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 (β = 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.

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.

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.

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.

Smoking Acquisition: Peer Influence and Self-Selection

The study examined and contrasted the extent that peer influence and self-selection for smoking peers may affect acquisition of smoking by adolescents. Data for a U.S. national cohort sample of adolescents ( N = 4,444) who were nonsmokers in the 1989 Teenage Attitudes and Practices Surveys and were re-interviewed in 1993 were included. The information included measures of smoking behavior and smoking status of both boys’ and girls’ best friends. Analysis demonstrated that, although the effects of both peer influence and self-selection of smoking friends occurred, self-selection may play a greater role in adolescents’ beginning to smoke. This implies that, while teaching adolescents to resist peer pressure may be necessary, it is perhaps more important to identify factors that influence adolescents’ decisions in choosing friends who smoke. This could lead to more effective preventive strategies.

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 [MVPA_2,020] 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 MVPA_2,020 (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.

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.

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.

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.

Cross-sectional association between physical activity and serum testosterone levels in US men: results from NHANES 1999-2004

Testosterone levels and physical activity each play important roles in men's health, but the relationship between the two remains unclear. We evaluated the cross-sectional association between self-reported total physical activity and serum testosterone levels in 738 men (mean age 42.4 years, range 20-≥85 years) who participated in National Health and Nutrition Examination Survey 1999-2004. We compared geometric mean testosterone concentrations measured by radioimmunoassay (RIA) and calculated the odds ratio (OR) of having low or low normal testosterone (≤3.46 ng/mL) across tertiles of total physical activity in all men, and men stratified by age (20-49, ≥50 years), and obesity status (BMI < 30, ≥30 kg/m(2) ). The geometric mean testosterone concentration was 5.31 ng/mL; 18.6% of the men had low or low normal serum testosterone levels. Physical activity tertiles were not associated with testosterone levels overall, or when stratified by age or obesity status. Similarly, there was no association between physical activity tertiles and the odds of low or low normal testosterone, overall or by age. However, among non-obese men, those in the highest physical activity tertile were significantly less likely to have low or low normal testosterone than those in the lowest tertile (OR 0.50; 95% CI = 0.26-0.95); there was no association among obese men. Greater physical activity was not associated with testosterone levels, but may be associated with a reduced odds of low or low normal testosterone in non-obese men, but not in obese men.

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.

The associations between increasing degrees of homeostatic model assessment for insulin resistance and muscular strengthening activities among euglycaemic US adults

PURPOSE

To examine the associations between the homeostatic model assessment for insulin resistance and self-reported muscular strengthening activity in a nationally representative sample of euglycaemic US adults.

METHODS

Sample included euglycaemic adults (⩾20 years of age (n = 2009)) from the 1999 to 2004 National Health and Nutrition Examination Survey. Homeostatic model assessment for insulin resistance was categorized into quartiles and was the primary independent variable of interest. No reported muscular strengthening activity was the dependent variable.

RESULTS

Following adjustment for covariates, those with homeostatic model assessment for insulin resistance values in fourth (odds ratio: 2.04, 95% confidence interval: 1.35-3.06, p < 0.001) quartile were found to have significantly greater odds of reporting no muscular strengthening activity. Following further adjustment for non-muscular strengthening activity specific aerobic leisure-time physical activity, results remained significant for the fourth (odds ratio: 2.30, 95% confidence interval: 1.50-3.52, p < 0.001) quartile. A significant trend was seen across quartiles of homeostatic model assessment for insulin resistance for increasing prevalence of no muscular strengthening activity (p < 0.001).

CONCLUSION

Having a higher homeostatic model assessment for insulin resistance value is associated with greater odds of reporting no muscular strengthening activity among euglycaemic US adults. This implies that subjects with an increasing degree of insulin resistance are more likely to not engage in muscular strengthening activity, an exercise modality that has been shown to reduce the risk of several cardiometabolic diseases and improve glycaemic status.

Classification of occupational activity categories using accelerometry: NHANES 2003-2004

Background

An individual’s occupational activity (OA) may contribute significantly to daily physical activity (PA) and sedentary behavior (SB). However, there is little consensus about which occupational categories involve high OA or low OA, and the majority of categories are unclassifiable with current methods. The purpose of this study was to present population estimates of accelerometer-derived PA and SB variables for adults (n = 1112, 20–60 years) working the 40 occupational categories collected during the 2003–2004 National Health and Nutrition Examination Survey (NHANES).

Methods

ActiGraph accelerometer-derived total activity counts/day (TAC), activity counts/minute, and proportion of wear time spent in moderate-to-vigorous PA [MVPA], lifestyle, and light PA organized by occupational category were ranked in ascending order and SB was ranked in descending order. Summing the ranks of the six accelerometer-derived variables generated a summary score for each occupational category, which was re-ranked in ascending order. Higher rankings indicated higher levels of OA, lower rankings indicated lower levels of OA. Tertiles of the summary score were used to establish three mutually exclusive accelerometer-determined OA groupings: high OA, intermediate OA, and low OA.

Results

According to their summary score, ‘farm and nursery workers’ were classified as high OA and ‘secretaries, stenographers, and typists’ were classified as low OA. Consistent with previous research, some low OA occupational categories (e.g., ‘engineers, architects, and scientists’, ‘technicians and related support occupations’, ‘management related occupations’, ‘executives, administrators, and managers’, ‘protective services’, and ‘writers, artists, entertainers, and athletes’) associated with higher education and income had relatively greater amounts of MVPA compared to other low OA occupational categories, likely due to the greater percentage of men in those occupations and/or the influence of higher levels of leisure time PA. Men had more TAC, activity counts/minute and time in MVPA, but similar proportions of SB compared to women in all three OA groupings.

Conclusions

Objectively measured PA allowed for a more precise estimate of the amount of PA and SB associated with different occupations and facilitated systematic classification of the 40 different occupational categories into three distinct OA groupings. This information provides new opportunities to explore the relationship between OA and health outcomes.

Associations between iliotibial band injury status and running biomechanics in women

Iliotibial band syndrome (ITBS) is a common overuse knee injury that is twice as likely to afflict women compared to men. Lower extremity and trunk biomechanics during running, as well as hip abductor strength and iliotibial band flexibility, are factors believed to be associated with ITBS. The purpose of this cross-sectional study was to determine if differences in lower extremity and trunk biomechanics during running exist among runners with current ITBS, previous ITBS, and controls. Additionally, we sought to determine if isometric hip abductor strength and iliotibial band flexibility were different among groups. Twenty-seven female runners participated in the study. Participants were divided into three equal groups: current ITBS, previous ITBS, and controls. Overground running trials, isometric hip abductor strength, and iliotibial band flexibility were recorded for all participants. Discrete joint and segment biomechanics, as well as hip strength and flexibility measures were analyzed using a one-way analysis of variance. Runners with current ITBS exhibited 1.8 (1.5)° greater trunk ipsilateral flexion and 7 (6)° less iliotibial band flexibility compared to runners with previous ITBS and controls. Runners with previous ITBS exhibited 2.2 (2.9) ° less hip adduction compared to runners with current ITBS and controls. Hip abductor strength 3.3 (2.6) %BM×h was less in runners with previous ITBS but not current ITBS compared to controls. Runners with current ITBS may lean their trunk more towards the stance limb which may be associated with decreased iliotibial band flexibility.

Population-referenced percentiles for waist-worn accelerometer-derived total activity counts in U.S. youth: 2003 - 2006 NHANES

Background

The total activity volume performed is an overall measure that takes into account the frequency, intensity, and duration of activities performed. The importance of considering total activity volume is shown by recent studies indicating that light physical activity (LPA) and intermittent moderate-to-vigorous physical activity (MVPA) have health benefits. Accelerometer-derived total activity counts (TAC) per day from a waist-worn accelerometer can serve as a proxy for an individual's total activity volume. The purpose of this study was to develop age- and gender-specific percentiles for daily TAC, minutes of MVPA, and minutes of LPA in U.S. youth ages 6 – 19 y.

Methods

Data from the 2003 – 2006 NHANES waist-worn accelerometer component were used in this analysis. The sample was composed of youth aged 6 – 19 years with at least 4 d of ≥ 10 hours of accelerometer wear time (N = 3698). MVPA was defined using age specific cutpoints as the total number of minutes at ≥4 metabolic equivalents (METs) for youth 6 – 17 y or minutes with ≥2020 counts for youth 18 – 19 y. LPA was defined as the total number of minutes between 100 counts and the MVPA threshold. TAC/d, MVPA, and LPA were averaged across all valid days.

Results

For males in the 50^th percentile, the median activity level was 441,431 TAC/d, with 53 min/d of MVPA and 368 min/d of LPA. The median level of activity for females was 234,322 TAC/d, with 32 min/d of MVPA and 355 min/d of LPA.

Conclusion

Population referenced TAC/d percentiles for U.S. youth ages 6-19 y provide a novel means of characterizing the total activity volume performed by children and adolescents.

Classification accuracy of the wrist-worn gravity estimator of normal everyday activity accelerometer

PURPOSE

The purpose of this study was to determine whether the published left-wrist cut points for the triaxial Gravity Estimator of Normal Everyday Activity (GENEA) accelerometer are accurate for predicting intensity categories during structured activity bouts.

METHODS

A convenience sample of 130 adults wore a GENEA accelerometer on their left wrist while performing 14 different lifestyle activities. During each activity, oxygen consumption was continuously measured using the Oxycon mobile. Statistical analysis used Spearman's rank correlations to determine the relationship between measured and estimated intensity classifications. Cross tabulations were constructed to show the under- or overestimation of misclassified intensities. One-way χ2 tests were used to determine whether the intensity classification accuracy for each activity differed from 80%.

RESULTS

For all activities, the GENEA accelerometer-based physical activity monitor explained 41.1% of the variance in energy expenditure. The intensity classification accuracy was 69.8% for sedentary activities, 44.9% for light activities, 46.2% for moderate activities, and 77.7% for vigorous activities. The GENEA correctly classified intensity for 52.9% of observations when all activities were examined; this increased to 61.5% with stationary cycling removed.

CONCLUSIONS

A wrist-worn triaxial accelerometer has modest-intensity classification accuracy across a broad range of activities when using the cut points of Esliger et al. Although the sensitivity and the specificity are less than those reported by Esliger et al., they are generally in the same range as those reported for waist-worn, uniaxial accelerometer cut points.

Changing step width alters lower extremity biomechanics during running

Step width is a spatiotemporal parameter that may influence lower extremity biomechanics at the hip and knee joint. The purpose of this study was to determine the biomechanical response of the lower extremity joints to step width changes during running. Lower extremity data from 30 healthy runners, half of them male, were collected during running in three step width conditions: preferred, wide, and narrow. Dependent variables and step width were analyzed using a mixed model ANOVA and pairwise t-tests for post hoc comparisons. Step width was successfully altered in the wide and narrow conditions. Generally, frontal plane peak values decreased as step width increased from narrow to preferred to wide. Peak hip adduction and rearfoot eversion angles decreased as step width increased from narrow to wide. Peak knee abduction moment and knee abduction impulse also decreased as step width increased from narrow to wide. Although men and women ran differently, gender only influenced the effect of step width on peak rearfoot inversion moment. In conclusion, step width influences lower extremity biomechanics in healthy runners. When step width increased from narrow to wide, peak values of frontal plane variables decreased. In addition to previously reported changes at the rearfoot, the hip and knee joint biomechanics were also influenced by changes in step width.

Association of physical activity, fitness, and race: NHANES 1999–2004

PURPOSE

Regular physical activity (PA) can be used to improve cardiorespiratory fitness (CRF). Previous research has shown differences in CRF (VO2max) among racial groups, but it is unclear how much of these differences can be explained by PA. Thus, we sought to examine the association between PA and CRF in different racial groups.

METHODS

As a part of the National Health and Nutrition Examination Survey (1999–2004), 3115 adults (18–49 yr) completed a submaximal graded treadmill exercise test to estimate VO2max. Independent variables were demographics (race, education, sex, partner status, and waist circumference), behavioral measures (smoking and alcohol consumption), self-reported PA from three domains (leisure-time, domestic, and transportational PA (MET x min x wk(-1)), and the proportion of PA at a vigorous intensity (VMET). CRF was the dependent variable. Multiple linear regression was performed using SUDAAN statistical software.

RESULTS

Results indicated that VO2max was significantly higher for Mexican Americans (40.9 T 0.5 mL x kg(-1) x min(-1)) and non-Hispanic whites (40.2 +/- 0.3 mL x kg(-1) x min(-1)) compared with non-Hispanic blacks (37.9 +/- 0.6 mL x kg(-1) x min(-1)) (P = 0.01). Demographics including race explained 18.5% of the variance in VO2max, with race being significant (P < 0.01) in the model. When PA was added to the model, the explained variance in VO2max increased to 19.3% (P = 0.001). VMET was more predictive of VO2max than total PA, and the model including VMET explained 20.4% of the variance in VO2max. Race remained a significant, independent predictor of VO2max after VMET and overall PA were added to the model.

CONCLUSION

Race, PA, and exercise intensity are important factors in explaining differences in CRF. After accounting for demographics, PA, and VMET, a large proportion of the variance in CRF remains unexplained. Thus, other factors should also be considered when examining racial/ethnic differences in CRF.

Do thigh circumference and mass changes alter knee biomechanics during walking?

Obese adults walk with different biomechanics compared to healthy weight adults. Previous studies have focused on knee biomechanics because they are associated with development and progression of osteoarthritis. Changes in thigh mass and circumference that occur as body weight increases may influence gait. The purpose of this study was to determine if increases in thigh mass and circumference alter gait biomechanics. For 20 healthy weight young adults (10 male and 10 female) knee kinematic, kinetic and gait temporospatial variables were collected using a three-dimensional motion capture system and a force platform during over ground walking. Data were collected during control, increased thigh mass, increased thigh circumference, and both increased mass and circumference conditions. Increases in thigh segment parameters reflected changes expected with a 10 point increase in body mass index. Step width was wider during the added circumference and combination conditions compared to the control condition. Increases in thigh circumference associated with obesity increase step width. This suggests the greater step width observed in obese adults compared to healthy weight adults is a result of the physical constraints introduced by their wider thigh segments. Peak knee flexion angle, peak knee extension moment, peak knee adduction angle, and peak knee abduction moment were similar in all conditions. Thus, acute changes in thigh segment parameters did not result in knee biomechanics suggestive of an increased risk of knee osteoarthritis.

Estimated energy expenditures for school-based policies and active living

BACKGROUND

Despite overwhelming evidence of the health benefits of physical activity, most American youth are not meeting the 60 minutes per day recommendation for moderate- to vigorous-intensity physical activity (MVPA). Policy changes have the potential to bring about substantial increases in physical activity in youth, within school and community settings.

PURPOSE

The purpose of this study was to quantify the increase in energy expenditure for school-based policies and built environment changes.

METHODS

Scientific literature reviews were consulted, and more than 300 published studies (1995-2011) in English were identified based on titles and abstracts. After an initial screening, 85 articles were included. Study quality was assessed, and the impact of various strategies for increasing physical activity in youth was estimated from objective measurements/direct observation.

RESULTS

Within school settings, the average minutes of MVPA gained per school day for studies in each intervention category were as follows: mandatory physical education (23 minutes); classroom activity breaks (19 minutes); afterschool activity programs (10 minutes); standardized physical education curricula (6 minutes more than traditional physical education); modified playgrounds (6 minutes); and modified recess (5 minutes more than traditional recess). Within community settings, significant MVPA was associated with active commuting (16 minutes) and park renovations (12 minutes), but proximity to parks had a small effect (1 minute). No conclusions could be drawn regarding joint-use agreements, because of a lack of studies quantifying their impact on energy expenditure.

CONCLUSIONS

Of the various policies and built environment changes examined, the largest effects were seen with mandatory physical education, classroom activity breaks, and active commuting to school. Policymakers can use this information along with estimates of the cost, feasibility, and population reach, to identify the best options for increasing physical activity in youth.

The Metabolic Syndrome: How Definition Impacts the Prevalence and Risk in U.S. Adults: 1999-2004 NHANES

BACKGROUND

To examine the relationships various medical society definitions have on metabolic syndrome (MetS) prevalence and the likelihood of a MetS diagnosis among a national sample of the United States (US) adult population.

METHODS

The sample for this study included adults, 20 years and older, (N = 5620) who completed the mobile examination center (MEC) examination in the 1999-2004 National Health and Nutrition Examination Survey (NHANES). SUDAAN statistical software was used to estimate age-adjusted prevalence and odds ratios.

RESULTS

The overall age-adjusted MetS prevalence ranged from a high of 38.9% (ACE/AACE), to a low of 21.2% (EGIR). For most MetS definitions, males, people in the eighth decade of life (70-79 years of age), Mexican-Americans, those without a high school education, and those living in poverty were found to have the greatest prevalence. Additionally, females were 21% to 33% less likely to be diagnosed with the MetS. People in the seventh decade of life were two to four times more likely to have the MetS compared to those in the third decade of life. Furthermore, adults with greater than a high school education were 26% to 30% less likely to be diagnosed with the MetS and adults in the >/=400% poverty category were 24% to 29% less likely to be diagnosed with the MetS compared to those living below the 100% poverty demarcation.

CONCLUSION

MetS prevalence and the likelihood of being diagnosed with the MetS within populations are highly dependent on the requisite criteria and medical society definition used.

Can sedentary behavior be made more active? A randomized pilot study of TV commercial stepping versus walking

Background

There is a growing problem of physical inactivity in America, and approximately a quarter of the population report being completely sedentary during their leisure time. In the U.S., TV viewing is the most common leisure-time activity. Stepping in place during TV commercials (TV Commercial Stepping) could increase physical activity. The purpose of this study was to examine the feasibility of incorporating physical activity (PA) into a traditionally sedentary activity, by comparing TV Commercial Stepping during 90 min/d of TV programming to traditional exercise (Walking).

Methods

A randomized controlled pilot study of the impact of 6 months of TV Commercial Stepping versus Walking 30 min/day in adults was conducted. 58 sedentary, overweight (body mass index 33.5 ± 4.8 kg/m²) adults (age 52.0 ± 8.6 y) were randomly assigned to one of two 6-mo behavioral PA programs: 1) TV Commercial Stepping; or 2) Walking 30 min/day. To help facilitate behavior changes participants received 6 monthly phone calls, attended monthly meetings for the first 3 months, and received monthly newsletters for the last 3 months. Using intent-to-treat analysis, changes in daily steps, TV viewing, diet, body weight, waist and hip circumference, and percent fat were compared at baseline, 3, and 6 mo. Data were collected in 2010–2011, and analyzed in 2011.

Results

Of the 58 subjects, 47 (81%) were retained for follow-up at the completion of the 6-mo program. From baseline to 6-mo, both groups significantly increased their daily steps [4611 ± 1553 steps/d vs. 7605 ± 2471 steps/d (TV Commercial Stepping); 4909 ± 1335 steps/d vs. 7865 ± 1939 steps/d (Walking); P < 0.05] with no significant difference between groups. TV viewing and dietary intake decreased significantly in both groups. Body weight did not change, but both groups had significant decreases in percent body fat (3-mo to 6-mo), and waist and hip circumference (baseline to 6-mo) over time.

Conclusions

Participants in both the TV Commercial Stepping and Walking groups had favorable changes in daily steps, TV viewing, diet, and anthropometrics. PA can be performed while viewing TV commercials and this may be a feasible alternative to traditional approaches for increasing daily steps in overweight and obese adults.

Trial Registration

This study is registered at ClinicalTrials.gov, NCT01342471

Muscular strengthening activity patterns and metabolic health risk among US adults

BACKGROUND

Many studies have examined the relationship between physical activity and metabolic disorders. However, few have focused on specific associations between these disorders and muscular strengthening activity (MSA) patterns. The aim of the present study was to examine the association(s) for each metabolic syndrome criterion and MSA patterns.

METHODS

The study sample (n = 5618) consisted of adults ≥20 years of age who participated in the 1999-2004 National Health and Nutrition Examination Survey. Cut-off points for metabolic syndrome criteria were derived from the American Heart Association/National Heart, Lung, and Blood Institute definition. The aggregate of data on weight lifting, push-ups, and sit-ups was used to establish patterns of MSA. Participants reporting ≥2 days/week MSA were coded as meeting current US MSA guidelines.

RESULTS

Following adjustments, participants reporting ≥2 days/week MSA were found to be 28% (OR 0.72; 95% CI 0.62, 0.83) less likely to have dyslipidemia, 29% (OR 0.71; 95% CI 0.54, 0.93) less likely to have impaired fasting glucose, 19% (OR 0.81; 95% CI 0.65, 0.99) less likely to have prehypertension, and 43% (OR 0.57; 95% CI 0.46, 0.72) less likely to have augmented waist circumference compared with those reporting engaging in no MSA. No association was found for hypertension and MSA.

CONCLUSION

Engaging in ≥2 days/week MSA as part of an overall physical activity regimen may be prudent in preserving metabolic health. These findings strengthen the relationship between MSA and metabolic health; thus, clinicians should include MSA when discussing lifestyle approaches to better health.