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We conducted two experiments to determine how differences in muscle contraction levels, muscle contraction types, and movement duration affect degree of postexercise depression (PED) after non-exhaustive, repetitive finger movement. Twelve healthy participants performed repetitive abduction movements of the right index finger at 2 Hz. In experiment 1, we examined the effects of muscle contraction levels at 10, 20, and 30% maximum voluntary contraction and the effects of muscle contraction types at isotonic and isometric contraction. In experiment 2, we examined the effects of movement duration at 2 and 6 min. Motor-evoked potentials (MEPs) were recorded from the right first dorsal interosseous muscle before movement tasks and 1-10 min after movement tasks. MEP amplitudes after isotonic contraction tasks were significantly smaller than those after isometric contraction tasks and decreased with increasing contraction levels, but were independent of movement duration. This study demonstrated that the degree of PED after non-exhaustive repetitive finger movement depended on muscle contraction levels and types. Thus, the degree of PED may depend on the levels of activity in the motor cortex during a movement task. This knowledge will aid in the design of rehabilitation protocols. [ABSTRACT FROM AUTHOR]

Nitsche and Paulus (2000) first described the efficacy of transcranial direct current stimulation (tDCS) for functional modulation of the human motor cortex. Since then, tDCS has been an increasingly useful technique for noninvasive brain stimulation that can be used not only for examining cortical function in healthy subjects, but also for facilitating treatments for various neurological disorders. The advantages of tDCS over other noninvasive brain stimulation methods include its ease of use, large electrode size allowing effect over a larger neural network, sham mode allowing controlled experiments and randomized controlled clinical trials. In this symposium, we plan to introduce the three points of studies about plastic changes of motor association cortex excitability induced by tDCS. 1) Transcranial direct current stimulation over the motor association cortex induces plastic changes in the ipsilateral primary motor and somatosensory cortices 2) The effects of cathodal transcranial direct current stimulation of the supplementary motor area on the function of anticipatory postural adjustments 3) Corticomotor excitability induced by anodal transcranial direct current stimulation with and without non-exhaustive movement. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the influence of passive movement repetition frequency at 1.5-Hz and 1-Hz on changes in cerebral oxygenation and assess the temporal properties of these changes using functional near-infrared spectroscopy (fNIRS). No significant differences in systemic hemodynamics were observed between resting and passive movement phases for either 1.5-Hz or 1-Hz trial. Changes in cortical oxygenation as measured by fNIRS in bilateral supplementary motor cortex (SMC), left primary motor cortex (M1), left primary somatosensory cortex (S1), and left posterior association area (PAA) during passive movement of the right index finger revealed greater cortical activity at only 1.5-Hz movement frequency. However, there were no significant differences in the time for peak oxyhemoglobin (oxyHb) among regions (bilateral SMC, 206.4 ± 14.4 s; left M1, 199.1 ± 14.8 s; left S1, 207.3 ± 9.4 s; left PAA, 219.1 ± 10.2 s). Therefore, our results that passive movement above a specific frequency may be required to elicit a changed in cerebral oxygenation, and the times of peak 1oxyHb did not differ significantly among measured regions. [ABSTRACT FROM AUTHOR]

Primary motor cortex (M1) excitability can be assessed using transcranial magnetic stimulation (TMS) and can be modulated by a conditioning electrical stimulus delivered to a peripheral nerve prior to TMS. This is known as afferent facilitation (AF). The aim of this study was to determine whether AF can be induced by digital nerve stimulation and to evaluate the relation between the interstimulus interval (ISI) required for AF and the latency of the E2 component of the cutaneomuscular reflex (CMR) and the prominent somatosensory evoked field (SEF) deflection that occurs approximately 70 ms after digital nerve stimulation (P60m). Stimulation of the digital nerve of the right index finger was followed, at various time intervals, by single-pulse TMS applied to the contralateral hemisphere. The ISI between digital nerve stimulation and TMS was 20, 30, 40, 50, 60, 70, 80, 100, 140, 180, 200, or 220 ms. Single-pulse TMS was performed alone as a control. SEFs were recorded following digital nerve stimulation of the index finger, and the equivalent current dipole of prominent deflections that occurred around 70 ms after the stimulation was calculated. CMRs were recorded following digital nerve stimulation during muscle contraction. Motor evoked potentials (MEPs) were facilitated at an ISI between 50 and 100 ms in 11 of 13 subjects, and the facilitated MEP amplitude was larger than the unconditioned MEP amplitude (p < 0.01). There was no significant correlation between the ISI at which AF was maximal and the latency of the P60m component of the SEF (r = <0.50, p = 0.12) or the E2 component of the CMR (r = <0.54, p = 0.88). These results indicate that the precise ISI required for AF cannot be predicted using SEF or CMR. [ABSTRACT FROM AUTHOR]

Abstract  Metabolic and circulatory disorders such as diabetes and hypertension are associated with cardiac dysfunction. Research on these types of experimental animals has observed abnormal calcium (Ca2) sparks and waves in cells; a potential mechanism altering excitation–contraction (e–c) coupling in the myocardium. The e–c coupling depends on the intricate spatial relationship between the sarcolemma and sarcoplasmic reticulum calcium release units (CRU’s). The objective of this study was to assess for a presence or absence of abnormalities in CRU’s from type II diabetic and hypertensive rat models. Myocardial tissue underwent perfusion fixation followed by selective staining of the CRU’s and the features observed using a high voltage electron microscope. Results revealed both diabetic groups had significant increases in body weight, a tendency toward an enlarged heart, and a significant disruption of the CRU’s and displacement of transverse (t)-tubules in a longitudinal direction. The hypertensive model characteristically showed a dramatic increase in heart size, a significant increase in disrupted CRU’s and a tendency towards longitudinal t-tubule orientation. We propose the two disorders of diabetes and hypertension have a similar etiology of cardiomyopathy resulting, in part, from an increase in the number of incomplete CRU’s, due to a morphological change in the architecture and orientation of the t-tubules. These architectural changes could potentially explain the impaired calcium signaling previously observed in diabetic and hypertensive cardiomyopathy. [ABSTRACT FROM AUTHOR]

Abstract  The transverse (t)-tubule is responsible for the rapid inward spread of excitation from the sarcolemma to the inside of the muscle fiber, and the compartments of the t-tubule become highly and regularly organized during development. Although it is known that skeletal muscle fibers lengthen by adding sarcomeres at the myotendinous junction (MTJ) during development, no specific model exists for the assembly of new t-tubule architecture at the MTJ. We performed an electron-microscopic examination of the assembly of t-tubule architecture at the MTJ in developing rat skeletal muscle fibers. Although the longitudinally oriented t-tubule elements represent only a small fraction of the total t-tubule system in adult muscle fibers, they were observed at both A-band and I-band regions of middle and MTJ regions in early developmental stages, and gradually disappeared in the middle regions of muscle fibers during development; however, they remained in the MTJ even in adult muscle fibers. The frequency of pentads and heptads (two or three t-tubule elements with three or four elements of terminal cisternae, closely aligned with terminal cisternae of the sarcoplasmic reticulum) decreased during development, with sudden decrease between 7 and 10 weeks of age in the middle regions. Interestingly, although the frequency of decrease appeared to be higher in the middle region than in the MTJ regions in early (3- to 7-week) development, this pattern reversed, and the frequency of decrease was higher in the MTJ in later development (after 10 weeks of age). The MTJ maintained the features of immature membrane systems involved in e-c coupling much longer than the middle region of the fiber during development. The assembly of t-tubule architecture during postnatal development thus follows different processes in the middle and MTJ regions of skeletal muscle fibers. [ABSTRACT FROM AUTHOR]

Purpose: The present study aimed to examine the effects of short-lasting high-intensity interval exercise (SHIIE) under hypoxic conditions on metabolic risk markers, such as glucose tolerance, blood lipid, and body composition. Methods: Twenty healthy male subjects (mean age, 22±1 years) who were matched for baseline measurements were randomized into two groups: a normoxic group (NORM; n=10); and a hypoxic group (HYPO; n= 10). The SHUT consisted of ten 15s bout at 175%VO2max with 10s active rest at 50%VO2max between each bout and was done twice a day, 4 days a week, for 4 weeks. The HYPO group had the training under hypobaric hypoxic conditions corresponding to 2500m above sea level. Before and after the training, blood lipid, body mass, %body fat, and preperitoneal fat thickness were measured. Also, 3-h oral glucose tolerance test (OGTT) was conducted. Results: After the 4 weeks of training, body mass, %body fat, and preperitoneal fat thickness were decreased significantly in both groups. On the other hand, no significant changes were found in blood lipid in both groups. Furthermore, neither area under the curve of blood glucose concentrations nor insulin concentrations during OGTT significantly changed. Discussion: These results suggest that SHIIE under hypoxic conditions, used in this study, does not induce necessarily improvements of metabolic risk markers more effectively, when compared to that performed under a normoxic condition. [ABSTRACT FROM AUTHOR]

Purpose: Present study aimed to examine the effects of active versus passive rest between bouts on metabolic profile of high-intensity interval exercises (HUE). Methods: Eight healthy male adults (21±1 yrs) performed HUE with active rest (AR) at an intensity corresponding to 50%VO;>max or passive rest (PR) on bicycle ergometer. The HUE consisted of 15s bout at an intensity corresponding to 175%VC>2max with 10s rest between each bout and was repeated to exhaustion. Accumulated O2 uptake (AOU), Cfi deficit (AOD), excess post-exercise O consumption (EPOC) during rest periods, and net AOD (AOD minus EPOC) during HIIE were determined. Results: AOU, AOD, and EPOC were significantly higher in PR condition that time to exhaustion was significantly longer, in the comparison to AR condition. On the other hand, net AOD did not differ significantly between conditions regardless of the difference in time to exhaustion. Discussion: These results demonstrated that AOU, time to exhaustion and thus total work in HIIE are higher in PR condition, when compared to AR condition, but that net AOD that is an index of anaerobic energy released during HIIE is unaffected by the active or the passive rest regardless of the difference in time to exhaustion. [ABSTRACT FROM AUTHOR]

Purpose: We characterized the in vivo strain environment of the rat tibia during low-frequency electrical stimulation-induced muscle contraction (LFES) and examined the effective strain rate in the reduction of bone loss in rats experiencing early stages of disuse bone loss. Methods: A strain gauge was attached to the medial surface of the tibial midshaft in adult rats (Fischer 344 male; 1-2 years). Firstly, bone strain and strain rate were determined during LFES of the tibialis anterior muscle at various stimulation intensities, which produced 10%, 20%, and 30% of maximal contraction force (MCF). Secondly, three mechanical strains (producing 4,200, 7,500, and 14,500 pe/s) induced by LFES treatment (10 FIz, 30 min per day, 6 days per week, for one week) were applied to the denervated (DN) left tibiae. The trabecular bone volume (BV/TB). thickness (Tb.Th), and number (Tb.N) were analyzed using 3D micro-computed tomography (CT). Results: The bone strain magnitude and strain rate varied depending on the muscle contraction force. A significant correlation was found between the bone strain magnitude and strain rates during LFES. Higher BV/TB, Tb.Th, and Tb.N. were observed in the group treated at 14,500 pe/s compared to other mechanical strain groups. Discussion: The results suggest that mechanical strain treatment at a strain rate of 14,500 ps/s may reduce disuse bone loss. [ABSTRACT FROM AUTHOR]

Purpose: We examined the effects of muscle electrical stimulation-induced muscle contractions (ESMS) on the mechanical properties in cortical bone in early stages of disused musculoskeletal atrophy in old rats. Methods: Direct ES (16mA, 10Hz, 30 min/d, 6 days/w) was performed on the tibialis anterior muscle after denervation in 2.0-2.5 years old male rats divided into groups as follows: control (CON); denervation (DN); and denervation with direct ES (DN+ES). The cortical regions of the mid-tibiae were analyzed using 3D micro Computed Tomography (CT) and histomorphometry. Bone strength parameters were assessed by the three-point bending methods using mechanical testing device. Results: Denervation resulted in significantly less tibialis anterior muscle weight and bone stiffness except for maximal load and elastic modulus. Maximum load and elastic modulus were 10-80 % higher in the DN+ES group than in the DN group, but not significantly different. Discussion: Our previous studied indicated that daily ESMS reduced trabecular bone loss in young and old rats. Present study suggest that ESMS could not ameliorate the decrease in bone mechanical strength at the early stages of disused musculoskeletal atrophy in old rats. [ABSTRACT FROM AUTHOR]

Purpose: This study focused on the effect of early and late treadmill exercise on motor functional recovery, lesion volume, and cortical thickness following intracerebral hemorrhage (ICH) in rats. Methods: ICH was induced in rats by an injection of collagenase into the left striatum. They were randomly assigned to no training ICH (ICH), no training placebo surgery (SHAM), vary early treadmill exercise (ICH + VET), early treadmill exercise (ICH + ET), and late treadmill exercise (ICH + LT) groups. The ICH + ET group trained for 7 days from the 2nd to 8th day after surgery. The ICH + LT group trained for 7 days from the 9th to 15th days after surgery. The ICH + VET was started within 24 hours of surgery. Sensorimotor function was assessed. Lesion volume and cortical thickness was analyzed using Nissl staining. Results: The cortical thickness of the ICH + ET group was significantly higher than that of ICH, ICH + VET and ICH + LT groups. Discussion:These results suggest that after cerebral hemorrhage, early treadmill exercise may promote sensorimotor functional recovery by inhibition of cortical atrophy compared with very early and late treadmill exercise. [ABSTRACT FROM AUTHOR]

Purpose: Present study examined the effects of different rest interval length on metabolic profile of high intensity intermittent exercise (HIE) in hypoxia. Methods: Eight healthy adult male (24±3 yrs) performed HIE under normal (N) and hypoxic conditions (H) corresponding to 3000m above sea level. The HIE consisted of six 5 s bouts with 15 s (5s-15s) or 30 s (5s-30s) rest between each bout, and was done at an intensity which cause exhaustion in around 15 s. Accumulated oxygen uptake (AOU), accumulated oxygen deficit (AOD) during the exercise bouts and excess post-exercise oxygen consumption (EPOC) in the recovery periods were determined, and net AOD was calculated as ΣAOD-ΣEPOC. Results: HIE was completed in all conditions. In 5s-30s, no significant differences were found in all measures between N and H. On the other hand, AOU and EPOC in H were significantly lower than those in N. This was because VO2 during exercise reached at maximal level in H. Consequently, AOU and net AOU in H was significantly higher than those in N. Discussion: Our findings suggest that metabolic profile of high intensity intermittent exercise in H would be influenced only when VO2 during exercise reached at maximal level in consequence of short rest interval length. [ABSTRACT FROM AUTHOR]

Purpose: Previous studies have demonstrated that long-term physical training with specific implements leads to functional and structural alterations in multiple brain areas in expert players of racket sports, such as tennis, badminton and table tennis. The present study was designed to investigate the different effects of motor imagery in athletes and novices when they handled a specific implement. Methods: Six active pitchers in baseball, and seven experienced baseball players and novices were compared when they held a specific implement such as a baseball and a non-specific implement such as a tennis ball. Transcranial magnetic stimulation was used to test the motor cortical excitability during motor imagery. Motor-evoked potentials (MEPs) in the first dorsal interosseous. Results: The amplitudes of MEPs recorded from novices in each motor imagery condition, such as with a baseball and a tennis ball, and no implement, were comparable. Active and experienced baseball players showed more MEPs facilitation when they held a baseball and tennis ball than no implement condition. Only active pitchers in baseball exhibited more MEPs facilitation when they held a baseball compared with they held a tennis ball. Discussion: These results in this study suggest that the effects of motor imagery with a specific implement are enhanced in active baseball players compared to experienced and novice players is caused by long-term training with the specific implement. [ABSTRACT FROM AUTHOR]

Purpose: The present study aimed to examine the effects of repeated short-term hypobaric hypoxic training on resting blood pressure (BP) and arterial stiffness. Methods: Fourteen healthy male subjects (24±3 yrs) were assigned into normobaric nonnoxic exercise group (N; n=8) and hypobaric hypoxic exercise group (H; n=6). The subjects had a 30-min aquatic exercise at the intensity of 50%VO2max level for consecutive 4 days, and repeated a series of the training following 2 weeks of detraining period. FI had the exercise in a hypobaric hypoxic condition corresponded to 2500m above sea level, and was exposed to the hypoxic condition for 2 hours/session. Before and after the first and second 4 days training period, BP and brachial-ankle pulse wave velocity (baPWV) were determined. Results: In N, neither BP nor baPWV changed significantly throughout the experimental period. BP in H did not significantly change, either. Flowever, baPWV decreased significantly after the first 4 days training (P<0.05), and it did not change to the end of the second 4 days training period. Discussion: These results suggest that the short-term (i.e. 4 days) hypobaric hypoxic training improves baPWV as an index of arterial stiffness but not resting BP, and that the improved baPWV is maintained even if 2 weeks of detraining period is taken. [ABSTRACT FROM AUTHOR]