The Physical Activity Guidelines and Diabetes-Related Mortality: National Health and Nutrition Examination Survey 1999-2006.

Background: Previous studies have indicated an inverse relationship between aerobic physical activity (PA) and risk of diabetes-related mortality (DRM). However, the contribution of aerobic PA across multiple domains, while also considering the contribution of muscle-strengthening activity (MSA), in reduction of risk for DRM has yet to be examined. Purpose: The aim of this study is to examine the individual and combined associations of aerobic PA and MSA with DRM. Methods: The study sample (n = 13,350) included adult (20-79 years of age) participants from the 1999 to 2006 National Health and Nutrition Examination Survey. PA was categorized into 6 categories based around the 2018 PA guidelines: category 1 (inactive), category 2 (insufficient aerobic PA and no MSA), category 3 [active (aerobic) and no MSA], category 4 (no aerobic PA and sufficient MSA), category 5 (insufficient aerobic PA and sufficient MSA), and category 6 (meeting both recommendations). The dependent variable in this study was DRM, which includes those who had diabetes as the primary cause of death as well as those with diabetes listed as an underlying cause of death. Cox proportional hazards models were used for all analyses. Results: Following adjustment for covariates, significant risk reductions for DRM were found only in category 3 (HR = 0.57; 95% confidence interval: 0.37-0.88). Conclusions: Results suggest that meeting the aerobic PA guidelines significantly reduces the risk for DRM. Those meeting versus not meeting the MSA guidelines seem to have no difference in risk for DRM independent of aerobic PA.

Associations among Motor Competence, Physical Activity, Perceived Motor Competence, and Aerobic Fitness in 10-15-Year-Old Youth.

(1) Background: The developmental model describes possible mechanisms that could impact the trajectory of children and adolescents' health behaviors related to obesity; however, few data are available that support this model in the adolescent population. This study investigated the associations among motor competence (MC), moderate-to-vigorous physical activity (MVPA), perceived motor competence (PMC), and aerobic fitness in children and adolescents and the mediating and moderating effects of PMC, aerobic fitness, and weight status on the MC-MVPA relationship. (2) Methods: Participants included 47 adolescents (12.2 ± 1.6 y; 55% male) who completed the Bruininks-Oseretsky Test of Motor Proficiency, 2nd Edition (MC), Harter's perceived self-competency questionnaire (PMC), and the PACER test (aerobic fitness) and whose MVPA was measured via accelerometry. The body mass index (BMI) was calculated from measured height and weight. (3) Results: There were positive correlations between MC and fitness [rs(47) = 0.469, p < 0.01], PMC and fitness [rs(47) = 0.682, p < 0.01], and PMC and MC [rs(47) = 0.416, p < 0.01]. There were no associations among MVPA and MC, PMC, or fitness (p > 0.05). There were inverse associations between BMI and both MVPA [rs(44) = -0.410, p < 0.01] and fitness [rs(47) = 0.295, p < 0.05]. The association between MC and MVPA was mediated by fitness (ß = 0.3984; 95% CI (0.0564-0.7985)). (4) Conclusions: The associations among MC, PMC, and fitness highlight the critical role of MC in health and partially support the proposed developmental model concerning the relationships that exist among MC, MVPA, PMC, fitness, and BMI.

A Community Profile of Walking and Cycling for Exercise or Transportation in a Rural County in the Southeastern United States.

People living in rural areas of the United States, especially in the southern region, are much less likely to walk or cycle for leisure time or transportation. The purpose of this study is to provide a more detailed community-level estimate of walking and cycling behaviors and attitudes among adults living in a rural county (Hardeman County, TN) participating in a High Obesity Program (HOP) from the Centers for Disease Control and Prevention. Telephone interviews and online surveys regarding walking and cycling behaviors, attitudes, and perceptions of the built environment were completed by 634 adults. Questions originated from the 2002 National Survey of Bicyclist and Pedestrian Attitudes and Behavior. Respondents were classified as walkers, cyclists, or both. Chi-square and logistic regression were used for data analysis. Of adults in this county, 67.2% were walkers and 16.2% cyclists. Both forms of active living tended to decrease with age, especially after 50 years. Walking was associated with younger ages, 2-person households, positive perceived health, and a feeling that walking was good for them. Cycling was only associated with age. Most people felt that their communities were safe places to walk or bike. Walking was most often done on roads or road shoulder. Social support and intrinsic motivators may also play a role in walking and bicycling in rural areas. Interventions that promote walking and cycling in rural areas should provide a means for social support, creating activity-friendly routes perceived to be safe, and enhanced destinations for places to be physically active.

Accelerometer-Measured Physical Activity and Cardiometabolic Risk Factors by Race-Ethnicity: 2003-2006 NHANES.

Previous studies suggest that the magnitude of morbidity/mortality reduction may differ between race-ethnic groups despite equated dose of physical activity (PA). The purpose of this study was to compare the potential racial-ethnic differences in cardiometabolic risk factors (CMRF) across quartiles of accelerometer-derived total activity counts/day (TAC/d) among US adults. The final sample (n=4144) included adults who participated in the 2003-2006 National Health and Nutrition Examination Survey (NHANES). CMRF included fasting glucose (FG), fasting insulin (FI), HOMA-IR, resting systolic (SBP) and diastolic blood pressure (DBP), waist circumference (WC), BMI, CRP, HDL-C, LDL-C, and triglycerides. Race-ethnic groups examined included non-Hispanic white (NHW), non-Hispanic black (NHB), and Mexican American (MA). In the highest quartile, NHW had significantly lower values of HOMA-IR, FI, SBP, BMI, WC, and HDL-C when compared to NHB. Compared to MA in the highest quartile, NHW had significantly lower values of HOMA-IR, FI, BMI, and triglycerides. Significant race-ethnic differences were found for several CMRF, especially among those who were in the top quartile of PA (e.g., the most active adults). It is probable that the protective effect of higher volumes of PA on CMRF is moderated by other non-PA factors distinct to NHB and MA.

What Parental Correlates Predict Children's Active Transportation to School in the Southeast United States?

BACKGROUND: School-aged children in the Southeast, compared with other United States of America (US) regions, have significantly lower levels of active transportation to school (ATS). The purpose of this study was to contrast the parental correlates of ATS choice specific to the Southeast with other areas of the US. METHODS: This study utilized national data from 2952 households with school-aged children located within a 20-minute walk to a school. Parents reported their children's ATS behavior and their own ATS beliefs and perceptions. Logistic regression contrasted correlates of parents from the Southeast with other regions. RESULTS: Parents in the Southeast, compared with parents across the US, were significantly less likely to allow their child to take ATS (12.9% vs 33.3%, respectively) (odds ratio [OR] = 0.46; 95% confidence interval [CI] = 0.36-0.59). Specific to the Southeast, parental correlates linked to increases in ATS were Black race/ethnicity (OR = 1.68; 95% CI, 1.31-2.60), being single, (OR = 1.71; 95% CI, 1.15-2.54), and any parental physical activity (P value for trend = .0053). The only correlate associated with a decrease in ATS in the Southeast was heightened safety concerns (eg, traffic speed, safe crossings) (OR = 0.44; 95% CI, 0.23-0.84). CONCLUSIONS: Among households with children in the Southeast, ATS interventions that allay parental safety concerns and that promote physical activity among parents might lead to increases in ATS.

Leisure-time aerobic physical activity and the risk of diabetes-related mortality: An analysis of effect modification by race-ethnicity.

AIMS: To examine the relationship between aerobic moderate-to-vigorous intensity leisure-time physical activity (LTPA) and the risk of diabetes-related mortality in the NHANES III (1988-1994) while considering potential effect modification by race-ethnicity. METHODS: The study sample (n = 14,006) included adults, 20-79 years of age, with Mobile Examination Center (MEC) data. An age-standardized physical activity score (PAS) was calculated from the self-reported frequency and intensity of 12 leisure-time aerobic activities. Three categories of PA were examined: inactive (PAS = 0), insufficiently active (PAS >0-<10), and active (PAS ≥10). Diabetes-related mortality was defined as death from diabetes mellitus. Cox Proportional Hazard models were used all analyses. RESULTS: A statistically significant reduction in risk was found for insufficiently active (HR 0.59, 95% CI 0.40-0.90) and active non-Hispanic black (NHB) (HR 0.54, 95% CI 0.34-0.88). Among active non-Hispanic white (NHW), a similar pattern of risk reduction was found, however, this relationship was borderline significance (HR 0.59, 95% CI 0.35-1.02, p = 0.06). CONCLUSIONS: Any volume of aerobic LTPA is beneficial in terms of reducing the risk of diabetes-related mortality. However, these benefits may differ by racial-ethnic group, with further research on health disparities in the area of PA being warranted.

Challenges and opportunities related to the objective assessment of physical activity within U.S. health surveys.

Public health surveillance is a vital component in the assessment of health-related behaviors such as physical activity (PA). With multiple active national health surveys in the United States, questions arise about how data are collected, what each data source contributes to the overall knowledge base about PA and health outcomes, and how to interpret PA data from different data sources to gain an understanding about PA at the population level. This article highlights specifically the challenges and opportunities with using wearable devices in population-level PA assessment. A major challenge faced by PA assessment researchers is that of which assessment methods and evaluation tools to use and under what circumstances to use them. This article discusses issues related to (1) what device to use, (2) how to collect data, (3) how to process data, (4) how to analyze the data, and (5) how to report the procedures used. These decisions shape not only the data collection process including collection time and cost but also directly impact data analysis and subsequently the outcomes of interest. This article discusses the implications of using different assessment methods and evaluation tools and how the use of sensor-based tools may impact the future of PA assessment at the population level. There are a number of opportunities emerging for population-level assessment of PA due in part to the technological advances occurring with wearable technology. These opportunities may afford surveillance systems new data streams to bolster what is currently being collected to provide more robust estimates of PA and other health behaviors. The article concludes with some discussion about how the landscape of population-level PA assessment is changing, thanks to increasing opportunities to collect wearable device data. With new data streams becoming available through advanced wearable devices containing multiple sensor types and the opportunity for corporate partnerships, the way PA is being assessed could change considerably in the near future. While acknowledging the limitations of wearable technology, it is an exciting time for PA assessment, given the possibilities on the horizon.

Demographic, health behavior, and cardiometabolic risk factor profile in yoga and non-yoga participants: NHANES 1999-2006.

OBJECTIVE: To examine and compare the demographic, health behavior, and cardiometabolic risk factor characteristics of participants who report 1) participating in yoga, 2) not participating yoga, or 3) are inactive, using a nationally representative sample of U.S. adults. DESIGN: Study participants were from the 1999-2006 National Health and Nutrition Examination Survey (NHANES) who self-reported participation in yoga (n = 74), no-yoga (n = 3,753) or were inactive (n = 1,285). Participants in the no-yoga group did engage in other types of physical activity, while the inactive group reported no activity during the survey period. RESULTS: Yoga participants were primarily female (80.7%), college educated (51.9%), mostly non-smokers (46.9%), and reported moderate alcohol consumption (72.1%). Yoga participants were found to be significantly less likely to have an elevated waist circumference (OR = 0.40, p < 0.01; OR = 0.30, p < 0.01), and a low HDL (OR = 0.43, p = 0.03; OR = 0.34, p < 0.05) compared to both non-yoga participants and inactive individuals, respectively. Yoga participants were 61% less likely to have elevated blood glucose compared to non-yoga participants (OR = 0.39, p < 0.05). Compared to inactive individuals, yoga participants were 52% (OR = 0.48, p < 0.05) and 66% (OR = 0.34, p < 0.05) less likely have an elevated body mass index and have elevated triglyceride levels, respectively. CONCLUSIONS: Given the emergence of yoga as a common form of physical activity, it is imperative to understand the characteristics of those who participate in yoga to further understand its relationship with cardiovascular risk. This study was one of the first to use nationally-representative data and objectively measured cardiometabolic variables. Key Words: complementary medicine, epidemiology, survey, population, physical activity, cardiovascular disease.

Health-enhancing physical activity during practice among student football managers at a Division I university.

Objective: Student football managers have demands on their time that may pose barriers to meeting recommended current physical activity (PA) guidelines. The study sought to assess the amount of PA obtained by student football managers at a NCAA Division I Football university. Participants: Subjects were student football managers (n = 14) with data collected in the fall 2015. Methods: Participants wore an Omron HJ-720ITFFP pedometer for seven consecutive days during football activities only, while self-reporting their overall PA on day 7. Measures were analyzed using repeated measures and mixed-design ANOVAs. Results: Managers averaged 8474 steps/day for each practice/game. All PA measures significantly varied by day and manager experience. Overall PA equated to 78 hours of walking. Conclusions: Student football managers easily met and surpassed the recommended aerobic health-enhancing PA guideline. While their manager-related PA was 140 minutes per week, other PA allowed them to easily reach significantly healthy levels of PA.

Daily Physical Activity by Occupational Classification in US Adults: NHANES 2005-2006.

BACKGROUND: Little is known about the daily physical activity (PA) levels of people employed in different occupational categories. METHODS: Nine ActiGraph accelerometer-derived daily PA variables are presented and ranked for adults (N = 1465, 20-60 y) working in the 22 occupational categories assessed by NHANES 2005-2006. A composite score was generated for each occupational category by summing the rankings of 3 accelerometer-derived daily PA variables known to have strong associations with health outcomes (total activity counts [TAC], moderate to vigorous PA minutes per week in modified 10-minute bouts [MVPA 10], and percentage of time spent in sedentary activity [SB%]). RESULTS: Classified as high-activity occupational categories, "farming, fishing, forestry," and "building & grounds cleaning, maintenance" occupations had the greatest TAC (461 996 and 449 452), most MVPA 10 (149.6 and 97.8), most steps per day (10 464 and 11 602), and near the lowest SB% (45.2% and 45.4%). "Community, social services" occupations, classified as low-activity occupational categories, had the second lowest TAC (242 085), least MVPA 10 (12.1), fewest steps per day (5684), and near the highest SB% (64.2%). CONCLUSIONS: There is a strong association between occupational category and daily activity levels. Objectively measured daily PA permitted the classification of the 22 different occupational categories into 3 activity groupings.

Effects of Knee Alignments and Toe Clip on Frontal Plane Knee Biomechanics in Cycling.

Effects of knee alignment on the internal knee abduction moment (KAM) in walking have been widely studied. The KAM is closely associated with the development of medial knee osteoarthritis. Despite the importance of knee alignment, no studies have explored its effects on knee frontal plane biomechanics during stationary cycling. The purpose of this study was to examine the effects of knee alignment and use of a toe clip on the knee frontal plane biomechanics during stationary cycling. A total of 32 participants (11 varus, 11 neutral, and 10 valgus alignment) performed five trials in each of six cycling conditions: pedaling at 80 rpm and 0.5 kg (40 Watts), 1.0 kg (78 Watts), and 1.5 kg (117 Watts) with and without a toe clip. A motion analysis system and a customized instrumented pedal were used to collect 3D kinematic and kinetic data. A 3 × 2 × 3 (group × toe clip × workload) mixed design ANOVA was used for statistical analysis (p < 0.05). There were two different knee frontal plane loading patterns, internal abduction and adduction moment, which were affected by knee alignment type. The knee adduction angle was 12.2° greater in the varus group compared to the valgus group (p = 0.001), yet no difference was found for KAM among groups. Wearing a toe clip increased the knee adduction angle by 0.95º (p = 0.005). The findings of this study indicate that stationary cycling may be a safe exercise prescription for people with knee malalignments. In addition, using a toe clip may not have any negative effects on knee joints during stationary cycling.

Protective role of physical activity on type 2 diabetes: Analysis of effect modification by race-ethnicity.

BACKGROUND: It is well known physical activity (PA) plays a role in the prevention of type 2 diabetes (T2D). However, the extent to which PA may affect T2D risk among different race-ethnic groups is unknown. Therefore, the aim of the present study was to systematically examine the effect modification of race-ethnicity on PA and T2D. METHODS: The PubMed and Embase databases were systematically searched through June 2016. Study assessment for inclusion was conducted in three phases: title review (n = 13 022), abstract review (n = 2200), and full text review (n = 265). In all, 27 studies met the inclusion criteria and were used in the analysis. Relative risks (RRs) and 95% confidence intervals (CIs) were extracted and analyzed using Comprehensive Meta-Analysis software. All analyses used a random-effects model. RESULTS: A significant protective summary RR, comparing the most active group with the least active PA group, was found for non-Hispanic White (RR 0.71, 95% CI 0.60-0.85), Asians (RR 0.76, 95% CI 0.67-0.85), Hispanics (RR 0.75, 95% CI 0.64-0.89), and American Indians (RR 0.73, 95% CI 0.60-0.88). The summary effect for non-Hispanic Blacks (RR 0.91, 95% CI 0.76-1.08) was not significant. CONCLUSIONS: The results of the present study indicate that PA (comparing most to least active groups) provides significant protection from T2D, with the exception of non-Hispanic Blacks. The results also indicate a need for race-ethnicity-specific reporting of RRs in prospective cohort studies that incorporate multiethnic samples.

Effect of Adding Online Social Support Tools to an Adult Walking Program: A Pilot Randomized Controlled Trial.

This pilot study examined the efficacy of providing access to online social support tools on adults' step counts during a technology-mediated walking intervention. Sixty-three insufficiently active adults were randomized to a 12-week walking intervention with (SUPPORT) or without (NO SUPPORT) access to online social support tools. Both groups received a pedometer, step goals, and access to relevant websites. The SUPPORT group also received access to online social support tools. A mixed-factor analysis of variance was conducted to examine within- and between-group differences in measures of daily steps, psychosocial indicators, and health. Both groups significantly (p < .05) increased their daily steps over time from baseline by 1,401 (SUPPORT) and 2,461 (NO SUPPORT), with no significant differences between groups. Psychosocial and health improvements were no greater for SUPPORT versus NO SUPPORT. The SUPPORT group's use of the online social support tools was low. Results suggest that giving adults access to online social support tools during a technology-mediated walking program did not lead to an enhanced increase in daily steps versus an identical program without these tools; however, the low use of these tools may have weakened their effect. Future studies should examine SUPPORT versus NO SUPPORT among groups with preexisting social ties.

Accuracy of Consumer Monitors for Estimating Energy Expenditure and Activity Type.

INTRODUCTION: Increasing use of consumer-based physical activity (PA) monitors necessitates that they are validated against criterion measures. Thus, the purpose of this study was to examine the accuracy of three consumer-based PA monitors for estimating energy expenditure (EE) and PA type during simulated free-living activities. METHODS: Twenty-eight participants (mean ± SD: age, 25.5 ± 3.7 yr; body mass index, 24.9 ± 2.6 kg·m) completed 11 activities ranging from sedentary behaviors to vigorous intensities. Simultaneous measurements were made with an Oxycon portable calorimeter (criterion), a Basis Peak and Garmin Vivofit on the nondominant wrist, and three Withings Pulse devices (right hip, shirt collar, dominant wrist). Repeated-measures ANOVA were used to examine differences between measured and predicted EE. Intraclass correlation coefficients were calculated to determine reliability of EE predictions between Withings placements. Paired samples t tests were used to determine mean differences between observed minutes and Basis Peak predictions during walking, running, and cycling. RESULTS: On average, the Basis Peak was within 8% of measured EE for the entire PA routine (P > 0.05); however, there were large individual errors (95% prediction interval, -290.4 to +233.1 kcal). All other devices were significantly different from measured EE for the entire PA routine (P < 0.05). For activity types, Basis Peak correctly identified ≥92% of actual minutes spent walking and running (P > 0.05), and 40.4% and 0% of overground and stationary cycling minutes, respectively (P < 0.001). CONCLUSIONS: The Basis Peak was the only device that did not significantly differ from measured EE; however, it also had the largest individual errors. Additionally, the Basis Peak accurately predicted minutes spent walking and running, but not cycling.

Psycho-Physiological Effects of Television Viewing During Exercise.

We propose that enjoyment is an important factor in the adoption and long-term maintenance of exercise. Television (TV) viewing is believed to be a highly enjoyed leisure-time activity, combining it with exercise may make for a more enjoyable exercise experience. The objective of this study was to examine the effects of television (TV) viewing on psychological and physiological variables during a moderate-intensity exercise bout. Twenty-eight insufficiently active (<150 minutes per week of moderate intensity PA and/or 75 minutes of vigorous PA) adults (Age: M = 47.4 ± 7.6 years) participated in this study. Each participant performed three separate 30-minute walking bouts on a motorized treadmill. During each bout, participants watched a program they selected (30-minute scripted show) (self-selected TV condition), a British Broadcasting Corporation (BBC) nature program (standardized TV condition), or no TV program (no TV condition). Participants were unable to select the nature program as their self-selected program, as it was not a 30-minute scripted program. A Polar Heart Rate (HR) monitor and validated surveys on affect and enjoyment were used. Participants reported greater enjoyment of exercise for both self-selected and standardized TV conditions (97.1 ± 15.2 and 92.7 ± 15.2), compared to the No TV condition (77.5 ± 13.4, p < 0.001). The two TV conditions resulted in similar levels of focus on TV viewing (self-selected TV: 81.2 ± 19.7; standardized TV: 79.1 ± 14.2, p > 0.05) and dissociation from walking (self-selected TV: 38.1 ± 6.7 and standardized TV: 33.2 ± 3.9); they also resulted in more dissociation than the no TV condition (TV: 72.6 ± 5.6, p = 0.002). The findings indicate that TV viewing, regardless of whether the programming is self-selected or standardized, associates with greater enjoyment of exercise.

Accelerometer-Derived Total Activity Counts, Bouted Minutes of Moderate to Vigorous Activity, and Insulin Resistance: NHANES 2003-2006.

INTRODUCTION: The objective of this study was to compare the associations of accelerometer-derived total activity counts per day and minutes of bouted moderate to vigorous physical activity (MVPA) with insulin resistance. METHODS: The sample included 2,394 adults (aged ≥20 y) from the 2003-2006 National Health and Nutrition Examination Survey. Time spent in MVPA, measured by using 2 cutpoints (≥2,020 counts/min [MVPA2,020] and ≥760 counts/min [MVPA760]), was calculated for bouts of at least 8 to 10 minutes. Total activity counts per day reflects the total amount of activity across all intensities. Insulin resistance was measured via the homeostatic model assessment of insulin resistance (HOMA-IR) and the quantitative insulin sensitivity check index (QUICKI). Two nested regression models regressed HOMA-IR and QUICKI, respectively, on minutes of bouted MVPA and total activity counts per day. We used an adjusted Wald F statistic to illustrate strength of association. RESULTS: After adjustment for covariates, total activity counts per day was more strongly associated with both HOMA-IR (adjusted Wald F = 36.83 , P < .001) and QUICKI (adjusted Wald F = 29.44, P < .001) compared with MVPA2,020 (HOMA-IR, adjusted Wald F = 4.00, P = .06; QUICKI, adjusted Wald F = 1.08, P = .31).Total activity counts per day was more strongly associated with both HOMA-IR (adjusted Wald F = 13.64, P < .001) and QUICKI (adjusted Wald F = 12.10, P < .001) compared with MVPA760 (HOMA-IR, adjusted Wald F = 1.13, P = .30; QUICKI, adjusted Wald F = 0.97, P = .33). CONCLUSION: Our study indicated that total activity counts per day has stronger associations with insulin resistance compared with minutes of bouted MVPA. The most likely explanation is that total activity counts per day captures data on light physical activity and intermittent MVPA, both of which influence insulin resistance.

Use of population-referenced total activity counts percentiles to assess and classify physical activity of population groups.

OBJECTIVES: Population-referenced total activity counts per day (TAC/d) percentiles provide public health practitioners a standardized measure of physical activity (PA) volume obtained from an accelerometer that can be compared across populations. The purpose of this study was to describe the application of TAC/d population-referenced percentiles to characterize the PA levels of population groups relative to US estimates. METHODS: A total of 679 adults participating in the 2011 NYC Physical Activity Transit survey wore an ActiGraph accelerometer on their hip for seven consecutive days. Accelerometer-derived TAC/d was classified into age- and gender-specific quartiles of US population-referenced TAC/d to compare differences in the distributions by borough (N=5). RESULTS: Males in Brooklyn, Manhattan, and Staten Island had significantly greater TAC/d than US males. Females in Brooklyn and Queens had significantly greater levels of TAC/d compared to US females. The proportion of males in each population-referenced TAC/d quartile varied significantly by borough (χ(2)(12)=2.63, p=0.002), with disproportionately more men in Manhattan and the Bronx found to be in the highest and lowest US population-referenced TAC/d quartiles, respectively. For females, there was no significant difference in US population-reference TAC/d quartile by borough (χ(2)(12)=1.09, p=0.36). CONCLUSIONS: These results demonstrate the utility of population-referenced TAC/d percentiles in public health monitoring and surveillance. These findings also provide insights into the PA levels of NYC residents relative to the broader US population, which can be used to guide health promotion efforts.

The Associations Between Increasing Degrees of HOMA-IR and Measurements of Adiposity Among Euglycemic U.S. Adults.

BACKGROUND: The purpose of this study was to examine the associations between increasing degrees of insulin resistance (using the homeostatic model assessment of insulin resistance [HOMA-IR]) and two measures of adiposity in a nationally representative sample of euglycemic U.S. adults. MATERIALS AND METHODS: Sample included adult participants (≥ 20 years of age) [N = 1586 (body mass index, BMI model), N = 1577 (waist circumference, WC model)] from the 1999-2004 National Health and Nutrition Examination Survey (NHANES). HOMA-IR was categorized into quartiles. BMI and WC were examined continuously as the dependent variables. RESULTS: Following adjustment for covariates, those with HOMA-IR values in the second, third, and fourth quartiles had significantly higher BMIs (P < 0.001) compared with subjects in the first quartile. In the model using WC, significantly higher WCs were found in subjects in the second, third, and fourth quartiles of HOMA-IR (P < 0.001) compared with those in the first quartile. A significant moderate correlation was found between HOMA-IR and BMI (R(2) = 0.4171, P < 0.001), as well as HOMA-IR and WC (R(2) = 0.4826, P < 0.001). CONCLUSIONS: Having a higher HOMA-IR value is associated with higher BMI and WC values in euglycemic subjects.

Physical Activity With and Without TV Viewing: Effects on Enjoyment of Physical Activity and TV, Exercise Self-Efficacy, and Barriers to Being Active in Overweight Adults.

BACKGROUND: Physical activity (PA) is enjoyable, but there are barriers to participation. TV viewing is highly enjoyable with limited barriers. Exercising while viewing TV may impact enjoyment, exercise self-efficacy, and barriers to PA, compared with exercising without TV. METHODS: 58 sedentary, overweight adults were randomized to 1 of 2 PA prescriptions: one that increased PA during TV viewing (TV Commercial Stepping), and another that focused solely on PA (Walking). Random effects models tested changes in enjoyment of TV and PA, exercise self-efficacy, and barriers to PA across time (baseline, 3, and 6 months) and PA prescription during a 6-month PA intervention. RESULTS: At baseline, TV was more enjoyable than PA. Over the 6-month intervention, enjoyment of TV viewing did not change, but enjoyment of PA and exercise self-efficacy significantly increased, while barriers to PA significantly decreased for both groups compared with baseline (P < .05). CONCLUSIONS: While enjoyment of TV viewing remained constant, PA became more enjoyable, confidence to exercise increased, and barriers to being active were reduced for previously sedentary adults participating in a behavioral PA intervention. These findings highlight the importance of encouraging inactive adults to engage in some form of PA, whether it occurs with or without TV viewing.

Effects of Workloads and Cadences on Frontal Plane Knee Biomechanics in Cycling.

UNLABELLED: Although effects of workload and cadence on sagittal plane knee biomechanics in cycling have been widely studied, few studies have examined their impact on the frontal plane. PURPOSE: The purpose of this study was to investigate the effects of different workloads and cadences on knee sagittal and frontal plane biomechanics. METHODS: Eighteen healthy participants (age, 55.7 ± 11.0 yr) volunteered for this study. A motion analysis system and a custom instrumented pedal were used to collect five cycles of three-dimensional kinematics (240 Hz) and pedal reaction force (PRF, 1200 Hz) during 2 min of cycling in each of eight testing conditions, including five workload conditions of 0.5, 1, 1.5, 2, and 2.5 kg at 60 rpm, and three cadence conditions of 70, 80, and 90 rpm with 1-kg workload. Two one-way repeated measures analyses of variance were used to examine the influence of cadence and workload on selected variables (P < 0.05). RESULTS: Increased workloads with constant rpm caused an increased peak knee abduction moment from 5.82 to 14.36 N · m and peak knee extension moment from 11.61 to 37.16 N · m. Increased workloads also significantly increased peak medial and vertical PRF. Increased cadences at the constant workload had no effects on peak knee abduction moment but caused increased peak anterior and vertical PRF and peak knee flexion moment. CONCLUSIONS: The findings of this study indicate that increasing workload at constant cadence significantly increased peak knee abduction moment. Further study may be needed to demonstrate the efficacy of appropriate levels of workload and cadence in knee osteoarthritis and other populations with knee problems.