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This systematic review aims to evaluate which effects nature exposure has on stress in women and get a more objective viewpoint using measurements of physiological markers of stress to complement the many studies using subjective questionnaires. A search was done on Scopus, Medline EBSCO, and Web of Science for peer-reviewed, published, and original research. Five studies met the inclusion criteria and were included in this review. The outcome measurements included were activity in the autonomic nervous system (ANS) measured with heart-rate variability (HRV) and cerebral activity measured by near-infrared spectroscopy (NIRS). With the definition of Shinrin-Yoku in mind, nature exposure was walking in or watching the natural environment, compared to walking in or watching an urban environment. In this systematic review, four of five studies found significant results that nature exposure alleviated stress in women compared to an urban environment. These findings contribute to a growing body of evidence suggesting that nature is valuable in reducing stress-related illnesses in women. On the individual level, these findings show that nature exposure can be used as an evidence-based intervention to reduce stress in women. Furthermore, these findings clarify the benefits of including elements from nature in urban environments on a societal level.

Biological theory proposes that autonomic nervous system (ANS) hypo-reactivity may be more specific to proactive aggression, while ANS hyper-reactivity may be specific to affective aggression. However, the literature finds mixed support, which may be because no study to date has concurrently examined emotion dysregulation, a highly related variable, as a potential moderator. The present study examined these relationships in 76 undergraduate participants (29 men, mean age = 21.49) who identified as Caucasian (51%), African-American (23%), Asian (21%), or Other (5%). Participants completed questionnaires, a resting state task, and a provocation task. Results found that blunted overall ANS reactivity was associated with proactive aggression. Emotion dysregulation moderated the relationship between parasympathetic nervous system (PNS) and sympathetic nervous system (SNS) reactivity with both proactive (at a trending level for SNS reactivity) and affective aggression. Specifically, among those slightly above average and high on emotion dysregulation, PNS augmentation and blunted SNS reactivity were associated with proactive and affective aggression, respectively. In contrast, among those low on emotion dysregulation, PNS augmentation was associated with decreased affective aggression. Thus, among those elevated on emotion dysregulation, it may be beneficial to teach counter-regulatory strategies to reduce the impact of ANS hypo-reactivity on aggression (across function). / Psychology

<p> Hypertension is a modifiable risk factor for cardiovascular disease. The current treatment options are drug therapy and lifestyle modifications. A promising lifestyle modification therapy for the management of hypertension is isometric exercise, as several studies have demonstrated that isometric handgrip (IHG) training reduces resting arterial blood pressure (ABP) (Peters et al., 2006; Taylor et al., 2003; Wiley et al., 1992). The purpose of the present investigation was two-fold: 1) to examine the effectiveness of IHG training in reducing resting ABP in newly diagnosed hypertensive patients, in comparison to matched controls receiving advice from a physician about lifestyle modifications; and 2) to examine markers of autonomic function, specifically, heart rate variability (HRV) to determine if changes in the autonomic nervous system (ANS) existed between the two groups of hypertensive adults.</p> <p> Resting blood pressure and heart rate were assessed with an automated acquisition system before, during and after the 6-week intervention period. Also, power spectral analysis of HRV was used to assess changes in modulation of the ANS. Participants in both groups (n=14) were given lifestyle modification recommendations regarding diet, exercise and stress reduction, while participants in the training group (n=8) also completed a bilateral IHG training protocol 3 times/week at 30% maximum voluntary contraction (MVC).</p> <p> Our results demonstrate that contrary to our hypothesis, isometric exercise in combination with lifestyle modification recommendations did not result in a reduction of resting ABP or change indices of HRV. Possible explanations for these results are that unlike previous IHG training, the present study was the first to use home-based training and the small sample size of this investigation would limit our ability to identify alterations in resting ABP or HRV.</p> / Thesis / Master of Science (MSc)

This study examined the effects of isometric handgrip (IHG) training on resting blood pressure (RBP), heart rate variability (HRV) and blood pressure variability (BPV) in older adults with hypertension. Nine subjects performed four 2-minute IHG contractions at 30% maximal voluntary contraction (MVC) 3 days/week for 10 weeks and 8 subjects served as controls. Power spectral analysis (PSA) of HRV and BPV was used to assess changes in modulation of the autonomic nervous system. After training, there was a marked attenuation in arterial pressure and evidence for a shift in HR.V and BPV sympathovagal balance. There was a reduction in systolic blood pressure (156 ± 9.4 to 137 ± 7.8 mm Hg; p<0.05), diastolic blood pressure (82 ± 9.3 to 75 ± 10.9 mm Hg; N.S), mean arterial pressure (107 ± 8.53 to 96 ± 8.7 mm Hg; p<0.05) and resting heart rate (RHR) (70 ± 14.2 to 68 ± 12.1 beats/min). In addition, PSA of HRV showed a decrease in sympathetic modulation represented by low frequency (LF) area, an increase in parasympathetic modulation represented by high frequency (HF) area (p<0.05) and a decrease in LF:HF area ratio. After training, BPV PSA showed a decrease in systolic blood pressure LF area (p<0.05), an increase in HF area (p<0.05) and decrease in LF:HF area (p<0.05). Similar, but non-significant changes occurred in diastolic BPV. It is concluded that isometric training at a moderate intensity can elicit a hypotensive response and can potentially alter sympathovagal balance of HRV and BPV in older adults with hypertension. / Thesis / Master of Science (MS)

The autonomic flexibility model has proven to be a useful theoretical tool relating reductions in physiological variability found to accompany anxiety and concomitant reductions in behavioral (e.g., cognitive and emotional) flexibility. The present study aimed to extend the autonomic flexibility model through the inclusion of individual differences in the sensitivity of the independent motivational systems presumed to underlie anxiety and impulsivity, namely the behavioral inhibition and activation systems (BIS/BAS; Gray, 1994). Contrary to the predicted inverse relationship between BIS sensitivity and measures of physiological variability, findings suggest BAS sensitivity is associated with increased trait-like vagally mediated heart rate variability across diverse tasks as well as greater flexibility in responding within tasks. Numerous BIS*BAS interactions emerged as significant predictors of trait reactivity. Results are discussed in terms of the interface between (1) mesolimbic dopaminergic projections to the nucleus accumbens and (2) the network of central nervous system structures believed to play a large role in controlling peripheral physiology. / Ph. D.

Cardiac time intervals (CTIs) are vital indicators of cardiac health and can be estimated using a combination of electrocardiography (ECG) and seismocardiography (SCG). This study investigates the impact of SCG sensor location across the sternum on CTI estimations and heart rate variability parameters. Signal processing algorithms were developed to detect the opening and closure of heart valves on SCG for CTI calculation. A novel ECG-independent method was also developed based on template matching to determine similar parameters solely based on SCG. Comparative analysis with gold-standard methods were conducted on the SCG fiducial points, evaluating accuracy and performance. Results indicate a high overall average F1 score and correlation for all fiducial point detections. The p values revealed significant differences in SCG-derived CTI estimations across the sensor locations, highlighting the importance of sensor placement for accurate assessments. This finding underscores a fundamental step toward precise evaluation of cardiac health.

Exercise-induced hypoalgesia (EIH) is the reduction in pain sensitivity following exercise. High-intensity or prolonged exercise is typically required to elicit an EIH response, but there is limited evidence suggesting that low-load resistance exercise with blood flow restriction (LL+BFR) may be able to elicit a robust EIH response. The purpose of these investigations was to assess the magnitude, duration, and proposed mechanisms of EIH following LL+BFR, LL with normobaric systemic hypoxemia, BFR only without exercise, high-load exercise, and a control intervention. The first study evaluated local and systemic pain pressure threshold and tolerance responses one-hour post-exercise. The results indicated that LL+BFR induced similar EIH responses to high-load resistance exercise 0- and 15-minutes post-exercise but only LL+BFR elicited an EIH response present 60-minutes post-exercise. The second study evaluated neuromuscular and perceptual responses, both proposed EIH mechanisms, during exercise. Similar neuromuscular responses were observed in all interventions. Participants reported higher ratings of perceived exertion during LL+BFR and high-load exercise, and higher levels of perceived pain during LL+BFR. These results suggested that despite high levels of motor unit recruitment, there were divergent EIH responses. However, increased pain during exercise may be a mediating factor of EIH after resistance exercise. The third study evaluated peripheral and central cardiovascular responses, which have also been hypothesized to mediate EIH. LL+BFR resulted in greater increases in systolic blood pressure during the first set of exercise, and diastolic blood pressure during all sets of exercise. LL+BFR and BFR only attenuated changes in heart rate variability (HRV). LL+BFR induced the largest increase in deoxyhemoglobin and total hemoglobin and lowered tissue saturation index. BFR only progressively increased oxyhemoglobin and total hemoglobin levels. The local and systemic cardiovascular responses suggested that prolonged EIH following LL+BFR could be related to increased central or peripheral cardiovascular stress.