We are the first to introduce the name “clinical brain sports medicine.”, Previously a “brain and sports” category had been discussed only for sports head injuries. We have therefore attempted to systematize the field for research and to develop this field. We introduced table tennis into brain rehabilitation ten years ago, and achieved good results. Table tennis is a safe and pleasant sport in which everyone makes quick progress without difficulties. It is the optimal sport for people of middle and advanced ages as well as for brain disease patients. The following three points were examined through the table tennis exercise: brain blood-flow, brain high function, and brain rehabilitation. The effect of table tennis exercise on brain blood flow was examined as follows: Six male volunteers played table tennis for 10 minutes and their brain blood flows were measured by SPECT (single photon emission computed tomography). An increase in brain blood flow was shown for four persons, no change for one, and a reduction for one. The increase areas were observed mainly on the cerebellum, brain stem, and frontal lobe. The effect of table tennis exercise on brain function was examined as follows: A “KANA Pickup test” reflecting the grade of “dotage” was performed by 2,900 players who participated in the game of table tennis, and the degree of “dotage” was analyzed. The results demonstrated that, in all age groups, the table tennis players gave many correct answers and had few degrees of “dotage” statistically compared with 256 persons who did not play table tennis. The effect of table tennis exercise on brain rehabilitation was examined as follows: Table tennis rehabilitation was introduced into the rehabilitation of 113 brain disease patients. The average period was two months. They started with easy rolling-over play, then showed gradual improvement. The treatment effect was evaluated by motor function, the degree of progress of skill, Benton visual test, Hasegawa dementia scale (HDS-R), and self-depressed scale (SDS). The results demonstrated that improvement was found by every appraisal method in many cases. It was thought that table tennis treatment had an effect not only on improvement of motor function but on improvement in a patient’s attentiveness, concentration, and endurance. For the purpose of performing brain sports medical treatment, we established the nation’s first “brain sports visitor” in June 2002, at the National Nishi Beppu Hospital. There are as many as 24 medical staffs there. I hope our “Oita project” will develop not only over Japan but also over the world.
The muscular arterioles are locally dilated in muscle contraction, and glucose, lipids, etc. are supplied from the blood in a large amount. Simultaneously oxygen is also supplied, and an anaerobic condition of muscular tissue is avoided. The action potential that traveled from a motor nerve propagates to a myolemma. Simultaneously it propagates to a T-tubule and then Ca2+ is released from a sarcoplasmic reticulum by depolarization of the T-tubule. The local ischemia causes large effects, namely energy crisis, and also affects the electrical characteristic of the cell membrane, and it seems to be also concerned in the propagation velocity of action potential on the muscle fiber. In this study, an intramuscular probe and measurement system were developed in order to measure muscle function under local ischemia. This probe is composed of a plastic optical fiber (500 μm in diameter) which measures blood flow and ten platinum fine electrodes (50 μm in diameter) for the action potential measurement. The distance between each electrode pair is about 170 μm. The probe is inserted in cannula of1.6 mm in diameter. Ten electrical buffer circuits are installed in the grip of the probe. Animal tests using rats were carried out in order to verify the developed probe and system. In gastrocnemius of the rat, the action potential waveform and blood flow were measured using this probe. In the experiment, tibial nerve was stimulated electrically and the action potentials were recorded. Their signals were sampled at 30 kHz and recorded for 10 ms. The amplitudes of potentials were about ±1.5 mV and they remained for about 5 ms. The latency of waves is about 1.5 ms and the phase between the two waves is about 0.25 ms. The similarity of both waves was examined, using a cross correlation function during the measurement. The distance between two electrodes is 517.6 μm and the propagation velocity was about 2.1 m/s. In the other experiment, a popliteal artery was ligated. With the progress of the ischemia, the action potential propagation velocity, which was calculated from the potential waveforms in the two electrodes, gradually decreased after the ligation. In all cases of several experiments, the propagation velocity decreased. A biosensor by which biochemistry markers etc. can be measured simultaneously will be built in a future measurement probe.
The purpose of this study was to clarify the relationship between the changes of surface electromyogram (EMG) and the single motor unit (MU) activity with muscle fatigue. It is well known that median power frequency (MDF) shifts to the low-frequency side and the muscle fiber conduction velocity (MFCV) decreases with muscle fatigue. We recorded the activity of the single MUs from the biceps brachii and the flexor carpi ulnaris during sustained contraction. The experiments were performed on four healthy male adults without signs of neuromuscular disease. Surface EMG signals were picked up with an electrode array consisting of four silver wire contacts. Deriving the single MU was enabled by displaying EMG signals on the CRT of a computer and presenting them to the subjects. The changes of the MU activity during muscle fatigue were analyzed by MFCV, MDF, and interspike intervals. As a result, the phenomenon that a single MU activity stopped suddenly in the process of muscle fatigue was observed. The durations of the single MU activity varied depending on MUs. MFCV of the biceps brachii was a level of 3.5 to 4.5 m/s and no large change was confirmed. MFCV of the flexor carpi ulnaris varied from 2.2 to 4.6 m/s. The changes of the muscle fatigue process were also various. MDF of the biceps brachii was a level of 104 to 138 Hz except that one MU increased by 20 Hz or more. MDF of the flexor carpi ulnaris varied from 76 to 178 Hz. The changes of the muscle fatigue process were not large. The interspike intervals of the biceps brachii were about 100 milliseconds, and increased before stopping discharge. The interspike intervals of the flexor carpi ulnaris also increased before stopping discharge. These results suggest that the substitution of MUs and the decrease of firing rate cause the changes to the surface EMG parameters during muscle fatigue.
The disuse syndrome is caused by low physical activity especially in the elderly. If muscles are not used for a long time, their strength will decrease. Weakened muscles accelerate reduced daily life activity. To overcome the disuse syndrome, appropriate training must be delivered with proper timing. The purpose of the present study was to clarify the mechanism of muscle deterioration at the beginning of the disuse syndrome. This kind of knowledge may contribute to developing training methods and training devices that can prevent the progress of the disuse syndrome. For this purpose, a model experiment was performed on ten healthy young adults. Their knee and ankle joints were immobilized in casts for one week. Before and after the immobilization, changes in their motor functions were measured. As an indication of the morphological changes, the muscle cross sectional area (CSA) was measured based on magnetic resonance images (MRIs). As a functional indication, the maximal voluntary contraction (MVC) torque of the ankle plantar flexion was measured. Since the MVC is affected both by the muscle itself and by the nervous system or the sensory feedback, the potential MVC and the EMG amplitude during the MVC were also measured. The potential MVC was estimated by the twitch interpolation method, which is an indicator of the muscle strength excluding the effect of the nervous system. The EMG was derived from the soleus and the gastrocnemius and is an indicator of the activation from the nervous system. The CSA of the soleus showed no significant change after the immobilization. The ratio of the change was 100.3±1.8%, which was comparable to the variability of the measurement. In contrast, the MVC decreased to 82.7±11.8% (p<0.01, t-test). The potential MVC and the EMG amplitude also decreased to 84.5±17.9% and 83.6±18.6%, respectively. These results indicate that there exists a state at the beginning of the disuse syndrome, in which the muscle CSA looks normal but invisible deterioration proceeds in the muscle. The deterioration also occurs in the nervous system, which in conjunction with the deterioration in the muscle, causes the decrease in the MVC.
Although a large number of studies have been conducted into negative influences on motor function after long-term muscle disuse, little is known about the effect of short-term muscle disuse and its mechanism. Moreover, the aspect of functional decrease during short-term muscle disuse may be different at high and low levels of muscle output. Knowledge of this will be useful for the development of appropriate exercise prescriptions and health-welfare devices that can prevent creeping functional decrease. This study examined the influence of seven days of immobilization on motor function at high- and low-level contraction force with abduction of the index finger. Healthy subjects (12 males, mean 25.9 years) participated in the present study. Their left hands were immobilized with plaster casts. Changes in the cross-sectional area (CSA) of the first dorsal interosseous (FDI) were evaluated with a magnetic resonance imaging system. Subjects performed maximum voluntary contraction (MVC) with isometric abduction of the index finger and they were regulated at the constant force levels of 500 g, 1000 g, 1500 g, and 2000 g. Standard deviation of the force trajectory (F-S.D.) was calculated at each force level as an index of stability of the force regulation. EMG activities were recorded with surface electrodes placed over the FDI. The root mean square (RMS) of the EMG amplitude was calculated at each force level and was normalized with the amplitude of supra-maximum M-wave in order to compare the degree of change by muscle immobilization. Twitch force evoked by supramaximum electrical stimulation at rest was measured to consider factors of the peripheral neuromuscular system. Twitch force at MVC was measured by the twitch interpolation method to consider central factors. Firing rate of motor units at super 80% MVC was then measured. These measurements were taken before and after the immobilization and again in the recovery period. The CSA of the FDI showed no significant changes by short-term immobilization. In contrast, MVC force and muscle activity (RMS) were lost after short-term immobilization. The decline of twitch force at rest suggests that several troubles occurred in neuromuscular function. In addition, the increased twitch force at MVC and the decreased firing rate suggest that the central drive was reduced by short-term immobilization. In the recovery period, these values almost returned to those before immobilization. Therefore, both the peripheral factor and central factor affect the decline of high-level contraction force during short-term disuse before muscular atrophy. The fluctuation (F-S.D.) during force regulation at the same force in the low level increased after immobilization. This result shows that it became more difficult to regulate constant force levels after short-term disuse. The RMS at the same force level also increased after immobilization. In the recovery period, these values almost returned to those before immobilization. Therefore, the decline of neuromuscular efficiency affects the functional decrease of low-level contraction force during short-term disuse.
Weightlessness is associated with the rapid onset of osteoporosis and muscle atrophy. Muscle bulk, for example, decreases in weightlessness twice as rapidly (1%/day) as it does during strict bed rest on the ground. In the space shuttle, astronauts are stabilized with an elastic band and perform resistance exercise using an ergometer in an attempt to reverse these processes. Despite these efforts, it remains very difficult to prevent musculoskeletal deterioration. We developed a “hybrid exercise ” technique that uses the force generated by an electrically stimulated antagonist muscle to provide resistance to a volitionally contracting agonist. In other words, the agonist performs a volitional concentric contraction against an electrically stimulated eccentric contraction of the antagonist. To learn more about the basic effects of stimulation, we examined comfortable maximal electrical stimulation voltage on the quadriceps femoris and also measured its concentric and eccentric torque using KIN-COM&R;. Seven sedentary young males (14 extremities) were involved in this study. Stimulation was performed 3 times a week for 6 weeks. The maximal comfortable stimulation voltage increased significantly at the midpoint (3 weeks) (from 31.81±12.01 V to 48.47±17.98 V). Electrically stimulated muscle torque also increased with increasing stimulation voltage (from 0.37±0.14 Nm/kg to 0.47±0.12 Nm/kg) over the same period. Electrically stimulated eccentric muscle contraction strengths were significantly greater (50%) than concentric contractions produced with the same stimulating voltages (p<0.001). The tension of the electrically stimulated eccentric contraction of the antagonist could be utilized effectively as a resistance of volitional contraction of the agonist at even low stimulation intensities. Hybrid exercise has several advantages. These include: 1) activation of type I muscle fiber as a result of the volitional contraction of agonist muscles, 2) simultaneous exercise of both agonist and antagonist musculature, 3) longitudinal bone force loads, 4) requiring minimal external stabilization of the subjects, and 5) the proven safety of electrical stimulation as a physical therapy modality. Hybrid exercise, which utilizes electrically stimulated antagonist force as a resistance of joint motion instead of gravity, would become a useful exercise method in a weightless environment.
The purpose of this study was to investigate muscle damage and reinforcement by electrical muscle stimulation (EMS). The first experiment involved two groups of athletes (Group 1 and Group 2) and one group of healthy volunteers who did not engage in daily exercises (Group 3 served as the control). The subjects’ triceps brachii muscles were stimulated electrically (EMS, subject&RSQUO;s variable tolerance: Group 1) and mechanically (concentric- and eccentric-resistance training of 60% MVC, RT: Group 2). For one of the subjects with EMS, the serum CPK levels of 3 and 4 days after the stimulation were approximately six times as high as that before the stimulation. The serum CPK levels of other subjects with EMS increased to twice or less of those before the stimulation. The serum CPK levels of subjects with RT did not change. The levels showed significant difference between subjects with EMS and RT, 2 and 5 days after the stimulation (Mann-Whitney test, p<0.05). In the second experiment, the quadriceps femoris muscles were stimulated. EMS generating a force of 60% MVC was applied to each subject in Group 4 for 30 minutes every other day for a week. RT of 60% MVC was applied to each subject in Group 5. The subject did 30 trials, with 60 s resting time between every 10 trials, every other day for a week. The serum CPK levels of the subjects with EMS increased, but the increase rate varied with subjects. One of the subjects had more than six times as high serum CPK levels as that before the stimulation. Another subject had only one and half times as high serum CPK levels as that before the stimulation. There were significant changes with time after the stimulation (Friedman test, p<0.05). However, there were no significant differences between subjects with EMS and the control. For subjects with RT, the serum CPK levels increased slightly but there were no significant changes with time after the stimulation (p>0.05). In the third experiment, EMS was applied to the triceps brachii muscles of Group 1 and Group 3 for eight weeks. The non-athletes with EMS showed 30% increase of the maximum voluntary contractile force and they showed 38-54% improvement of endurance. The maximum voluntary contractile force of athletes with EMS did not change but the endurance showed 59% improvement. However the maximum voluntary contractile force of athletes without EMS decreased and the endurance did not change. In conclusion, we suggest that EMS could cause more severe muscle damage than concentric-, eccentric-resistance training. EMS reinforced the muscles of both athletes and non-athletes. Moreover, EMS showed stronger effects on non-athletes compared with the athletes.
A programmable hybrid FES system for restoration of pinch motion disabled C5 quadriplegics has been developed. Because of the paralysis of wrist motion as well as hand motion in persons who have spinal cord injury at the cervical fifth level, pinch orthosis can not be applied for these persons. In the developed hybrid system, the FES system was utilized for restoration of wrist motion. The FES-generated wrist motion was converted to thumb and index finger motion by using a pinch orthosis. The system consists of magnetic distance sensors for the detection of stimulation control motion, a two-channel electrical stimulator, and a PIC16F877 microprocessor for system control and stimulation pulse generation. The processor manages the magnetic sensor monitoring through a 10-bit analog-to-digital converter, generation of stimulating pulses, modulation of the stimulation pulse width for stimulus strength control, the state of the “stimulation mode,” and monitoring of the switches for mode control at 50-millisecond intervals. Use of a microprocessor offers system flexibility which enables modification of the system function after implementation, and storage of settings such as sensor threshold. The developed system was evaluated in able-bodied volunteers. The maximal pinch force was measured under voluntary, voluntary with extended fingers, voluntary with pinch orthosis, and hybrid FES conditions. The average pinch force with hybrid FES system was 1.5 kgf, which is about twenty percent of the voluntary pinch with finger extension in nine volunteers. It appears sufficient for light activity for daily living, such as writing and eating. The working efficiency was also evaluated in an object moving task. Six volunteers were required to move pens on a desk from right to left, and each task time was recorded. The stimulus increment/decrement rate was varied and the working efficiency was compared. The best performance was obtained at the rate of 100 percent per second. Under that condition, the average task time for pinch and move was 4.0 seconds and the release and move time was 2.7 seconds. Clinical evaluation and further development for extension of the applicable subject remain to be done.
Postural control may be performed on the basis of certain reference frames. Two kinds of reference are usually adopted, one based on the support surface and the other, head-centered reference. In usual cases, these two may be flexibly and dynamically integrated. To understand such integration, we investigated the air-righting movement in rats. Because of lack of a support surface during falling, air-righting may be evoked by a control system based on the head-centered reference. Air-righting movements were evoked in male Wistar rats. In some rats the cerebellar vermis was ablated in various degrees (decerebellate animals). Righting movements and muscle activities were analyzed. Righting movements were recorded on a videocassette recorder (30 frames/sec). Video pictures were captured into a computer frame by frame. Muscle activities were recorded from axial muscles (m. longissimus thoracis) on both sides. Air-righting consisted of three kinds of movement in rats with intact brain: head and upper body rotation against the lower body, lower body rotation against the upper body, and four limbs extension in the prone posture. These movements occurred sequentially in the above-mentioned order. After the head and upper body rotations, the head almost righted in space, and the hip maximally twisted. This torsion of the hip was removed by the second movement, the lower body rotation. After the second movement, the whole body righted and the animal could take a prone posture. Then, the third movement, limb extension, occurred. In decerebellate animals, the same basic movements were induced during air-righting. However, the magnitudes of rotations were different from those of intact rats. Sometimes magnitudes of rotations were so small that air-righting movements were incomplete (undershooting). In other cases, rotations were so large that air-righting was excessive (overshooting). In extreme cases, decerebellate rats rotated their bodies more than twice during a single fall. In both undershooting and overshooting, the removal of axial torsion of the body at the hip seemed to take place; thus, the whole body in such cases inclined along the long axis after the second movement. In such cases, the third movement was not evoked. To elicit the third movement, the animal was assumed to be in the prone position.
The purpose of this study was to examine postural control against perturbation during treadmill walking. In addition, we hypothesized a strategy of postural control in such a situation and suggested the effect of aging on postural control. Ten young and twenty-nine elderly subjects participated in this study. We used a separated-belt treadmill, and perturbations were produced by rapidly decelerating one side of the walking-belt for 500 ms while walking. To young subjects, two types of the perturbation were given five times each in three minutes of walking: 50% deceleration of the initial speed (moderate perturbation) and 100% deceleration of the initial speed (strong perturbation). To elderly subjects, moderate perturbations were given five times in three minutes of walking. The electromyogram responses of leg, thigh, and trunk muscles on both sides and acceleration at the pelvis were measured. We classified subjects from reaction patterns of muscles, and compared them. Four reaction patterns of muscles were observed: “ankle strategy,” “mixed ankle and hip strategy,” and others. Comparing the ankle strategy seen in young and elderly subjects, the response of tibialis anterior on the perturbed side after the perturbation was significantly delayed in elderly subjects. The “mixed ankle and hip strategy” observed in this study did not change with advancing trials, although the mixed strategy in standing is defined as the transitory pattern to pure ankle strategy or hip strategy when the stimulus exceeds the control limit. We therefore concluded that the mixed strategy observed in this study was different from the mixed strategy seen in standing. The pattern of muscle recruitment was immediate antero-distal muscle activities followed by postero-proximal muscle activities after perturbation. This pattern resembled whiplash. We suggest this mixed strategy be established as a new strategy. It is thought that the posture of a subject moves like striking a whip since this new strategy showed the ankle strategy followed by the hip strategy, and we considered this new strategy to be a “whiplash strategy”. Also, this new strategy was seen when the body shake was large, so it is suggested that it is an important strategy for subjects who have low ability of postural control. From these results, we concluded that there is a specific postural control strategy in walking, and there are differences in postural control ability between elderly and young subjects.
In recent years the population of elderly people in Japan has increased tremendously, necessitating modifications of many of the houses they live in. Recent surveys show that about half of the elderly people want to modify their houses. Stairs and slopes are obstacles frequently encountered by elderly people in daily living activities. Ascending and descending stairs and slopes are quite demanding and therefore these should be constructed according to recommended values of the Japanese Ministry of Construction for older people. However a lot of staircases and slopes are constructed using upper limit values of the Building Standards Act, a factor which makes it difficult for older persons to use them safely. In order to determine advantages of the recommended values, we have to prove the effects of these values for body load and safety objectively in respect to ADL. Although there have been a lot of studies about biomechanics for ascending and descending stairs, there are very few for slopes. Also there are some studies, which only investigated the lower extremity joint moment during ascending and descending, but there is no study that has investigated the low back joint moment during ascending and descending stairs and slopes. The purpose of this study was to show the effects of dimensions of stairs and slopes on the low back load and to show the differences of low back load between young healthy adults and older people during ascent and descent. We investigated the low back joint moment when subjects ascended and descended two stairs and two slopes of different dimensions using force plates and a three-dimensional motion analysis system (staircase A and slope A were based on recommended values of the Japanese Ministry of Construction for older people, while staircase B and slope B were based on upper limit values of the Building Standards Act in Japan). This study was performed on eight healthy men and eight elderly men. Results showed that the low back joint moments when older subjects ascended stairs and slopes was larger than those of young subjects, while no change was noticed when both subjects descended stairs. Also low back joint moment became larger during ascent and descent of staircase B than that of staircase A, while no change was noticed during ascent and descent of the two types of slope. Low back joint moment was largest when elderly subjects ascended staircase B. Differences of staircase values had distinct effects on elderly subjects when ascending. Although knee extensor moment and ankle plantar flexor moment were moderately exerted when a healthy young subject ascended staircases A and B; when older subjects ascended staircase A, hip extensor moment was excessively exerted and knee extensor moment and ankle plantar flexor moment couldn't be moderately exerted when older subjects ascended staircase B. This hip strategy caused large trunk bending angle and resulted in increased low back joint moment in the older persons. These results showed that using a type B staircase required a large low back load and therefore is inappropriate for elderly persons.
Diagnosis of a shoulder joint injury, particularly one brought about during sports activities, necessitates measurement of its motion accurately and noninvasively. Conventional measurement of shoulder joint movement, however, deals solely with relative movement between humerus and thorax, neglecting other components of the joint. We have focused on 6-DOF measurement of scapula movement relative to the thorax, a subdominant component of shoulder movement. Such motion data, however, cannot easily be obtained by means of a marker-based motion-capture system, due to the skin mobility relative to the skeleton. The objective of this study was to validate measurement accuracy of scapula movement when measuring markers are attached to the skin above the scapula’s bony landmarks. We employed an open MRI (Magnetom Open, Siemens, Germany) to measure the shoulder joint and markers attached to the subject’s skin. Five and three markers were attached to the skin above the scapula and thorax, respectively. Three volunteers (24.0±2.64 years old), who possessed no distinct kinetic dysfunctions in their shoulders, served as subjects, in this preliminary study. Their shoulder movements were sampled at three humeral elevation angles (0°, 90°, 150°) on a frontal plane by open MRI. In order to reduce the skin mobility, the same movements were recorded, using a more accurate method in which the scapula’s markers were relocated into correct positions, determined through the palpation of an experienced physical therapist, at each humeral elevation. In an attempt to validate the skin mobility, we measured the deviation of the markers from the scapula’s bony landmarks during humeral elevation. Next, the scapula movements were estimated by two different methods as follows: the registration technique using bony shape and the least squares method using the set of markers. The results demonstrated that the deviation of the markers could be reduced into less than or equal to 19.0 mm if the markers were remounted at each elevation angle. Using the remounted markers, we verified the estimated error of position and orientation of the scapula to lie within 10.1° and 6.4 mm, respectively. In conclusion, we validated measurement accuracy of the scapula movement using skin markers above the scapula’s bony landmarks. The results showed that a motion-capture system is capable of quantitatively measuring the static shoulder joint movement with the scapula.
The shoulder and elbow joint of a baseball pitcher are frequently overused by the repetition of throwing. The overuse causes throwing injuries of the shoulder or the elbow joint. To prevent the injuries or find them as soon as possible at an early stage, it is important to understand and evaluate each individual’s baseball pitching motion exactly. Therefore, we are developing an analysis system of the baseball pitching motion for clinical use. The pitching motion is classified into four major pitch styles, as follows: overhand, three-quarter, sidearm, and underhand. In the long-term clinical experience in Nobuhara Hospital, we have expected that one of the causes of throwing injuries is related to the pitch styles. A previous paper reported that different pitch styles produced different kinematic and kinetic results of pitching motion analysis (Matsuo, 2000). The difference of pitch styles will influence analysis results of the pitching motion. The classification, however, was performed qualitatively by a person having baseball experience. There is no standard method to classify the pitch styles quantitatively. The pitch styles also have to be classified quantitatively in order to investigate various factors of injuries. The aim of this study was to classify baseball pitchers of various levels into four pitch styles quantitatively and compare the kinematic and kinetic parameters. We measured the pitching motions of the baseball pitchers, using a motion-capture system at 500 Hz. Ages of the 104 subjects of this experiment ranged from 10 to 38 years. We suggested four kinematic parameters in order to classify the pitch styles. The measured pitching motions were then classified into four pitch styles, using multivariate discriminant analysis. The correct answer rate was 89.4%. ANOVA revealed significant differences of the antero-posterior direction of resultant force at the time of ball release among four classified pitch styles. The A-P force vector had high correlation (r=0.82) with horizontal adduction angle of the upper arm. The shear force on the shoulder is one of causes of injury during pitching. To reduce the risk of shoulder injuries, we believe it is necessary to reduce shear forces on the pitcher’s shoulder. Our results showed that the sidearm group had 50% lower shear force than the other groups. In conclusion, we suggested four kinematic parameters in order to classify the pitch styles. This result shows that these parameters are appropriate for classifying the pitch styles without relation to age or skill differences. The results of kinematic and kinetic parameters showed the significant differences between four pitch styles. Our next task is to increase the number of subjects, especially sidearm and underhand pitchers.
The purpose of this study was to investigate (1) the activities of shoulder muscle under varying positions, loads, and motion angles during scapular plane abduction and (2) the effectiveness of exercise for an abductor, examined from muscular activity of each shoulder muscle. Seven healthy male subjects (age 23.4±1.4 years) without any history of shoulder pathology participated in the experiment. The three conditions of scapula plane abduction, 1) with humeral external rotated (Full can position), 2) with humeral internal rotated (Empty can position), and 3) both middle (Neutral position), were performed from 0 to 90 degrees of abduction angle. During the scapular plane abduction, the applied load was 0-16 Nm. A Cybex 770-NORM dynamometer was used to control the angular velocity at 15 deg/sec. The electromyogram (EMG) was recorded from the supraspinatus with a fine-wire intramuscular electrode, the anterior, middle and posterior deltoid, and the upper trapezius with bipolar surface. The raw EMG signals for each muscle and load were divided at each 5 deg, then rectified, and the RMS (root mean square) calculated. The RMS of each muscle and load, which was normalized with the RMS in the manual muscle test used to elicit maximum activity, was compared for each load and muscle. Additionally, the increase aspect of %RMS with the change of the abduction angle of the supraspinatus, the middle deltoid, and the upper trapezius was compared. For loads lower than 4 Nm with motion angle below 30 degrees, %RMS of the supraspinatus showed significant activity compared with no-load conditions in Full can and Neutral positions. In contrast, %RMS of the supraspinatus and the middle deltoid showed significant activity compared with no-load condition in Empty can position. For loads of 8 to 16 Nm and abduction angles of 30 to 90 degrees, %RMS of the supraspinatus and the middle deltoid demonstrated equivalent activity in Full can position and significant activity, in which the middle deltoid was comparable with the supraspinatus in Neutral and Empty can positions. The activity aspect of the upper trapezius in Empty can position showed differences between Full can and Neutral positions. In conclusion, these findings suggest that abduction position (Full can position, Empty can position, and Neutral position), load, and motion angle are closely related to shoulder muscle activity and coordination. In addition, the Full can position and Neutral position seem to strengthen the functionality of the supraspinatus below 4 Nm for motion angles below 30 degrees.
The purpose of this study was to develop a new joint system based on the human shoulder mechanism. The human shoulder joint is constrained by multiple muscles and ligaments which surround the ball joint, and is driven by the balance of those forces. It is thought that the construction of the human shoulder mechanism could provide motion with three degrees of freedom and with compact size and light weight in comparison with an industrial robot arm composed of the usual pin joints. Therefore, the authors thought that the new joint mechanism for a robot arm with three degrees of freedom should be a ball joint mechanism driven by wires. In the development of the new joint mechanism, we tried to construct two types of joints. These were a five-wire model and a six-wire model. An anatomical skeletal structure has been introduced to the mechanism, especially on the muscle arrangements of the human shoulder. The movability of the new joint mechanism was evaluated by the ratio of moment arm to ball radius produced from the wires that surround the ball joint. The method of estimating moment arm was to find the slope of the wire excursion against the joint angle. Thus, to compensate some deficiency of moment arm, occurring in a specific area of flexion-extension or rotation motion, the wire position corresponding to the lack of moment arm was adjusted to an adequate position using evaluation of the moment arm. As a result of improvement processes, the effective movability was ascertained in the specified movable area for the six-wire model. Sufficient movability was not acquired in the five-wire model, however, because the movable area was considerably reduced. When the joint is driven as a robot arm, an inverse kinematics must be solved. In the present study, the problem was solved by utilizing an artificial neural network (NN), which learns data sets for arm posture and wire displacement. The additional differential outputs installed in the learned NN and consideration of a theory of virtual work balance were applied to a control system to drive the joint by a feedback control system in the range of three degrees of freedom. It was properly and precisely driven by the control system on the six-wire model. Thus, the movability and capability of the new joint system of a robot arm based on the human shoulder mechanism, as described in this paper, was demonstrated to be satisfactory.
Geometry of living things is one of the most attractive subjects for researchers in the field of biomechanisms. Recently, not only anatomists, but mathematicians and engineers are tackling the problem of clarifying how living organs geometry is optimized to its functions. Such study was accelerated by the development of shape-measurement equipment, such as the CT scanner, MRI, and 3-D digitizer. Dental prostheses are among oldest artificial organs, having been used by edentulous patients for hundreds of years. Since the design and manufacturing of dental prostheses require advanced skills, their quality cannot easily be maintained within acceptable limits. Attempts have been made to apply advanced CAD/CAM technology to this production field. Currently, several dental CAD systems are commercially available. Their detailed and optimum design, however, cannot easily be accomplished under present CAD circumstances, because conventional manufacturing techniques matured in dentistry have yet to be fully computerized. In an attempt to realize a more sophisticated dental CAD, this paper proposes a novel tooth model with both surface and solid descriptions, and an innovative partial metamorphosis operator, to which the Hit-or-Miss transform developed in the field of mathematical morphology was applied. Our tooth model consists of a solid description of the occlusal surface and a surface description of the entire crown. The use of a solid model enables easy detection of the contact and interference of the opposing teeth. In order to make the two different models agree with each other in corresponding portions, we introduced a mutual transform between them, which is always determined uniquely if one of the models is deformed infinitesimally. Our partial deformation operator, on the other hand, can partially dilate or erode the contour around the deformation center without loss of smoothness, by adjusting only two parameter values representing the amount and extension of the deformation. Large deformation is always accomplished by repeating a minute deformation, thus maintaining the agreement of the two models. In order to evaluate the effectiveness of this model and deformation operator, we applied them to the positional adjustment of tooth cusps and the one-point contact formation to neighboring teeth in a dental 3-D CAD, Vocs1/B. In experiments of designing a lower first molar, tooth cusps was successfully modified semiautomatically into a required form, without loss of natural tooth contour, and the contact to a neighboring tooth was also created at a point without interference or loss of smoothness. Thus, our fusion model and partial deformation operator were both verified to be effective for detailed optimum design of a dental crown.
This theoretical investigation of the mechanics of the vascular endothelial cells that line the luminal side of blood vessels focused on two points. First, we formulated a hypothesis on the orientation of stress fibers, i.e., bundles of actin filaments, under cyclic deformation, and used numerical simulation to predict their orientation under various types of substrate deformation. Second, we created a finite element model of cultured endothelial cells adhering to a substrate, i.e., a silicone membrane, and a vascular endothelial cell on the luminal side of a vascular wall, and used finite element analyses to determine the stress and strain under various types of deformation. To predict the orientation of stress fibers, we hypothesized that they are oriented only in the direction in which the strain component in the fiber direction does not exceed the strain limit, either with maximum deformation of the substrate or during deformation of the substrate. We found that stress fibers have a minimum length during the process of substrate stretching, and investigated the importance of considering substrate deformation during cyclic stretching. The numerical simulation showed that the effect is small over the physiological range of cyclic deformation experienced in blood vessels. We also predicted the out-of-plane orientations of stress fibers during cycles of simple elongation, pure uniaxial stretching, and equibiaxial stretching. With cyclic equibiaxial stretching and the assumption of a certain cell height, the predicted orientation of stress fibers agreed with the reported range of orientation of the actin cytoskeleton. Second, using finite element modeling and analyses, we modeled a cell adherent to a substrate and a vascular endothelial cell on the luminal side of the vascular wall. We assumed that a cell consists of a nucleus and cytoplasm, and that both are incompressible, isotropic, hyperelastic materials. We also assumed that the bottom surface of the cell completely attaches to the substrate surface. The analyses of the stress and strain in the cell showed that the strain was greatest at the substrate and decreased in higher positions in the cell; the amount of strain in the top region of the cell depended on its shape. Moreover, the existence of the nucleus caused a complicated distribution of stress and strain in the cytoplasm. This result provides important information for predicting the orientation of stress fibers with nonuniform deformation of a cell.
Pedicle screw fixation is a typical surgical method for lumbar scoliosis using spinal instruments such as metal screws, connectors, and rods. In correcting scoliosis, this method is stronger than other methods. However, screw loosening or rod breaking happens occasionally. In this study, a whole lumbar and instruments were modeled by rigid bodies and springs in three dimensions. An abdominal pressure and muscle forces acted on this model. Inserted pedicle loads and corrected lumbar postures were estimated using this model. Five lumbar vertebrae and ten screws are modeled as rigid bodies, and soft tissues and rods are represented as springs. A ligament is modeled by a linear spring for a tensile deformation, and an intervertebral disc is simplified as three axial springs and three torsional springs. A screw and a connector are combined as one rigid body. The 40-mm-long screw passes through 29 mm of cancellous bone in the vertebral body, 9 mm of subcortical bone in the pedicle, and 2 mm of cortical bone on the surface of the vertebra. These three kinds of bone are replaced with pullout, radial, and torsional springs, respectively. Each spring constant is obtained from experimental data in the literature. The spring constant of the rod is assumed to be equivalent to the uniform column beam. Muscle forces in daily simple motions are obtained from the three-dimensional musculoskeletal model developed in the previous study. The simple motions are represented by a flexion of 30 degrees, a right lateral bending of 20 degrees, and a counterclockwise rotation of 10 degrees. The relative displacements (3 D.O.F. times 15 rigid bodies) and angles (3 times 15) are calculated applying the Runge-Kutta-Gill method. The initial load of the calculation is the gross weight of the upper body (0.25 kN) . The following three types of fixation for scoliosis with a Cobb’s angle of 30 degrees were simulated: (a) screws inserted into both sides of L1-5; (b) both sides of L1, 3, and 5; and (c) only the right side of L1-5. In the case of (a) and (b), the relative displacements and rotation angles are almost the same values, but pullout forces on L3 in (b) are close to the maximum limitation (1.0 kN) . In (c), the radial forces are very large. These estimates indicate that only case (a) can correct the scoliosis without loosening the screws. Additionally, since all the corrected postures are lumbar coupled motions, the above results show that three-dimensional models are available. The force of the connection along the rod between the connector and the rod needs 1.2 kN, and the moment around the rod needs 1.8 Nm in simple motions. In order to prevent this force and moment from exceeding a fatigue stress (Ti-6Al-4V: 0.54 GPa), the diameter of the rod should be at least 4.2 mm. This design is given only by modeling of the instruments and of the in vivo conditions such as an abdominal pressure and muscle forces.
The objectives of the current research were to clarify differences in beginners' and nurses' techniques for manipulation of a syringe and to propose methods of education for mastering quick and accurate techniques. In this paper, differences in techniques for manipulation of a syringe by nursing students and nurses are discussed from two perspectives. One is the effects of combining the syringe and injection needle in terms of the pressure in the syringe. The other is differences in methods of grasping the syringe. Based on these results, problems relating to adjustment of the force used by a nurse to manipulate a syringe and contact of the fingertip with the plunger become apparent. For measurement of the pressure in the syringe, a processed syringe is connected to a strain gauge type of force conversion device and strain is converted to pressure. For pressing of the plunger, hypodermic injection and extrusion of a drug solution into a vial were performed. For drawing of the plunger, collection of blood and suctioning from a plastic ampule were performed. With regard to pressure in the syringe, the maximum gauge pressure was large for a finer injection needle when the syringe was the same size in all techniques for nursing students as well as nurses. In simulated hypodermic injection, nursing students had a larger maximum gauge pressure with a larger syringe with the same injection needle. However, nurses considered the effects on the body and adjusted force so that the maximum gauge pressure did not increase. Because extrusion from a syringe and suctioning from an ampule are techniques that do not insert a needle in the body, nurses added substantial force and manipulated the syringe in a short period of time. In addition, limits for the addition of force were also considered. Based on classification of patterns of waveforms with regard to drawing of the plunger in suctioning from an ampule, nursing students often had multiple valley-shaped waveforms. Patterns produce waveforms like this because the syringe is passed from hand to hand. Differences in the appearance of waveforms due to the size of the syringe were noted for nurses, indicating separate use of methods of manipulating a syringe plunger as needed. With regard to the grasping of a syringe, nursing students grasp it so as not place their fingertip in contact with the plunger. This is because they are taught in class not to make contact with the plunger based on the perspective of preventing infection. However, a majority of nurses make contact with the plunger when drawing the plunger. That is, making contact with the plunger for drawing of the plunger is a technique in which the plunger is easy to manipulate. Nurses may have adopted an efficient method in clinical settings. Even if the stance that contact with the plunger should be avoided to prevent infection is learned, making contact with the plunger as experience is acquired leads one to conclude that education in techniques for manipulation of injections is vague. Having nurses change the techniques they have acquired is difficult, so sterile gloves should be worn as a general rule when manipulating a syringe. In the future, force added to the suction head of a syringe plunger will be measured and the relationship with internal pressure will be verified.
The purpose of this paper is introduction of simulated prostheses and orthoses which support research and development relevant to disabilities. Dederich in Germany (1970) devised a simple device for patients who are expected to receive limb amputation in a few days. By using the device, the patients can perform gait exercise before amputation and also can obtain preliminary knowledge about their prostheses. Taking a hint from that, we devised a simulated prosthesis which can be used for tests of newly developed prostheses and prosthetic components (1979). Using the simulated prosthesis, we studied basic problems of the sensory feedback system for an artificial limb and also evaluated effects of the system. Furthermore, we used the simulated prosthesis for tests of a load-actuated brake knee. Many kinds of simulated prostheses and orthoses have previously been developed by other researchers. Almost all of them are introduced in this paper. The merits of the simulated prostheses and orthoses that can be used by healthy, instead of disabled, persons are reductions in both cost and manufacturing time for every subject. These advantages of simulated prostheses and orthoses are particularly suited to research carried out by undergraduate and graduate students in an engineering university.
This paper describes the optimization of hip joint characteristics of a hip disarticulation prosthesis. We attempted to optimize the characteristics for improved ability to walk using our passive walking model, which can walk by utilizing mechanical properties of rigid body segments and joint resistance. In order to understand how the hip disarticulation prosthesis gait is performed, we interviewed two hip disarticulation prosthesis users. The interviews showed that practical gait in daily life is different from the gait at a training stage. These two types of gaits were named “practical gait” and “training gait.” Users indicated that the training gait velocity was slower than that of the practical gait. Moreover, in the practical gait the heel contact on the prosthesis side was more natural in comparison with the training gait. Gait measurements showed that the lumbar angle pattern has rapid extension and lateral bending involving the swing prosthesis in training gait. Step length on the sound side is in agreement despite the different types of gait. In practical gait, step length on the sound side agrees with that on the prosthesis side. Gait velocity in practical gait compared with training gait was 28% faster with subject 1 and 7% faster with subject 2. Therefore, practical gait has an improved gait velocity by swinging the prosthesis, as step length on each side is the same. Motion of prosthesis is achieved not by sound lower extremities but by lumbar flexion, extension, and lateral bending. Furthermore, practical gait reduces lumbar motion as much as possible, and reduces muscle force around the lumbar area. We developed a passive swing model by applying the above characteristics. This model is composed of eight rigid segments: upper torso, pelvis, upper extremities, thigh, shank-foot. Each joint has passive resistance by ligament. The sound hip and lumbar joint have active moments by muscle, which were obtained from measurement. The objective function for practical gait is defined by the following parameters: (1) difference of each step length, (2) amplitude of active moments, (3) difference of cycles between gait patterns and active moments. As these parameters are minimized, postures of segments, translational velocity, angular velocities and cycle, and amplitude of active moment are recorded. In comparison of subjects, calculated motion patterns on the prosthesis side were well in agreement, so this model is available to estimate hip joint characteristics. When this model simulates a condition of the current hip elastic characteristic weakened by half, the gait velocity is 6% faster and amplitude of lumbar lateral bending moment is reduced 26%. For this reason, weakening current elastic characteristics around the hip joint can easily control the swing of the prosthesis. As a result, adjustment of the hip elastic characteristic can improve the walk capability.
Several mouse emulator devices are commercially available for patients with high-level cervical cord injury (CCI), muscular dystrophy, and rheumatoid arthritis. These include head mounting pointers which linearly convert the 2-dimensional deviation of head motion to the 2-axis movements of the cursor. Limitations of inherent accuracy of the neck movement controllability restrict the use of these pointers to people with a good range of motion of the trunk and neck. Other mouse emulators utilize a miniature 2-dimensional position sensor which can be activated by mouth, then convert the information to the cursor movements. When the transformation is from 2-dimensional deviations to the position of the cursor, a problem similar to the head mounting pointers arises. When the 2-dimensional deviation is converted to the velocity of the cursor, the problem is solved. However, the currently available devices of this last type have other problems, e.g., overshoot and drift of the cursor during no input. The purpose of this study was to develop an inexpensive mouse emulator device utilizing a mini joystick and analog pressure sensor, and to test its clinical utility in short-term experiments and middle-term field tests conducted by volunteer monitors. The study also aimed to combine this mouse emulator with commercially available automatic Japanese voice recognition software to enable those who cannot use their fingers for striking keyboards. The new mouse emulator, named “Joystick,” converts the 2-dimensional angular deviation nonlinearly, i.e., stepwise parabolically, to the velocity of the cursor, and also provides a dead movement zone and automatic tracking of mechanically neutral position to prevent drift of the cursor during a resting state. A thorough investigation was made to find the automatic voice recognition software best suited for the present purpose. Japan IBM’s Via Voice with ATOK15 was selected. Four CCI patients and four healthy subjects participated in the short-term evaluation of the device. The first task was to control the movement of the cursor around the monitor, and to drag and drop certain portions of the text. The second task was to activate Word, define text format, input predetermined text, revise it, and store it as a file with a name. The performance of each subject using the new device was compared with the performance of one C4 CCI subject using a conventional mouth stick and a track ball. The results were promising. Twelve volunteer monitors participated in the mid-term field evaluation of the device, and 6 out of 9 monitors wanted to buy the device after the 2- to 4-week monitor period, which proved that the device is useful for a large part of the subject population at which the present study was aimed.
Body care motions apply a large amount of stress on caregivers’ muscles and spines, so most of them suffer from low back pain. One of the major factors of low back pain is the low back muscular load to keep the deep flexion posture. This study concerned development of a suit-type back muscle supporter named “the care suit,” which reduces low back load. Elastic fiber belts (support lines) are arranged on the back and leg parts of the suit. The support lines are relaxed so as not to interfere with daily trunk motion, arm motion, walking, and sitting motion, but to exert tensile force and extension moment in the deep flexion posture. The care suit is a two-piece design to improve comfort and convenience. To optimize the layout of the support lines we developed a small reel-type device to measure body surface deformation. As the result of measurement by this device and a system for posture measurement during several motions, the back support lines are arranged in an x-shape from the side neck point to the point internally dividing the Jacoby-line at a ratio of 1 to 2. The leg support lines branch at the rear face of the thigh and are attached to the apex of the patella. The maximum tension of support lines is limited by the user’s shoulder pain to 140 N for males and 85 N for females. The effect of the care suit was evaluated by electromyograms of back muscles. The action potential in the deep flexion posture was 25% decreased. In comparison with the conventional corset, the effect of the care suit for back muscle was equal, but the care suit is superior in that it does not interfere with flexion motion. The lumbar joint muscular moment during a diaper change operation was calculated from body posture through a rigid body link model. The results of this calculation showed that the stored load during the operation was decreased by 30% by the care suit. Furthermore the summation of intervertebral disk compressive force was reduced by 15% during the operation. Therefore the care suit is effective for reduction of not only continuous muscular load but also spinal load. Practical use by caregivers also resulted in good evaluations as it reduced continuous muscle load for a diaper change operation, bed making operation, etc. Conclusively, the low back load during body care motions can be reduced by the care suit developed in this research. This care suit is under patent application.