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Open Access Publications from the University of California

Scholarly Works (81 results)

  • Article
  • Peer Reviewed
UC Irvine Previously Published Works (2020)
Atherosclerosis originates in childhood and adolescence. The goal of this review is to highlight how exercise and physical activity during childhood and adolescence, critical periods of growth and development, can prevent adult cardiovascular disease (CVD), particularly through molecular mechanisms of monocytes, a key cell of the innate immune system. Monocytes are heterogeneous and pluripotential cells that can, paradoxically, play a role in both the instigation and prevention of atherosclerosis. Recent discoveries in young adults reveal that brief exercise affects monocyte gene pathways promoting a cell phenotype that patrols the vascular system and repairs injuries. Concurrently, exercise inhibits pro-inflammatory monocytes, cells that contribute to vascular damage and plaque formation. Because CVD is typically asymptomatic in youth, minimally invasive techniques must be honed to study the subtle anatomic and physiologic evidence of vascular dysfunction. Exercise gas exchange and heart rate measures can be combined with ultrasound assessments of vascular anatomy and reactivity, and near-infrared spectroscopy to quantify impaired O2 transport that is often hidden at rest. Combined with functional, transcriptomic, and epigenetic monocyte expression and measures of monocyte-endothelium interaction, molecular mechanisms of early CVD can be formulated, and then translated into effective physical activity-based strategies in youth to prevent adult-onset CVD.
    Cover page: Exercise-associated prevention of adult cardiovascular disease in children and adolescents: monocytes, molecular mechanisms, and a call for discovery.
    • Article
    • Peer Reviewed
    UC Irvine Previously Published Works (2020)
    Atherosclerosis originates in childhood and adolescence. The goal of this review is to highlight how exercise and physical activity during childhood and adolescence, critical periods of growth and development, can prevent adult cardiovascular disease (CVD), particularly through molecular mechanisms of monocytes, a key cell of the innate immune system. Monocytes are heterogeneous and pluripotential cells that can, paradoxically, play a role in both the instigation and prevention of atherosclerosis. Recent discoveries in young adults reveal that brief exercise affects monocyte gene pathways promoting a cell phenotype that patrols the vascular system and repairs injuries. Concurrently, exercise inhibits pro-inflammatory monocytes, cells that contribute to vascular damage and plaque formation. Because CVD is typically asymptomatic in youth, minimally invasive techniques must be honed to study the subtle anatomic and physiologic evidence of vascular dysfunction. Exercise gas exchange and heart rate measures can be combined with ultrasound assessments of vascular anatomy and reactivity, and near-infrared spectroscopy to quantify impaired O2 transport that is often hidden at rest. Combined with functional, transcriptomic, and epigenetic monocyte expression and measures of monocyte-endothelium interaction, molecular mechanisms of early CVD can be formulated, and then translated into effective physical activity-based strategies in youth to prevent adult-onset CVD.
      Cover page: Exercise-associated prevention of adult cardiovascular disease in children and adolescents: monocytes, molecular mechanisms, and a call for discovery
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2015)
      NIH Director Francis Collins noted that the Common Fund initiative would lead to unprecedented insights into the mechanisms responsible for the health effects of physical activity. He noted: “Armed with this knowledge, researchers and clinicians may one day be able to define optimal physical activity recommendations for people at various stages of life, as well as develop precisely targeted regimens for individuals with particular health needs.” Given the ominous burden of physical inactivity-related diseases and conditions in otherwise healthy children, and the growing number of children who survive chronic diseases in whom we know little about what constitutes healthy exercise, it is essential that the community of child health researchers develop compelling strategies and proposals in response to the unique opportunity offered through the Common Fund mechanism.
        Cover page: The Common Fund Initiative and Its Implication for Advancing Exercise and Physical Activity Research in Child Health.
        • Article
        • Peer Reviewed
        UC Irvine Previously Published Works (2016)
        In this review, we highlight promising new discoveries that may generate useful and clinically relevant insights into the mechanisms that link exercise with growth during critical periods of development. Growth in childhood and adolescence is unique among mammals and is a dynamic process regulated by an evolution of hormonal and inflammatory mediators, age-dependent progression of gene expression, and environmentally modulated epigenetic mechanisms. Many of these same processes likely affect molecular transducers of physical activity. How the molecular signaling associated with growth is synchronized with signaling associated with exercise is poorly understood. Recent advances in "omics"-namely genomics and epigenetics, metabolomics, and proteomics-now provide exciting approaches and tools that can be used for the first time to address this gap. A biologic definition of "healthy" exercise that links the metabolic transducers of physical activity with parallel processes that regulate growth will transform health policy and guidelines that promote optimal use of physical activity.
          Cover page: Bridging the Gaps: the Promise of Omics Studies in Pediatric Exercise Research.
          • Article
          • Peer Reviewed
          UC Irvine Previously Published Works (2007)
          Exercise elicits an immunological "danger" type of stress and inflammatory response that, on occasion, becomes dysregulated and detrimental to health. Examples include anaphylaxis, exercise-induced asthma, overuse syndromes, and exacerbation of intercurrent illnesses. In dangerous exercise, the normal balance between pro- and anti-inflammatory responses is upset. A possible pathophysiological mechanism is characterized by the concept of exercise modulation of previously activated leukocytes. In this model, circulating leukocytes are rendered more responsive than normal to the immune stimulus of exercise. For example, in the case of exercise anaphylaxis, food-sensitized immune cells may be relatively innocuous until they are redistributed during exercise from gut-associated circulatory depots, like the spleen, into the central circulation. In the case of asthma, the prior activation of leukocytes may be the result of genetic or environmental factors. In the case of overuse syndromes, the normally short-lived neutrophil may, because of acidosis and hypoxia, inhibit apoptosis and play a role in prolongation of inflammation rather than healing. Dangerous exercise demonstrates that the stress/inflammatory response caused by physical activity is robust and sufficiently powerful, perhaps, to alter subsequent responses. These longer term effects may occur through as yet unexplored mechanisms of immune "tolerance" and/or by a training-associated reduction in the innate immune response to brief exercise. A better understanding of sometimes failed homeostatic physiological systems can lead to new insights with significant implication for clinical translation.
            Cover page: Dangerous exercise: lessons learned from dysregulated inflammatory responses to physical activityCreative Commons 'BY' version 4.0 license
            • Thesis
            • Peer Reviewed
            UC Irvine Electronic Theses and Dissertations (2019)

            The benefits of regular physical activity are well known. In recent years, the health industry focused on developing motivational products to get people to exercise, with habit forming as a key concept. Studies that have shown that exergaming can result in immediate health benefits. However, benefits tend to be short term with a player’s initial excitement declining over time. Current exergames are unable to meet long-term exercising challenges because the underlying game design criterion to sustain player engagement is absent.

            To address this issue, I incorporated innovative game design principles to create the iXercise platform, a virtual environment exergame that provides an adjusted intervention fitness program targeted to special needs populations. Chapter 2is focused on a discussion of the iXercise platform. I describe the system design and how I implemented the various iXercise system components such as a web-based interface, a cloud gaming application, middleware, sensors, embedded systems firmware and communication channels. In chapter 3, I introduce how a novel exergame, named “MineBike”, encourages and maintains the participant’s motivation. I describe game design elements for the immersive exergaming experience that encourages mid-to high-level exercise intensity. In chapter 4, I present the evaluation of the iXercise platform. To evaluate the platform, 1) exercise intensity (measured by workload) and duration was observed, 2) physiological responses (heart rate and oxygen uptake) was measured, 3) behavioral assessment (enjoyment, motivation and engagement) were assessed through a questionnaire, 4) correlation of physiological responses to game activities was observed, and 5) sex and age group differences were compared. Twenty-two 9-15 y/o healthy children were recruited for the study. Over three visits, the children exercised on an adjusted stationary bike and played the game for about 40 minutes while wearing multiple sensors. After each gameplay they answered behavioral assessment questionnaires.

            From the collected results, I was able to observe that MineBike successfully increased participants’ heart rate (> 120 bpm) for the target time (20 minutes). Also, MineBike was able to induce mid- to high- intensity exercise. Survey results were universally positive. Children enjoyed the game, wanted to continue playing, and thought that they would be more motivated to exercise with the Minebike exergame than without. They remarked that they especially liked the game content and the bike pedaling experiences.

            In summary, I, 1) developed the cloud based iXercise exergaming platform, 2) built prototype devices to retrofit exercise equipment, specifically cycle ergometers, 3) developed an exergame “MineBike” based on a popular game Minecraft, 4) collaborated with medical experts at the Pediatrics Exercise Research Center (PERC) at UC Irvine School of Medicine, on the design concepts that will suit the fitness abilities of a young recuperating population.

            • 3 supplemental PDFs
            Cover page: iXercise: An Immersive Exergaming Platform to Promote Physical Activity in the Pediatric Population
            • Article
            • Peer Reviewed
            ICTS Publications (2013)
            Natural killers (NK) cells are unique innate immune cells that increase up to fivefold in the circulating blood with brief exercise and are known to play a key role in first-response defense against pathogens and cancer immunosurveillance. Whether exercise alters NK cell gene and microRNA (miRNA) expression is not known. Thirteen healthy men (20–29 yr old) performed ten 2-min bouts of cycle ergometer exercise at a constant work equivalent to an average of 77% of maximum O2 consumption interspersed with 1-min rest. Blood was drawn before and immediately after the exercise challenge. NK cells were isolated from peripheral blood mononuclear cells using a negative magnetic cell separation method. We used Affymetrix U133+2.0 arrays for gene expression and Agilent Human miRNA V2 Microarray for miRNAs. A stringent statistical approach (false discovery rate < 0.05) was used to determine that exercise significantly altered the expression of 986 genes and 23 miRNAs. Using in silico analysis, we found exercise-related gene pathways where there was a high likelihood of gene-miRNA interactions. These pathways were predominantly associated with cancer and cell communication, including p53 signaling pathway, melanoma, glioma, prostate cancer, adherens junction, and focal adhesion. These data support the hypothesis that exercise affects the gene and miRNA expression pattern in the population of NK cells in the circulation and suggest mechanisms through which physical activity could alter health through the innate immune system.
              Cover page: Impact of brief exercise on peripheral blood NK cell gene and microRNA expression in young adults
              • Article
              • Peer Reviewed
              UC Irvine Previously Published Works (2020)
              BACKGROUND: Asthma is the most common chronic illness in children and is independently impacted by obesity and by fitness. The National Youth Fitness Survey collected data on aerobic fitness, body composition, and health outcomes in children 6 to 11 years old. The goal of this study is to test hypotheses regarding relationships between asthma, aerobic fitness, and sedentary time in this uniquely studied cohort of young children. METHODS: A total of 665 children (6-11 years old; 49% male) were included in analyses. We explored relationships between asthma outcomes and aerobic fitness (measured by endurance time), self-reported sedentary time, and body mass index categories. Fitness was categorized as unfit (lowest 25% of endurance times) or fit. Multivariate logistic regression models were created for asthma outcomes and adjusted for race, age, sex, poverty status, and overweight/obesity. RESULTS: Among the participants, 17.9% had a previous history of asthma and 11.4% had current asthma. Additionally, 37.3% of participants were overweight or obese. Low fitness was significantly associated with increased odds of past asthma, current asthma, asthma attacks, wheeze with exercise, and wheeze with activity limitations in multivariate models. Increased sedentary time was significantly associated with increased odds of previous asthma, current asthma, asthma attacks, and wheeze with activity limitations. CONCLUSION: Decreased aerobic fitness and increased sedentary time were associated with worse asthma outcomes in this group of children (6-11 years old). This data suggest that fitness and sedentary time, both modifiable factors, each have an independent effect on asthma and should be included in assessments and management of asthma health.
                Cover page: Low fitness and increased sedentary time are associated with worse asthma-The National Youth Fitness Survey.
                • Article
                • Peer Reviewed
                UC Irvine Previously Published Works (2021)

                Background

                Low physical fitness (PF) levels during childhood affect healthy growth and development, and increase the risk of cardiovascular diseases. Physical education standards exist for nearly all states in the United States, but evaluation of PF in youth has yet to be systematic, reproducible, and harmonized. The purpose of this project was to describe publicly available data of school-based PF testing (SB-PFT).

                Methods

                A list of state-mandated SB-PFT programs published by SHAPE 2016 was confirmed by contacting appropriate authorities. SB-PFT data were obtained through each state's department of education.

                Results

                Sixteen states mandate SB-PFT, with 10 states providing publicly available data; 92% to 100% of states perform the pacer/mile, curl-up, and push-up; 54.2% to 78.5% of elementary and 44% to 66.5% of high-school youth are in the "healthy fitness zone" for aerobic capacity.

                Conclusions

                SB-PFT provided PF data in children across the United States. The variability and inconsistency in reporting and in the values, however, raises questions about the current status of SB-PFT data and its utility in assessing PF in children. The critical nature of PF assessments is highlighted in the current COVID-19 pandemic, during which physical education has been curtailed, and emerging data demonstrate worsening of the already low levels of PF in youth.
                  Cover page: US School‐Based Physical Fitness Assessments and Data Dissemination
                  • Article
                  • Peer Reviewed
                  UC Irvine Previously Published Works (2016)
                  Obesity increases the risk of asthma throughout life but the underlying mechanisms linking these all too common threats to child health are poorly understood. Acute bouts of exercise, aerobic fitness, and levels of physical activity clearly play a role in the pathogenesis and/or management of both childhood obesity and asthma. Moreover, both obesity and physical inactivity are associated with asthma symptomatology and response to therapy (a particularly challenging feature of obesity-related asthma). In this article, we review current understandings of the link between physical activity, aerobic fitness and the asthma-obesity link in children and adolescents (e.g., the impact of chronic low-grade inflammation, lung mechanics, and direct effects of metabolic health on the lung). Gaps in our knowledge regarding the physiological mechanisms linking asthma, obesity and exercise are often compounded by imprecise estimations of adiposity and challenges of assessing aerobic fitness in children. Addressing these gaps could lead to practical interventions and clinical approaches that could mitigate the profound health care crisis of the increasing comorbidity of asthma, physical inactivity, and obesity in children.
                    Cover page: Obesity, Asthma, and Exercise in Child and Adolescent Health.
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