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1.  Multimodal Physical Activity Recognition by Fusing Temporal and Cepstral Information 
A physical activity (PA) recognition algorithm for a wearable wireless sensor network using both ambulatory electrocardiogram (ECG) and accelerometer signals is proposed. First, in the time domain, the cardiac activity mean and the motion artifact noise of the ECG signal are modeled by a Hermite polynomial expansion and principal component analysis, respectively. A set of time domain accelerometer features is also extracted. A support vector machine (SVM) is employed for supervised classification using these time domain features. Second, motivated by their potential for handling convolutional noise, cepstral features extracted from ECG and accelerometer signals based on a frame level analysis are modeled using Gaussian mixture models (GMMs). Third, to reduce the dimension of the tri-axial accelerometer cepstral features which are concatenated and fused at the feature level, heteroscedastic linear discriminant analysis is performed. Finally, to improve the overall recognition performance, fusion of the multi-modal (ECG and accelerometer) and multidomain (time domain SVM and cepstral domain GMM) subsystems at the score level is performed. The classification accuracy ranges from 79.3% to 97.3% for various testing scenarios and outperforms the state-of-the-art single accelerometer based PA recognition system by over 24% relative error reduction on our nine-category PA database.
doi:10.1109/TNSRE.2010.2053217
PMCID: PMC4326092  PMID: 20699202
Accelerometer; cepstrum; electrocardiogram; multimodal signal processing; physical activity recognition
2.  Pioneering the Transdisciplinary Team Science Approach: Lessons Learned from National Cancer Institute Grantees 
The National Cancer Institute has been a leader in supporting transdisciplinary (TD) team science. From 2005-2010, the NCI supported Transdisciplinary Research on Energetic and Cancer I (TREC I), a center initiative fostering the TD integration of social, behavioral, and biological sciences to examine the relationships among obesity, nutrition, physical activity and cancer. In the final year of TREC I, we conducted qualitative in-depth-interviews with 31 participating investigators and trainees to learn more about their experiences with TD team science, including challenges, facilitating factors, strategies for success, and impacts. Five main challenges emerged: (1) limited published guidance for how to engage in TD team science, when TREC I was implemented; (2) conceptual and scientific challenges inherent to efforts to achieve TD integration; (3) discipline-based differences in values, terminology, methods, and work styles; (4) project management challenges involved in TD team science; and (5) traditional incentive and reward systems that do not recognize or reward TD team science. Four main facilitating factors and strategies for success emerged: (1) beneficial attitudes and beliefs about TD research and team science; (2) effective team processes; (3) brokering and bridge-building activities by individuals holding particular roles in a research center; and (4) funding initiative characteristics that support TD team science. Broad impacts of participating in TD team science in the context of TREC I included: (1) new positive attitudes about TD research and team science; (2) new boundary-crossing collaborations; (3) scientific advances related to research approaches, findings, and dissemination; (4) institutional culture change and resource creation in support of TD team science; and (5) career advancement. Funding agencies, academic institutions, and scholarly journals can help to foster TD team science through funding opportunities, institutional policies on extra-departmental and cross-school collaboration, promotion and tenure policies, and publishing opportunities for TD research.
PMCID: PMC4280018  PMID: 25554748
Cross-disciplinary; Transdisciplinary; Team science; Cancer; Energetics
3.  Hierarchical Linear Models for Energy Prediction using Inertial Sensors: A Comparative Study for Treadmill Walking 
Walking is a commonly available activity to maintain a healthy lifestyle. Accurately tracking and measuring calories expended during walking can improve user feedback and intervention measures. Inertial sensors are a promising measurement tool to achieve this purpose. An important aspect in mapping inertial sensor data to energy expenditure is the question of normalizing across physiological parameters. Common approaches such as weight scaling require validation for each new population. An alternative is to use a hierarchical approach to model subject-specific parameters at one level and cross-subject parameters connected by physiological variables at a higher level. In this paper, we evaluate an inertial sensor-based hierarchical model to measure energy expenditure across a target population. We first determine the optimal movement and physiological features set to represent data. Periodicity based features are more accurate (p<0.1 per subject) when generalizing across populations. Weight is the most accurate parameter (p<0.1 per subject) measured as percentage prediction error. We also compare the hierarchical model with a subject-specific regression model and weight exponent scaled models. Subject-specific models perform significantly better (p<0.1 per subject) than weight exponent scaled models at all exponent scales whereas the hierarchical model performed worse than both. However, using an informed prior from the hierarchical model produces similar errors to using a subject-specific model with large amounts of training data (p<0.1 per subject). The results provide evidence that hierarchical modeling is a promising technique for generalized prediction energy expenditure prediction across a target population in a clinical setting.
doi:10.1007/s12652-012-0150-y
PMCID: PMC3891737  PMID: 24443658
Accelerometer; Bayesian Linear regression; Gyroscope; Hierarchical Linear Model
4.  Meal Skipping Linked to Increased Visceral Adipose Tissue and Triglycerides in Overweight Minority Youth 
Obesity (Silver Spring, Md.)  2013;22(5):E77-E84.
Objective
To investigate the impact of eating frequency on dietary intake, physical activity (PA), metabolic, and adiposity measures in minority youth.
Design and Methods
This analysis included 185 overweight (≥85th BMI percentile) Hispanic and African American youth (8–18 years) with the following cross-sectional measures: height, weight, BMI, dietary intake, body composition, metabolic parameters, PA, visceral adipose tissue (VAT), and subcutaneous adipose tissue. Each eating occasion (EO) was defined as ≥50 calories and ≥15 minutes from any previous EO. Participants were dichotomized based on EOs per 24-h into meal skippers <3 EO (MS; n=27) or normal/frequent eaters ≥3 EO (NFE; n=158). ANCOVAs were used to assess dietary intakes, metabolic outcomes, adiposity, and PA between eating frequency groups.
Results
MS compared to NFE consumed 24% fewer calories per 24-h (p≤0.01), 21% more calories per EO (p≤0.01), ate 40% less often (p≤0.01), had 18% higher triglycerides (p=0.03), and 26% more VAT (p=0.03), with no differences in PA.
Conclusions
Although meal skipping was associated with decreased energy intake, it was linked to increased calories per EO and higher triglycerides and VAT, which are strong indicators of deleterious metabolic profiles. These findings elucidate that meal skipping may be associated with increased VAT and related metabolic diseases in high-risk minority youth.
doi:10.1002/oby.20487
PMCID: PMC3759606  PMID: 23613461
Eating Behaviors; Life Styles; Minorities; Visceral Fat; Triglyceride
5.  Temporal Relationship Between Insulin Sensitivity and the Pubertal Decline in Physical Activity in Peripubertal Hispanic and African American Females 
Diabetes Care  2013;36(11):3739-3745.
OBJECTIVE
Little attention has been paid to possible intrinsic biological mechanisms for the decline in physical activity that occurs during puberty. This longitudinal observational study examined the association between baseline insulin sensitivity (SI) and declines in physical activity and increases in sedentary behavior in peripubertal minority females over a year.
RESEARCH DESIGN AND METHODS
Participants were Hispanic and African American girls (n = 55; 76% Hispanic; mean age 9.4 years; 36% obese). SI and other insulin indices were measured at baseline using the frequently sampled intravenous glucose tolerance test. Physical activity was measured on a quarterly basis by accelerometry and self-report.
RESULTS
Physical activity declined by 25% and time spent in sedentary behaviors increased by ∼13% over 1 year. Lower baseline SI predicted the decline in physical activity measured by accelerometry, whereas higher baseline acute insulin response to glucose predicted the decline in physical activity measured by self-report. Time spent in sedentary behavior increased by ~13% over 1 year, and this was predicted by lower baseline SI. All models controlled for adiposity, age, pubertal stage, and ethnicity.
CONCLUSIONS
When evaluated using a longitudinal design with strong outcome measures, this study suggests that lower baseline SI predicts a greater decline in physical activity in peripubertal minority females.
doi:10.2337/dc13-0083
PMCID: PMC3816891  PMID: 23846812
6.  Current mHealth Technologies for Physical Activity Assessment and Promotion 
Context
Novel mobile assessment and intervention capabilities are changing the face of physical activity (PA) research. A comprehensive systematic review of how mobile technology has been used for measuring PA and promoting PA behavior change is needed.
Evidence acquisition
Article collection was conducted using six databases from February to June 2012 with search terms related to mobile technology and PA. Articles that described the use of mobile technologies for PA assessment, sedentary behavior assessment, and/or interventions for PA behavior change were included. Articles were screened for inclusion and study information was extracted.
Evidence synthesis
Analyses were conducted from June to September 2012. Mobile phone–based journals and questionnaires, short message service (SMS) prompts, and on-body PA sensing systems were the mobile technologies most utilized. Results indicate that mobile journals and questionnaires are effective PA self-report measurement tools. Intervention studies that reported successful promotion of PA behavior change employed SMS communication, mobile journaling, or both SMS and mobile journaling.
Conclusions
mHealth technologies are increasingly being employed to assess and intervene on PA in clinical, epidemiologic, and intervention research. The wide variations in technologies used and outcomes measured limit comparability across studies, and hamper identification of the most promising technologies. Further, the pace of technologic advancement currently outstrips that of scientific inquiry. New adaptive, sequential research designs that take advantage of ongoing technology development are needed. At the same time, scientific norms must shift to accept “smart,” adaptive, iterative, evidence-based assessment and intervention technologies that will, by nature, improve during implementation.
doi:10.1016/j.amepre.2013.05.012
PMCID: PMC4199827  PMID: 24050427
7.  Bidirectional Associations Between Future Time Perspective and Substance Use Among Continuation High-School Students 
Substance use & misuse  2013;48(8):574-580.
We examined whether a bidirectional, longitudinal relationship exists between future time perspective (FTP), measured with the Zimbardo Time Perspective Inventory, and any past 30-day use of alcohol, tobacco, marijuana, or hard drugs among continuation high school students (N = 1,310, mean age 16.8 years) in a large urban area. We found increased FTP to be protective against drug use for all substances except alcohol. While any baseline use of substances did not predict changes in FTP 1 year later. The discussion explores why alcohol findings may differ from other substances. Future consideration of FTP as a mediator of program effects is explored.
doi:10.3109/10826084.2013.787092
PMCID: PMC4181553  PMID: 23750661
future time perspective; future orientation; continuation high school; tobacco; alcohol; marijuana; hard drugs; adolescent; toward no drug abuse; substance use
8.  Does community type moderate the relationship between parent perceptions of the neighborhood and physical activity in children? 
Purpose
To examine whether residing in a community designed to promote physical activity moderates the relationship between parent perceptions of the neighborhood and general physical activity or active commuting to school in their children.
Design
Cross-sectional
Setting
San Bernardino County, California.
Subjects
365 families (one parent and one child in grades 4th-8th). 85 reside in a smart growth community designed to be more conducive to physical activity.
Measures
Parent perceptions assessed using the Neighborhood Environment Walkability Scale. General child physical activity measured using accelerometers, and active commuting was self-reported by children.
Analysis
Two sets of regressions were performed: one for general physical activity, and one for active commuting. Separate models were run in the two sets for each of the 14 NEWS factors, while controlling for demographics.
Results
For general physical activity, walking infrastructure, lack of cul-de-sacs and social interaction had significant main effect associations (p≤0.05). No factors were moderated by community. The relationships between active commuting to school and perceived crime, traffic hazards, hilliness, physical barriers, cul-de-sac connectivity, aesthetics, and walking infrastructure were significant for those in the smart growth community only (p≤0.05).
Conclusions
Living in an activity friendly environment is associated with positive relationships between parent perceptions and active commuting behaviors in children. Future interventions should account for both the perceived neighborhood environment and available physical activity infrastructure.
doi:10.4278/ajhp.100827-QUAN-290
PMCID: PMC4124624  PMID: 22747320
physical activity; built environment; active commuting; smart growth; moderation; perceptions; Manuscript format: research; Research purpose: modeling/relationship testing; Study design: quasi-experimental; Outcome measure: behavioral; Setting: family; local community; Health format: physical activity; Strategy: built environment; Target population age: youth, adults; Target population circumstance: geographic location
9.  Mobile Health Technology Evaluation 
Creative use of new mobile and wearable health information and sensing technologies (mHealth) has the potential to reduce the cost of health care and improve well-being in numerous ways. These applications are being developed in a variety of domains, but rigorous research is needed to examine the potential, as well as the challenges, of utilizing mobile technologies to improve health outcomes. Currently, evidence is sparse for the efficacy of mHealth. Although these technologies may be appealing and seemingly innocuous, research is needed to assess when, where, and for whom mHealth devices, apps, and systems are efficacious.
In order to outline an approach to evidence generation in the field of mHealth that would ensure research is conducted on a rigorous empirical and theoretic foundation, on August 16, 2011, researchers gathered for the mHealth Evidence Workshop at NIH. The current paper presents the results of the workshop. Although the discussions at the meeting were cross-cutting, the areas covered can be categorized broadly into three areas: (1) evaluating assessments; (2) evaluating interventions; and, (3) reshaping evidence generation using mHealth. This paper brings these concepts together to describe current evaluation standards, future possibilities and set a grand goal for the emerging field of mHealth research.
doi:10.1016/j.amepre.2013.03.017
PMCID: PMC3803146  PMID: 23867031
10.  Modifying Influence of Dietary Sugar in the Relationship Between Cortisol and Visceral Adipose Tissue in Minority Youth 
Obesity (Silver Spring, Md.)  2013;22(2):474-481.
Objective
Cortisol has been associated with preferential visceral adipose tissue (VAT) deposition; however findings in humans are mixed, which may be clarified when diet is considered.
Design and Methods
Participants included 165 African American and Latino, overweight adolescents (BMI% 97.2±3.2%, ages 13-18, 67% Latino, 66% female). Body composition was determined by DEXA, abdominal fat depots (VAT, subcutaneous (SAT)) by multiple-slice MRI, time-controlled serum sample to measure cortisol, and 2-day multi-pass 24-hour dietary recall. Linear regression analysis examined the cross-sectional relationship between cortisol, and the interaction of diet and cortisol on adiposity measures. Sex, race, age and total body fat were a priori covariates.
Results
There was a significant interaction between cortisol and sugar (total and added) in the prediction of VAT (pinteraction<=0.05). Amongst participants with high total or added-sugar intake, cortisol was significantly associated with VAT (β=0.031 p<0.001; β=0.026 p<0.001), with no relationship in low consumers of total or added-sugar.
Conclusion
Dietary sugar may play an important role in modifying the relationship between cortisol and VAT, such that cortisol is significantly associated with elevated VAT under conditions of high sugar intake.
doi:10.1002/oby.20594
PMCID: PMC3946447  PMID: 23929660
Adolescence; Cortisol; Omega-3 fatty acids; Sugar; visceral fat
11.  Momentary Assessment of Affect, Physical Feeling States, and Physical Activity in Children 
Objective
Most research on the interplay of affective and physical feelings states with physical activity in children has been conducted under laboratory conditions and fails to capture intraindividual covariation. The current study used Ecological Momentary Assessment (EMA) to bi-directionally examine how affective and physical feeling states are related to objectively-measured physical activity taking place in naturalistic settings during the course of children’s everyday lives.
Methods
Children (N = 119) (ages 9–13 years) (52% male, 32% Hispanic) completed eight days of EMA monitoring, which measured positive affect (PA), negative affect (NA), feeling tired, and feeling energetic up to seven times per day. EMA responses were time-matched to accelerometer assessed moderate-to-vigorous physical activity (MVPA) in the 30 minutes before and after each EMA survey.
Results
Higher ratings of feeling energetic and lower ratings of feeling tired were associated with more MVPA in the 30 minutes after the EMA prompt. More MVPA in the 30 minutes before the EMA prompt was associated with higher ratings of PA and feeling energetic, and lower ratings of NA. Between-subject analyses indicated that mean hourly leisure-time MVPA was associated with less intraindividual variability in PA and NA.
Conclusions
Physical feeling states predict subsequent physical activity levels, which in turn, predict subsequent affective states in children. Active children demonstrated higher positive and negative emotional stability. Although the strength of these associations were of modest magnitude and their clinical relevance is unclear, understanding the antecedents to and consequences of physical activity may have theoretical and practical implications for the maintenance and promotion of physical activity and psychological well-being in children.
doi:10.1037/a0032640
PMCID: PMC4113469  PMID: 23668846
positive affect; negative affect; fatigue; physical activity; ecological momentary assessment
12.  Genetic and Clinical Markers of Elevated Liver Fat Content in Overweight and Obese Hispanic Children 
Obesity (Silver Spring, Md.)  2013;21(12):10.1002/oby.20523.
Objective
Genetic variation in six genes has been associated with elevated liver fat and nonalcoholic fatty liver disease in adults. We sought to determine the influence of these genes on liver fat and whether a genetic risk score (GRS) would improve upon the ability of common clinical risk factors to predict elevated liver fat content (ELF) in Hispanic children.
Design and Methods
223 obese Hispanic children were genotyped for six SNPs. MRI was used to measure liver fat. A GRS was tested for association with ELF using multivariate linear regression. Predictors were assessed via ROC curves and pair-wise analysis was used to determine significance alone and combined with clinical markers.
Results
Only variants in PNPLA3 and APOC3 genes were associated with liver fat (p<0.001, p=0.01, respectively). Subjects with a GRS=4 had ~3-fold higher liver fat content than subjects with GRS of 0 (15.1±12.7% vs. 5.1±3.7%, p=0.03). While the addition of the GRS to a model containing BMI and liver enzymes increased ROC AUC from 0.83 to 0.85 [95% CI, 0.79-0.89], (p=0.01), it does not improve detection of ELF from a clinical perspective.
Conclusions
Only PNPLA3 and APOC3 were related to ELF and a GRS comprised of these susceptibility alleles did not add to the discriminatory power of traditional biomarkers for clinical assessment of liver fat.
doi:10.1002/oby.20523
PMCID: PMC3855210  PMID: 23804528
NAFLD; liver fat; Hispanic; obesity; genetic risk
13.  Prevalence and co-occurrence of addictive behaviors among former alternative high school youth 
Background and Aims
Recent work has studied multiple addictions using a matrix measure, which taps multiple addictions through single responses for each type.
Methods
The present study investigated use of a matrix measure approach among former alternative high school youth (average age = 19.8 years) at risk for addictions. Lifetime and last 30-day prevalence of one or more of 11 addictions reviewed in other work (Sussman, Lisha & Griffiths, 2011) was the primary focus (i.e., cigarettes, alcohol, other/hard drugs, eating, gambling, Internet, shopping, love, sex, exercise, and work). Also, the co-occurrence of two or more of these 11 addictive behaviors was investigated. Finally, the latent class structure of these addictions, and their associations with other measures, was examined.
Results
We found that ever and last 30-day prevalence of one or more of these addictions was 79.2% and 61.5%, respectively. Ever and last 30-day co-occurrence of two or more of these addictions was 61.5% and 37.7%, respectively. Latent Class Analysis suggested two groups: a generally Non-addicted Group (67.2% of the sample) and a “Work Hard, Play Hard”-addicted Group that was particularly invested in addiction to love, sex, exercise, the Internet, and work. Supplementary analyses suggested that the single-response type self-reports may be measuring the addictions they intend to measure.
Discussion and Conclusions
We suggest implications of these results for future studies and the development of prevention and treatment programs, though much more validation research is needed on the use of this type of measure.
doi:10.1556/JBA.3.2014.005
PMCID: PMC3969796  PMID: 24701344
multiple addictions; prevalence; co-occurrence; latent class analysis; addiction groups; convergent validity
14.  Psychometrics of the Eating in Emotional Situations Questionnaire (EESQ) among low-income Latino elementary-school children 
Eating behaviors  2011;12(2):156-159.
The current study examines the psychometric properties of the Eating in Emotional Situations Questionnaire (EESQ) and the frequency of eating in emotional situations among 159 low-income Latino fourth graders. The EESQ assesses eating in emotional situations that are emotion-driven (“I eat when I am lonely”) and context-driven (“I eat when I get a really bad grade”). Internal consistencies for the EESQ subscales and total scale ranged from .70 to .86. Criterion validity of the EESQ was established by statistically significant correlations between the EESQ subscales and total scale, and uncontrollable eating, external eating, and junk food intake. Eating in emotional situations was common in the sample; almost one-half reported eating in at least 3 of the 11 types of emotional situations (e.g. when stressed, sad, bored) and 28% reported eating in at least 6 types. Overall, these findings provide support for the internal consistency and validity of the EESQ in low-income Latino children, and suggest that eating in emotional situations is moderately present in this demographic. Future studies are needed to validate the EESQ in other ethnic groups and examine the longitudinal tracking of eating in emotional situations among Latino youth.
doi:10.1016/j.eatbeh.2011.01.004
PMCID: PMC3947794  PMID: 21385647
Eating in Emotional Situations Questionnaire (EESQ); emotional eating; children; Latino; Hispanic
15.  Prevalence and co-occurrence of addictive behaviors among former alternative high school youth 
Background and Aims: Recent work has studied multiple addictions using a matrix measure, which taps multiple addictions through single responses for each type. Methods: The present study investigated use of a matrix measure approach among former alternative high school youth (average age = 19.8 years) at risk for addictions. Lifetime and last 30-day prevalence of one or more of 11 addictions reviewed in other work (Sussman, Lisha & Griffiths, 2011) was the primary focus (i.e., cigarettes, alcohol, other/hard drugs, eating, gambling, Internet, shopping, love, sex, exercise, and work). Also, the co-occurrence of two or more of these 11 addictive behaviors was investigated. Finally, the latent class structure of these addictions, and their associations with other measures, was examined. Results: We found that ever and last 30-day prevalence of one or more of these addictions was 79.2% and 61.5%, respectively. Ever and last 30-day co-occurrence of two or more of these addictions was 61.5% and 37.7%, respectively. Latent Class Analysis suggested two groups: a generally Non-addicted Group (67.2% of the sample) and a “Work Hard, Play Hard”-addicted Group that was particularly invested in addiction to love, sex, exercise, the Internet, and work. Supplementary analyses suggested that the single-response type self-reports may be measuring the addictions they intend to measure. Discussion and Conclusions: We suggest implications of these results for future studies and the development of prevention and treatment programs, though much more validation research is needed on the use of this type of measure.
doi:10.1556/JBA.3.2014.005
PMCID: PMC3969796  PMID: 24701344
multiple addictions; prevalence; co-occurrence; latent class analysis; addiction groups; convergent validity
16.  Locations of Joint Physical Activity in Parent-Child Pairs Based on Accelerometer and GPS Monitoring 
Background
Parental factors may play an important role in influencing children’s physical activity levels.
Purpose
This cross-sectional study sought to describe the locations of joint physical activity among parents and children.
Methods
Parent-child pairs (N = 291) wore an Actigraph GT2M accelerometer and GlobalSat BT-335 Global Positioning Systems (GPS) device over the same 7-day period. Children were ages 8–14 years. Joint behavior was defined by a linear separation distance of less than 50m between parent and child. Land use classifications were assigned to GPS data points.
Results
Joint physical activity was spread across residential locations (35%), and commercial venues (24%), and open spaces/parks (20%). Obese children and parents performed less joint physical activity in open spaces/parks than under/normal weight children and parents (p’s < .01).
Conclusions
Understanding where joint parent-child physical activity naturally occurs may inform location-based interventions to promote these behaviors.
doi:10.1007/s12160-012-9417-y
PMCID: PMC3562385  PMID: 23011914
moderate-to-vigorous physical activity; sedentary behavior; parents; children; global positioning systems; environments
17.  Imagine HEALTH: results from a randomized pilot lifestyle intervention for obese Latino adolescents using Interactive Guided ImagerySM 
Background
There is an urgent need for innovative and developmentally appropriate lifestyle interventions to promote healthy lifestyle behaviors and to prevent the early onset of type 2 diabetes and cardiovascular disease risk in obese Latino adolescents. Guided imagery offers promise to reduce stress and promote lifestyle behavior change to reduce disease risk in obese adolescents. Our objectives were: 1) To pilot test a new 12-wk lifestyle intervention using a randomized trial design in obese Latino adolescents, in order to determine the effects of the mind-body modality of Interactive Guided ImagerySM (IGI), over and above those of a didactic lifestyle education, on insulin resistance, eating and physical activity behaviors, stress and stress biomarkers; and 2) To explore the role of intervention-related changes in stress and stress biomarkers on changes in metabolic outcomes, particularly insulin resistance.
Methods
Obese (BMI > 95th percentile), Latino adolescents (n = 35, age 14-17) were randomized to receive either 12 weekly sessions of a lifestyle education plus guided imagery program (GI), or lifestyle education plus a digital storytelling computer program (DS). Between-group differences in behavioral, biological, and psychological outcomes were assessed using unpaired T-tests and ANCOVA in the 29 subjects who completed the intervention.
Results
The GI group demonstrated significant reductions in leisure sedentary behavior (p < .05) and increases in moderate physical activity (p < .05) compared to DS group, and a trend toward reduced caloric intake in GI vs DS (p = .09). Salivary cortisol was acutely reduced by stress-reduction guided imagery (p < .01). There were no group differences in adiposity, insulin resistance, perceived stress, or stress biomarkers across the 12-week intervention, though decrease in serum cortisol over the course of the intervention was associated with improved insulin sensitivity (p = .03) independent of intervention group and other relevant co-variates.
Conclusions
The improvements in physical activity and stress biomarkers following this pilot intervention support the role of guided imagery in promoting healthy lifestyle behavior change and reducing metabolic disease risk in obese Latino adolescent populations. Future investigations will be needed to determine the full effects of the Imagine HEALTH intervention on insulin resistance, stress, and stress biomarkers.
Trial registration
Clinicaltrials.gov Registry #: NCT01895595
doi:10.1186/1472-6882-14-28
PMCID: PMC3931490  PMID: 24433565
Guided imagery; Obesity; Childhood; Latino; Adolescents; Lifestyle; Diabetes
18.  Evaluation of the Psychometric Properties of the Revised Inventory of the Dimensions of Emerging Adulthood (IDEA-R) in a Sample of Continuation High School Students 
Evaluation & the health professions  2012;10.1177/0163278712452664.
It is now presumed that youth do not move directly from adolescence to adulthood, but rather pass through a transitional period, “emerging adulthood.” The Revised Inventory of the Dimensions of Emerging Adulthood (IDEA-R) is a self-report instrument developed to examine the attributes of this period. “At-risk” youth appear to enter emerging adulthood developmental tasks at a slightly earlier age than general population youth. In the present study, a 21-item version of the IDEA was administered to a sample of 1676 “at-risk” continuation (alternative) high school students in Southern California. Principal component factor analysis with orthogonal rotation revealed three factors the authors labeled “Identity Exploration,” “Experimentation/Possibilities,” and “Independence.” Overall, the measure demonstrated high internal consistency. Construct validity analyses indicated that the measure was correlated with demographics, risk behaviors, and psychological measures. The authors conclude that the IDEA-R is a useful instrument for measuring emerging adulthood in at-risk populations.
doi:10.1177/0163278712452664
PMCID: PMC3796175  PMID: 22786874
emerging adulthood; continuation high school; at-risk youth; inventory of the dimensions of emerging adulthood (IDEA); psychometrics
19.  Motivational Interviewing for Adolescent Substance Use: A Review of the Literature 
Addictive behaviors  2012;37(12):1325-1334.
Motivational Interviewing (MI) is a widely-used approach for addressing adolescent substance use. Recent meta-analytic findings show small but consistent effect sizes. However, differences in intervention format and intervention design, as well as possible mediators of change, have never been reviewed. This review of the literature summarizes the most up-to-date MI interventions with adolescents, looks at differences between intervention format and design, and discusses possible theory-based mechanisms of change. Of the 39 studies included in this review, 67% reported statistically significant improved substance use outcomes. Chi square results show no significant difference between interventions using feedback or not, or interventions combined with other treatment versus MI alone. The need for systematic investigation in theory-based mechanisms of change is presented.
doi:10.1016/j.addbeh.2012.07.001
PMCID: PMC3496394  PMID: 22958865
Motivational Interviewing; Adolescent; Substance Use; Alcohol; Tobacco; Marijuana
20.  mHealth approaches to child obesity prevention: successes, unique challenges, and next directions 
Childhood obesity continues to be a significant public health issue. mHealth systems offer state-of-the-art approaches to intervention design, delivery, and diffusion of treatment and prevention efforts. Benefits include cost effectiveness, potential for real-time data collection, feedback capability, minimized participant burden, relevance to multiple types of populations, and increased dissemination capability. However, these advantages are coupled with unique challenges. This commentary discusses challenges with using mHealth strategies for child obesity prevention, such as lack of scientific evidence base describing effectiveness of commercially available applications; relatively slower speed of technology development in academic research settings as compared with industry; data security, and patient privacy; potentially adverse consequences of increased sedentary screen time, and decreased focused attention due to technology use. Implications for researchers include development of more nuanced measures of screen time and other technology-related activities, and partnering with industry for developing healthier technologies. Implications for health practitioners include monitoring, assessing, and providing feedback to child obesity program designers about users' data transfer issues, perceived security and privacy, sedentary behavior, focused attention, and maintenance of behavior change. Implications for policy makers include regulation of claims and quality of apps (especially those aimed at children), supporting standardized data encryption and secure open architecture, and resources for research–industry partnerships that improve the look and feel of technology. Partnerships between academia and industry may promote solutions, as discussed in this commentary.
doi:10.1007/s13142-013-0222-3
PMCID: PMC3830013  PMID: 24294329
Childhood; Obesity; Mobile technology; mHealth; Screen time; Focused attention; Sedentary behavior
21.  Joint Physical Activity and Sedentary Behavior in Parent-Child Pairs 
Purpose
Research examined joint physical activity and sedentary behavior among 291 parent-child pairs who both wore an accelerometer and global positioning systems (GPS) device over the same 7-day period.
Methods
Children were 52.2% female, 8-14 years, and 43.0% Hispanic. Parents were 87.6% female. An Actigraph GT2M accelerometer and GlobalSat BT-335 GPS device collected activity and global positioning data, respectively. Linear distance between the parent and child for each 30-sec. epoch was calculated using geographic coordinates from the GPS. Joint behavior was defined as a separation distance less than 50m between parents and children.
Results
On average during non-school waking hours, parents and children spent 2.4 min. (SD = 4.1) per day performing moderate-to-vigorous physical activity (MVPA) together and 92.9 min. (SD = 40.1) per day in sedentary behavior together. Children engaged in an average of 10 min. per day of MVPA during non-school waking hours when their parent was nearby but not engaging in MVPA. During this same period, parents engaged in 4.6 min. per day of MVPA when their child was nearby but not engaging in MVPA. Household income level and the child’s age were negatively associated with joint MVPA. Girls engaged in a greater percentage of their total MVPA together with their parent than boys. Girls and older children engaged in more sedentary behavior together with their parent than boys and younger children. Older parents engaged in a greater percentage of their sedentary behavior together with their children than younger parents.
Conclusion
Replacing the time that parents and children spend together in sedentary pursuits with joint physical activity could have health benefits, especially for girls, older children, older parents, and higher income families.
doi:10.1249/MSS.0b013e31825148e9
PMCID: PMC3399090  PMID: 22367744
moderate-to-vigorous physical activity; accelerometer; global positioning systems; age; sex
22.  Predicting Self-Initiated Marijuana Use Cessation among Youth at Continuation High Schools 
The current article reports a large scale study of the prediction of marijuana use cessation among individuals attending alternative high schools who were regular users at baseline. Based on the Triadic Influence Theory, predictors of marijuana use cessation at 1-year follow-up were organized by type of influence (e.g., interpersonal, cultural and attitudinal, and intrapersonal) and level of influence (e.g., distal and ultimate). Among the 522 students who were past 30-day marijuana users at baseline, quitting was defined as having not used marijuana in the last 30 days at 1-year follow-up (43% of baseline users). To account for the level of influence we employed a theory-based analytic strategy, hierarchical regression. In the final multivariate model, lower level of baseline marijuana use and less of a likelihood to endorse pro-drug-use myths remained predictors of marijuana use cessation 1-year later. Implications of these findings include the need to develop cessation programs that reduce psychological dependence on marijuana use, and correct cognitive misperceptions about drug use in order to help adolescents make decisions that lead to health-promoting behaviors.
doi:10.3389/fpsyt.2013.00069
PMCID: PMC3724123  PMID: 23898305
marijuana; cessation; adolescents; youth; cannabis; self-initiated; predictors
23.  Physical activity is related to insulin sensitivity in children and adolescents, independent of adiposity: a review of the literature 
In adults, there is evidence that physical activity effectively improves insulin sensitivity regardless of adiposity. Whether this is also the case in children and adolescents has been less clear. Whether this is also the case in children and adolescents is less clear. Clarifying this matter may help to identify the best outcomes to target in exercise programs for these age groups, where changes in adiposity may not always be desirable or realistic. A review of the literature was conducted on studies that examined the relationships of physical activity, cardiorespiratory fitness and strength with insulin sensitivity independent of adiposity in children and adolescents. Experimental (intervention) and correlational (longitudinal and cross-sectional) studies on participants ages 18 and younger were identified. A total of 42 studies were included in this review. Sample sizes in the studies ranged from 14 to 4,955 participants, with individual ages ranging from 5 to 19 years. A significant relationship with SI existed in 78% of studies on physical activity, 69% of studies on cardiorespiratory fitness and 66% of studies on strength. In studies that examined both physical activity and cardiorespiratory fitness concurrently, evidence suggests that they are both correlated with insulin sensitivity independent of adiposity, especially when physical activity is at higher intensities. However the strength of this relationship might be influenced by study design, measurement techniques and participant characteristics. This is the first review of its type to take research design into account, and to examine study outcomes according to participant ethnicity, gender, age, pubertal status and weight status.
doi:10.1002/dmrr.2292
PMCID: PMC3390444  PMID: 22389103
24.  One-year outcomes of a drug abuse prevention program for older teens and emerging adults: Evaluating a motivational interviewing booster component 
Health Psychology  2011;31(4):476-485.
Objective
The present study tested the efficacy of motivational interviewing-based booster sessions for Project Towards No Drug Abuse (TND), a 12-session school-based curriculum targeting youth at risk for drug abuse. In addition, generalization of effects to risky sexual behavior was assessed. The one-year outcomes evaluation of the project is presented.
Methods
A total of 24 schools were randomized to one of three conditions: Standard Care Control (SCC), TND classroom program only (TND-only), and TND plus Motivational Interviewing booster (TND+MI). A total of 1186 participants completed baseline and one-year follow-up surveys. Following the classroom program, youth in the TND+MI condition received up to three sessions of MI in person or by telephone. Effects were examined on 30-day cigarette, alcohol, marijuana, and hard drug use, as well as measures of risky sexual behavior (number of sex partners, condom use, having sex while using drugs or alcohol).
Results
Collapsed across the two program conditions, results showed significant reductions in alcohol, hard drug use, and cigarette smoking, relative to controls. These effects held for an overall substance use index. The MI booster component failed to achieve significant incremental effects above and beyond the TND classroom program. No effects were found on risky sexual behavior.
Conclusions
While the program effects of previous studies were replicated, the study failed to demonstrate that an adequately implemented MI booster was of incremental value at one-year follow-up.
doi:10.1037/a0025756
PMCID: PMC3276711  PMID: 21988096
one-year follow-up; drug prevention; continuation high schools; Motivational Interviewing; boosters
25.  Increasing Physical Activity Decreases Hepatic Fat and Metabolic Risk Factors 
This study assessed the changes in time spent in moderate to vigorous physical activity (MVPA) on fat depots, insulin action, and inflammation. Longitudinal data were generated from 66 Hispanic adolescents (15.6±1.1 yr; BMI percentile 97.1±3.0) who participated in a 16-wk nutrition or nutrition+exercise intervention. There were no effects of the intervention on PA, but there were inter-individual changes in PA. For purposes of this analysis, all intervention groups were combined to assess how changes in PA during 16 wk affected changes in adiposity, insulin action, and markers of inflammation. MVPA was assessed by 7-day accelerometry, total body fat via DXA, liver fat by MRI, and insulin, glucose and HOMA-IR via a fasting blood draw. A repeated measures ANCOVA was used to assess the effect of MVPA on fat depots, insulin action, and inflammatory markers. Sixty-two percent of participants increased MVPA (mean increase, 19.7±16.5 min/day) and 38% decreased MVPA (mean decrease, 10.7±10.1 min/day). Those who increased MVPA by as little as 20 min per day over 16 wk, compared to those who decreased MVPA, had significant reductions in liver fat (−13% vs. +3%; P=0.01), leptin levels (−18% vs. +4%; P=0.02), and fasting insulin (−23% vs. +5%; P=0.05). These findings indicate that a modest increase in MVPA can improve metabolic health in sedentary overweight Hispanic adolescents.
PMCID: PMC3695481  PMID: 23814456
Moderate-to-Vigorous Physical Activity; Obesity

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