imputation procedures that rely on sample group or population data ( Kang et al., 2009 ; Kang et al., 2005 ; Zhuang et al., 2013 ). Alhassan et al.’s ( 2008 ) Within-Minute Average The current study included Alhassan et al.’s ( 2008 ) accelerometer data cleaning protocol. This method is not an imputation
Hotaka Maeda, Chris C. Cho, Young Cho and Scott J. Strath
Kelly R. Evenson, Amy H. Herring and Fang Wen
Few studies measure physical activity objectively or at multiple time points during postpartum. We describe physical activity at 3- and 12-months postpartum among a cohort of women using both self-reported and objective measures.
In total, 181 women completed the 3-month postpartum measures, and 204 women completed the 12-month postpartum measures. Participants wore an ActiGraph accelerometer for 1 week and completed in-home interviews that included questions on physical activity. A cohort of 80 women participated at both time points. Poisson regression models were used to determine whether physical activity differed over time for the cohort.
For the cohort, average counts/minute were 364 at 3-months post-partum and 394 at 12-months postpartum. At both time periods for the cohort, vigorous activity averaged 1 to 3 minutes/day, and moderate activity averaged 16 minutes/day. Sedentary time averaged 9.3 hours at 3-months postpartum and 8.8 hours at 12-months postpartum, out of a 19-hour day. Average counts/minute increased and sedentary behavior declined from 3- to 12-months postpartum.
Interventions are needed to help women integrate more moderate to vigorous physical activity and to capitalize on the improvements in sedentary behavior that occur during postpartum.
Emily Borgundvaag, Michael McIsaac, Michael M. Borghese and Ian Janssen
participants reduces study power and would compromise the validity of the findings if the participants who are excluded because of excessive nonwear time are systematically different from the participants who are included. Imputation has been used, albeit on a limited basis, as an analytical approach to
Gil Rodas, Lourdes Osaba, David Arteta, Ricard Pruna, Dolors Fernández and Alejandro Lucia
first examined the association between SNPs and tendinopathy risk in a hypothesis-free case-control GWAS. Thereafter, we augmented the SNP set by performing synthetic variant imputation and then used ML-based multivariate modeling. Methods Design We used 2 research lines to evaluate the effect of
Nathan Parker, Darran Atrooshi, Lucie Lévesque, Edtna Jauregui, Simón Barquera, Juan Lopez y Taylor and Rebecca E. Lee
Obesity is a critical problem among Mexican youth, but few studies have investigated associations among physical activity (PA) modes and anthropometrics in this population. This study examined associations among active commuting to school (ACS), sports or other organized PA, outdoor play, and body mass index (BMI) percentile and waist circumference (WC) among Mexican youth.
Parents of school children (N = 1996, ages 6 to 14 years, 53.1% female) in 3 Mexican cities reported PA participation using the (modified) fourth grade School Physical Activity and Nutrition Survey. Trained assessors measured BMI percentile and WC in person.
Parents reported that 52.3% of children engaged in ACS, 57.3% participated in sports or organized PA, and a median of 2 days in the previous week with at least 30 minutes of outdoor play. In complete case analyses (n = 857), ACS was negatively associated with BMI percentile, and outdoor play was negatively associated with WC after adjusting for school, age, sex, and income. In analyses incorporating data from multiple imputation (N = 1996), outdoor play was negatively associated with WC (all Ps < . 05).
ACS and outdoor play are favorably associated with anthropometrics and may help prevent childhood obesity in Mexico. ACS and outdoor play should be priorities for increasing youth PA in Mexico.
Brian G. Pietrosimone, Adam S. Lepley, Hayley M. Ericksen, Phillip A. Gribble and Jason Levine
Disability is common in a proportion of patients after anterior cruciate ligament reconstruction (ACL-R). Neuromuscular quadriceps deficits are a hallmark impairment after ACL-R, yet the link between muscle function and disability is not understood.
To evaluate the ability of quadriceps strength and cortical excitability to predict self-reported disability in patients with ACL-R.
Fifteen participants with a history of ACL-R (11 female, 4 male; 172 ± 9.8 cm, 70.4 ± 17.5 kg, 54.4 ± 40.9 mo postsurgery) were included in this study. Corticospinal excitability was assessed using active motor thresholds (AMT), while strength was assessed with maximal voluntary isometric contractions (MVIC). Both voluntary strength and corticospinal excitability were used to predict disability measured with the International Knee Documentation Committee Index (IKDC).
The overall multiple-regression model significantly predicted 66% of the variance in self-reported disability as measured by the IKDC index (R 2 = .66, P = .01). Initial imputation of MVIC into the model accounted for 61% (R 2 = .61, P = .01) of the variance in IKDC. The subsequent addition of AMT into the model accounted for an insignificant increase of 5% (Δ R 2 = .05, P = .19) in the prediction capability of the model.
Quadriceps voluntary strength and cortical excitability predicted two-thirds of the variance in disability of patients with ACL-R, with strength accounting for virtually all of the predictive capability of the model.
PA levels discarded 26.0% to 28.6% of the data. We suggest practitioners to use the within-minute average method for adults over 18 years of age, and the day-level imputation method for children and teenagers. To note, the day-level imputation method may be unstable for sample sizes of less than 50
Tim Op De Beéck, Arne Jaspers, Michel S. Brink, Wouter G.P. Frencken, Filip Staes, Jesse J. Davis and Werner F. Helsen
steps before application of gradient-boosted regression tree. EL indicates external load; IL, internal load. a Used to compute cumulative EL and IL. b Reasonable data imputation not possible. First, perceived wellness scores were not reported on most rest and match days. Consequently, FPW value on
Anders Raustorp and Andreas Fröberg
with self-reported values of <1000 or >30,000 steps were excluded from further analysis as previously recommended. 25 During the 5 times of measurement, several participants had incomplete data. If data from time 4 and time 5 were missing, imputation was conducted 26 in 2 ways. First, the last
Frank E. DiLiberto, Deborah A. Nawoczenski and Jeff Houck
maintain the statistical power and a sample size of 12 participants, missing data for the 2 cases pertaining to the high-step activity were addressed via a mean imputation method with random variability that was based on the present distribution. 31 , 32 Mean imputation with random variability reduces