Moderate and vigorous physical activity intensity cut-points for the Actical accelerometer

Accelerometry is increasingly used as a physical activity surveillance device that can quantify the amount of time spent moving at a range of intensities. This study proposes physical activity intensity cut-points for the Actical accelerometer. Thirty-eight volunteers completed a multi-stage treadmill protocol at 3, 5, and 8 km · h?1 (2, 3.3, and 8 METs) while wearing Actical accelerometers initialized to collect data in 60-s epochs. Using a decision boundary analytical approach, moderate and vigorous physical activity intensity cut-points were derived for the Actical accelerometer. In adults (n = 26), the cut-point for moderate physical activity intensity occurred at 1535 counts per minute and the vigorous cut-point occurred at 3960 counts per minute. In children (n = 12), the cut-point for moderate physical activity intensity occurred at 1600 counts per minute and the vigorous cut-point occurred at 4760 counts per minute. Improved classification of physical activity intensity using the decision boundary cut-points was observed compared with using mean values for each protocol stage. The cut-points derived are recommended for use in adults. The cut-points derived for children confirm the findings of previous studies.     

Wrist-based cut-points for moderate- and vigorous-intensity physical activity for the Actical accelerometer in adults

Wrist-based accelerometers are increasingly used to assess physical activity (PA) in population-based studies; however, cut-points to translate wrist-based accelerometer counts into PA intensity categories are still needed. The purpose of this study was to determine wrist-based cut-points for moderate- and vigorous-intensity ambulatory PA in adults for the Actical accelerometer. Healthy adults (n = 24) completed a four-phase treadmill exercise protocol (1.9, 3.0, 4.0 and 5.2 mph) while wearing an Actical accelerometer on their wrist. Metabolic equivalent of task (MET) levels were assessed by indirect calorimetry. Receiver operating characteristics (ROC) curves were generated to determine accelerometer counts that maximised sensitivity and specificity for classification of moderate (≥3 METs) and vigorous (>6 METs) ambulatory activity. The area under the ROC curves to discriminate moderate- and vigorous-intensity ambulatory activity were 0.93 (95% confidence interval [CI]: 0.90–0.97; P < 0.001) and 0.96 (95% CI: 0.94–0.99; P < 0.001), respectively. The identified cut-point for moderate-intensity ambulatory activity was 1031 counts per minute, which had a corresponding sensitivity and specificity of 85.6% and 87.5%, respectively. The identified cut-point for vigorous intensity ambulatory activity was 3589 counts per minute, which had a corresponding sensitivity and specificity of 88.0% and 98.7%, respectively. This study established intensity-specific cut-points for wrist-based wear of the Actical accelerometer which are recommended for quantification of moderate- and vigorous-intensity ambulatory activity.     

Evaluation of Actical equations and thresholds to predict physical activity intensity in young children

This study examined the validity of current Actical activity energy expenditure (AEE) equations and intensity cut-points in preschoolers using AEE and direct observation as criterion measures. Forty 4–6-year-olds (5.3 ± 1.0 years) completed a ~150-min room calorimeter protocol involving age-appropriate sedentary behaviours (SBs), light intensity physical activities (LPAs) and moderate-to-vigorous intensity physical activities (MVPAs). AEE and/or physical activity intensity were calculated using Actical equations and cut-points by Adolph, Evenson, Pfeiffer and Puyau. Predictive validity was examined using paired sample t-tests. Classification accuracy was evaluated using weighted kappas, sensitivity, specificity and area under the receiver operating characteristic curve. The Pfeiffer equation significantly overestimated AEE during SB and underestimated AEE during LPA (P < 0.0125 for both). There was no significant difference between measured and predicted AEEs during MVPA. The Adolph cut-point showed significantly higher accuracy for classifying SB, LPA and MVPA than all others. The available Actical equation does not provide accurate estimates of AEE across all intensities in preschoolers. However, the Pfeiffer equation performed reasonably well for MVPA. Using cut-points of ≤6 counts · 15 s^?1, 7–286 counts · 15 s^?1 and ≥ 287 counts · 15 s^?1 when classifying SB, LPA and MVPA, respectively, is recommended.     

Comparison of ActiGraph GT3X+ and Actical accelerometer data in 9–11-year-old Canadian children

Accelerometry is the gold standard for field-based physical activity assessment in children; however, the plethora of devices, data reduction procedures, and cut-points available limits comparability between studies. This study aimed to compare physical activity variables from the ActiGraph GT3X+ and Actical accelerometers in children under free-living conditions. A cross-sectional study of 379 children aged 9–11 years from Ottawa (Canada) was conducted. Children wore the ActiGraph GT3X+ and Actical accelerometers on the hip simultaneously for 7 consecutive days (24-h protocol). Moderate-to-vigorous (MVPA), vigorous (VPA), moderate (MPA), and light (LPA) physical activity, as well as sedentary time, (SED) were derived using established data reduction protocols. Excellent agreement between devices was observed for MVPA (ICC = 0.73–0.80), with fair to good agreement for MPA, LPA and SED, and poor agreement for VPA. Bland-Altman plots showed excellent agreement for MVPA, LPA, and SED, adequate agreement for MPA, and poor agreement for VPA. MVPA derived from the Actical was 11.7% lower than the ActiGraph GT3X+. The ActiGraph GT3X+ and Actical are comparable for measuring children’s MVPA. However, comparison between devices for VPA, MPA, LPA, and SED are highly dependent on data reduction procedures and cut-points, and should be interpreted with caution.     

Evaluating the Responsiveness of Accelerometry to Detect Change in Physical Activity

The responsiveness to change of the Actical and ActiGraph accelerometers was assessed in children and adolescents. Participants (N = 208) aged 6 to 16 years completed two simulated free-living protocols, one with primarily light-to-moderate physical activity (PA) and one with mostly moderate-to-vigorous PA. Time in sedentary, light, moderate, and vigorous PA was estimated using 8 previously developed cut-points (4 for Actical and 4 for ActiGraph) and 5-sec, 15-sec, and 30-sec epochs. Accelerometer responsiveness for detecting differences in PA between protocols was assessed using standardized response means (SRMs). SRM values ≥.8 represented high responsiveness to change. Both accelerometers showed high responsiveness for all PA intensities (SRMs = 1.2–4.7 for Actical and 1.1–3.3 for ActiGraph). All cut-points and epoch lengths yielded high responsiveness, and choice of cut-points and epoch length had little effect on responsiveness. Thus, both the Actical and ActiGraph can detect change in PA in a simulated free-living setting, irrespective of cut-point selection or epoch length.     

Decision boundaries and receiver operating characteristic curves: New methods for determining accelerometer cutpoints

Abstract

We propose and evaluate the utility of an alternative method (decision boundaries) for establishing physical activity intensity-related accelerometer cutpoints. Accelerometer data collected from seventy-six 11- to 14-year-old boys during controlled bouts of moderate- and vigorous-intensity field physical activities were assessed. Mean values and standard deviations for moderate- and vigorous-intensity activities were obtained and normal equivalents generated. The decision boundary (the point of intersection of overlapping distributions) was used to create a lower-bound vigorous-intensity cutpoint. Receiver operating characteristic (ROC) curves compared the sensitivity and specificity of the new cutpoint and mean values with the actual activity. There was a 96.5% probability that participants performing vigorous-intensity physical activity were accurately classified when using the decision boundary of 6700 counts per minute, in contrast to the 50% accurately classified when the mean value was used. Inspection of the empirical ROC curve indicated that the decision boundary provided the optimal threshold to distinguish between moderate and vigorous physical activity for this dataset. In conclusion, decision boundaries reduced the error associated with determining accelerometer threshold values. Applying these methods to accelerometer data collected in specific populations will improve the precision with which accelerometer thresholds can be identified.     

Decision boundaries and receiver operating characteristic curves: new methods for determining accelerometer cutpoints

We propose and evaluate the utility of an alternative method (decision boundaries) for establishing physical activity intensity-related accelerometer cutpoints. Accelerometer data collected from seventy-six 11- to 14-year-old boys during controlled bouts of moderate- and vigorous-intensity field physical activities were assessed. Mean values and standard deviations for moderate- and vigorous-intensity activities were obtained and normal equivalents generated. The decision boundary (the point of intersection of overlapping distributions) was used to create a lower-bound vigorous-intensity cutpoint. Receiver operating characteristic (ROC) curves compared the sensitivity and specificity of the new cutpoint and mean values with the actual activity. There was a 96.5% probability that participants performing vigorous-intensity physical activity were accurately classified when using the decision boundary of 6700 counts per minute, in contrast to the 50% accurately classified when the mean value was used. Inspection of the empirical ROC curve indicated that the decision boundary provided the optimal threshold to distinguish between moderate and vigorous physical activity for this dataset. In conclusion, decision boundaries reduced the error associated with determining accelerometer threshold values. Applying these methods to accelerometer data collected in specific populations will improve the precision with which accelerometer thresholds can be identified.     

The translation of preschoolers’ physical activity guidelines into a daily step count target

This study aimed at translating the physical activity (PA) guideline (180 min of total PA per day) into a step count target in preschoolers. 535 Flemish preschoolers (mean age: 4.41 ± 0.58) wore an ActiGraph accelerometer (GT1M, GT3X and GT3X+) – with activated step count function – for four consecutive days. The step count target was calculated from the accelerometer output using a regression equation, applying four different cut-points for light-to-vigorous PA: Pate, Evenson, Reilly, and Van Cauwenberghe. The present analysis showed that 180 min of total PA per day is equivalent to the following step count targets: 5,274 steps/day using the Pate cut-point, 4,653 steps/day using the Evenson cut-point, 11,379 steps/day using the Reilly cut-point and 13,326 steps/day using the Van Cauwenberghe cut-point. Future studies should focus on achieving consensus on which cut-points to use in preschoolers before a definite step count target in preschoolers can be proposed. Until then, we propose to use a provisional step count target of 11,500 steps/day as this step count target is attainable, realistic and helpful in promoting preschoolers’ PA.     

Combinations of Epoch Durations and Cut-Points to Estimate Sedentary Time and Physical Activity Among Adolescents

The purpose of the current study was to investigate how combinations of different epoch durations and cut-points affect the estimations of sedentary time and physical activity in adolescents. Accelerometer data from 101 adolescents were derived and 30 combinations were used to estimate sedentary time, light, moderate, vigorous, and combined moderate-to-vigorous physical activity. Data were analyzed with repeated measurement analyses of variance. Large differences of sedentary time and times of different physical activity intensities were observed between 1 s and longer epoch durations using virtually all cut-points. Generally, sedentary time, moderate physical activity, vigorous physical activity, and combined moderate-to-vigorous physical activity progressively decreased, whereas light physical activity increased with longer epoch durations. The extreme differences between cut-points were large and increased with longer epoch durations for sedentary time and for all physical activity intensities except for vigorous physical activity per epoch duration. Caution is required when cross-comparing studies using different epoch durations and cut-points. To accurately register adolescents’ spontaneous intermittent physical activity behavior, short epoch durations are recommended.     

Validating the multimedia activity recall for children and adolescents in a large New Zealand sample

Abstract

The aim of the study was to validate the self-report Multimedia Activity Recall for Children and Adolescents (MARCA) against accelerometry for the assessment of physical activity in New Zealand children. Participants (n = 716, 10–18 years) recalled 3–4 days of activity using the MARCA and underwent a partially overlapping 7-day accelerometry protocol during a national survey. Spearman correlation coefficients (ρ) assessed the association between accelerometer-derived counts per minute and MARCA-derived physical activity level and time in locomotion. Both data sources estimated time spent in light and moderate–vigorous physical activity. Association and agreement between methods for light physical activity and moderate–vigorous physical activity was assessed using correlations and Bland–Altman plots respectively, and paired t-tests conducted. Accelerometer-derived activity counts were moderately correlated with both MARCA-derived physical activity level and locomotion (ρ = 0.38, P < 0.0001). The correlation between methods was –0.14 for light physical activity and 0.28 for moderate–vigorous physical activity (P < 0.0001). The MARCA overestimated moderate–vigorous physical activity compared with accelerometry (120 min, P < 0.0001), which increased as moderate–vigorous physical activity time increased. Some sex and ethnicity (Māori [indigenous] versus non-Māori) differences were observed. Overall, the MARCA indicated moderate validity for assessment of physical activity level, locomotion and moderate–vigorous physical activity and poor validity for assessment of light physical activity. This was comparable to other self-report tools. The MARCA has utility for future large-scale research.     

Classification of Physical Activity Cut-Points and the Estimation of Energy Expenditure During Walking Using the GT3X+ Accelerometer in Overweight and Obese Adults

This study establishes tri-axial activity count (AC) cut-points for the GT3X+ accelerometer to classify physical activity intensity in overweight and obese adults. Further, we examined the accuracy of established and novel energy expenditure (EE) prediction equations based on AC and other metrics. Part 1: Twenty overweight or obese adults completed a 30 minute incremental treadmill walking protocol. Heart rate (HR), EE, and AC were measured using the GT3X+ accelerometer. Part 2: Ten overweight and obese adults conducted a self-paced external walk during which EE, AC, and HR were measured. Established equations (Freedson et al., 1998; Sasaki et al., 2011) overestimated EE by 40% and 31%, respectively (p < .01). Novel gender-specific prediction equations provided good estimates of EE during treadmill and outdoor walking (standard error of the estimate = .91 and .65, respectively). We propose new cut-points and prediction equations to estimate EE using the GT3X+ tri-axial accelerometer in overweight and obese adults.     

Validity of the Actical activity monitor for assessing steps and energy expenditure during walking

This study examined the validity of the Actical accelerometer step count and energy expenditure (EE) functions in healthy young adults. Forty-three participants participated in study 1. Actical step counts were compared to actual steps taken during a 200 m walk around an indoor track at self-selected pace and during treadmill walking at different speeds (0.894, 1.56 and 2.01 m · s^–1) for 5 min. The Actical was also compared to three pedometers. For study 2, 15 participants from study 1 walked on a treadmill at their predetermined self-selected pace for 15 min. Actical EE was compared to EE measured by indirect calorimetry. One-way analysis of variance and t-tests were used to examine differences. There were no statistical difference between Actical steps and actual steps in self-selected pace walking and during treadmill walking at moderate and fast speeds. During treadmill walking at slow speed, the Actical step counts significantly under predicted actual steps taken. For study 2, there was no statistical difference between measured EE and Actical-recorded EE. The Actical provides valid estimates of step counts at self-selected pace and walking at constant speeds of 1.56 and 2.01 m · s^–1. The Actical underestimates EE of walking at constants speeds ≥1.38 m · s^–1.     

Calibration of two objective measures of physical activity for children

A calibration study was conducted to determine the threshold counts for two commonly used accelerometers, the ActiGraph and the Actical, to classify activities by intensity in children 5 to 8 years of age. Thirty-three children wore both accelerometers and a COSMED portable metabolic system during 15 min of rest and then performed up to nine different activities for 7 min each, on two separate days in the laboratory. Oxygen consumption was measured on a breath-by-breath basis, and accelerometer data were collected in 15-s epochs. Using receiver operating characteristic curve (ROC) analysis, cutpoints that maximised both sensitivity and specificity were determined for sedentary, moderate and vigorous activities. For both accelerometers, discrimination of sedentary behaviour was almost perfect, with the area under the ROC curve at or exceeding 0.98. For both the ActiGraph and Actical, the discrimination of moderate (0.85 and 0.86, respectively) and vigorous activity (0.83 and 0.86, respectively) was acceptable, but not as precise as for sedentary behaviour. This calibration study, using indirect calorimetry, suggests that the two accelerometers can be used to distinguish differing levels of physical activity intensity as well as inactivity among children 5 to 8 years of age.     

Development of raw acceleration cut-points for wrist and hip accelerometers to assess sedentary behaviour and physical activity in 5–7-year-old children

ABSTRACT

This study validated sedentary behaviour (SB), moderate-to-vigorous physical activity (MVPA) and vigorous physical activity (VPA) accelerometer cut-points in 5–7-year-old children. Participants (n = 49, 55% girls) wore an ActiGraph GT9X accelerometer, recording data at 100 Hz downloaded in 1 s epochs, on both wrists and the right hip during a standardised protocol and recess. Cut-points were generated using ROC analysis with direct observation as a criterion. Subsequently, cut-points were optimised using Confidence intervals equivalency analysis and then cross-validated in a cross-validation group. SB cut-points were 36 mg (Sensitivity (Sn) = 79.8%, Specificity (Sp) = 56.8%) for non-dominant wrist, 39 mg (Sn = 75.4%, Sp = 70.2%) for dominant wrist and 20 mg (Sn = 78%, Sp = 50.1%) for hip. MVPA cut-points were 189 mg (Sn = 82.6%, Sp = 78%) for non-dominant wrist, 181 mg (Sn = 79.1%, Sp = 76%) for dominant wrist and 95 mg (Sn = 79.3%, Sp = 75.6%) for hip. VPA cut-points were 536 mg (Sn = 75.1%, Sp = 68.7%) for non-dominant wrist, 534 mg (Sn = 67.6%, Sp = 95.6%) for dominant wrist and 325 mg (Sn = 78.2%, Sp = 96.1%) for hip. All placements demonstrated adequate levels of accuracy for SB and PA assessment.     

Discrepancies in accelerometer-measured physical activity in children due to cut-point non-equivalence and placement site

Abstract This study examined dissonance in physical activity (PA) between two youth-specific hip-derived intensity cut-points for the Actiwatch (AW), and compared PA between hip and wrist placements using site-specific cut-points. Twenty-four children aged 11.2?±?0.5 years wore the AW on the right hip and non-dominant wrist during a typical school day. Minutes of sedentary behaviour and vigorous activity were greater using Puyau et al. (2002) cut-points, but light, moderate, and moderate-to-vigorous (MVPA) were greater when derived using Puyau et al. (2004) cut-points (P?相似文献   

Influence of moderate intensity physical activity levels and gender on conditioned pain modulation

This study examined the potential influence of moderate intensity physical activity (PA) levels and gender on central pain modulation using conditioned pain modulation (CPM) in healthy men and women. Twenty four individuals (12 men and 12 women) who reported engaging in the moderate intensity PA for 150 min or more per week and 24 individuals (12 men and 12 women) who reported engaging in moderate intensity PA for 60 min or less per week completed a self-report PA questionnaire and a 7-day PA assessment using an accelerometer. Furthermore, the participants completed the CPM testing to evaluate the efficiency of central pain modulation. The active individuals scored higher on the PA questionnaire and spent more minutes for light, lifestyle, moderate and vigorous intensity PA than the less active individuals. The active men and women exhibited comparable magnitudes of CPM, and showed a greater magnitude of CPM when compared to their less active counterparts. However, these beneficial effects of higher dose moderate intensity PA disappeared when time spent for vigorous intensity PA was statistically controlled for. These results suggest that the higher dose moderate intensity PA does not add to the benefits from vigorous intensity PA to further improve central pain modulatory systems.     

Sedentary time and vigorous physical activity are independently associated with cardiorespiratory fitness in middle school youth

Abstract

The purpose of this cross-sectional study was to examine the relationship between objectively measured physical activity, sedentary time, and cardiorespiratory fitness in a diverse sample of youth. Participants were recruited from three middle schools and completed assessments of height, weight, cardiorespiratory fitness, and wore an accelerometer for a minimum of four days. Hierarchical general linear models controlling for age, body mass index (BMI) percentile, and sex were used to evaluate the association of time (minutes per day) spent sedentary, and in moderate physical activity and vigorous physical activity with cardiorespiratory fitness (i.e., heart rate response [beats per minute], dependent variable). Results indicated age (β = –0.16, P < 0.05), BMI percentile (β = 0.33, P <0.05), being male (β = 0.17, P < 0.05), sedentary time (β = 0.11, P <0.05), moderate (β = –0.03, P > 0.05) and vigorous (β = –0.22, P < 0.05) physical activity explained 29% of the variance in cardiorespiratory fitness. Evaluation of fitness among high sedentary/high vigorous, high sedentary/low vigorous, low sedentary/low vigorous, and low sedentary/high vigorous groups (defined by the median split) showed that high levels of vigorous activity removed the detrimental effect of high levels of sedentary time on cardiorespiratory fitness. These analyses suggest that the negative impact of sedentary time can be mitigated by engaging in vigorous activity.     

Accelerometry to measure physical activity in toddlers: Determination of wear time requirements for a reliable estimate of physical activity

Accelerometry is widely used to evaluate physical activity in toddlers however recommendations regarding wear time are needed to understand physical activity behaviours in this age group. This study aimed to determine the minimum wear time to reliably evaluate physical activity in toddlers. Children from the 3D Birth Cohort (n = 255, 49.8% boys, 2.1 ± 0.2 years) were asked to wear an accelerometer (GT3X+, ActiGraph) for 7 days. Physical activity was expressed in active time (min/day) and counts per minute (CPM). Single day intraclass correlation coefficients (ICCs) were calculated to assess the effect of varying minimal wear time on reliability estimates. The Spearman-Brown formula was used to determine wear time required to achieve reliability levels of 70%, 80% and 90%. For active time, a reliability of 72.1% was achieved with wearing the accelerometer for ≥ 4 days of ≥ 6 h, which comprised 85.9% of the sample. For CPM, ≥ 4 days of ≥ 6 h provided a reliability of 74.7% and comprised 85.9% of the children. Results differed slightly when girls and boys were analysed separately, but restricting analyses to children with a weekend day did not. In summary, a minimum of 4 days with ≥ 6 h of accelerometry data provides a reliable estimate of physical activity in 2-year toddlers.     

Park use and physical activity among adolescent girls at two time points

This longitudinal study described park usage and assessed the contribution of parks to moderate to vigorous physical activity (MVPA) among adolescent girls. High school girls from California (n = 131) and Minnesota (n = 134) wore a global positioning system (GPS) monitor and accelerometer for 6 consecutive days at two time points, one year apart. Park visits were classified by linking the GPS, accelerometer, and park and built environment data around home and school locations into a geographic information system. At baseline, 20% of girls visited a park at least once (mean 0.1 times/day), which was similar one year later (19%, mean 0.1 times/day). Girls lived a mean Euclidean distance of 0.2 miles to the nearest park at both times. Among all park visits, the mean Euclidean distance of the park visited was 4.1 (baseline) and 3.9 miles (follow-up). The average duration of park visits was higher at baseline (63.9 minutes) compared to follow-up (38.4 minutes). On days when a park was visited, MVPA was higher than on days when a park was not visited. On average, 1.9% (baseline) and 2.8% (follow-up) of MVPA occurred in parks. In this study, parks were an under-used resource for adolescent girls, particularly for MVPA.     

Accelerometer responsiveness to change between structured and unstructured physical activity in children and adolescents

This study examined if accelerometer-based assessments of physical activity were responsive to changes in physical activity level commensurate with performing structured versus unstructured activity in youth. Youth (6–16 years; N = 206) participated in a simulated after-school program that included structured and unstructured games on four occasions over a 3-year period. Recruitment occurred in 2007/2008 and data collection ended in 2011. Participants wore an Actigraph GT1M accelerometer on the hip. The Evenson cut-points were used to determine the time spent in each physical activity intensity, and standardized response means (SRM) were calculated and converted to standard effect sizes to be interpreted according to Cohen’s guidelines. SRMs ranged from trivial (0.16) to high (2.07), with the majority (75%) being classified as moderate or high. Our findings suggest that accelerometry was sensitive to differences in physical activity associated with structured compared to unstructured play, supporting the utility of accelerometry in evaluating activity-promoting interventions.