Charlotte L. Ridgway

Physical activity intensity, sedentary time, and body composition in preschoolers

BACKGROUND Detailed associations between physical activity (PA) subcomponents, sedentary time, and body composition in preschoolers remain unclear. OBJECTIVE We examined the magnitude of associations between objectively measured PA subcomponents and sedentary time with body composition in 4-y-old children. DESIGN We conducted a cross-sectional study in 398 preschool children recruited from the Southampton Womens Survey. PA was measured by using accelerometry, and body composition was measured by using dual-energy X-ray absorptiometry. Associations between light physical activity, moderate physical activity (MPA), vigorous physical activity (VPA), and moderate-to-vigorous physical activity (MVPA) intensity; sedentary time; and body composition were analyzed by using repeated-measures linear regression with adjustment for age, sex, birth weight, maternal education, maternal BMI, smoking during pregnancy, and sleep duration. Sedentary time and PA were also mutually adjusted for one another to determine whether they were independently related to adiposity. RESULTS VPA was the only intensity of PA to exhibit strong inverse associations with both total adiposity [P < 0.001 for percentage of body fat and fat mass index (FMI)] and abdominal adiposity (P = 0.002 for trunk FMI). MVPA was inversely associated with total adiposity (P = 0.018 for percentage of body fat; P = 0.022 for FMI) but only because of the contribution of VPA, because MPA was unrelated to fatness (P ≥ 0.077). No associations were shown between the time spent sedentary and body composition (P ≥ 0.11). CONCLUSIONS In preschoolers, the time spent in VPA is strongly and independently associated with lower adiposity. In contrast, the time spent sedentary and in low-to-moderate-intensity PA was unrelated to adiposity. These results indicate that efforts to challenge pediatric obesity may benefit from prioritizing VPA.

Does Birth Weight Influence Physical Activity in Youth? A Combined Analysis of Four Studies Using Objectively Measured Physical Activity

Animal models suggest growth restriction in utero leads to lower levels of motor activity. Furthermore, individuals with very low birth weight report lower levels of physical activity as adults. The aim of this study was to examine whether birth weight acts as a biological determinant of physical activity and sedentary time. This study uses combined analysis of three European cohorts and one from South America (n = 4,170). Birth weight was measured or parentally reported. Height and weight were measured and used to calculate Body Mass Index (BMI). PA was objectively measured using accelerometry for ≥3 days, ≥10 hours day. Data was standardized to allow comparisons between different monitors. Total physical activity was assessed as counts per minute (cpm), with time spent above moderate activity (MVPA) >2,000 counts and time spent sedentary (<100 counts). There was no evidence for an association between birth weight and total physical activity (p = 0.9) or MVPA (p = 0.7). Overall there was no evidence for an association between birth weight and sedentary time (p = 0.8). However in the Pelotas study we did find an association between higher birth weight (kg) and lower overall physical activity (cpm) (β = −31, 95%CI: −58, −46, p = 0.03) and higher birth weight and greater sedentary time (mins/day) (β = 16.4, 95%CI: 5.3, 27.5, p = 0.004), although this was attenuated and no longer significant with further adjustment for gestational age. Overall this combined analysis suggests that birth weight may not be an important biological determinant of habitual physical activity or sedentary behaviour in children and adolescents.

Birth size, infant weight gain, and motor development influence adult physical performance.

PURPOSE Adult physical performance is recognized as a marker of both current physical capacity and future health. The aim of the study was to examine the independent influences of birth weight, infant weight gain, and infant motor development on a variety of adult physical performance outcomes, in terms of muscular strength, muscular endurance, and aerobic fitness. METHODS The study population consisted of 4304 individuals from the Northern Finland Birth Cohort 1966 (NFBC 1966) with anthropometry measured at birth and at 1 yr. Infant motor development at age 1 yr was assessed by parentally reported age at first walking supported and standing unaided. At follow-up, aged 31 yr, muscle strength was measured using a handgrip dynamometer, muscle endurance was measured using a timed trunk extension test, and aerobic fitness was estimated from heart rate immediately after a standardized step test. RESULTS Birth weight was positively associated with muscle strength and aerobic fitness at age 31 yr, and these associations were independent of adult body size (P < 0.001). Greater infant weight gain between 0 and 1 yr was associated with lower muscle endurance (P = 0.004) and poorer aerobic fitness (P = 0.002); these associations seemed to be mediated by adult body size. Independent of infant birth weight and adult body size (height and weight), earlier infant motor development was associated with greater adult muscle strength (P < or = 0.001), muscle endurance (P < 0.001), and aerobic fitness (P < 0.001). CONCLUSIONS Higher birth weight, lower infant weight gain, and earlier infant motor development independently predict higher levels of adult physical performance for muscle strength, muscle endurance, and aerobic fitness at age 31 yr.

Physical Activity Awareness of British Adolescents.

OBJECTIVES To assess adolescent physical activity (PA) awareness and to investigate associations with biologic and psychosocial factors. DESIGN Cross-sectional study from November 1, 2005, through July 31, 2007 (the ROOTS study). SETTING Population-based sample recruited from Cambridgeshire and Suffolk schools (United Kingdom). PARTICIPANTS Of 799 participants, 43.6% were male. The mean (SD) age was 14.5 (0.5) years. MAIN EXPOSURES Self-rated PA perception, self-reported psychosocial factors, and measured anthropometry. MAIN OUTCOME MEASURES We measured PA with accelerometry for 5 days. Inactive was defined as less than 60 minutes per day of moderate and vigorous PA (MVPA) measured by accelerometry. Associations between awareness (agreement between self-rated and accelerometry-measured active/inactive) and potential correlates were investigated using multinomial logistic regression. RESULTS Approximately 70.1% of adolescents were inactive (81.2% of girls and 55.8% of boys; odds ratio [OR], 3.41; 95% confidence interval [CI], 2.41-4.82). There were 52.6% of all girls (64.8% of inactive girls) and 33.6% of all boys (60.3% of inactive boys) who inaccurately rated themselves as active (overestimators). Compared with girls accurately describing themselves as inactive (28.6%), girl overestimators had lower fat mass (OR, 0.84; 95% CI, 0.70-0.99), higher socioeconomic status (high vs low OR, 2.38; 95% CI, 1.07-5.32), more parent support (OR, 1.57; 95% CI, 1.12-2.22), and better family relationships (OR, 0.25; 95% CI, 0.09- 0.67). Among boys accurately describing themselves as inactive (22.1%), overestimators had lower fat mass (OR, 0.86; 95% CI, 0.77-0.96) and reported more peer support (OR, 1.75; 95% CI, 1.32-2.30) and less teasing (OR, 0.75; 95% CI, 0.61-0.92). CONCLUSIONS A substantial number of adolescents believe themselves to be more physically active than they really are. They may be unaware of potential health risks and unlikely to participate in PA promotion programs. Increasing information of PA health benefits beyond weight control might encourage behavior change.

Infant Motor Development Predicts Sports Participation at Age 14 Years: Northern Finland Birth Cohort of 1966

Background Motor proficiency is positively associated with physical activity levels. The aim of this study is to investigate associations between the timing of infant motor development and subsequent sports participation during adolescence. Methods Prospective observational study. The study population consisted of 9,009 individuals from the Northern Finland Birth Cohort 1966. Motor development was assessed by parental report at age 1 year, using age at walking with support and age at standing unaided. At follow up aged 14 years, data were collected on the school grade awarded for physical education (PE). Self report was used to collect information on the frequency of sports participation and number of different sports reported. Principal Findings Earlier infant motor development was associated with improved school PE grade, for age at walking supported (p<0.001) and standing unaided (p = <0.001). Earlier infant motor development, in terms of age at walking supported, was positively associated with the number of different sports reported (p = 0.003) and with a greater frequency of sports participation (p = 0.043). These associations were independent of gestational age and birth weight, as well as fathers social class and body mass index at age 14 years. Conclusions Earlier infant motor development may predict higher levels of physical activity as indicated by higher school PE grade, participation in a greater number of different types of sports and increased frequency of sports participation. Identification of young children with slower motor development may allow early targeted interventions to improve motor skills and thereby increase physical activity in later life.

Do physical activity and aerobic fitness moderate the association between birth weight and metabolic risk in youth?: the European Youth Heart Study.

OBJECTIVE Lower birth weight has been associated with a greater risk of metabolic diseases. The aim of this study was examine whether physical activity and aerobic fitness may modify associations between birth weigh and metabolic risk. RESEARCH DESIGN AND METHODS The European Youth Heart Study is a population-based study of 9 and 15 year olds (n = 1,254). Birth weight was maternally reported. Skin fold measures were used to calculate body fat and fat mass index (FMI = fat mass [kilograms]/height2). Insulin was measured using fasting blood samples. Physical activity was measured using a hip-worn accelerometer (MTI Actigraph) for >600 min/day for ≥3 days and is expressed as “average activity” (counts per minute) and time spent in above moderate intensity activity (>2000 cpm). Aerobic fitness was assessed using a maximal cycle ergometry test (watts per kilogram fat-free mass). RESULTS Higher birth weight was associated with higher FMI (β = 0.49 [95% CI 0.21–0.80]; P = 0.001) and greater waist circumference (0.90 [0.32–1.47]; P < 0.001), adjusted for sex, age-group, sexual maturity, height, and socioeconomic status. Lower birth weight was associated with higher fasting insulin only after further adjustment for adolescent waist circumference and height (−0.059 [−0.107 to −0.011]; P = 0.016). There was no evidence for any modification of the associations after adjustment for physical activity or aerobic fitness. CONCLUSIONS The present study did not find any evidence that physical activity or aerobic fitness can moderate the associations among higher birth weight and increased fat mass and greater waist circumference or between lower birth weight and insulin resistance in healthy children and adolescents.

Prospective associations between sedentary time, sleep duration and adiposity in adolescents

Highlights • We examined sedentary time and sleep length relative to changes in youth adiposity.• Sedentary time was not associated with change in adiposity in either gender.• Sleep duration was significantly inversely associated with adiposity gain in boys.• The association for sleep in boys was attenuated by physical activity and depression.

Is wearing a pedometer associated with higher physical activity among adolescents

Objective To examine whether wearing a pedometer was associated with higher objectively-measured physical activity (PA) among adolescents independent of other behavior change strategies, and whether this association differed by sex or day of wear. Method In a parallel-group population-based cohort study, 892 adolescents (43.4% male, mean ± SD age, 14.5 ± 0.5 years) from Eastern England were recruited. PA was measured (in 2005–2006) by accelerometry over four days; a sub-group (n = 345) wore a pedometer coterminously with the accelerometer. Three-level (individual, day of wear and school level) multiple linear regression was used to examine the association between accelerometry (counts/min, cpm) and pedometer wear, stratified by sex and adjusted for weekday/weekend. Results For the entire cohort, there was a significant decline in cpm over four days (p < 0.01). Girls wearing pedometers had higher mean cpm than those not wearing a pedometer, independent of BMI z-score, socio-economic status, weekday/weekend, and school clustering (β = 5.1; 95% CI: 0.8 to 9.5, p = 0.02). This association was not seen in boys. Conclusion Pedometer wear was associated with higher PA among adolescent girls, but not boys. Findings may support sex-specific intervention strategies. In addition to pedometer monitoring, additional strategies may be required to promote PA levels, especially among boys.

Breakfast consumption and physical activity in adolescents: daily associations and hourly patterns

Background: The association between breakfast consumption and physical activity (PA) is inconclusive. Objective: We aimed to investigate daily associations and hourly patterns of PA and breakfast consumption in British adolescents. Design: Daily PA [accelerometry-derived moderate and vigorous physical activity (MVPA)] and breakfast consumption (diet diary) were measured simultaneously over 4 d in 860 adolescents (boys: 43.4%; mean ± SD age: 14.5 ± 0.5 y). Associations between MVPA and breakfast consumption were assessed by using a multilevel mixed-effects logistic regression separately by sex and for weekends and weekdays. Hourly patterns of MVPA by breakfast consumption status were displayed graphically, and differences were tested by using ANOVA. Multilevel linear regression was used to investigate differences in log MVPA on days when 570 inconsistent breakfast consumers ate or skipped breakfast. Results: On weekends, boys and girls with higher MVPA were more likely to eat breakfast [OR (95% CI): boys, 1.78 (1.30, 2.45) (P < 0.001); girls, 2.30 (1.66, 3.08) (P < 0.001)] when adjusted for socioeconomic status, percentage of body fat, and total energy intake. Peak hourly MVPA differed for breakfast consumers compared with nonconsumers on weekends (P < 0.001). Inconsistent breakfast consumers did more MVPA on days when they ate breakfast [exponentiated β coefficients (95% CIs): 1.2 (1.0, 1.5) on weekdays and 1.4 (1.1, 1.8) on weekends for boys and 1.6 (1.3, 2.1) on weekends for girls; all P < 0.03]. Conclusions: Eating breakfast was associated with higher MVPA on weekends. The time of peak MVPA differed between breakfast consumers and nonconsumers on weekends. Breakfast consumption at weekends is worth additional investigation to potentially inform PA promotion in adolescents.

Fat-free mass mediates the association between birth weight and aerobic fitness in youth

OBJECTIVE To investigate whether birth weight acts as a biological determinant of later aerobic fitness, and whether fat-free mass may mediate this association. METHODS The European Youth Heart Study (EYHS) is a population-based cohort of two age groups (9 and 15 years) from Denmark, Portugal, Estonia and Norway. Children with parentally reported birth weight >1.5 kg were included (n = 2 749). Data were collected on weight, height, and skinfold measures to estimate fat mass and fat-free mass. Aerobic fitness (peak power, watts) was assessed using a maximal, progressive cycle ergometer test. Physical activity was collected in a subset (n = 1 505) using a hip-worn accelerometer and defined as total activity counts/wear time, all children with >600 minutes/day for ≥3 days of wear were included. RESULTS Lower birth weight was associated with lower aerobic fitness, after adjusting for sex, age group, country, sexual maturity and socio-economic status (ß = 5.4; 95% CI: 3.5, 7.3 W per 1 kg increase in birth weight, p < 0.001). When fat-free mass was introduced as a covariate in the model, the association between birth weight and aerobic fitness was almost completely attenuated (p = 0.7). Birth weight was also significantly associated with fat-free mass (ß = 1.4; 95% CI: 1.1, 1.8, p < 0.001) and fat-free mass was significantly associated with aerobic fitness (ß = 3.6; 95% CI: 3.4, 3.7, p < 0.001). Further adjustment for physical activity did not alter the findings. CONCLUSION Birth weight may have long-term influences on fat-free mass and differences in fat-free mass mediate the observed association between birth weight and aerobic fitness.