Paula S. McKinley

The Effect of Aerobic Training and Cardiac Autonomic Regulation in Young Adults

OBJECTIVES We tested the effect of aerobic exercise on autonomic regulation of the heart in healthy young adults. METHODS Healthy, sedentary young adults (n = 149; age = 30.4 +/- 7.53 years) were randomized to receive 12 weeks of either aerobic conditioning or strength training. Primary outcomes were heart rate and RR interval variability (RRV) measured before and after training and after 4 weeks of sedentary deconditioning. RRV, a noninvasive index of cardiac autonomic regulation, reflects variability in the intervals between consecutive R waves of the electrocardiogram. RESULTS Aerobic conditioning but not strength training led to a significant increase in aerobic capacity (3.11 mL/kg/min), a decrease in heart rate (-3.49 beats per minute), and an increase in high-frequency RRV (0.25 natural log msec2), each of which returned to pretraining levels after deconditioning. Significant 3-way interactions, however, revealed autonomic effects only in men. CONCLUSIONS In sedentary, healthy young adults, aerobic conditioning but not strength training enhances autonomic control of the heart, but post hoc analyses suggested that gender plays a significant role in this exercise-related cardioprotection.

A Pilot Randomized Controlled Trial of a Commercial Diet and Exercise Weight Loss Program in Minority Breast Cancer Survivors

Obesity is associated with poorer breast cancer outcomes and losing weight postdiagnosis may improve survival. As Hispanic and black women have poorer breast cancer prognosis than non‐Hispanic whites diagnosed at similar age and stage, and have higher rates of obesity, effective weight loss strategies are needed. We piloted a randomized, waitlist‐controlled, crossover study to examine the effects and feasibility of the commercial Curves weight loss program among Hispanic, African American and Afro‐Caribbean breast cancer survivors.

THE IMPACT OF MENSTRUAL CYCLE PHASE ON CARDIAC AUTONOMIC REGULATION

This study investigated menstrual cycle phase differences in heart rate (HR) and RR interval variability (RRV) in 49 healthy, premenopausal, eumenorrheic women (age 30.2+/-6.2 years). HR and RRV were computed from ambulatory 24-h electrocardiogram, collected for up to 6 days, with at least 1 day each during early to midfollicular and midluteal menstrual phases. Phase effects on HR and RRV were assessed using linear mixed effects models with a random intercept to account for the correlation of observations within each subject as well as intrasubject variation. During follicular phase monitoring, women had significantly lower average HR (-2.33 bpm), and higher standard deviation, the root mean squared successive difference, and high frequency (0.04-0.15 Hz) and low frequency (0.15-0.40 Hz) RRV than during the luteal phase. These results provide strong support for the influence of menstrual phase on cardiac autonomic regulation in premenopausal women.

Cultural Differences in Conceptual Models of Everyday Fatigue A Vignette Study

The present study used a qualitative methodology to examine cultural differences in representations of everyday fatigue. Thirty-seven European American women and 36 South Asian immigrant women responded to a vignette describing fatigue. A dimensional model of illness representation was used to develop a coding scheme and analyze the data. Results indicate both similarities and differences in conceptual models of fatigue. European Americans were more likely to medicalize fatigue symptoms and view them as acute, severe and in need of treatment. The social and familial context of womens everyday lives strongly influenced their representations.

Cardiac Autonomic Control and Treatment of Hostility: A Randomized Controlled Trial

Objective: To test whether reduction in hostility increases autonomic regulation of the heart. Methods: In this randomized controlled trial, participants were 158 healthy adults, aged 20 years to 45 years, who were 1 standard deviation (SD) above national norms on the Cook-Medley Hostility and the Spielberger Trait Anger Indices. Participants also were interviewed, using the Interpersonal Hostility Assessment Technique (IHAT). They were randomly assigned to a 12-week cognitive behavior therapy program for hostility reduction or a wait-list control condition. The main outcome measure was cardiac autonomic modulation, measured as RR interval variability (RRV) derived from 24-electrocardiographic recordings. Results: In a multivariate analysis of variance assessing psychological outcomes of hostility, anger, and IHAT scores, there was a significant treatment effect with an average reduction across the three outcomes that was approximately 0.7 SD (ES = 0.685, SE = 0.184, p < .001) greater for the intervention group than for the control group. In contrast, the change in heart rate was −0.14 beat/min (95% Confidence Interval [CI] = −2.43, 2.14) in treatment participants and −1.36 beat/min (95% CI = −3.28, 0.61) in wait-list participants. High-frequency RRV, an index of cardiac parasympathetic modulation, increased by 0.07 ln ms2 (95% CI = −0.10, 0.24) for participants in the treatment condition and decreased by 0.04 ln ms2 (95% CI = −0.18, 0.10) for participants in the wait-list condition. These differences were not significant. The findings for other indices of RRV were similar. Conclusions: Reduction of hostility and anger was not accompanied by increases in cardiac autonomic modulation. These findings raise questions about the status of disordered autonomic nervous system regulation of the heart as a pathophysiological mechanism underlying the hostility-heart disease relationship and about whether hostility itself is a mechanism or merely a marker of elevated risk of heart disease. SD = standard deviation; CBT = cognitive behavior therapy; RRV = RR interval variability; ECG = electrocardiogram; HR = heart rate; HF = high frequency; ln = natural log; CI = confidence interval; ANS = autonomic nervous system; STAXI = State Trait Anger Expression Inventory; SDRR = standard deviation of normal to normal RR intervals; ES = effective size; SE = standard error; LF = low frequency; CHD = coronary heart disease.

Heart rate variability predicts levels of inflammatory markers: Evidence for the vagal anti-inflammatory pathway

Evidence from numerous animal models shows that vagal activity regulates inflammatory responses by decreasing cytokine release. Heart rate variability (HRV) is a reliable index of cardiac vagal regulation and should be inversely related to levels of inflammatory markers. Inflammation is also regulated by sympathetic inputs, but only one previous paper controlled for this. In a larger and more representative sample, we sought to replicate those results and examine potential sex differences in the relationship between HRV and inflammatory markers. Using data from the MIDUS II study, we analyzed the relationship between 6 inflammatory markers and both HF-HRV and LF-HRV. After controlling for sympathetic effects measured by urinary norepinephrine as well as a host of other factors, LF-HRV was found to be inversely associated with fibrinogen, CRP and IL-6, while HF-HRV was inversely associated with fibrinogen and CRP. We did not observe consistent sex differences. These results support the existence of the vagal anti-inflammatory pathway and suggest that it has similar effects in men and women.

The Association of Cardiac Vagal Control and Executive Functioning – Findings from the MIDUS Study

Cardiac vagal control (CVC), an index of parasympathetic contribution to cardiac regulation, has been linked to enhanced executive functioning (EF). However, findings to date have been based on small or unique samples. Additionally, previous studies assessed the CVC-EF link only during rest or recovery period from a cognitive challenge, but not during both states. In the present study, data on 817 socioeconomically diverse participants were obtained from the Midlife Development in the United States (MIDUS) study. As part of this study, participants completed cognitive tests, including EF, along with laboratory-based measures of CVC during rest and following recovery from a cognitive challenge. Regression analyses adjusting for respiratory rate revealed no effect of CVC at rest or during recovery on a global index of EF. However, exploratory post-hoc analyses of the components of the global EF index revealed a significant association between faster vagal recovery and better attention-switching and response inhibition abilities, as indexed by faster reaction time to the mixed SGST. This association remained significant after controlling for demographic, clinical (BMI, diseases and medications altering cardiac autonomic functioning, etc.), and health behavior covariates (Beta = .148, p = .010). Our findings suggest that future studies may need to investigate the links of CVC to specific EF abilities, rather than global measures of EF. Additionally, our results highlight the importance of assessing CVC during both rest and recovery from a cognitive challenge. The authors discuss the putative neurobiological underpinning of this link, as well as suggestions for future basic and clinical research.

The interactive effect of change in perceived stress and trait anxiety on vagal recovery from cognitive challenge.

The present study tested the hypothesis that the change in state negative affect (measured as perceived stress) after cognitive challenge moderates the relationship of trait anxiety and anger to vagal recovery from that challenge. Cardiac vagal control (assessed using heart rate variability) and respiratory rate were measured in a sample of 905 participants from the Midlife in the United States Study. Cognitive challenges consisted of computerized mental arithmetic and Stroop color-word matching tasks. Multiple regression analyses controlling for the effects of the demographic, lifestyle, and medical factors influencing cardiac vagal control showed a significant moderating effect of change in perceived stress on the relationship of trait anxiety to vagal recovery from cognitive challenges (Beta=.253, p=.013). After adjustment for respiratory rate, this effect became marginally significant (Beta=.177, p=.037). In contrast, for the relationship of trait anger to vagal recovery, this effect was not significant either before (Beta=.141, p=.257) or after (Beta=.186, p=.072) adjusting for respiratory rate. Secondary analyses revealed that among the individuals with higher levels of trait anxiety, greater reductions in perceived stress were associated with greater increases in cardiac vagal control after the challenge. In contrast, among the individuals with lower levels of trait anxiety, changes in perceived stress had no impact on vagal recovery. Therefore, change in perceived stress moderates the relationship of trait anxiety, but not trait anger, to vagal recovery from cognitive challenge.

Impact of aerobic training on cardiovascular reactivity to and recovery from challenge.

Objective: To test the hypothesis that aerobic, but not strength, training would lead to attenuated reactivity to and more rapid recovery from cognitive and orthostatic challenge and that deconditioning would reverse this effect. Methods: We conducted a randomized controlled trial contrasting the effects of aerobic versus strength training on heart rate, four indices of RR interval variability, and blood pressure reactivity to and recovery from psychological and orthostatic challenge in 149 healthy, young, sedentary adults. Subjects were randomized to 12-week aerobic or strength training programs and studied before and after training and again after 4 weeks of sedentary deconditioning. The data were analyzed by performing a Group (aerobic versus strength) by Session (study entry, post training, and deconditioning), by Period (baseline, speech, Stroop, math, tilt) three-way analysis of variance with prespecified contrasts of the effect of group assignment on reactivity and recovery. Results: Aerobic capacity increased in response to conditioning and decreased after deconditioning in the aerobic, but not the strength, training group. However, the two groups did not differ on heart rate, RR interval variability, or blood pressure reactivity to or recovery from laboratory challenge. Conclusions: These findings, from the largest randomized controlled trial to address this matter to date, raise doubts about attenuation of reactivity or enhancement of recovery as a putative mechanism underlying the cardioprotective effects of aerobic exercise. Trial Registration: ClinicalTrials.gov Identifier: NCT00365196. RCT = randomized controlled trial; RRV = RR interval variability; BP = blood pressure; SBP = systolic blood pressure; DBP = diastolic blood pressure; CAD = coronary artery disease; HR = heart rate; ECG = electrocardiogram; HF = high frequency; AUC = area under the curve; ln = natural log.

Heart Rate Recovery After Cognitive Challenge Is Preserved With Age

Objective: To investigate the effect of age on heart rate recovery (HRR) from cognitive challenge. Background: Aging is an independent risk factor for the development of cardiovascular disease. HRR from exercise is an established predictor of cardiac morbidity and mortality, and evidence suggests that HRR from cognitive challenge is predictive of cardiac morbidity as well. Aging is associated with delayed HRR from exercise stress, but little is known about the effect of aging on HRR from psychological stress. We tested the hypothesis that age would be related to delayed HRR from psychological stress. Methods: HRR post exposure to cognitive challenge (mental arithmetic and Stroop) was investigated in a sample of 436 participants aged 35 to 84 years in MIDUS II, a national study of health and well-being. HRR was measured as 1) the amount of change from the stress level; 2) time to recover; and 3) the area under the curve. The analyses were controlled for medical comorbidities and medications that influence HR, such as body mass index, smoking, sex, menopausal status, and amount of physical activity/exercise. Results: There was no effect for age on HRR as evaluated by all three recovery assessment methods. Conclusions: Contrary to expectation and in contrast to findings concerning HRR from exercise, HRR from cognitive challenge was preserved with age. These findings require further inquiry into differential mechanism(s) underlying HRR from psychological versus exercise stress, including any role for improved emotion regulation with greater age. HR = heart rate; HRR = heart rate recovery; AUC = area under the curve; ECG = electrocardiogram.