We assessed the characteristics of receptor response for the purpose of developing a vibration stimulator and stimulation methods aiming to improve standing balance. Vibration detection thresholds and the degree to which the site of stimulation matches the site of perception were examined in 22 feet of 11 healthy adults (21.0±1.8 years). Stimulation was applied at a frequency of 225Hz using an original vibration stimulator comprising a frequency oscillator and piezoelectric element. Threshold was determined by averaging measurements obtained by ascending and descending methods. In the ascending method, the applied voltage was measured at the point at which vibration could be perceived, and in the descending method, the applied voltage was measured at the point at which vibration could no longer be detected. The concordance between the site of stimulation and the site of perception was determined by asking subjects to indicate the site at which vibration was perceived using the ascending method. Vibration thresholds were 6.6±3.6V at the base of the fifth metatarsal bone, 5.5±3.3V at the navicular bone, 7.8±3.8V at the lateral malleolus, 6.5±3.1V at the medial malleolus, and 11.9±4.5V at the head of the fibula. A significantly higher threshold was observed at the head of the fibula [F(4,105)=10.186, p<.001]. The site of stimulation and the site of perception matched, were nearby, and were unclear in 11, 8, and 3 feet, respectively, at the base of the fifth metatarsal bone;9, 9, and 4 feet, respectively, at the navicular bone;9, 7, and 6 feet, respectively, at the lateral malleolus;10, 4, and 8 feet, respectively, at the medial malleolus;and 9, 0, and 13 feet, respectively, at the head of the fibula. The degree of concordance was ‘unclear’(p<.05) at the base of the fifth metatarsal bone and ‘nearby’(p<.01) at the head of the fibula in a significantly smaller number of subjects, and was ’unclear’ at the head of the fibula in a significantly larger number of subjects. These results probably reflect the influence of the distribution of receptor density and vibration transmission to the surrounding soft tissues.
Continuous sensing of respiratory volume is valuable for evaluating exercise ability and managing health condition. However, continuous sensing of respiratory volume without interfering with exercise and breathing is difficult using conventional methods. This research proposed a novel sensing method of respiratory volume using electromagnetic induction coils placed on ventral and dorsal aspects of the chest. The induced signal changed due to chest movement from breathing, and was used for estimating respiratory volume. This paper revealed experimentally the effective frequency of the electromagnetic wave for achieving high sensitivity. By measuring and analysing the output signal of the proposed system and chest displacement using an optical motion tracker during rest and stepping exercise, we showed that the system can detect chest displacement caused by respiration with adequate accuracy. An experiment in which we measured the output of the proposed system and the respiratory volume using a calibrated owmeter showed that our system can estimate the respiratory volume within an error of 0.228L.
In this study, we examined the relationship between performance and muscle strength of the upper limbs. The muscle strength of the upper limbs is a determining factor of performance for wheelchair marathon racers. Ten wheelchair marathon racers participated in the study, and they were classified into two groups based on their official personal records:six subjects were classified into Group A (<100 min, or 1 hour 40 min) and four subjects were classified into Group B (≥100 min, or 1 hour 40 min). The isokinetic muscle strength during extension and flexion (angular velocity of 60 and 240°/s) of both elbow was measured. The peak torque and peak work of extension for the right elbow (at both angular velocities), the peak work of extension averaged for two elbows (at an angular velocity of 240°/s), the peak torque and peak work of flexion averaged for two elbows (at an angular velocity of 240°/s), the torque acceleration energy of extension and flexion averaged for two elbows (at both angular velocities) and the total work of extension and flexion averaged for two elbows (at an angular velocity of 240°/s) were higher in Group A than in Group B. These results suggest that the maximum muscle strength, instantaneous force, and muscular endurance are the characteristics of the muscle strength of upper limbs which are necessary to ensure high performance for a wheelchair marathon racer.
During hemodialysis, blood pressure decreases to a state of hypotension in some patients, and temporary measures to increase blood pressure are given. Typically, fluid replacement, medication, and passive leg raising are used. As each strategy has pros and cons, we attempted to find simple and fast-acting measures. Fifteen healthy men participated in this study. Continuous blood pressure, electrocardiograms, stroke volume, and plethysmograms were obtained at various time intervals. The protocol consisted of 15 min of acclimation in a supine position, resting for 5 min, performance of one of the methods to increase blood pressure for 5 or 15 min, and then resting for 1 min. This protocol was performed repeatedly for different methods in random order. The following methods were selected:passive one-leg-bending exercise (5 min), using a leg massage machine (15 min), applying medical stocking (15 min), and talking (5 min). Systolic blood pressure increased significantly only for talking. Diastolic blood pressure also tended to increase for talking, although not significantly. Further, heart rate increased significantly for talking only. Heart rate increased temporarily for passive one-leg-bending exercises for 5 min. Stroke volume tended to decrease for all the methods but not for control. Total peripheral resistance, which was calculated from blood pressure, stroke volume and HR, increased significantly for using a massage machine at the beginning of massage. Pulse wave amplitude tended to decrease for talking. Overall, talking increased heart rate and consequently increased systolic blood pressure, although none of the methods increased stroke volume. These results identified talking as a feasible and fast-acting method to manage hypotension during dialysis.
Second harmonic generation (SHG) microscopy allows in situ visualization of dermal collagen fibers in human skin due to its selectivity for collagen fiber. It is an attractive tool because it does not require staining, is non-invasiveness, and has high-resolution 3D imaging capability. However, its practical use in the dermatological field is still limited due to the bulky and complicated setup. Incorporation of fiber transmission of the laser light and a compact probe head into the microscope would enhance its compactness, robustness, flexibility, and hence convenience. In this study, we constructed a photonic-crystal-fiber (PCF) -coupled, hand-held SHG microscope for in situ monitoring of collagen fibers in human skin. By transmitting pulse light from a mode-locked Cr:Forsterite laser source via a large mode area PCF, it was possible to deliver pulse light with median wavelength of 1250nm and pulse width of 80 fs to the SHG microscope, without the need for external dispersion compensation. Components of a SHG microscope;galvano mirrors, relay lenses, objective lens, dichroic mirror, optical filters, and photon-counting photomultiplier, were mounted into a hand-held probe head (width=310mm, height=150mm, and depth=50mm), which is only 2% of the size of a conventional SHG microscope. We compared the imaging performance between the conventional SHG microscope and the hand-held SHG microscope, and confirmed comparable performance of the two. Finally, we demonstrated in situ visualization of collagen fibers in human skin using the hand-held SHG microscope with a compact probe head coupled to PCF. The hand-held SHG microscope greatly enhances the operability of in situ measurement of the human skin. The novel system will be a powerful tool for various dermatological applications.
Collagen fibers in the dermis are closely related to skin aging because collagen is one of structural proteins and hence plays an important role to determine the morphology and mechanical properties of the skin. Although histological and/or biochemical studies have been used to reveal the age-related decrease and disorganization of dermal collagen fibers, such invasive methods cannot be used for simple assessment or serial monitoring of skin aging. Therefore, there is a considerable need for non-invasive assessment method of skin aging. Recently, second-harmonic-generation (SHG) microscopy has attracted attention for in situ visualization of human dermal collagen fibers. Due to its specific collagen selectivity without the need for staining, non-invasiveness, and high-resolution 3D imaging capability, collagen fiber structure can be visualized as high-contrast SHG image in situ. However, extraction of quantitative parameters reflecting the collagen fiber structure from SHG image presents difficulties. In this article, we applied two-dimensional auto-correlation analysis to SHG images of dermal collagen fibers in human cheek skin. The collagen fiber structure index obtained from the analysis decreased significantly with aging. Furthermore, we confirmed a moderate correlation between the collagen fiber structure index and skin elasticity measured by a Cutometer®.This correlation indicates that the dermal collagen fiber structure plays an important role to determine skin elasticity. In other words, the auto-correlation analysis of SHG image can be used for evaluation of skin elasticity from the viewpoint of dermal collagen. The proposed method will be a powerful tool in the fields of skin cosmetics and anti-aging dermatology.