A comprehensive three-dimensional dynamic model of the human head and trunk for estimating lumbar and cervical joint torques and forces from upper body kinematics.

Linked-segment representations of human body dynamics have been used extensively in biomechanics, ergonomics, and rehabilitation research to systemize thinking, make predictions, and suggest novel experiments. In the scope of upper body biomechanics, these models play an even more essential role as the human spine dynamics are difficult to study in vivo. No study exists to date, however, that specifically disseminates the technical details of a comprehensive three-dimensional model of the upper body for the purpose of estimating spinal joint torques and forces for a wide range of scenarios. Consequently, researchers are still bound to develop and implement their own models. Therefore, the objective of this study was to design a dynamic model of the upper body that can comprehensively estimate spinal joint torques and forces from upper body kinematics. The proposed three-dimensional model focuses on the actions of the lumbar and cervical vertebrae and consists of five lumbar segments (L1 to L5), the thorax, six cervical segments (C2 to C7), and the head. Additionally, the model: (1) is flexible regarding the kinematic nature of the spinal joints (free, constrained, or fixed); (2) incorporates all geometric and mass-inertia parameters from a single, high-resolution source; and (3) can be feasibly implemented via different inverse dynamics formulations. To demonstrate its practicality, the model was finally employed to estimate the lumbar and cervical joint torques during perturbed sitting using experimental motion data. Considering the growing importance of mathematical predictions, the developed model should become an important resource for researchers in different fields.

Acute effects of exercise on posture in arthritic patients.

In this study, we aimed to investigate the acute effects of exercise on postural measures in arthritic patients. We obtained posturographic measurements of 8 women with lower extremity arthritis for 30 s before and after a 60-min aquatic exercise. The center of pressure (COP) was recorded while the volunteers were in an upright position with their eyes open. The time domain measures and the frequency domain measures of the COP time series in the anterior-posterior (AP) and medial-lateral (ML) directions were calculated. In addition, the frequency domain measures were calculated for the COP velocity time series. A paired T-test revealed no significant differences in any time domain measures between pre- and post-exercise; however, there were significant decreases in the 95% power frequency of the COP in the AP direction (0.834 ± 0.296 to 0.627 ± 0.230 Hz, p=0.027) for the frequency domain measures. For the velocity time series, the mean power frequency in both the AP (1.47 ± 0.528 to 1.22 ± 0.360 Hz, p=0.047) and ML (1.28 ± 0.245 to 1.13 ± 0.151 Hz, p=0.022) directions, and the 95% power frequency in the ML direction (3.41 ± 0.653 to 2.96 ± 0.468 Hz, p=0.038) decreased significantly in the post-exercise condition. This study reports that a single session of exercise has a subtle but detectable acute effect on postural balance in arthritic patients.

Video game-based neuromuscular electrical stimulation system for calf muscle training: a case study.

A video game-based training system was designed to integrate neuromuscular electrical stimulation (NMES) and visual feedback as a means to improve strength and endurance of the lower leg muscles, and to increase the range of motion (ROM) of the ankle joints. The system allowed the participants to perform isotonic concentric and isometric contractions in both the plantarflexors and dorsiflexors using NMES. In the proposed system, the contractions were performed against exterior resistance, and the angle of the ankle joints was used as the control input to the video game. To test the practicality of the proposed system, an individual with chronic complete spinal cord injury (SCI) participated in the study. The system provided a progressive overload for the trained muscles, which is a prerequisite for successful muscle training. The participant indicated that he enjoyed the video game-based training and that he would like to continue the treatment. The results show that the training resulted in a significant improvement of the strength and endurance of the paralyzed lower leg muscles, and in an increased ROM of the ankle joints. Video game-based training programs might be effective in motivating participants to train more frequently and adhere to otherwise tedious training protocols. It is expected that such training will not only improve the properties of their muscles but also decrease the severity and frequency of secondary complications that result from SCI.

Positive effect of balance training with visual feedback on standing balance abilities in people with incomplete spinal cord injury.

OBJECTIVES: (1) To evaluate the learning potential and performance improvements during standing balance training with visual feedback (VBT) in individuals with incomplete spinal cord injury (SCI) and (2) to determine whether standing static and dynamic stability during training-irrelevant tasks can be improved after the VBT. SETTING: National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan. METHODS: Six participants with chronic motor and sensory incomplete SCI who were able to stand for at least 5 min without any form of assistive device performed the VBT, 3 days per week, for a total of 12 sessions. During the training, participants stood on a force platform and were instructed to shift their center of pressure in the indicated directions as represented by a cursor on a monitor. The performance and the rate of learning were monitored throughout the training period. Before and after the program, static and dynamic stability was assessed. RESULTS: All participants showed substantial improvements in the scores, which varied between 236±94 and 130±14% of the initial values for different exercises. The balance performance during training-irrelevant tasks was significantly improved: for example, the area inside the stability zone after the training reached 221±86% of the pre-training values. CONCLUSION: Postural control can be enhanced in individuals with incomplete SCI using VBT. All participants showed substantial improvements during standing in both game performance and training-irrelevant tasks after the VBT.

Effects of 20-day bed rest with and without strength training on postural sway during quiet standing.

AIM: To examine the effect of unweighting as a possible contributory factor to a reduced calf muscle volume on postural sway during quiet standing, changes in postural sway following bed rest with or without strength training were investigated. METHODS: Twelve young men participated in a 20-day bed-rest study. Subjects were divided into a non-training group (BR-Con) and a strength training group (BR-Tr). For the BR-Tr group, training was comprised of dynamic calf-raise and leg-press exercises to maintain the muscle volume of the plantar flexors. Before and after bed rest, subjects maintained quiet standing in a barefoot position on a force platform with their eyes open or closed. During the quiet stance, foot centre-of-pressure (CoP) and the mean velocity of CoP was calculated. Muscle volume of the plantar flexors was computed using axial magnetic resonance images of the leg. RESULTS: After the bed-rest period, the muscle volume decreased in the BR-Con group but not in the BR-Tr group. The mean velocity of CoP as an assessment of postural sway, however, increased in both groups. These results indicate that the strength training during bed rest cannot counteract the increase in postural sway. CONCLUSION: We concluded that postural sway increases following 20 days of bed rest despite maintenance of the muscle volume of plantar flexors as the main working muscles for the human postural standing.

Effects of equivolume isometric training programs comprising medium or high resistance on muscle size and strength.

Isometric unilateral elbow extension training was conducted for 10 weeks (3 times per week) on 12 young adult men to investigate the effects of equivolume exercise programs with different combinations of intensity and duration on the morphological and functional aspects of the triceps brachii muscle. One group of 6 subjects trained by developing maximal voluntary contraction (MVC) for 6 s per set with 12 sets per session (100%G), while the other group of 6 subjects trained at 60% of MVC for 30 s per set with 4 sets per session (60%G). Training significantly increased the muscle volume ( V(m)), fascicle pennation angle of the triceps brachii, and torque output during concentric and eccentric elbow extensions at three constant velocities of 0.52, 1.57, and 3.14 rad.s(-1) as well as under the training condition, with no significant differences in the relative gains between the two programs. However, 100%G showed significantly greater V(m) than 60%G after training, when V(m) before training was normalized. Thus, only 60%G significantly increased the ratio of torque to V(m) developed in the eccentric actions at the three velocities and concentric action at 1.57 rad.s(-1). The present results indicate that isometric training programs of medium resistance/long duration and high resistance/short duration produce different effects on V(m) and dynamic strength relative to V(m), even if the training volume is equalized between the two protocols.

Fractal correlation of initial trajectory dynamics vanishes at the movement end point in human rapid goal-directed movements.

Many researchers have investigated the variability of discrete goal-directed movements. However, a possible time-dependent property for them has been ignored. We investigated the time-dependent property of the kinematic variability in human rapid goal-directed movements by using fractal analysis. The variability of the peak acceleration had fractal time correlation characterized by a non-negligible frequency-spectral exponent (beta=0.3). This beta value was reduced at the peak velocity (beta=0.2) and nearly reached zero at the peak movement amplitude, indicating that the variability became white noise with no time correlation. A similar result was observed in the progress of the positional trajectory. The functional significance of this phenomenon for the goal-directed task demand is discussed.

Reciprocal angular acceleration of the ankle and hip joints during quiet standing in humans.

Human quiet standing is often modeled as a single inverted pendulum rotating around the ankle joint, under the assumption that movement around the hip joint is quite small. However, several recent studies have shown that movement around the hip joint can play a significant role in the efficient maintenance of the center of body mass (COM) above the support area. The aim of this study was to investigate how coordination between the hip and ankle joints is controlled during human quiet standing. Subjects stood quietly for 30 s with their eyes either opened (EO) or closed (EC), and we measured subtle angular displacements around the ankle (thetaa) and hip (thetah) joints using three highly sensitive CCD laser displacement sensors. Reliable data were obtained for both angular displacement and angular velocity (the first derivative of the angular displacement). Further, measurement error was not predominant, even among the angular acceleration data, which were obtained by taking the second derivative of the angular displacement. The angular displacement, velocity, and acceleration of the hip were found to be significantly greater (P<0.001) than those of the ankle, confirming that hip-joint motion cannot be ignored, even during quiet standing. We also found that a consistent reciprocal relationship exists between the angular accelerations of the hip and ankle joints, namely positive or negative angular acceleration of ankle joint is compensated for by oppositely directed angular acceleration of the hip joint. Principal component analysis revealed that this relationship can be expressed as: thetah=gammathetaa with gamma=-3.15+/-1.24 and gamma=-3.12+/-1.46 (mean +/-SD) for EO and EC, respectively, where theta is the angular acceleration. There was no significant difference in the values of y for EO and EC, and these values were in agreement with the theoretical value calculated assuming the acceleration of COM was zero. On the other hand, such a consistent relationship was never observed for angular displacement itself. These results suggest that the angular motions around the hip and ankle joints are not to keep the COM at a constant position, but rather to minimize acceleration of the COM.

A simple quantitative in vitro macrophage migration assay.

An in vitro macrophage chemotaxis model using mouse peritoneal non-elicited resident macrophage cells and chemotaxins containing mediators of non-specific elicitors such as oyster glycogen or sodium caseinate has been described. Macrophage cells accumulation in mouse peritoneal cavity was maximum at 48 hr after injecting (i.p.) oyster glycogen (2.5%) or sodium caseinate (12%), 0.5 ml/mouse. Chemotaxins containing mediators were prepared from these mice by peritoneal lavage and termed as routine 'diluted' cocktail and 'concentrated (3 times)' cocktail. Chemotaxis assays were carried out in a modified Boyden chamber using a 48-well microchemotaxis assembly. In vitro results showed higher macrophage chemotaxis response against the 'concentrated' cocktails as compared to routine 'diluted' cocktail. Macrophages exhibited cell density dependent increase in the responsiveness to chemoattractant and macrophage cell density of 4 x 10(6) per ml concentration in the upperwell was found to be optimum. Macrophage responsiveness was seen better with sodium caseinate cocktail as compared to oyster glycogen in vitro as well as in vivo. DMSO (Dimethyl Sulphoxide) solvent (0.25% conc.) did not interfere with normal macrophage chemotaxis. Both CO2 incubator (5% CO2 in air) and BOD incubator with humidified chamber favoured chemotaxis. In vitro test system described can be used as a model to study the effect of anti-inflammatory compounds directly on the macrophage chemotaxis.

A comparative study of experimental caecal amoebiasis and the evaluation of amoebicides.

Caecal amoebiasis models (mouse, hamster and rat) were compared for amoebic infection and chemotherapeutic evaluation using a pathogenic strain of Entamoeba histolytica of human origin. Caecal infection in the hamster was of the acute type, with a large number of amoebae in the caecal tissue, whereas the amoebae in rats were seen in the lumen, on the mucosal surface. Amoebic lesions in the mouse caecum were of moderate severity. The mouse model responded to both metronidazole (tissue amoebicide) and diloxanide furoate (luminal amoebicide), whereas the hamster model only responded well to metronidazole and the rat model only to diloxanide furoate. Using the mouse as a primary screening model, a new oxadiazole compound, BTI 2405E, was found to have tissue and luminal amoebicidal activity. In rodent caecal models, a single dose of BTI 2405E was found to be more effective than one of metronidazole or diloxanide furoate. The mouse model appears to be the most useful for primary screening of anti-amoebic compounds.

Comparative pharmacokinetics and amoebicidal activity of metronidazole and satranidazole in the golden hamster, Mesocricetus auratus.

The pharmacokinetic properties of metronidazole and satranidazole were studied in the golden hamster (Mesocricetus auratus), at a dose of 80 mg/kg po. Blood and liver samples were collected at frequent time intervals and assayed for metronidazole and satranidazole by HPLC. Satranidazole exhibited significantly higher plasma concentrations than metronidazole at 1 and 2 h post-dose, but the comparative Cmax values were not significantly different. The satranidazole plasma elimination half-life of 1.01 h was significantly shorter than the corresponding metronidazole half-life of 3.62 h. The comparative liver pharmacokinetic parameters Cmax, Tmax and T1/2 did not differ significantly. Satranidazole however exhibited significantly higher liver concentrations at 1 h post-dose and Cmax and AUC0-infinity values were approximately 35% higher. The in-vivo amoebicidal activity of both compounds was evaluated in the acute hamster hepatic model of amoebiasis. Both metronidazole and satranidazole were administered as single graded doses po, and their dose-response profiles were characterized. Satranidazole demonstrated significantly greater amoebicidal activity than metronidazole with an ED50 value of 19.5 mg/kg, compared to an ED50 value of 45 mg/kg for metronidazole. These data suggest that higher plasma and liver concentrations of satranidazole and greater intrinsic potency probably contribute to superior amoebicidal activity in the hamster model of hepatic infection.

Activity of a new oxadiazole compound, against experimental infections with Entamoeba histolytica and Giardia lamblia in animal models.

BTI 2286E(+/-)-E-3-(4-methylsulphinylstyryl)-1,2,4-oxadiazole has demonstrated potent amoebicidal activity in a single-dose treatment against Entamoeba histolytica infection in the livers of golden hamsters and the caeca of mice, hamsters and rats. It has intra luminal activity against Entamoeba criceti, a natural infection in golden hamster, and anti-giardial activity against Giardia lamblia infection in suckling mice. BTI 2286E is more potent than metronidazole in extra intestinal, intra luminal amoebiasis models and has significant advantages in that it is non-mutagenic in the Ames test and has a shorter duration of effective treatment.