Adiposity in preadolescent children: Associations with cardiorespiratory fitness

Lifestyle factors contribute to childhood obesity risk, however it is unclear which lifestyle factors are most strongly associated with childhood obesity. The purpose of this cross-sectional study was to simultaneously investigate the associations among dietary patterns, activity behaviors, and physical fitness with adiposity (body fat %, fat mass, body mass index [BMI], and waist to hip ratio) in preadolescent children. Preadolescent children (N = 392, 50% female, age: 9.5 ± 1.1year, BMI: 17.9 ± 3.3 kg/m2) were recruited. Body fat (%) and fat mass (kg) were measured with bioelectrical impedance analysis. Cardiorespiratory fitness (VO2 max), muscular strength (hand-grip strength), activity, sleep, and dietary pattern was assessed. Multivariable analysis revealed that cardiorespiratory fitness associated most strongly with all four indicators of adiposity (body fat (%) (β = -0.2; p < .001), fat mass (β = -0.2; p < .001), BMI (β = -0.1; p < .001) and waist to hip ratio (β = -0.2; p < .001). Additionally, fruit and vegetable consumption patterns were associated with body fat percentage, but the association was negligible (β = 0.1; p = 0.015). Therefore, future interventions should aim to promote the use of cardiorespiratory fitness as a means of reducing the obesity epidemic in children.

Sedentary behavior and cardiovascular disease risk: An evolutionary perspective

A ubiquitous aspect of contemporary societies is sedentary behavior (SB), defined as low intensity activities in a seated, reclined, or supine posture. Leading public health agencies, including the World Health Organization, have recognized the strong association between SB and poor health outcomes, particularly cardiovascular disease. However, while public health agencies have begun to advocate for “reductions” in SB, the current US guidelines are typically vague and non-specific. There is good reasoning behind this non-committal advocacy—there is limited mechanistic and clinical evidence to support policy development. To guide SB policy development, it is important to first consider the origins and evolution of SB, including the following: 1) is SB really a novel/contemporary behavior? i.e., how has this behavior evolved? 2) how did our ancestors sit and in what contexts? 3) how does SB interact with 24-hour activity behaviors, including physical activity and sleep? 4) what other historical and contemporary facets of life interact with SB? and 5) in what context do these behaviors occur and how might they provide different evolutionarily novel stressors? This perspective article will synthesize the available evidence that addresses these questions and stimulate discussion pertaining to the lessons that we can learn from an historical and evolutionary perspective. Last, it will outline the gaps in current SB interruption literature that are hindering development of feasible SB reduction policy.

Protocol for a Longitudinal Study of the Determinants of Metabolic Syndrome Risk in Young Adults

Context

As many as 76.7% of U.S. young adults have at least one metabolic syndrome risk factor. Often undetected, metabolic syndrome risk factors cluster with other risk factors increasing risk of future cardiometabolic disease. The prevention of metabolic syndrome risk accrual through early behavioral interventions is crucial for at-risk populations.

Objectives

This paper outlines the protocol for the Health E Start study, including the objectives, methodology, ethics, and dissemination. Additionally, we discuss the goals of the National Institutes of Health Research Enhancement Award (R15) that funded this project and how this funding will facilitate the comprehensive training of undergraduate researchers. The long-term goal of the study is to develop a theoretically driven intervention for the prevention of metabolic syndrome risk development in college students. To facilitate this goal, the aims are to identify 1) behavioral targets for the prevention of metabolic syndrome risk development and 2) the motivations behind such behaviors to develop a theoretical framework for use in intervention design.

Design

Longitudinal observational design.

Setting

Transition from living at home to independent living at colleges across the U.S.

Participants

High school seniors (n = 150) who will be transitioning to college within 3 months of graduating.

Main Outcome Measure

For aim 1, metabolic syndrome risk will be quantified into a risk score using a principal components analysis of traditional risk factors. Associations between changes in lifestyle behaviors and changes in the risk score will identify population-specific behavioral targets. For aim 2, changes in psychological, social, and environmental antecedents of observed behaviors will be identified.

Conclusions

Identifying the relationship between behavior change and metabolic syndrome risk, and the psychosocial and environmental predictors of observed behavior changes will facilitate the design of targeted interventions for the prevention of metabolic syndrome risk progression in the early college years.

The Effects of 16 Weeks of Exercise Training on Neutrophil Functions in Breast Cancer Survivors

Following therapy, breast cancer survivors (BCS) have an increased risk of infections because of age and cancer dysregulation of inflammation and neutrophil functions. Neutrophil functions may be improved by exercise training, although limited data exist on exercise and neutrophil functions in BCS.Sixteen BCS [mean age: 56 (SD 11) years old] completed 16 weeks of community-based exercise training and a 45-minute acute bout of cycling before (Base) and after (Final) the exercise training program. Exercise training consisted of 3 x 40 – 60 minute mixed mode aerobic exercises, comprising 10 – 30 minutes aerobic and 30 minutes resistance training. At Base and Final, we took BCS blood samples before (PRE), immediately after (POST), and 1 hour after (1Hr) acute exercise to determine neutrophil counts, phenotype, bacterial killing, IL-6, and IL-8 levels. Eleven healthy, age- and physical activity levels-matched women (Control) completed the acute bout of exercise once as a healthy response reference. Resting Responses. BCS and Controls had similar Base PRE absolute neutrophil counts [mean (SD): 3.3 (1.9) v 3.1 (1.2) x 10⁹/L, p=0.801], but BCS had lower bacterial phagocytosis [3991 (1233) v 4881 (417) MFI, p=0.035] and higher oxidative killing [6254 (1434) v 4709 (1220) MFI, p=0.005], lower CD16 [4159 (1785) v 7018 (1240) MFI, p<0.001], lower CXCR2 [4878 (1796) v 6330 (1299) MFI, p=0.032] and higher TLR2 [98 (32) v 72 (17) MFI, p=0.022] expression, while IL-6 [7.4 (5.4) v 4.0 (2.7) pg/mL, p=0.079] levels were marginally higher and IL-8 [6.0 (4.7) v 7.9 (5.0) pg/mL, p=0.316] levels similar. After 16 weeks of training, compared to Controls, BCS Final PRE phagocytosis [4510 (738) v 4881 (417) MFI, p=0.146] and TLR2 expression [114 (92) v 72 (17) MFI, p=0.148] were no longer different. Acute Exercise Responses. As compared to Controls, at Base, BCS phagocytic Pre-Post response was lower [mean difference, % (SD): 12% (26%), p=0.042], CD16 Pre-Post response was lower [12% (21%), p=0.016] while CD16 Pre-1Hr response was higher [13% (25%), p=0.022], TLR2 Pre-Post response was higher [15% (4%) p=0.002], while IL-8 Pre-Post response was higher [99% (48%), p=0.049]. As compared to Controls, following 16 weeks of training BCS phagocytic Pre-Post response [5% (5%), p=0.418], CD16 Pre-1Hr response [7% (7%), p=0.294], TLR2 Pre-Post response [6% (4%), p=0.092], and IL-8 Pre-Post response [1% (9%), p=0.087] were no longer different. Following cancer therapy, BCS may have impaired neutrophil functions in response to an acute bout of exercise that are partially restored by 16 weeks of exercise training. The improved phagocytosis of bacteria in BCS may represent an exercise-induced intrinsic improvement in neutrophil functions consistent with a reduced risk of infectious disease.

Associations of Sedentary Time with Heart Rate and Heart Rate Variability in Adults: A Systematic Review and Meta-Analysis of Observational Studies

PURPOSE

To evaluate if sedentary time (ST) is associated with heart rate (HR) and variability (HRV) in adults.

METHODS

We systematically searched PubMed and Google Scholar through June 2020. Inclusion criteria were observational design, humans, adults, English language, ST as the exposure, resting HR/HRV as the outcome, and (meta-analysis only) availability of the quantitative association with variability. After qualitative synthesis, meta-analysis used inverse variance heterogeneity models to estimate pooled associations.

RESULTS

Thirteen and eight articles met the criteria for the systematic review and meta-analysis, respectively. All studies were cross-sectional and few used gold standard ST or HRV assessment methodology. The qualitative synthesis suggested no associations between ST and HR/HRV. The meta-analysis found a significant association between ST and HR (β = 0.24 bpm per hour ST; CI: 0.10, 0.37) that was stronger in males (β = 0.36 bpm per hour ST; CI: 0.19, 0.53). Pooled associations between ST and HRV indices were non-significant (p > 0.05). Substantial heterogeneity was detected.

CONCLUSIONS

The limited available evidence suggests an unfavorable but not clinically meaningful association between ST and HR, but no association with HRV. Future longitudinal studies assessing ST with thigh-based monitoring and HRV with electrocardiogram are needed.

Current and Future Implications of COVID-19 among Youth Wheelchair Users: 24-Hour Activity Behavior

Preventative measures taken worldwide to decrease the transmission of COVID-19 have had a tremendous impact on youth. Following social restrictions, youth with and without physical disabilities are engaging in less physical activity, more increased sedentary behavior, and poor sleep habits. Specifically, youth wheelchair users (YWU) are likely disproportionately affected by COVID- 19 and have a higher risk of contraction due to underlying comorbidities. While we cannot control all of the negative long-term implications of COVID-19 for YWU, participation in positive 24-h activity behaviors can decrease chronic disease risk and the likelihood of long-term complications resulting from infection. This commentary is to extend the discourse on the importance of 24-h activity behaviors by focusing on YWU. Specifically, we discuss the importance of chronic disease prevention, provide a brief overview of 24-h activity behaviors, and outline some of the lessons that can be learned from the COVID-19 pandemic.

Exercise training partially rescues impaired mucosal associated invariant t-cell mobilization in breast cancer survivors compared to healthy older women

Exercise may attenuate immunosenescence with aging that appears to be accelerated following breast cancer treatment, although limited data on specific cell types exists and acute and chronic exercise have been investigated independently in older adults.

PURPOSE

To determine the mucosal associated invariant T (MAIT) cell response to acute exercise before (PRE) and after (POST) 16 weeks of exercise training in breast cancer survivors (BCS) and healthy older women (CON).

METHODS

Age-matched BCS and CON performed 45 min of intermittent cycling at 60% peak power output wattage. Blood samples were obtained at rest, immediately (0 h) and 1 h after exercise to determine MAIT cell counts, frequency, and intracellular cytokine expression.

RESULTS

At PRE, MAIT cell counts were greater in CON (137%) than BCS at 0 h (46%, p < 0.001), with increased MAIT cell frequency in CON but not BCS. TNFα⁺ and IFNγ⁺ MAIT cell counts increased at 0 h by ~120% in CON (p < 0.001), while BCS counts and frequencies were unchanged. Similar deficits were observed in CD3⁺ and CD3⁺ CD8⁺ cells. At POST, exercise-induced mobilization and egress of MAIT cell counts and frequency showed trends towards improvement in BCS that approached levels in CON. Independent of group, TNFα frequency trended to improve (p = 0.053).

CONCLUSIONS

MAIT mobilization in older BCS following acute exercise was attenuated; however, exercise training may partially rescue these initial deficits, including greater sensitivity to mitogenic stimulation. Using acute exercise before and after interventions provides a unique approach to identify age- and cancer-related immuno-dysfunction that is less apparent at rest.

Effects of Acute Prolonged Sitting and Interrupting Prolonged Sitting on Heart Rate Variability and Heart Rate in Adults: A Meta-Analysis

Prolonged sitting increases cardiovascular disease (CVD) risk, however the physiological mechanisms contributing to CVD from acute sitting exposure are not well-understood. Therefore, this study investigated the heart rate (HR) and variability (HRV) responses to prolonged sitting and after interrupting prolonged sitting (e.g., walking). Electronic databases were searched (inception-August 2020) for studies which exposed adults to prolonged (≥1 h) sitting with and/or without interruptions. Twenty-one articles (27 trials, n = 537) met inclusion criteria. Prolonged sitting non-significantly increased HR (weighted mean difference (WMD) = 0 bpm, 95% CI: −2, 3) and HRV (standardized mean difference (SMD) = 0.12, 95% CI: −0.08, 0.33) compared to pre-sitting baseline. Interrupting prolonged sitting yielded a non-significant small increase in HR (WMD = 4 bpm, 95% CI: 0, 7) compared to pre-sitting baseline. Sub-group analyses investigating interrupting prolonged sitting revealed small-to-moderate increases in HR in healthy populations (WMD = 6 bpm, 95% CI: 1, 10) and following walking interruptions (WMD = 7 bpm, 95% CI: 3, 11). In conclusion, prolonged sitting does not significantly affect HR or HRV. However, interrupting prolonged sitting yielded a small non-significant increase in HR, potentially indicative of increased metabolic demand. Further research is needed to investigate poor CVD outcomes via autonomic disruption from prolonged sitting.

Targeting sedentary behavior as a feasible health strategy during COVID-19

Sedentary behavior is associated with poor physical and mental health. Targeting sedentary behavior is a simple strategy that may help counter physical and mental health concerns associated with COVID-19-related social restrictions. Of course, traditional strategies such as achieving optimal exercise and physical activity levels are also important and should be recommended. However, even under normal circumstances, the difficulty in promoting lasting exercise habits at multiple levels (e.g. individual, environment, policy) are well documented, and chances of maintaining or improving these factors is now even lower. Thus, relative to other lifestyle behaviors - sedentary behavior may be more amenable to change. Moreover, reducing sedentary behavior may be less susceptible to influence from factors associated with health disparities such as age, race, and socio-economic status compared to exercise or physical activity. Sedentary behavior is a feasible health strategy that should be targeted during COVID-19.

Does exercise attenuate age- and disease-associated dysfunction in unconventional T cells? Shining a light on overlooked cells in exercise immunology

Unconventional T Cells (UTCs) are a unique population of immune cells that links innate and adaptive immunity. Following activation, UTCs contribute to a host of immunological activities, rapidly responding to microbial and viral infections and playing key roles in tumor suppression. Aging and chronic disease both have been shown to adversely affect UTC numbers and function, with increased inflammation, change in body composition, and physical inactivity potentially contributing to the decline. One possibility to augment circulating UTCs is through increased physical activity. Acute exercise is a potent stimulus leading to the mobilization of immune cells while the benefits of exercise training may include anti-inflammatory effects, reductions in fat mass, and improved fitness. We provide an overview of age-related changes in UTCs, along with chronic diseases that are associated with altered UTC number and function. We summarize how UTCs respond to acute exercise and exercise training and discuss potential mechanisms that may lead to improved frequency and function.

COVID-19 Impact on Behaviors across the 24-Hour Day in Children and Adolescents: Physical Activity, Sedentary Behavior, and Sleep

In the wake of the COVID-19 pandemic, social restrictions to contain the spread of the virus have disrupted behaviors across the 24-h day including physical activity, sedentary behavior, and sleep among children (5–12 years old) and adolescents (13–17 years old). Preliminary evidence reports significant decreases in physical activity, increases in sedentary behavior, and disrupted sleep schedules/sleep quality in children and adolescents. This commentary discusses the impact of COVID-19-related restrictions on behaviors across the 24-h day in children and adolescents. Furthermore, we suggest recommendations through the lens of a socio-ecological model to provide strategies for lasting behavior change to insure the health and well-being of children and adolescents during the COVID-19 pandemic.