of the level of force output. Effects of the other arm starting to generate force (30%MVC, 60%MVC, MVC) on force level of one arm already holding a target force (30%MVC, 60%MVC, MVC) for 2 s were also investigated additionally. The magnitude of BLD was significantly larger for the additional condition compared to that seen in the simultaneous force generation by both arms from the beginning. To examine BLD during repeated muscle contractions, 14 male students performed 100 maximal isometric elbow flexions with right and left arms simultaneously (2-s contraction and 4-s rest) with right and left arms alternatively (2-s contraction and 4-s rest for each arm) in Experiment 2. BI values were calculated over the 100 contractions. During 100 maximal isometric contractions, force decreased to approximately 70% of the initial force at the end. The BI value increased from -8.6 (1^st) to -0.1 (25^th) then 3.3 (100^th) during exercise, indicating that BLD disappeared as the muscular fatigue proceeds.

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The purpose of this study was to noninvasively extract information about the size and muscle fiber density of muscular units through the inverse analysis of surface electromyograms. Surface motor unit action potentials (MUAPs) were recorded with a multi-channel electrode array arranged along the circumference direction of the biceps brachii. The depth and intensity of equivalent current dipoles were estimated through the inverse analysis of surface MUAPs. The simulation of inverse analysis of surface potentials generated by the muscular unit models showed that the relationship between the depth and the intensity depends on the muscular unit size and muscle fiber density.
In the simulation, we systematically varied the model parameters including distance from the skin, radius, and fiber density and used the inverse analysis to estimate the depth and intensity of current dipoles. And, our method to estimate the radius and fiber density of muscular units using estimated depth and intensity is demonstrated. Mean values (± SD) estimated from the surface MUAPs were 3.0±1.8mm for depth and 13.8±32.0nAm for intensity. The estimated distance ranged from slightly less than 1 mm to slightly more than 2 mm. The estimated radius ranged from 1.8 to 4.6 mm and fiber density from 0.7 to 5.4 fibers/mm².

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Disused rat hindlimb caused by sciatic neurectomy is characterized by skeletal muscle atrophy and bone loss accompanying alterations in trabecular bone architecture. We studied the time course responses of the two-dimensional architecture of trabecular bone and the relationships between bone loss and muscle atrophy using a unilateral sciatic nerve denervation model of disuse atrophy.
Fischer-344 male rats aged 11 weeks were denervated. The right and left tibiae, soleus and extensor digitorum longus muscle of denervated and control rats were obtained at 1, 3, 7, 10 days and 2, 3, 4, 5, 6, 7, 8, 10 weeks after surgery. Histomorphometric analyses were performed on longitu-dinal sections of proximal tibial metaphyseal secondary spongiosa.
Marked trabecular bone loss and muscle weight loss were observed mainly at 7-10 days and 1-3 days after denervation, respectively. Time courses of the percent decrease in trabecular width and length from 0 day (i, e., thinning rate; TR and fragmentation rate; FR) were not matched at 7-10 days and 5-6 weeks after denervation. The scatterplot for TR; FR showed that the FR changed stepwise with the first threshold between 12-25% of TR.

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The present study was aimed to investigate the physical ability of javelin throwers among uni-versity students using the magnetic resonance imaging (MRI), and Capacity Test, compared with other throwers.
The anatomical cross-sectional areas (ACCAs) of trunk muscles were determined using MRI. Capacity Test is composed of 30 m sprint, standing triple jump from a double-legged, backward over the head shot, forward over the head shot, sargent jump, snatch, and shoulder flexibility test with a javelin.
Results are as follows:
1. The male javelin throwers (MJT) group showed significant correlation between javelin throw records and ASCAs per body mass of body trunk extensor muscles (r=0.722, p<0.05) .
2. There was significant correlation between the forward over the head shot, and javelin throw in MJT group (r=0.800, p<0.01) . And the same tendency was also seen in female javelin throwers (FJT) group (r=0.735, p=0.055) .
3. The MJT group showed some correlation between javelin throw records and ASCAs per body mass of psoas major muscle (r=0.657, p=0.060) .
By the above-mentioned results, it was considered that the trunk extensors are important for male javelin throwers.

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The purpose of this study was to compare joint torque and the activity pattern of eight muscles crossing the ankle, knee and hip joints during three kinds of squats with different speeds (Slow, Normal, Quick) . Ten male athletes performed squats at three different speeds. Variables such as net torque and power about the joint were calculated during the descending and ascending phase of each squat. At the same time, surface electrodes were placed over the eight lower extremity muscles, and %iEMG was also measured during the ascending phase of each squat.
During the descending phase, the activity of elector spinae (ES), Gluteus maximus (Gmax), Gluteus medius (Gmed), Rectus femoris (RF), Biceps femoris (BF), Adductor longus (AL), and Vastus lateralis (VL) muscles was significantly greater for Quick squats than Normal and Slow squats, whereas during the ascending phase, activity was significantly greater for Quick and Normal squats than for Slow squats. Mean torque around the hip joint increased significantly when switching from Slow to Quick squats in the descending phase; and during the ascending phase, mean torque was sig nificantly greater for Quick and Normal squats than for Slow squats. The median frequency (MDF) of an electromyogram of the Gmax was significantly lower for Normal squats than for Quick squats ; and in the ascending phase, the MDF of the BF was significantly lower for Normal squats than for Quick and Slow squats.
Quick squats use the stretch-shortening cycle so that the load around the Gmax may increase. Although mean muscle activity for Slow squats was smaller than for Nomal squats, MDF was greater. MDF was greater for Slow squats suggesting that Slow squats mobilize type-II fibers in spite of the slow movement ; and is, therefore, useful for strength training with low risk of injury.

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The changes in physique of Japanese professional baseball players from 1950 to 2002 were stu died and compared with that of Major League players and Japanese adult males. The study found that the average heights of Japanese professional baseball players were 170.7 cm in 1950 and 180.1 cm in 2002 ; his respective average weights were 65.0 kg and 79.8 kg. The average BMI of Japanese players continuously increased during that period. In detail, the heights of the pitchers were the greatest of the four categorized positions, and the weights of the catchers were the highest, from 1969 until today. The average BMI of the catchers were higher than the other players, and that of the pitchers were lower, compared to that of the other players from 1973 until today. Furthermore, the average heights of Japanese players were greater than, and their average weights were higher than, the average Japanese adult males. Regarding Japanese players compared to Major League players, the difference in their average heights were 11.4 cm in 1950 and 4.9 cm in 2002 ; the difference in respective average weights were 17.7 kg and 13.1 kg. It can thus be concluded that from 1950 to 2002 the physique of Japanese players significantly increased while that of Major League players changed little over the same period. This means that the difference in the physiques of both sets of players has gradually decreased over the last 53 years.

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