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Dana L. Wolff-Hughes, Eugene C. Fitzhugh, David R. Bassett and James R. Churilla

Background:

Accelerometer-derived total activity count is a measure of total physical activity (PA) volume. The purpose of this study was to develop age- and gender-specific percentiles for daily total activity counts (TAC), minutes of moderate-to-vigorous physical activity (MVPA), and minutes of light physical activity (LPA) in U.S. adults.

Methods:

Waist-worn accelerometer data from the 2003-2006 National Health and Nutrition Examination Survey were used for this analysis. The sample included adults >20 years with >10 hours accelerometer wear time on >4 days (N = 6093). MVPA and LPA were defined as the number of 1-minute epochs with counts >2020 and 100 to 2019, respectively. TAC represented the activity counts acquired daily. TAC, MVPA, and LPA were averaged across valid days to produce a daily mean.

Results:

Males in the 50th percentile accumulated 288 140 TAC/day, with 357 and 22 minutes/day spent in LPA and MVPA, respectively. The median for females was 235 741 TAC/day, with 349 and 12 minutes/day spent in LPA and MVPA, respectively.

Conclusions:

Population-referenced TAC percentiles reflect the total volume of PA, expressed relative to other adults. This is a different approach to accelerometer data reduction that complements the current method of looking at time spent in intensity subcategories.

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Dana L. Wolff-Hughes, Eugene C. Fitzhugh, David R. Bassett and James R. Churilla

Purpose:

To contrast associations of accelerometer-measured moderate-to-vigorous physical activity (MVPA) accumulated in bouts and total activity counts (TAC) with cardiometabolic biomarkers in U.S. adults.

Methods:

Using 2003–2006 National Health and Nutrition Examination Survey (NHANES) data, the sample was comprised of adults ≥ 20 years, not pregnant or lactating, with self-reported PA and at least 4 days of ≥ 10 hours accelerometer wear time (N = 5668). Bouted MVPA represented the minutes/day with ≥ 2020 counts/minute in bouts of 10 minutes or longer and TAC represented the total activity counts per day. Biomarkers included: cholesterol, triglyceride, glycohemoglobin, plasma glucose, C-peptide, insulin, C-reactive protein, homocysteine, blood pressure, body mass index (BMI), waist circumference, and skinfolds. Nested regression models were conducted which regressed each biomarker on bouted MVPA and TAC simultaneously, while adjusting for relevant covariates.

Results:

Results indicated TAC was more strongly associated with 11 biomarkers: HDL-C, triglyceride, plasma glucose, C-peptide, insulin, C-reactive protein, homocysteine, systolic blood pressure, waist circumference, triceps skinfold, and subscapular skinfold. Bouted MVPA, however, only displayed stronger associations with BMI.

Conclusions:

The total volume of physical activity, represented by TAC, appears to have stronger associations with cardiometabolic biomarkers than MVPA accumulated in bouts.

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Michael R. Richardson, Tammie M. Johnson, Peter T. Katzmarzyk, Earl S. Ford, William R. Boyer and James R. Churilla

Background:

Few studies have examined the gender differences between C-reactive protein (CRP) and muscle strengthening activity (MSA).

Methods:

The sample (n = 7533) included U.S. adult (≥20 years of age).participants in the 1999–2004 National Health and Nutrition Examination Survey (NHANES). Created categories of MSA participation included no MSA (referent group), some MSA (≥1 to <2 days/week), and meeting the 2008 Department of Health and Human Services (DHHS) recommendation (≥2 days/week). The dependent variable was elevated CRP (>3 to 10 mg/L).

Results:

Analysis revealed significantly lower odds of having elevated CRP for women reporting some MSA (OR 0.64; 95% CI 0.44–0.93, P = .0191). Significantly lower odds of men having elevated CRP was observed in those reporting MSA volumes meeting the DHHS recommendation (OR 0.72; 95% CI 0.59–0.88, P = .0019). Following adjustment for waist circumference (WC) these odds remained significant in men but not women.

Conclusions:

These results suggest that WC may mediate the associations between MSA and CRP and this relationship may be stronger in women.