Moderate- And Vigorous-intensity Physical Activity Research Articles

Objectively measured physical activity trajectories predict adolescent bone strength: Iowa Bone Development Study

BackgroundPhysical activity improves bone strength and reduces the risk for osteoporotic fractures. However, there are substantial gaps in our knowledge as to when, how and how much activity is optimal...

Longitudinal Change in Active and Sedentary Behavior During the After-School Hours

Relatively little is known regarding after-school behavior. This study examined after-school active and sedentary behaviors among youth participating in the Study of Early Child Care and Youth Development. An interview guided time-use approach was used to obtain detailed longitudinal information about after-school (3-6 PM) behavior of a mixed gender cohort (n = 886) at ages 9 and 11 yrs. Responses obtained in 15-min intervals were coded into 29 exclusive behaviors and separated into 3 main categories [moderate and vigorous-intensity physical activity (MVPA), light-intensity physical activity, and sedentary]. Sedentary category was further divided into screen and nonscreen categories. A mixed ANOVA design was used to examine gender and age-related differences in MVPA, light-intensity physical activity, sedentary, screen, and nonscreen. MVPA was higher among boys compared with girls (P < .001) and decreased from 9 to 11 yrs (P < .001). Overall, total sedentary time was comparable between boys and girls despite a difference in reported screen time (boys > girls; P < .001) and nonscreen time (boys < girls; P < .001). Total sedentary time increased from 9 to 11 yrs (P < .001). Engagement in after-school behavior appears to change during preadolescence. Additional research is needed to understand factors associated with the selection of active and sedentary behavior over time.

Tracking of accelerometry-measured physical activity during childhood: ICAD pooled analysis

BackgroundUnderstanding of physical activity (PA) tracking during childhood is important to predict PA behaviors and design appropriate interventions. We compared tracking of PA according to PA level and type of day (weekday/weekend) in a pool of five children’s cohort studies.MethodsData from ALSPAC, CLAN, Iowa Bone Development Study, HEAPS, PEACH were extracted from the International Children’s Accelerometry Database (ICAD), resulting in 5,016 participants with age, gender, and accelerometry data at both baseline and follow-up (mean age: 10.3 years at baseline, 12.5 years at follow-up). Daily minutes spent in moderate- and vigorous-intensity PA (MVPA) and vigorous-intensity PA (VPA) was categorized into quintiles. Multinomial logistic regression models were fit to predict follow-up (M)VPA from baseline (M)VPA (reference: 20- < 80%tile), age at follow-up, and follow-up duration.ResultsFor the weekday, VPA tracking for boys with high baseline VPA was higher than boys with low baseline VPA (ORs: 3.9 [95% CI: 3.1, 5.0] vs. 2.1 [95% CI: 1.6, 2.6]). Among girls, high VPA was less stable when compared low VPA (ORs: 1.8 [95% CI: 1.4, 2.2] vs. 2.6 [95% CI: 2.1, 3.2]). The pattern was similar for MVPA among girls (ORs: 1.6 [95% CI: 1.2, 2.0] vs. 2.8 [95% CI: 2.3, 3.6]). Overall, tracking was lower for the weekend.ConclusionsPA tracking was higher on the weekday than the weekend, and among inactive girls than active girls. The PA “routine” of weekdays should be used to help children establish healthy PA patterns. Supports for PA increase and maintenance of girls are needed.

Progressive resistance training improves overall physical activity levels in patients with early osteoarthritis of the knee: a randomized controlled trial.

Prescription of resistance training (RT) exercises is an essential aspect of management for knee osteoarthritis (OA). However, whether patients with knee OA who are randomly assigned to receive RT simply substitute RT for other modes of physical activity remains unclear. The aim of this study was to determine the effect of a structured RT intervention on overall levels of moderate- and vigorous-intensity physical activity (MVPA) in patients with early-onset knee OA. The study compared patients with early-onset OA who participated in an RT program, those who participated in a self-management (SM) program, and those who participated in both RT and SM. Because participants randomly assigned to receive the RT intervention may simply switch activity modes, resulting in little net effect, we assessed total MVPA in addition to tracking changes in strength (force-generating capacity). This study was a randomized controlled trial comparing the effectiveness of SM alone, RT alone, and combined RT+SM on MVPA in patients with early OA of the knee. The study was conducted on a university campus, with patient recruitment from the local community. The participants in this study were 171 patients (74% women, 26% men) with knee OA. They had a mean age of 55.1 (SD=7.1) years, a mean body mass index of 27.6 (SD=4.2) kg/m(2), and radiographic status of grade II OA (and no higher) in at least one knee, as defined by the Kellgren and Lawrence classification. They wore an accelerometer while awake (X=14.2 [SD=2.2] hours) for 5 to 7 contiguous days (X=6.8 [SD=0.5] days) at baseline and at 3 and 9 months of intervention. The participants engaged in MVPA a mean of 26.2 (SD=19.3) minutes per day at baseline. Both groups significantly increased their MVPA from baseline to 3 months (RT group by 18% [effect size (d)=0.26]; SM group by 22% [effect size (d)=0.25]), but only the RT group sustained those changes at 9 months (RT group maintained a 10% increase [effect size (d)=0.15]; SM group maintained a 2% increase [effect size (d)=0.03]). A significant group x time interaction for MVPA indicated that the RT group maintained higher MVPA levels than the SM group. Lack of direct measures of energy expenditure and physical function was a limitation of the study. Patients with early-onset OA of the knee can engage in an RT program without sacrificing their overall MVPA levels. These results support the value of RT for management of knee OA.

Objectively Measured Sedentary Time May Predict Insulin Resistance Independent of Moderate- and Vigorous-Intensity Physical Activity

OBJECTIVETo examine the prospective association between objectively measured time spent sedentary and insulin resistance and whether this association is independent of moderate- and vigorous-intensity physical activity (MVPA) and other relevant confounders.RESEARCH DESIGN AND METHODSThis was a population-based study (Medical Research Council Ely study) in 376 middle-aged adults (166 men; 210 women) over 5.6 years of follow-up. Physical activity and sedentary time were measured objectively by individually calibrated minute-by-minute heart rate monitoring at both baseline and follow-up. Sedentary time was calculated as the heart rate observations (in minutes) below an individually predetermined threshold (flex heart rate) and expressed as a percentage of total monitored time during waking hours over 4 days. The percentage of time spent above 1.75 × resting heart rate represented MVPA. Fasting plasma insulin was used as a surrogate measure of insulin resistance.RESULTSTime spent sedentary at baseline was significantly and positively associated with log fasting insulin at follow-up (β = 0.003, 95% CI 0.0006–0.006, P = 0.015) independent of baseline age, sex, fat mass, fasting insulin, smoking status, and follow-up time. After further adjustment for MVPA, this association was somewhat strengthened (β = 0.004, 95% CI 0.0009–0.006, P = 0.009).CONCLUSIONSTime spent sedentary predicts higher levels of fasting insulin independent of the amount of time spent at moderate- and vigorous-intensity activity levels. This highlights the importance of reducing sedentary time in order to improve metabolic health, possibly in addition to the benefits associated with a physically active lifestyle.

Is it possible to assess free-living physical activity and energy expenditure in young people by self-report?

Background: It is unclear whether it is possible to accurately estimate physical activity energy expenditure (PAEE) by self-report in youth.Objective: We assessed the validity and reliability of 4 self-reports to assess PAEE and time spent at moderate and vigorous intensity physical activity (MVPA) over the previous week in British young people between 4 and 17 y of age.Design: PAEE and MVPA were derived from the Children’s Physical Activity Questionnaire, Youth Physical Activity Questionnaire, and Swedish Adolescent Physical Activity Questionnaire; a lifestyle score indicative of habitual activity was derived from the Child Heart and Health Study in England Questionnaire. These data were compared with criterion methods, PAEE, and MVPA derived from simultaneous measurements by doubly labeled water and accelerometry in 3 age groups: 4–5 y (n = 27), 12–13 y (n = 25), and 16–17 y (n = 24). Validity was assessed by using Spearman correlations and the Bland-Altman method, and reliability was assessed by using intraclass correlation coefficients.Results: The strength of association between questionnaire and criterion methods varied (r = 0.09 to r = 0.46). Some questionnaires were able to accurately assess group-level PAEE and MVPA for some age groups, but the error was large for individual-level estimates throughout. Reliability of the Youth Physical Activity Questionnaire and Child Heart and Health Study in England Questionnaire was good (intraclass correlation coefficient: 0.64–0.92).Conclusions: Absolute PAEE and MVPA estimated from these self-reports were not valid on an individual level in young people, although some questionnaires appeared to rank individuals accurately. Age (the outcome of interest) and whether individual or group-level estimates are necessary will influence the best choice of self-report method when assessing physical activity in youth.

Objectively Measured Moderate- and Vigorous-Intensity Physical Activity but Not Sedentary Time Predicts Insulin Resistance in High-Risk Individuals

OBJECTIVELow levels of physical activity appear to be associated with insulin resistance. However, the detailed associations of these complex relationships remain elusive. We examined the prospective associations between self-reported TV viewing time, objectively measured time spent sedentary, at light-intensity activity, and at moderate- and vigorous-intensity physical activity (MVPA) with insulin resistance.RESEARCH DESIGN AND METHODSIn 192 individuals (81 men and 111 women) with a family history of type 2 diabetes, we measured physical activity and anthropometric and metabolic variables at baseline and after 1 year of follow-up in the ProActive UK trial. Physical activity was measured objectively by accelerometry. Insulin resistance was expressed as fasting insulin and the homeostasis model assessment score (HOMA-IR).RESULTSBaseline MVPA was a significant predictor of fasting insulin at follow-up (β = −0.004 [95% CI −0.007 to −0.0001], P = 0.022), and the association approached significance for HOMA-IR (β = −0.003 [−0.007 to 0.000002], P = 0.052), independent of time spent sedentary, at light-intensity activity, sex, age, smoking status, waist circumference, and self-reported TV viewing. Time spent sedentary and at light-intensity activity were not significantly associated with insulin resistance. The change in MVPA between baseline and follow-up was inversely related to fasting insulin (β = −0.003 [−0.007 to −0.0003], P = 0.032) and the HOMA-IR score (β = −0.004 [−0.008 to −0.001], P = 0.015) at follow-up, after adjustment for baseline phenotype in addition to the same confounders as above.CONCLUSIONSThese results highlight the importance of promoting moderate-intensity activity such as brisk walking for improving insulin sensitivity and possibly other metabolic risk factors to prevent type 2 diabetes.

Decreases in Physical Activity from Elementary School to Middle School in both Boys and Girls in Missoula, MT

Physical activity is linked to enhanced health and reduced youth onset of adult chronic disease. It has been recommended by the CDC that children and adolescents participate in at least 60 minutes of moderate to vigorous intensity physical activity most days of the week. Participation in physical activity declines in adolescence. PURPOSE: To evaluate changes in the physical activity patterns of Missoula, MT across elementary and middle schools. METHODS: 342 elementary and middle school students from 6 schools, grades 2-8, were randomly selected from a pool of volunteers. Descriptive data were collected. Participating students wore Actical ® accelerometer for 5 days on the non dominant wrist with data collected in 1m epochs. The data were corrected using a double pass smoothing spline developed in our lab. Activity count data were converted to activity energy expenditure (mlâЄ¢min-1âЄ¢kg-1) using the methods of Heil, et al. The data were evaluated for time in sedentary, light, moderate and vigorous activity and separated by age, grade, and gender. The data were further separated by looking at Elementary vs. Middle School physical activity in; weekdays vs. weekend; in school vs. out of school, time in recess, time in physical education and time in sport. RESULTS: There is a dramatic drop in overall moderate and vigorous intensity physical activity (MVPA) when students go from elementary school to middle school. The data also shows a significant drop in MVPA both in and out of school, during PE and in minutes of sport participation between elementary and middles school CONCLUSIONS: The large overall drop (36.13%) in physical activity from elementary to middle school is concerning. School and community programs are being developed by our team to work on these issues.

Relation between physical activity and energy expenditure in a representative sample of young children

Strategies for the prevention and treatment of childhood obesity require a better understanding of the relation between the pattern of free-living physical activity and total energy expenditure (TEE). We assessed the relations between TEE and physical activity level (PAL) during engagement in different intensities of physical activity. We used a cross-sectional study of 104 children (median age: 5.4 y) in Scotland. TEE was measured with use of doubly labeled water (DLW), and resting energy expenditure was predicted to determine PAL. Time spent sedentary and in light-intensity activity and in moderate- and vigorous-intensity physical activity (MVPA) was assessed by accelerometry concurrent with DLW measurements. Correlation and regression were used to assess the relations between measures of sedentary behavior, intensities of activity, and PAL as the dependent variable. Time spent sedentary was negatively correlated with PAL (r = -0.33, P < 0.01), and time spent in light-intensity activity was positively correlated with PAL (r = 0.31, P < 0.01). In multiple regression analyses, both time spent sedentary and in light-intensity activities were significantly associated with PAL. Time spent in MVPA was not associated with PAL; engagement in MVPA was limited in this sample (median: 3% of waking hours; range: 0-14%). PAL was significantly higher in boys than in girls. In this sample and setting, PAL was not influenced by engagement in MVPA but was influenced by time spent sedentary and in light-intensity activities. This study suggests that in young children, MVPA could make only a minor contribution to free-living TEE and PAL.