Electrophysiology and kinesiology for health and disease

Differences in autonomic nervous system activity between long-acting injectable aripiprazole and oral aripiprazole in schizophrenia

BACKGROUND

Distinct oral atypical antipsychotics have different effects on autonomic nervous system (ANS) activity. Among them, oral aripiprazole has been linked to dysfunction of the ANS in schizophrenia. Long-acting injectable aripiprazole is a major treatment option for schizophrenia, but the effect of the aripiprazole formulation on ANS activity remains unclear. In this study, we compared ANS activity between oral aripiprazole and aripiprazole once-monthly (AOM) in schizophrenia.

METHODS

Of the 122 patients with schizophrenia who participated in this study, 72 received oral aripiprazole and 50 received AOM as monotherapy. We used power spectral analysis of heart rate variability to assess ANS activity.

RESULTS

Patients who received oral aripiprazole showed significantly diminished sympathetic nervous activity compared with those who received AOM. Multiple regression analysis revealed that the aripiprazole formulation significantly influenced sympathetic nervous activity.

CONCLUSION

Compared with oral aripiprazole, AOM appears to have fewer adverse effects, such as sympathetic nervous dysfunction.

Supplementation with Whey Protein, Omega-3 Fatty Acids and Polyphenols Combined with Electrical Muscle Stimulation Increases Muscle Strength in Elderly Adults with Limited Mobility: A Randomized Controlled Trial

Age-related sarcopenia is a progressive and generalized skeletal muscle disorder associated with adverse outcomes. Herein, we evaluate the effects of a combination of electrical muscle stimulation (EMS) and a whey-based nutritional supplement (with or without polyphenols and fish oil-derived omega-3 fatty acids) on muscle function and size. Free-living elderly participants with mobility limitations were included in this study. They received 2 sessions of EMS per week and were randomly assigned to ingest an isocaloric beverage and capsules for 12 weeks: (1) carbohydrate + placebo capsules (CHO, n = 12), (2) whey protein isolate + placebo capsules (WPI, n = 15) and (3) whey protein isolate + bioactives (BIO) capsules containing omega-3 fatty acids, rutin, and curcumin (WPI + BIO, n = 10). The change in knee extension strength was significantly improved by 13% in the WPI + BIO group versus CHO on top of EMS, while WPI alone did not provide a significant benefit over CHO. On top of this, there was the largest improvement in gait speed (8%). The combination of EMS and this specific nutritional intervention could be considered as a new approach for the prevention of sarcopenia but more work is needed before this approach should be recommended. This trial was registered at the Japanese University Hospital Medical Information Network (UMIN) clinical trial registry (UMIN000008382).

The association of genetic polymorphisms in CYP1A2, UGT1A4, and ABCB1 with autonomic nervous system dysfunction in schizophrenia patients treated with olanzapine

BACKGROUND

Use of the antipsychotic drug olanzapine by patients with schizophrenia is associated with autonomic nervous system (ANS) dysfunction. It is presumed that there are interindividual differences in ANS dysfunction that correspond to pharmacogenetics. In this study, we investigated whether genetic polymorphisms in ABCB1, CYP1A2, and UGT1A4 are associated with this observed ANS dysfunction.

METHODS

A total of 91 schizophrenia patients treated with olanzapine monotherapy participated in this study. A power spectral analysis of heart rate variability was used to assess ANS activity. The TaqMan system was used to genotype seven single nucleotide polymorphisms (SNPs) in CYP1A2 (rs2069514 and rs762551), UGT1A4 (rs2011425), and ABCB1 (rs1045642, rs1128503, rs2032582, rs2235048).

RESULTS

Sympathetic nervous activity was significantly higher in individuals with the UGT1A4 rs2011425 G allele than in those with the UGT1A4 rs2011425 non-G allele (sympathetic activity, p = .001). Furthermore, sympathetic nervous activity was also significantly associated with UGT1A4 rs2011425 genotype as revealed by multiple regression analysis (sympathetic activity, p = .008).

CONCLUSIONS

We suggest that the UGT1A4 rs2011425 polymorphism affects olanzapine tolerability because it is associated with the observed side effects of olanzapine in schizophrenia patients, namely sympathetic dysfunction.

A return to work program improves parasympathetic activity and psychiatric symptoms in workers on sick leave due to depression

Background

People with depression have autonomic function disturbances. In Japan, workers who take leave due to depression often undergo a work-focused intervention program called the return to work (RTW) program at a mental health hospital during their leave of absence. However, its biological efficacy remains unclear. We investigated the biological efficacy of the RTW program, including changes in autonomic nervous system (ANS) activity, in workers on sick leave due to depression in Japan.

Methods

The study involved 104 workers on sick leave due to major depressive disorder or bipolar disorder who underwent the RTW program for 3 months in Yokohama City University Hospital. The ANS activity of all patients was evaluated using heart rate variability at the beginning and end of the 3-month RTW program. Psychiatric symptoms were evaluated using the Montgomery-Åsberg Depression Rating Scale-Japanese (MADRS-J) and Social Adaptation Self-evaluation Scale (SASS). We followed up 3 months after the end of the program and investigated the association between the success in returning to work within 3 months after the end of the RTW program and several factors, including ANS activity, depressive symptoms, and demographic factors.

Results

Parasympathetic activity was significantly higher and depressive symptom severity was significantly lower at program end than at baseline. Logistic regression analysis showed that the change in depressive symptoms was significantly associated with success in returning to work.

Conclusion

We suggest that the RTW program improves parasympathetic activity as well as psychiatric symptoms. ANS activity was not a predictor of a successful return to work within 3 months after the end of the program in workers on sick leave due to depression, but further studies with a larger sample size are needed.

Association between dysfunction of autonomic nervous system activity and mortality in schizophrenia

BACKGROUND

Patients with schizophrenia have a higher mortality risk than the general population. Additionally, the autonomic nervous system (ANS) activity of patients with schizophrenia is lower and more dysfunctional than that of the general population. Nonetheless, the association between ANS dysfunction and mortality in schizophrenia is unclear. The aim of this study was to investigate the association between ANS activity and mortality in schizophrenia and to evaluate the predictive values of heart rate variability for long-term survival.

METHODS

This study involves the 10-year follow-up of a sample population consisting of 59 Japanese inpatients with schizophrenia between 60 and 70 years of age from 2007 to 2016. The ANS activity of all patients was evaluated using heart rate variability in 2007.

RESULTS

Fifty-three participants could be followed up because they stayed in the hospital during the follow-up period. Of these patients, 11 died during follow-up. Their mean age at death was 70.55 ± 3.45 years. The parasympathetic activity of nonsurvivors was significantly lower than that of survivors, and multiple logistic regression analysis showed a significant association between death and parasympathetic activity.

CONCLUSION

We suggest that decreased parasympathetic activity could be associated with 10-year all-cause mortality in older schizophrenic patients.

Effects of long-acting injectable antipsychotics versus oral antipsychotics on autonomic nervous system activity in schizophrenic patients

OBJECTIVE

Long-acting injections (LAIs) of antipsychotics show distinct pharmacokinetic profiles from oral antipsychotics (OAPs). Although there may be differences in adverse event frequency, any differences in their effects on autonomic nervous system (ANS) remain unclear.

PATIENTS AND METHODS

In total, 270 schizophrenic patients were recruited in this study: 241 received OAPs (risperidone, olanzapine, quetiapine, or aripiprazole) and 29 received LAIs (risperidone LAI, aripiprazole LAI, or paliperidone palmitate) as monotherapy. Heart rate variability was measured as an index of ANS activity, and the low-frequency (0.03-0.15 Hz) component, high-frequency (0.15-0.40 Hz) component, and total power (0.03-0.40 Hz) were calculated. Components were compared between the groups using t-tests.

RESULTS

A significant difference was detected in the low-frequency component between the OAP and LAI groups (P=0.046). No significant difference was found in total power or the high-frequency component between the two groups.

CONCLUSION

Compared with OAPs, LAIs have fewer adverse effects on ANS activity, particularly the low-frequency component, as determined using a spectral analysis of heart rate variability.

Effects of ABCB1 gene polymorphisms on autonomic nervous system activity during atypical antipsychotic treatment in schizophrenia

BACKGROUND

There are interindividual differences in the adverse effects of atypical antipsychotics, which include autonomic nervous system (ANS) dysfunction. Accordingly, to clarify the interindividual differences in the adverse effects of specific atypical antipsychotics in schizophrenia, we investigated the association between ANS dysfunction and ATP-binding cassette transport sub-family B member 1 (ABCB1) gene polymorphisms in patients with schizophrenia.

METHODS

In total, 233 Japanese patients with schizophrenia participated in this study. All of the participants received an atypical antipsychotic as monotherapy: 89 participants received risperidone, 69 olanzapine, 48 aripiprazole, and 27 quetiapine. ANS activity was assessed by means of a power spectral analysis of heart rate variability. Four single nucleotide polymorphisms (SNPs) in ABCB1 (rs1045642, rs1128503, rs2032582, and rs2235048) were genotyped using the TaqMan method.

RESULTS

For aripiprazole, sympathetic and total autonomic nervous activities were significantly lower in the rs1045642 T allele carrier-rs2235048 C allele carrier group than in the rs1045642 non-T allele carrier-rs2235048 non-C allele carrier group. In addition, in the aripiprazole group, the T-C-T-A haplotype (rs1045642-rs2235048-rs1128503-rs2032582) was associated with decreased ANS activity. However, there were no significant associations between ANS activity and ABCB1 gene polymorphisms in the risperidone, olanzapine, and quetiapine groups. Multiple regression analysis revealed that sympathetic and total nervous activities were significantly associated with the ABCB1 rs1045642-rs2235048 genotype and the T-C-T-A haplotype (rs1045642-rs2235048-rs1128503-rs2032582).

CONCLUSION

We suggest that ABCB1 genetic polymorphisms affect aripiprazole-related ANS dysfunction but do not affect risperidone-, olanzapine-, or quetiapine-related ANS dysfunction.

Effects of four atypical antipsychotics on autonomic nervous system activity in schizophrenia

Antipsychotic drugs are associated with autonomic nervous system (ANS) dysfunction in patients with schizophrenia, but the effects of individual atypical antipsychotic drugs are not clear. This study investigated how four atypical antipsychotic drugs-risperidone, olanzapine, aripiprazole, and quetiapine-differ in their effects on ANS activity. A total of 241 Japanese patients with schizophrenia participated in this study. All of the participants received an atypical antipsychotic as monotherapy: 90 participants received risperidone, 68 olanzapine, 52 aripiprazole, and 31 quetiapine. ANS activity was assessed by means of a power spectral analysis of heart rate variability. The quetiapine group showed significantly diminished sympathetic and parasympathetic activity compared with the risperidone and aripiprazole groups and significantly lower sympathetic activity relative to olanzapine. In addition, multiple regression analysis showed that the type of antipsychotic drug significantly influenced ANS activity. We suggest that, among the antipsychotics examined-risperidone, olanzapine, aripiprazole and quetiapine-quetiapine has the strongest effect on ANS activity.

Long term effects of smoking cessation in hospitalized schizophrenia patients

BACKGROUND

The prevalence of smoking in patients with schizophrenia is higher than that in the general population and is an important medical issue. Short-term smoking cessation tends to worsen psychiatric symptoms in patients with schizophrenia but decreases sympathetic nervous system activity and improves plasma cholesterol levels in healthy people. Few studies have assessed the long-term effects of smoking cessation in patients with schizophrenia.

METHODS

Subjects were 70 Japanese patients with schizophrenia (38 smokers, 32 non-smokers). We compared the following clinical parameters between the two groups at baseline (before smoking cessation) and in each group separately between baseline and at three years after smoking cessation: autonomic nervous system activity, plasma cholesterol levels, body weight, drug therapy, and Global Assessment of Functioning scores. We also compared the mean changes in clinical parameters throughout this study between the groups at both time points. Autonomic nervous system activity was assessed by power spectral analysis of heart rate variability.

RESULTS

Parasympathetic nervous system activity and the doses of antiparkinsonian drugs in smokers were significantly higher than those in non-smokers at baseline. Smoking cessation was associated with significantly decreased sympathetic nervous system activity and decreased doses of antipsychotics and antiparkinsonian drugs at three years after smoking cessation. However, there was no significant difference in the mean change in clinical factors scores, except for Global Assessment of Functioning scores, between smokers and non-smokers at three years after smoking cessation.

CONCLUSIONS

Our results suggest that smoking reduces both autonomic nervous system activity and the effectiveness of drug therapy with antipsychotics and antiparkinsonian drugs in patients with schizophrenia, but that both factors could be ameliorated over the long term by smoking cessation. Taken together with the findings of previous studies, smoking cessation in patients with schizophrenia has many long-term positive physiological effects.

Association of the Cholinergic Muscarinic M2 Receptor with Autonomic Nervous System Activity in Patients with Schizophrenia on High-Dose Antipsychotics

BACKGROUND

Patients with schizophrenia have abnormal autonomic nervous system (ANS) activity compared with the general population. One reason for this difference is the muscarinic affinity for antipsychotic drugs; therefore, single nucleotide polymorphisms (SNPs) of the muscarinic receptor gene influence this ANS dysfunction. This study sought to determine the effect of SNPs of the cholinergic muscarinic receptor (CHRM) gene on ANS activity in patients with schizophrenia receiving antipsychotic drugs.

METHODS

A total of 173 Japanese patients with schizophrenia were included in this study. Heart rate variability (HRV) was measured as an index of ANS activity. SNPs in CHRM1 (rs542269 and rs2075748), CHRM2 (rs324640, rs8191992, rs1824024, and rs7810473), and CHRM3 (rs3738435, rs4620530, and rs6429157) were genotyped using the TaqMan® method. Patients were grouped according to standard equivalent conversions of chlorpromazine (CP) into a high-CP group (HG; ≥1,000 mg) and a low-CP group (LG; <1,000 mg). ANS activity was compared between the groups. In addition, we compared the total, low-frequency (LF), high-frequency (HF), and LF/HF components of the patients' HRV, and the genotype of the SNPs in both the HG and LG groups. Bonferroni correction was applied for multiple comparisons, and the Bonferroni-corrected critical p value was <0.005.

RESULTS

The A allele of the CHRM2 rs8191992 polymorphism in HG was associated with decreased ANS activity.

CONCLUSION

Our results show reduced ANS activity in association with the CHRM2 rs8191992 polymorphism in patients with schizophrenia on high-dose antipsychotics. CHRM2 polymorphisms may play an important role in ANS activity in patients with schizophrenia.

Assessment of stress and autonomic nervous activity in Japanese female ambulance paramedics working 24-hour shifts

OBJECTIVES

We studied the physical and mental conditions of 8 healthy young female ambulance paramedics working 24-hour shifts during their menstrual cycle, including assessment of cardiac autonomic nervous system activity by heart rate variability power spectral analysis.

METHODS

The autonomic activity during the awake period of on- and off-duty days in the follicular, late luteal, and menstruation phases was measured. Questionnaires regarding fatigue and menstrual distress were administered and correlated with the autonomic profile.

RESULTS

While degrees of fatigue significantly increased after work, the changes in autonomic activity during the awake period on on-duty days were not significantly different from those on off-duty days (LF/HF, p=0.123; HF/(HF+LF), p=0.153). As for the sleeping period, there were no significant differences. Although the Menstrual Distress Questionnaire (MDQ) revealed the presence of mild menstrual discomfort in the late luteal and menstruation phases, no significant difference was observed in the autonomic profile of the three menstrual cycle phases. No significant correlation was observed between the degree of menstrual distress and autonomic profile, though there was a significant correlation in the late luteal phase between degree of menstrual distress and fatigue after work (p<0.01).

CONCLUSION

These results showed that, while subjects experienced menstrual discomfort and fatigue after work, their autonomic profile did not alter in the menstrual cycle. It is suggested that healthy young female ambulance paramedics may tolerate 24-hour shifts, though attention should be paid to subjective menstrual symptoms and fatigue.

Metabolic and cardiovascular responses during voluntary pedaling exercise with electrical muscle stimulation

PURPOSE

We aimed to test the effect of additional electrical muscle stimulation (EMS) during moderate-intensity voluntary pedaling exercise on metabolic and cardiovascular responses.

METHODS

Eleven healthy male subjects performed moderate-intensity pedaling exercise at a constant workload (80% of ventilatory threshold) for 20 min while EMS was applied to thigh muscles from 5 to 10 min and from 15 to 20 min during the exercise.

RESULTS

A significantly higher oxygen uptake (VO₂), heart rate, and respiratory gas exchange ratio were observed during the exercise periods with EMS despite the constant workload. These changes were accompanied by an elevated blood lactate concentration, suggesting the existence of additional fast-twitch motor unit (MU) recruitment during the exercise with EMS.

CONCLUSION

Our data suggest that the use of intermittent EMS during a constant load exercise mimics the high-intensity interval training, possibly due to additional fast-twitch MU recruitment and co-contractions of the quadriceps and hamstrings muscles, leading to higher anaerobic metabolism and a lower mechanical efficiency.

Evaluation of autonomic nervous system by salivary alpha-amylase level and heart rate variability in patients with schizophrenia

Several researches indicate that autonomic nervous system (ANS) dysfunction in patients with schizophrenia. Recently, salivary alpha-amylase (sAA) has been employed as a useful marker for ANS function. We investigated the extent of ANS dysfunction by measuring sAA and heart rate variability (HRV) of 25 patients with schizophrenia compared with controls. Schizophrenia group demonstrated a significant increase in sAA and markedly lower parasympathetic nervous system (PNS) activity in the HRV. However, there were no significant differences between two groups in sympathetic nervous system (SNS) activity. We concluded that PNS might be suppressed and the SNS shows relatively high activity in schizophrenia.

Does lavender aromatherapy alleviate premenstrual emotional symptoms?: a randomized crossover trial

Background

A majority of reproductive-age women experience a constellation of various symptoms in the premenstrual phase, commonly known as premenstrual syndrome (PMS). Despite its prevalence, however, no single treatment is universally recognized as effective, and many women turn to alternative approaches, including aromatherapy, a holistic mind and body treatment. The present study investigated the soothing effects of aromatherapy on premenstrual symptoms using lavender (Lavandula angustifolia), a relaxing essential oil, from the perspective of autonomic nervous system function.

Methods

Seventeen women (20.6 ± 0.2 years) with mild to moderate subjective premenstrual symptoms participated in a randomized crossover study. Subjects were examined on two separate occasions (aroma and control trials) in the late-luteal phases. Two kinds of aromatic stimulation (lavender and water as a control) were used. This experiment measured heart rate variability (HRV) reflecting autonomic nerve activity and the Profile of Mood States (POMS) as a psychological index before and after the aromatic stimulation.

Results

Only a 10-min inhalation of the lavender scent significantly increased the high frequency (HF) power reflecting parasympathetic nervous system activity in comparison with water (aroma effect: F = 4.50, p = 0.050; time effect: F = 5.59, p = 0.017; aroma x time effect: F = 3.17, p = 0.047). The rate of increase in HF power was greater at 10–15 min (p = 0.051) and 20–25 min (p = 0.023) in the lavender trial than in the control trial with water. In addition, POMS tests revealed that inhalation of the aromatic lavender oil significantly decreased two POMS subscales—depression–dejection (p = 0.045) and confusion (p = 0.049)—common premenstrual symptoms, in the late-luteal phase, as long as 35 min after the aroma stimulation.

Conclusions

The present study indicated that lavender aromatherapy as a potential therapeutic modality could alleviate premenstrual emotional symptoms, which, at least in part, is attributable to the improvement of parasympathetic nervous system activity. This study further implies that HRV could evaluate the efficacy of aromatherapy using various fragrances to relieve premenstrual symptoms, and ultimately, support the mind and body health of women.

Dose-dependent effect of antipsychotic drugs on autonomic nervous system activity in schizophrenia

BACKGROUND

Antipsychotic drugs are considered a trigger factor for autonomic dysregulation, which has been shown to predict potentially fatal arrhythmias in schizophrenia. However, the dose-dependent effect of antipsychotic drugs and other psychotropic drugs on autonomic nervous system (ANS) activity remain unclear. The purpose of this study was to investigate the dose-dependent effect of antipsychotic drugs and other clinical factors on ANS activity in an adequate sample size of patients with schizophrenia.

METHODS

A total of 211 Japanese patients with schizophrenia and 44 healthy subjects participated in this study. ANS activity was assessed by means of heart rate variability (HRV) power spectral analysis. Antipsychotic drug treatment and various clinical factors were investigated for each participant. The patient group was categorized into three subgroups according to daily dose of antipsychotic drug, and HRV was compared between groups.

RESULTS

The results showed significantly decreased low-frequency and high-frequency components of HRV in the patient group compared to the control group. The high-dose group showed a significantly lower HRV than the medium-dose group and an even lower HRV than the low-dose group. In addition, a significant association between HRV and antipsychotic drug dose was identified by multiple regression analysis. HRV was not associated with age, sex, body mass index, duration of illness, or daily dose of other psychotropic drugs.

CONCLUSION

These results suggest that antipsychotic drugs exert a significant dose-dependent effect on the extent of decline in ANS activity, and that optimal antipsychotic medication is required to avoid possible cardiovascular adverse events in patients with schizophrenia.

Comparative effect of a 1 h session of electrical muscle stimulation and walking activity on energy expenditure and substrate oxidation in obese subjects

It has previously been shown that low-frequency neuromuscular electrical stimulation (NMES) techniques can induce increases in energy expenditure similar to those associated with exercise. This study investigated the metabolic and cardiovascular effects of a 1 h session of lower limb NMES and compared cardiovascular response with that observed during walking in nine obese subjects (three males) (age = 43.8 ± 3.0 years; body mass index (BMI) = 41.5 ± 1.8 kg/m(2)). The NMES protocol consisted of delivering a complex pulse pattern to the thigh muscles for 1 h. The walking test consisted of five 4-min bouts starting at 2 km/h with 1 km/h increments up to 6 km/h. In both tests, an open-circuit gas analyser was used to assess O(2) consumption ([Formula: see text]O(2)), CO(2) production ([Formula: see text]CO(2)), respiratory exchange ratio (RER), and heart rate (HR). Rates of fat oxidation (RFO) and carbohydrate oxidation (CHO) were estimated by indirect calorimetry. One hour of NMES significantly increased [Formula: see text]O(2), HR, RER, and mean energy expenditure compared with resting values, reaching 8.7 ± 1.3 mL·min(-2)·kg(-1) (47% of [Formula: see text]O(2peak)), 114.8 ± 7.5 bpm, 0.95, and 318.5 ± 64.3 kcal/h, respectively. CHO, but not RFO, increased during 1 h of NMES. With NMES, CHO was greater and RFO was less than at all walking speeds except 6 km/h. Lactate also increased more with NMES, to 3.5 ± 0.7 mmol versus a maximum of 1.5 ± 0.3 mmol with the walking protocol. These results suggest that NMES can be used in an obese population to induce an effective cardiovascular exercise response. In fact, the observed increase in energy expenditure induced by 1 h of NMES is clinically important and comparable with that recommended in weight management programs.

Autonomic nervous system activity and psychiatric severity in schizophrenia

AIMS

Schizophrenia patients have a mortality rate two to three-fold higher than that of the general population. Despite the disorder's widespread recognition, how and to what extent autonomic nervous system (ANS) activity contributes to schizophrenia remains inconclusive. The aim of the present study, therefore, was to determine the extent of ANS activity depression with respect to healthy, well-matched control subjects and the severity of psychiatric disorders as determined using the Global Assessment of Functioning (GAF) scale among schizophrenia patients with special reference to antipsychotic dose.

METHODS

This study included 71 schizophrenia patients and 72 healthy controls. ANS activity was assessed by means of heart rate variability power spectral analysis.

RESULTS

ANS-related spectral parameters were three-four-fold lower in the patients compared to the control group (P < 0.01). Furthermore, when the patients without cardiovascular complications were classified according to GAF score, overall ANS (P = 0.033) and parasympathetic nervous system (PNS) activity (P = 0.025) were significantly reduced in the low-GAF as compared to the high-GAF group. Partial correlation analyses demonstrated that ANS activity was significantly correlated with GAF score while statistically eliminating the effects of age, gender, body mass index, antipsychotic dose, and lipid profiles of the patient population.

CONCLUSION

The significantly lower ANS activity in the low-GAF group suggests that such autonomic functional depression could be associated with the severity of schizophrenia. The present data further imply that schizophrenia patients with more depressed overall ANS and PNS activity might encounter increasing risks for cardiovascular events such as sudden death.

Análise da fadiga muscular localizada em atletas e sedentários através de parâmetros de freqüência do sinal eletromiográfico

Embora a análise no domínio da freqüência do sinal eletromiográfico (EMG) seja empregada na caracterização do processo de fadiga muscular localizada, sua aplicação, especificamente a da freqüência mediana (Fmed), é pouco explorada no âmbito esportivo. O objetivo do presente estudo foi verificar a viabilidade da aplicação do sinal EMG, através de sua análise no domínio da freqüência, como parâmetro para determinação e diferenciação no comportamento da fadiga muscular localizada. Dois grupos de sujeitos, um caracterizado como atletas (n =12) e outro como sedentários (n =12), foram submetidos a análises baseadas em procedimentos executados em três diferentes situações experimentais, todos envolvendo a modalidade de exercício isométrico: i) teste máximo para determinação da contração isométrica voluntária máxima (CIVM); ii) teste de fadiga, sustentado por 35 seg. a 80% da CIVM; iii) teste de recuperação, sustentado por 10 seg. a 80% da CIVM; neste ultimo foi monitorado o comportamento da Fmed nos três primeiros (Fmedi) e três últimos segundos (Fmedf) do sinal EMG no músculo tibial anterior durante o teste de fadiga. Durante os 10 segundos do teste de recuperação foi calculada a Fmed referente a todo o período (Fmedr). parâmetro utilizado no cálculo do índice de recuperação muscular (IRM). Os resultados apontam que a Fmedf apresentou valor menor em relação à Fmedi em ambos os grupos (p < 0,05). Quando comparado com o grupo de sedentários, o grupo de atletas apresentou valores maiores de Fmedi e Fmedf (p < 0,05). O valor médio e desvio-padrão do IRM para o grupo de atletas foram de 62,1% ± 28,7 e, para o grupo de sedentários, de 55,2% ± 27,8 (p > 0,05). Dessa forma, os resultados apresentados neste estudo permitem inferir a viabilidade na aplicação de parâmetros no domínio da freqüência do sinal EMG para a determinação e diferenciação do comportamento da fadiga muscular localizada.

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

BACKGROUND

Premenstrual 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.

METHODS

Sixty-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.

RESULTS

No 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.

CONCLUSION

Several 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.

The reaction strategy of lower extremity muscles when slips occur to individuals with trans-femoral amputation

The aim of this study is to investigate the surface electromyography (sEMG) responses of lower extremity muscles for both healthy people and individuals with trans-femoral amputation (TFA), when slip events occur during level walking. Six male individuals with unilateral TFA and five healthy subjects participated in this study. Each subject was required to walk at a self-selected comfortable pace along a 5m plastic walkway, and to perform walking trials on dry and oily conditions respectively. The sEMG signals of muscles on legs and around waist were recorded in each trial and the normalized instantaneous muscle power (IMP) values were employed to quantify the response intensity. The IMP profiles of each muscle in oily-surface walking trials were compared quantitatively with that in dry-surface trials. There are three main findings in this study. (1) Different muscle reaction strategies are employed in slip events by the healthy persons and the individuals with TFA, respectively. Moreover, when the slip event occurs on the prosthetic leg and the intact leg of the individuals with TFA respectively, the muscle reaction strategies are also different. (2) The individuals with TFA face higher risks of fall than the healthy persons no mater slips occur on the prosthetic side or the intact side. (3) The hip muscles, especially the gluteus maximus (GMA) muscles, always enormously contribute to posture adjustment and balance recovery in slip events.

The effects of interelectrode distance on electromyographic amplitude and mean power frequency during incremental cycle ergometry

The purpose of this study was to examine the effects of interelectrode distance (IED) on the relationships of absolute and normalized EMG amplitude and mean power frequency (MPF) versus power output during incremental cycle ergometry. Eleven adults (mean +/- S.D. age = 24.2 +/- 2.6 y; V(O2max) = 49.4 +/- 8.3 ml kg(-1) min(-1)) performed incremental cycle ergometry tests. Surface EMG signals were recorded simultaneously from bipolar electrode arrangements placed over the VL muscle with IEDs of 20, 40, and 60 mm. Polynomial regression analyses were used to describe the relationships for absolute and normalized EMG amplitude (muV(rms) and % max) and MPF (Hz and % max) versus power output (%max) for each subject at the three IEDs. In addition, separate one-way repeated measures ANOVAs were used to examine mean differences between the three IEDs for absolute and normalized EMG amplitude and MPF at power outputs of 80, 110, 140, and 170 W. The results of the polynomial regression revealed that the best fit model for each IED for the absolute and normalized EMG amplitude was linear for six of the 11 subjects and quadratic for five of the subjects. For EMG MPF, four of the 11 subjects exhibited significant relationships (linear or quadratic) across power outputs for at least one IED. The one-way repeated measures ANOVAs revealed significant mean differences between the IEDs for absolute EMG amplitude and MPF at 80, 110, 140, and 170 W. There were no significant mean differences, however, between the IEDs for normalized EMG amplitude or MPF at 80, 110, 140, and 170 W. The results of the study indicated that there were no consistent patterns of responses between individual subjects for EMG amplitude or MPF versus power output relationships for IEDs of 20, 40, and 60 mm during incremental cycle ergometry. The current findings supported the process of normalization for EMG amplitude and MPF data obtained during cycle ergometry when comparisons are made for different IEDs.