Oxygen Consumption and Heart Rate Responses in Different Vinyasa Yoga Sequences.

Yoga is widely practiced for its numerous health benefits, and it can also increase energy expenditure. Vinyasa yoga, a system of hatha yoga, meets criteria for moderate-intensity physical activity. It is unclear whether the individual sequences produce different oxygen consumption (VO2) and heart rate responses. The purpose of the present study was therefore to evaluate potential differences in VO2 and heart rate responses across sequences of a 60-minute vinyasa session. Participants included 40 healthy male (n = 20) and female (n = 20) adults (age 30.9 ± 8.8 y) with self-reported yoga experience. The sequence implemented was based on Baron Baptiste's Journey into Power sequence. This vinyasa yoga practice included several sequences: integration, sun salutation, crescent lunges, balancing, standing, back bending, and restorative. VO2 (mL/kg/min) was measured by portable indirect calorimetry and expressed as metabolic equivalents (MET). Heart rate was measured using a Polar HR monitor and presented as a percentage of age-predicted maximal heart rate (APMHR). METs and APMHR differed significantly across sequences (each p < 0.001). METs for the integration, sun-salutation, crescent-lunges, balancing, standing, back-bending, and restorative sequences were significantly different from one another (p < 0.001); balancing and back-bending sequences, however, were similar. During the integration and restorative sequences, APMHR was similar (p = 1.00) and significantly lower compared to sun-salutation, crescent-lunge, balancing, standing, and back-bending sequences (each p < 0.001). METs and APMHR differed significantly across sequences of a vinyasa yoga practice. These data could inform an individualized yoga series based on current fitness levels to maintain or improve cardiorespiratory fitness.

Bidirectional relationship between sleep and sedentary behavior in adults with overweight or obesity: A secondary analysis.

STUDY OBJECTIVES: The relationships between daytime sedentary behavior and that night's sleep and sleep and next day's sedentary behavior are unknown. The purpose of this analysis was to examine these potentially bidirectional associations. METHODS: This study was a secondary analysis of baseline data from an ecological momentary assessment study to determine the triggers for dietary lapses during a weight loss intervention. Sedentary behavior, physical activity, and sleep were objectively measured using accelerometers. Linear mixed modeling was used to examine the bidirectional multivariate associations between activity and sleep characteristics for each outcome examined separately. The models included sex, age, body mass index (BMI), education, and day of the week (weekday vs. weekend). RESULTS: Participants were predominantly white (81.5%) and female (88.9%) with a mean age of 51.2 ± 10.6 years. Longer previous night's total sleep time (TST) (b = -0.320, standard error [SE] = 0.060; p < .001) and being a weekend (b = -63.845, SE = 9.406; p < .001) were associated with less sedentary time the next day. More daytime sedentary time was associated with less wake after sleep onset (b = -0.018, SE = 0.008; p = .016), fewer awakenings (b = -0.010, SE = 0.004; p = .016), and less TST (b = -0.060, SE = 0.028; p = .029) that night. CONCLUSIONS: The bidirectional relationships between sedentary time and sleep characteristics are complex and may vary depending on participant characteristics and duration of sedentary and sleep time. Interventions to decrease sedentary behavior may benefit by targeting sleep duration and weekday activity.

Frequent restful sleep is associated with the absence of depressive symptoms and higher grade point average among college students.

OBJECTIVES: To examine how health behaviors and outcomes differ based on restful nights of sleep among college students. DESIGN: This is a cross-sectional study. SETTING: The study was conducted in a large, northeastern United States university. PARTICIPANTS: The participants include college students (n = 4376), the majority of whom were women (59.2%) and non-Hispanic white (76.1%). MEASUREMENTS: Students completed an online survey, self-reporting sex, height, weight, cumulative grade point average (GPA), physical activity (PA), fruit and vegetable consumption (FVC), substance use, and depressive symptoms, along with nights of restful sleep. Participants were grouped into those who had frequent (≥4 nights/week) or infrequent (<4 nights/week) nights of restful sleep. Analyses included independent sample t-tests, chi-square tests for independence, and logistic regression analyses to compute odds ratios. RESULTS: Parametric analyses indicated a significant, although unmeaningful, association between frequent restful sleep and PA and GPA, but not body mass index or FVC. Nonparametric analyses indicated a positive association between frequent restful sleep and the absence of depressive symptoms. Odds ratios revealed a positive association between the absence of depressive symptoms and GPA with frequent restful sleep. CONCLUSIONS: Findings indicate that restful sleep is associated with the absence of depressive symptoms and higher GPA among college students. Further research is required to examine the relationship, particularly directionality, between the amount of sleep and health behaviors and outcomes. Future researchers should consider using better measures of mental health, dietary quality, and objective measures of sleep and PA were possible. College administrators and health professionals should consider ways in which they can educate students about the benefits of sleep to mental health and academic performance.

Sleep-Wake Concordance in Couples Is Inversely Associated With Cardiovascular Disease Risk Markers.

Aim: To determine whether interdependence in couples' sleep (sleep-wake concordance i.e., whether couples are awake or asleep at the same time throughout the night) is associated with two markers of cardiovascular disease (CVD) risk, ambulatory blood pressure (BP) and systemic inflammation. Methods: This community-based study is a cross-sectional analysis of 46 adult couples, aged 18-45 years, without known sleep disorders. Percent sleep-wake concordance, the independent variable, was calculated for each individual using actigraphy. Ambulatory BP monitors measured BP across 48 h. Dependent variables included mean sleep systolic BP (SBP) and diastolic BP (DBP), mean wake SBP and DBP, sleep-wake SBP and DBP ratios, and C-reactive protein (CRP). Mixed models were used and were adjusted for age, sex, education, race, and body mass index. Results: Higher sleep-wake concordance was associated with lower sleep SBP (b = -.35, SE = .01) and DBP (b = -.22, SE = .10) and lower wake SBP (b = -.26, SE = .12; all p values < .05). Results were moderated by sex; for women, high concordance was associated with lower BP. Men and women with higher sleep-wake concordance also had lower CRP values (b = -.15, SE = .03, p < .05). Sleep-wake concordance was not associated with wake DBP or sleep/wake BP ratios. Significant findings remained after controlling for individual sleep quality, duration, and wake after sleep onset. Conclusions: Sleep-wake concordance was associated with sleep BP, and this association was stronger for women. Higher sleep-wake concordance was associated with lower systemic inflammation for men and women. Sleep-wake concordance may be a novel mechanism by which marital relationships are associated with long-term CVD outcomes.

Objective Sleep Duration Is Prospectively Associated With Endothelial Health.

Study Objectives: The mechanisms linking short sleep duration to cardiovascular disease (CVD) are poorly understood. Emerging evidence suggests that endothelial dysregulation may lie along the causal pathway linking sleep duration to cardiovascular risk, although current evidence in humans is based on cross-sectional studies. Our objective was to evaluate the prospective association between objectively assessed sleep duration and clinical indices of endothelial health. Methods: A total of 141 medically healthy adults underwent an overnight laboratory sleep study when they were between the ages of 21 and 60 years. Total sleep time was objectively assessed by polysomnography at study entry. Endothelial health, including brachial artery diameter (BAD) and flow-mediated dilation (FMD), was measured 18.9 ± 4.6 years later. Medical health and psychiatric status were assessed at both time points. Approximately half of the sample had a lifetime history of major depressive disorder. Results: In univariate analyses, shorter sleep duration was associated with increased BAD (ß = -0.24, p = .004) and decreased FMD (ß = 0.17, p = .042). BAD, but not FMD, remained significantly associated with sleep duration after adjusting for sex, age, body mass index (BMI), smoking, diabetes, hypertension, and lifetime history of major depressive disorder (MDD) at T2. The association between sleep duration and BAD was stronger than the association between BAD and an aggregate measure of CVD risk including three or more of the following risk factors: male sex, age ≥ 65 years, smoker, BMI ≥ 30, diabetes, hypertension, and MDD. Conclusions: Objectively assessed short sleep duration was prospectively associated with increased BAD over a 12- to 30-year period.

Bedtime Variability and Metabolic Health in Midlife Women: The SWAN Sleep Study.

STUDY OBJECTIVES: Circadian misalignment, as seen in shift workers, can disrupt metabolic processes. Associations between sleep timing in nonshift workers and metabolic health are unknown. We examined sleep timing and indices of metabolic health in a community sample of midlife women. METHODS: Caucasian (n = 161), African American (n = 121) and Chinese (n = 56) non-shift-working women aged 48-58 y who were not taking insulin-related medications, participated in the Study of Women's Health Across the Nation (SWAN) Sleep Study and were subsequently examined approximately 5.39 (standard deviation = 0.71) y later. Daily diary-reported bedtimes were used to calculate four measures of sleep timing: mean bedtime, bedtime variability, bedtime delay and bedtime advance. Body mass index (BMI) and insulin resistance (homeostatic model assessment-insulin resistance, HOMA-IR) were measured at two time points. Linear regressions evaluated whether sleep timing was associated with BMI and HOMA-IR cross-sectionally and prospectively. RESULTS: In cross-sectional models, greater variability in bedtime and greater bedtime delay were associated with higher HOMA-IR (ß = 0.128; P = 0.007, and ß = 0.110; P = 0.013, respectively) and greater bedtime advance was associated with higher BMI (ß = 0.095; P = 0.047). Prospectively, greater bedtime delay predicted increased HOMA-IR at Time 2 (ß = 0.152; P = 0.003). Results were partially explained by shifted sleep timing on weekends. CONCLUSION: Frequent shifts in sleep timing may be related to metabolic health among non-shift working midlife women. COMMENTARY: A commentary on this article appears in this issue on page 269.

The Effect of Changes in Cardiorespiratory Fitness and Weight on Obstructive Sleep Apnea Severity in Overweight Adults with Type 2 Diabetes.

STUDY OBJECTIVES: To examine the effect of changes in cardiorespiratory fitness on obstructive sleep apnea (OSA) severity prior to and following adjustment for changes in weight over the course of a 4-y weight loss intervention. METHODS: As secondary analyses of a randomized controlled trial, 263 overweight/obese adults with type 2 diabetes and OSA participated in an intensive lifestyle intervention or education control condition. Measures of OSA severity, cardiorespiratory fitness, and body weight were obtained at baseline, year 1, and year 4. Change in the apnea-hypopnea index (AHI) served as the primary outcome. The percentage change in fitness (submaximal metabolic equivalents [METs]) and change in weight (kg) were the primary independent variables. Primary analyses collapsed intervention conditions with statistical adjustment for treatment group and baseline METs, weight, and AHI among other relevant covariates. RESULTS: At baseline, greater METs were associated with lower AHI (B [SE] = -1.48 [0.71], P = 0.038), but this relationship no longer existed (B [SE] = -0.24 [0.73], P = 0.75) after adjustment for weight (B [SE] = 0.31 [0.07], P < 0.0001). Fitness significantly increased at year 1 (+16.53 ± 28.71% relative to baseline), but returned to near-baseline levels by year 4 (+1.81 ± 24.48%). In mixed-model analyses of AHI change over time without consideration of weight change, increased fitness at year 1 (B [SE] = -0.15 [0.04], P < 0.0001), but not at year 4 (B [SE] = 0.04 [0.05], P = 0.48), was associated with AHI reduction. However, with weight change in the model, greater weight loss was associated with AHI reduction at years 1 and 4 (B [SE] = 0.81 [0.16] and 0.60 [0.16], both P < 0.0001), rendering the association between fitness and AHI change at year 1 nonsignificant (B [SE] = -0.04 [0.04], P = 0.31). CONCLUSIONS: Among overweight/obese adults with type 2 diabetes, fitness change did not influence OSA severity change when weight change was taken into account. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov identification number NCT00194259.

The bidirectional relationship between exercise and sleep: Implications for exercise adherence and sleep improvement.

Exercise has long been associated with better sleep, and evidence is accumulating on the efficacy of exercise as a nonpharmacologic treatment option for disturbed sleep. Recent research, however, has noted that poor sleep may contribute to low physical activity levels, emphasizing a robust bidirectional relationship between exercise and sleep. This article will briefly review the evidence supporting the use of exercise as a nonpharmacologic treatment for sleep disturbance, outline future research that is needed to establish the viability of exercise as a behavioral sleep treatment, describe recent research that has emphasized the potential influence of poor sleep on daytime activity levels, and discuss whether improving sleep may facilitate adoption and/or better adherence to a physically active lifestyle. With poor sleep and physical inactivity each recognized as key public health priorities, additional research into the bidirectional relationship between exercise and sleep has significant implications for facilitating greater exercise adherence and improving sleep in society.

Admixture analysis of a rural population of the state of Guerrero, Mexico.

We studied 156 individuals of Native American descent from the city of Tlapa in the state of Guerrero in western Mexico. Most individuals' ethnicity was either Nahua, Mixtec, or Tlapanec, but self-identified Mestizos and individuals of mixed ethnicities were also included in the sample. We typed 24 autosomal, one Y-chromosome, and four mitochondrial ancestry-informative markers (AIMs) to estimate group and individual admixture proportions, and determine whether the admixture process involved directional gene flow between parental groups. When genetically defined (GD) Mestizos were excluded from the analysis, Native American ancestry represented approximately 98% of the population's gene pool, while European and West African ancestry represented approximately 1% each. Maternally inherited markers also showed an exceptionally high Native American contribution (98.5%), as did the paternally inherited marker, DYS199 (90.7%). We did not detect genetic structure in this population using these AIMs, which appears consistent with the homogeneity of the sample in terms of admixture proportions. The addition of GD Mestizos to the sample did not produce a considerable change in admixture estimates, but it had a major effect on population structure. These results show that the population of Tlapa in Guerrero, Mexico, has experienced little admixture with Europeans and/or West Africans. They also show that the impact of a small number of admixed individuals on an otherwise homogeneous population might have profound implications on subsequent ancestry/phenotype analysis and mapping strategies. We suggest that heterogeneity is a major characteristic of Mexican populations and, as a consequence, should not be disregarded when designing epidemiological studies of Mexican and Mexican American populations.