Youngdeok Kim

Convergent validity of the International Physical Activity Questionnaire (IPAQ): meta-analysis

OBJECTIVE The purpose of the present study was to use a meta-analytic approach to examine the convergent validity of the international physical activity questionnaire (IPAQ). DESIGN Systematic review by meta-analysis. SETTING The relevant studies were surveyed from five electronic databases. Primary outcomes of interest were the product-moment correlation coefficients between IPAQ and other instruments. Five separate meta-analyses were performed for each physical activity (PA) category of IPAQ: walking, moderate PA (MPA), total moderate PA (TMPA), vigorous PA (VPA) and total PA (TPA). The corrected mean effect size (ESρ) unaffected by statistical artefacts (i.e., sampling error and reliability) was calculated for each PA category. Selected moderator variables were length of IPAQ (i.e., short and long form), reference period (i.e., last 7 d and usual week), mode of administration (i.e., interviewer and self-reported), language (i.e., English and translated) and instruments (i.e., accelerometer, pedometer and subjective measure). SUBJECTS A total of 152 ESρ across five PA categories were retrieved from twenty-one studies. RESULTS The results showed small- to medium-sized ESρ (0.27-0.49). The highest value was observed in VPA while the lowest value was found in MPA. The ESρ were differentiated by some of the moderator variables across PA categories. CONCLUSIONS The study shows the overall convergent validity of IPAQ within each PA category. Some differences in degree of convergent validity across PA categories and moderator variables imply that different research conditions should be taken into account prior to deciding on use of the appropriate type of IPAQ.

Extracting Objective Estimates of Sedentary Behavior from Accelerometer Data: Measurement Considerations for Surveillance and Research Applications

BACKGROUND Accelerometer-based activity monitors are widely used in research and surveillance applications for quantifying sedentary behavior (SB) and physical activity (PA). Considerable research has been done to refine methods for assessing PA, but relatively little attention has been given to operationalizing SB parameters (i.e., sedentary time and breaks) from accelerometer data - particularly in relation to health outcomes. This study investigated: (a) the accrued patterns of sedentary time and breaks; and (b) the associations of sedentary time and breaks in different bout durations with cardiovascular risk factors. METHODS Accelerometer data on 5,917 adults from the National Health Examination and Nutrition Survey (NHANES) 2003-2006 were used. Sedentary time and breaks at different bout durations (i.e., 1, 2-4, 5-9, 10-14, 15-19, 20-24, 25-29, and ≥ 30-min) were obtained using a threshold of < 100 counts per minute. Sedentary time and breaks were regressed on cardiovascular risk factors (waist circumference, triglyceride, and high-density lipoprotein cholesterol) and body mass index across bout durations. RESULTS The results revealed that the majority of sedentary time occurred within relatively short bout durations (≈ 70% and ≈ 85% for < 5-min and < 10-min, respectively). The associations of sedentary time and breaks with health outcomes varied depending on how bout time was defined. Estimates of SB parameters based on bout durations of 5 min or shorter were associated with reduced cardiovascular risk factors while durations longer than 10-min were generally associated with increased risk factors. CONCLUSIONS The present study demonstrates that the duration of sedentary bouts should be further considered when operationalizing the SB parameters from accelerometer data. The threshold of 5 minutes to define a bout is defensible, but a 10 minute threshold would provide a more conservative estimate to clearly capture the prolonged nature of sedentary behavior. Additional research is needed to determine the relative sensitivity and specificity of these thresholds.

Validation of the ActiGraph GT3X and activPAL Accelerometers for the Assessment of Sedentary Behavior

This study examined (a) the validity of two accelerometers (ActiGraph GT3X [ActiGraph LLC, Pensacola, FL, USA] and activPAL [PAL Technologies Ltd., Glasgow, Scotland]) for the assessment of sedentary behavior; and (b) the variations in assessment accuracy by setting minimum sedentary bout durations against a proxy for direct observation using an automated wearable camera in free-living environments. Time spent in sedentary behavior estimated from the GT3X, with varying identification methods (i.e., a hybrid machine learning algorithm, Sojourn, and activity count thresholds), and the activPAL were compared to the criterion measure with and without applying minimum sedentary bout durations. The activPAL assessed sedentary behavior most accurately followed by GT3X with the Sojourn method. The performance of the GT3X is improved when identifying sedentary bouts ≥ 15 min with the Sojourn method or a threshold of < 150 cpm. The activPAL should be considered for studies focusing on sedentary behavior. The ability of the GT3X to assess sedentary behavior is improved when focusing on sedentary bouts ≥ 15 min using the Sojourn method or the threshold of < 150 cpm.

Sleep Disorders, Physical Activity, and Sedentary Behavior Among U.S. Adults: National Health and Nutrition Examination Survey

BACKGROUND Disruptive sleeping patterns have been linked to serious medical conditions. Regular physical activity (PA) has a positive impact on health; however, few research have investigated the relationships between PA, body mass index (BMI), sedentary behaviors (SB), and sleep disorders (SD). METHODS Data from the 2005-2006 NHANES were analyzed for this study. Participants (N = 2989; mean age = 50.44 years) were grouped based upon responses to SD questions. Accelerometers were used to measure the average time spent in moderate or vigorous physical activity (MVPA) and SB. Multinomial logistic regression analyses were used to examine the associations between PA, SB, and SD after controlling for covariates and to explore potential moderation effects among common risk factors and the main study variables. RESULTS Among middle-aged adults, PA was significantly associated with SD [Wald χ2 (8) = 22.21; P < .001]. Furthermore, among adults in the highest tertile of SB, PA was significantly associated with SD [Wald χ2 (8) = 32.29; P < .001]. CONCLUSIONS These results indicate that middle-aged adults who are less active may have increased likelihoods of SD. It is important for health care professionals to continue developing methods for increasing PA to decrease the risk of SD.

Establishing a threshold for the number of missing days using 7 d pedometer data

The purpose of this study was to examine the threshold of the number of missing days of recovery using the individual information (II)-centered approach. Data for this study came from 86 participants, aged from 17 to 79 years old, who had 7 consecutive days of complete pedometer (Yamax SW 200) wear. Missing datasets (1 d through 5 d missing) were created by a SAS random process 10,000 times each. All missing values were replaced using the II-centered approach. A 7 d average was calculated for each dataset, including the complete dataset. Repeated measure ANOVA was used to determine the differences between 1 d through 5 d missing datasets and the complete dataset. Mean absolute percentage error (MAPE) was also computed. Mean (SD) daily step count for the complete 7 d dataset was 7979 (3084). Mean (SD) values for the 1 d through 5 d missing datasets were 8072 (3218), 8066 (3109), 7968 (3273), 7741 (3050) and 8314 (3529), respectively (p > 0.05). The lower MAPEs were estimated for 1 d missing (5.2%, 95% confidence interval (CI) 4.4-6.0) and 2 d missing (8.4%, 95% CI 7.0-9.8), while all others were greater than 10%. The results of this study show that the 1 d through 5 d missing datasets, with replaced values, were not significantly different from the complete dataset. Based on the MAPE results, it is not recommended to replace more than two days of missing step counts.

Prediction of bone mineral density and content from measures of physical activity and sedentary behavior in younger and older females

Background Little is known regarding the extent to which physical activity (PA) and sedentary behavior (SB) influence bone mineral content (BMC) and bone mineral density (BMD) in females across the lifespan. Methods Data from 2232 females aged 12 years and older collected as part of the 2007–2008 National Health and Nutrition Examination Survey were analyzed. Categories of PA and SB were used to predict femoral and spinal BMD and BMC in four age groups (G1: 12–17; G2: 18–39; G3: 40–64; G4: ≥ 65 years). Self-reported PA categories included sufficient moderate-to-vigorous recreational PA (S-MVRPA) and insufficient MVRPA (I-MVRPA). Results G1 females who accumulated S-MVRPA displayed greater femoral and spinal BMC and BMD compared to G1 females who displayed I-MVRPA. For G4 females, higher levels of SB were associated with lower femoral BMC and BMD. Conclusions These findings highlight the importance of engaging in sufficient moderate-to-vigorous physical activity during adolescence and reducing sedentary behavior in older adults to improve bone health in females.

Does l‐citrulline supplementation improve exercise blood flow in older adults?

What is the central question of this study? Does short‐term supplementation with l‐citrulline in order to increase l‐arginine improve exercise blood flow and peripheral dilatation responses to exercise in older adults? What is the main finding and its importance? l‐Citrulline increased femoral blood flow by 11% and vascular conductance by 14% during lower‐limb exercise in older men, whereas no changes were observed in older women. This modest improvement in bulk muscle blood flow in older men has implications for altering muscle metabolism that may result in enhanced exercise tolerance in older adults.

Sedentary Behavior, Physical Activity, and Bone Health in Postmenopausal Women

The purpose of this study was to determine if bone health at the femoral neck (FN) and lumbar spine (LS) can be predicted from objectively-measured sedentary behavior and physical activity data in postmenopausal women. Waist-mounted ActiGraph GT1M and GT3X devices were used to quantify levels of sedentary and moderate-to-vigorous intensity behavior during a 7-day period in 44 older females. Bone health (normal and osteopenia/osteoporosis) of FN and LS was derived from T scores generated using dual energy x-ray absorptiometry. Binomial logistic regression analysis indicated that sedentary time and number of breaks in sedentary behavior were significant predictors of osteopenia/osteoporosis at the FN, but not at the LS. Adherence to physical activity guidelines was not a significant predictor of bone health at the FN or LS. Our findings suggest that more frequent interruptions in sedentary behavior are associated with improved bone health in postmenopausal women.

The influence of physical characteristics on the resting energy expenditure of youth: A meta-analysis.

To examine the literature on resting energy expenditure (REE) of youth and determine the influence of age, sex, BMI, and body composition on REE.

The influence of a consumer-wearable activity tracker on sedentary time and prolonged sedentary bouts: secondary analysis of a randomized controlled trial

ObjectiveA recent meta-analysis surmised pedometers were a useful panacea to independently reduce sedentary time (ST). To further test and expand on this deduction, we analyzed the ability of a consumer-wearable activity tracker to reduce ST and prolonged sedentary bouts (PSB). We originally conducted a 12-month randomized control trial where 800 employees from 13 organizations were assigned to control, activity tracker, or one of two activity tracker plus incentive groups designed to increase step count. The primary outcome was accelerometer measured moderate-to-vigorous physical activity.ResultsWe conducted a secondary analysis on accelerometer measured daily ST and PSB bouts. A general linear mixed model was used to examine changes in ST and prolonged sedentary bouts, followed by between-group pairwise comparisons. Regression analyses were conducted to examine the association of changes in step counts with ST and PSB. The changes in ST and PSB were not statistically significant and not different between the groups (P < 0.05). Increases in step counts were concomitantly associated with decreases in ST and PSB, regardless of intervention (P < 0.05). Caution should be taken when considering consumer-wearable activity trackers as a means to reduce sedentary behavior.Trial registration NCT01855776 Registered: August 8, 2012