Biomedical subjects

Kerry L McIver

Publications and source records attributed to Kerry L McIver.

5 recordsLinked to original sources

PubMed2006

Sport participation and physical activity in adolescent females across a four-year period.

PURPOSE: To determine the odds of engaging in future moderate-to-vigorous physical activity (MVPA) and vigorous physical activity (VPA) in adolescent female sport participants. A secondary purpose was to compare activity levels of three groups of girls, those who played sports at three time points, those who dropped out, and those who did not participate in sports. METHODS: Data were collected at three time points, eighth, ninth, and 12th grades, in 429 adolescent girls across the state of South Carolina. Demographic, sport participation and physical activity (PA) data were collected using surveys. Odds ratios were calculated to determine the association between sport participation and future PA behavior. PA was also compared for three sport participation groups (nonparticipants, dropouts, or three-year participants) using analysis of variance. RESULTS: For MVPA, ninth grade participants were more likely to be active in 12th grade (OR = 1.74 [1.13, 2.67]), and eighth and ninth grade participants more likely to be active in 12th grade than nonparticipants (OR = 1.54 [confidence interval 1.01, 2.35]). For VPA, sport participants had higher odds of being active at all future time points. Three-year participants were significantly more vigorously active than nonparticipants and dropouts at all three time points (p < .01). CONCLUSIONS: Adolescent girls who participate in sports in eighth, ninth, and 12th grades are more likely to be vigorously active in 12th grade. These findings are novel in providing evidence that sport participation contributes to overall vigorous physical activity during late adolescence, when overall physical activity is known to decline precipitously.

Adolescent↗

PubMed2006

Validation and calibration of an accelerometer in preschool children.

OBJECTIVE: Obesity rates in young children are increasing, and decreased physical activity is likely to be a major contributor to this trend. Studies of physical activity in young children are limited by the lack of valid and acceptable measures. The purpose of this study was to calibrate and validate the ActiGraph accelerometer for use with 3- to 5-year-old children. RESEARCH METHODS AND PROCEDURES: Thirty preschool children wore an ActiGraph accelerometer (ActiGraph, Fort Walton Beach, FL) and a Cosmed portable metabolic system (Cosmed, Rome, Italy) during a period of rest and while performing three structured physical activities in a laboratory setting. Expired respiratory gases were collected, and oxygen consumption was measured on a breath-by-breath basis. Accelerometer data were collected at 15-second intervals. For cross-validation, the same children wore the same instruments while participating in unstructured indoor and outdoor activities for 20 minutes each at their preschool. RESULTS: In calibrating the accelerometer, the correlation between Vo(2) (ml/kg per min) and counts was r = 0.82 across all activities. The only significant variable in the prediction equation was accelerometer counts (R(2) = 0.90, standard error of the estimate = 4.70). In the cross-validation, the intraclass correlation coefficient between measured and predicted Vo(2) was R = 0.57 and the Spearman correlation coefficient was R = 0.66 (p < 0.001). Cut-off points for moderate- and vigorous-intensity physical activity were identified at 420 counts/15 s (Vo(2) = 20 mL/kg per min) and 842 counts/15 s (Vo(2) = 30 mL/kg per min), respectively. When these cutpoints were applied to the cross-validation data, percentage agreement, kappa, and modified kappa for moderate activity were 0.69, 0.36, and 0.38, respectively. For vigorous activity, the same measures were 0.81, 0.13, and 0.62. DISCUSSION: Accelerometer counts were highly correlated with Vo(2) in young children. Accelerometers can be appropriately used as a measure of physical activity in this population.

Acceleration↗

PubMed2006

Validation and calibration of the Actical accelerometer in preschool children.

PURPOSE: Decreased physical activity (PA) is likely a contributor to the rising prevalence of obesity in children. Lack of valid and acceptable measures of PA has been an issue in studies involving young children. The Actical accelerometer is a promising tool for measurement of PA in young children. The purpose of this study was to calibrate and validate the Actical accelerometer for use with 3- to 5-yr-old children. METHODS: Eighteen preschool children wore an Actical accelerometer and a Cosmed portable metabolic system during a period of rest, while performing three structured activities in a laboratory setting (used for calibration), and during 20 min each of unstructured indoor and outdoor activities at their preschool (used for cross-validation). Expired respiratory gases were collected, and oxygen consumption was measured on a breath-by-breath basis. Accelerometer data were collected in 15-s intervals. RESULTS: For the accelerometer calibration, the correlation between VO2 and counts was r = 0.89 across all activities. The calibration equation established was VO2 = counts x 15 s(-1) (0.01437) + 9.73 (R2 = 0.96, SEE = 3.02). The cut-point for moderate activity (20 mL x kg(-1) x min(-1)) was 715 counts x 15 s(-1) (sensitivity 97.2%, specificity 91.7%), and the cut-point for vigorous activity (30 mL x kg(-1) x min(-1)) was 1411 counts x 15 s(-1) (sensitivity 98.2%, specificity 61.1%). For the cross-validation, the intraclass correlation coefficient was R = 0.59 and the Spearman correlation coefficient was R = 0.80 (P < 0.001) between measured and predicted VO2. Percentage of agreement, kappa, and modified kappa for moderate activity were 0.73, 0.40, and 0.46, respectively. For vigorous activity, the same measures were 0.85, 0.26, and 0.71, respectively. CONCLUSION: The Actical accelerometer is a valid tool for measuring PA in young children.

Acceleration↗

PubMed2005

Physical activity and active commuting to elementary school.

PURPOSE: This study was conducted to determine if fifth-grade students who walked or bicycled to school on a regular basis were more physically active than those that did not. METHODS: The sample consists of 219 fifth-grade students (10.3 +/- 0.6 yr, 44% male, 58% minority) from eight randomly selected urban and suburban elementary schools. Students wore an Acti-Graph physical activity monitor during the same week that they completed a daily survey to report their mode of transportation to and from school. Students were categorized on the number of reported active commuting trips, to and from school, per week (regular;>or=5 (N=11), irregular; 1-4 (N=25), nonactive; 0 (N=183)). RESULTS: Compared with both other groups, regular active commuters accumulated 3% more minutes of moderate-to-vigorous physical activity (MVPA; P=0.04) during weekdays. This weekday difference was because of regular active commuters accumulating 8.5% more minutes of MVPA both before and after school (P <or= 0.01). No difference in physical activity was seen among groups during school or in the evening. Based on the mean number of minutes the students wore their monitors on weekdays (800 min.d), the 3% difference translates into approximately 24 additional minutes of MVPA per day for the regular active commuters. CONCLUSION: Walking to school was associated with approximately 24 additional minutes of MVPA per day in fifth-grade students. Additional observational and experimental research in larger, more diverse samples is needed to further clarify the effects of active commuting to school on total daily physical activity and other health outcomes.

Bicycling↗

PubMed2005

Conducting accelerometer-based activity assessments in field-based research.

PURPOSE: The purpose of this review is to address important methodological issues related to conducting accelerometer-based assessments of physical activity in free-living individuals. METHODS: We review the extant scientific literature for empirical information related to the following issues: product selection, number of accelerometers needed, placement of accelerometers, epoch length, and days of monitoring required to estimate habitual physical activity. We also discuss the various options related to distributing and collecting monitors and strategies to enhance compliance with the monitoring protocol. RESULTS: No definitive evidence exists currently to indicate that one make and model of accelerometer is more valid and reliable than another. Selection of accelerometer therefore remains primarily an issue of practicality, technical support, and comparability with other studies. Studies employing multiple accelerometers to estimate energy expenditure report only marginal improvements in explanatory power. Accelerometers are best placed on hip or the lower back. Although the issue of epoch length has not been studied in adults, the use of count cut points based on 1-min time intervals maybe inappropriate in children and may result in underestimation of physical activity. Among adults, 3-5 d of monitoring is required to reliably estimate habitual physical activity. Among children and adolescents, the number of monitoring days required ranges from 4 to 9 d, making it difficult to draw a definitive conclusion for this population. Face-to-face distribution and collection of accelerometers is probably the best option in field-based research, but delivery and return by express carrier or registered mail is a viable option. CONCLUSION: Accelerometer-based activity assessments requires careful planning and the use of appropriate strategies to increase compliance.

Acceleration↗