Tamaki Matsumoto

Oxygen availability and motor unit activity in humans

SummarySix men were studied to determine the interrelationships among blood supply, motor unit (MU) activity and lactate concentrations during intermittent isometric contractions of the hand grip muscles. The subjects performed repeated contractions at 20% of maximal voluntary contraction (MVC) for 2 s followed by 2-s rest for 4 min with either unhindered blood circulation or arterial occlusion given between the 1st and 2nd min. The simultaneously recorded intramuscular MU spikes and surface electromyogram (EMG) data indicated that mean MU spike amplitude, firing frequency and the parameters of surface EMG power spectra (mean power frequency and root mean square amplitude) remained constant during the experiment with unhindered circulation, providing no electrophysiological signs of muscle fatigue. Significant increases in mean MU spike amplitude and frequency were, however, evident during the contractions with arterial occlusion. Similar patterns of significant changes in the surface EMG spectra parameters and venous lactate concentration were also observed, while the integrated force-time curves remained constant. These data would suggest that the metabolic state of the active muscles may have played an important role in the regulation of MU recruitment and rate coding patterns during exercise.

The relationship between anaerobic threshold and electromyographic fatigue threshold in college women.

SummaryThe purpose of this study was to investigate the relationship between anaerobic threshold (Than) and muscle fatigue threshold (EMGFT) as estimated from electromyographic (EMG) data taken from the quadriceps muscles (vastus lateralis) during exercise on a cycle ergometer. The subjects in this study were 20 female college students, including highly trained endurance athletes and untrained sedentary individuals, whose fitness levels derived from their maximal oxygen consumption ranged from 24.9 to 62.2 ml · kg−1·min−1. The rate of increase in integrated EMG (iEMG) activity as a function of time (iEMG slope) was calculated at each of four constant power outputs (350, 300, 250, 200 W), sufficiently high to bring about muscle fatigue. The iEMG slopes so obtained were plotted against the exercise intensities imposed, resulting in linear plots which were extrapolated to zero slope to give an intercept on the power axis which was in turn interpreted as the highest exercise intensity sustainable without electromyographic evidence of neuromuscular fatigue (EMGFFT). The Than was estimated from gas exchange parameters during an incremental exercise test on the same cycle ergometer. The mean results indicated that oxygen uptake (VO2) at Than was 1.391·min−1, SD 0.44 andVO2 at EMGFT was 1.33 1·min−1, SD 0.57. There was no significant difference between these mean values (P>0.05) and there was a highly significant correlation betweenVO2 at Than andVO2 at EMGFT (r=0.823,P<0.01). These data supported the concept of Than on the basis that Than was associated with the highest exercise intensity that could be sustained without evidence of neuromuscular fatigue and thus suggested that EMGFT may provide an attractive alternative to the measurement of Than.

Autonomic nervous system activity in the late luteal phase of eumenorrheic women with premenstrual symptomatology.

The majority of women of reproductive age experience a regular recurrence of various symptoms in the premenstrual phase. The etiopathogenesis of premenstrual symptomatology, however, remains inconclusive. The present study was proposed to evaluate whether the activity of the autonomic nervous system (ANS), which largely contributes to the relative stability of a humans internal environment, is altered during the menstrual cycle of women with premenstrual symptomatology. Thirty eumenorrheic young women participated in this study. All subjects were investigated during the follicular and late luteal phases. The ANS activity was assessed by means of heart rate variability power spectral analysis during supine rest. No intramenstrual cycle differences in the ANS activity were found in women experiencing no or small increases in premenstrual symptoms. In contrast, the sympathetic nervous system (SNS) activity significantly increased and the parasympathetic nervous system (PNS) activity apparently decreased in the late luteal phase in subjects whose premenstrual symptomatology was not unbearable, but substantially increased (>20%) compared to the symptom-free follicular phase. The women with greater degrees of premenstrual distress possessed higher SNS activity and lower PNS activity in the late luteal phase than the women with less symptomatology. The ANS activity in the follicular phase did not differ among the subjects regardless of their premenstrual symptoms. Although causes and consequences continue to elude, the present study provides additional intriguing evidence that the altered functioning of ANS in the late luteal phase could be associated with diverse psychosomatic or behavioral symptoms appearing premenstrually.

Altered autonomic nervous system activity as a potential etiological factor of premenstrual syndrome and premenstrual dysphoric disorder.

BackgroundPremenstrual syndrome (PMS) encompasses a wide variety of cyclic and recurrent physical, emotional, and behavioral symptoms occurring during the late luteal phase of the menstrual cycle and abating shortly following the beginning of menses. Although PMS is widely recognized, its etiopathogenesis is not yet understood. The present study investigates whether the activity of the autonomic nervous system, which plays a vital role in orchestrating physiological homeostasis within the human body, is altered during the menstrual cycle of women with different degrees of premenstrual symptomatology.MethodsSixty-two women in their 20s to 40s with regular menstrual cycles participated in this study. All subjects were examined during the follicular and late luteal phases. Cycle phase was determined by the onset of menstruation and oral temperature and was verified by concentrations of ovarian hormones, estrone, and pregnanediol in a urine sample taken early in the morning. Autonomic nervous system activity was assessed by means of heart-rate variability (HRV) power spectral analysis during supine rest. The Menstrual Distress Questionnaire was used to evaluate physical, emotional, and behavioral symptoms accompanying the menstrual cycle of the subjects. The subjects were categorized in three groups, Control, PMS, and premenstrual dysphoric disorder (PMDD) groups, depending on the severity of premenstrual symptomatology.ResultsNo intramenstrual cycle difference in any of the parameters of HRV was found in the Control group, which had no or a small increase in premenstrual symptoms. In contrast, Total power and high frequency power, which reflect overall autonomic and parasympathetic nerve activity, respectively, significantly decreased in the late luteal phase from the follicular phase in the PMS group. As for the PMDD group, which had more severe symptoms premenstrually, heart-rate fluctuation as well as all components of the power spectrum of HRV were markedly decreased regardless of the menstrual cycle compared to those of the other two groups.ConclusionSeveral theories have been proposed to explain the underlying mechanisms of PMS with its complex web of bio-psycho-social factors. Although causes and consequences continue to elude, the present study provides intriguing and novel findings that the altered functioning of the autonomic nervous system in the late luteal phase could be associated with diverse psychosomatic and behavioral symptoms appearing premenstrually. In addition, when symptoms become more severe (as seen in women with PMDD), the sympathovagal function might be more depressed regardless of the menstrual cycle.

Lower peripheral circulation in eumenorrheic young women with premenstrual symptoms

BackgroundA majority of women from all cultures and socioeconomic levels experience diverse psychosomatic and behavioral symptoms premenstrually, a phenomenon commonly termed premenstrual syndrome, although symptoms and discomfort levels vary from woman to woman. The underlying pathological mechanisms of premenstrual syndrome remain unknown; however, altered function or even slight disorder of the blood circulation system, which contributes to the orchestrations of the human internal environment, could cause bio-psychological changes leading to complaints and ultimately compromising a womans overall health. The present study, therefore, investigates to what extent and how the menstrual cyclicity of peripheral circulation is associated with premenstrual symptomatology.MethodsTwenty-one eumenorrheic young women participated in this study. All subjects were investigated during the follicular and late luteal phases. Cycle phase was determined by the onset of menstruation and oral temperature and was verified by concentrations of ovarian hormones, estrone, and pregnanediol in a urine sample taken early in the morning. Peripheral circulation was evaluated with the Astrim (Sysmex, Kobe), a portable non-invasive monitoring device using the principle of near-infrared spectroscopy, which calculates the venous oxygenation index (VOI) based on the ratio of light absorption of oxyhemoglobin and deoxyhemoglobin, a proven reliable indicator of peripheral blood circulation. The Menstrual Distress Questionnaire was applied to measure physical, emotional, and behavioral symptoms accompanying the menstrual cycle of the subjects.ResultsThe oral temperature and urinary ovarian hormones adjusted for creatinine significantly increased in the late luteal phase in all subjects. While 10 subjects experienced no symptoms during the menstrual cycle, 11 subjects had apparent physical and psychological discomfort in the late luteal phase. We found that VOI decreased more significantly in the late luteal phase than in the follicular phase only in women with premenstrual discomfort although the symptoms were not unbearable enough to cause the disruption of daily activities.ConclusionSeveral models have tried to explain the etiopathogenesis of premenstrual syndrome. Although causes and consequences remain enigmatic, our data suggest that the peripheral circulation could alter in the luteal phase, which might be partly associated with premenstrual psychosomatic symptoms in eumenorrheic young women.

Human myotatic reflex development of the lower extremities

Lower extremity (LE) myotatic reflexes were tested by percussion (taps) to the patellar and Achilles tendons. Surface electromyographic recordings were obtained from 5 LE muscles during tendon taps. Results indicated that LE myotatic reflexes underwent considerable change during early human development. The changes were non-linear and highly variable. Reflex irradiation (the presence of reflex responses in muscles other than the one being directly stimulated by a tendon tap) was present in the newborn but to a lesser extent than was in evidence later on during the first year of life. The percentage of time reflex irradiation was detected in heteronymous muscle groups appeared to achieve maximal levels during the first year and then progressively decline. The decline in reflex irradiation was most dramatic between the first and second years of life. Irradiated responses were still recorded from 2 year-old children but with less frequency than in children less than 1 year of age. With the exception of responses in muscles that were direct antagonists to the stimulated muscle, irradiation was not observed in children 3-5 years of age.

Effects of Olfactory Stimulation from the Fragrance of the Japanese Citrus Fruit Yuzu (Citrus junos Sieb. ex Tanaka) on Mood States and Salivary Chromogranin A as an Endocrinologic Stress Marker

OBJECTIVE This study investigated the soothing effects of fragrance from yuzu, a Japanese citrus fruit (Citrus junos Sieb. ex Tanaka), with salivary chromogranin A (CgA) used as an endocrinologic stress marker reflecting sympathetic nervous system activity. METHODS Twenty healthy women (mean age, 20.5 ± 0.1 years) participated in a randomized, controlled, crossover study. Participants were examined on two separate occasions-once using the yuzu scent and once using unscented water as a control-in the follicular phase. This experiment measured salivary CgA and the Profile of Mood States (POMS) as a psychological index before and after the aromatic stimulation. RESULTS Ten-minute inhalation of the yuzu scent significantly decreased salivary CgA. At 30 minutes after the inhalation period, the salivary CgA level further decreased. In addition, POMS revealed that inhalation of the aromatic yuzu oil significantly decreased total mood disturbance, a global measure of affective state, as well as four subscores of emotional symptoms (tension-anxiety, depression-dejection, anger-hostility, and confusion), as long as 30 minutes after the olfactory stimulation. CONCLUSIONS Yuzus aromatic effects may alleviate negative emotional stress, which, at least in part, would contribute to the suppression of sympathetic nervous system activity.

H-reflex modulations during voluntary and automatic movements following upper motor neuron damage.

OBJECTIVES It is not known whether similar mechanisms account for the impairments of voluntary movement and automatic postural responses of individuals with spasticity secondary to damage to the sensorimotor cortex and its projections (i.e. upper motor neuron syndrome (UMN)). METHODS The present study examined changes in soleus H-reflexes preceding and during voluntary tibialis anterior (TA) muscle contraction of standing subjects and during balance platform induced postural perturbations that elicited similar TA muscle contractions. Twenty-two subjects (12 non-disabled; 4 with spastic-type cerebral palsy; 6 with adult-onset cerebral vascular accident) participated in the study. Data were analyzed using ANOVAs and Tukey HSD post-hoc comparison tests to assess the timing and magnitude of soleus H-reflex amplitude changes relative to the onset of TA muscle activation. RESULTS Results indicated that, regardless of the level of TA activation, soleus H-reflexes of subjects with UMN involvement did not demonstrate inhibition either. during voluntary movements or during automatic postural perturbations. CONCLUSIONS These findings indicate that postural reflexes, as well as volitional movements, are impaired following UMN damage and that deficits in neural pathways subserving reciprocal inhibition contribute to the impairments.