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Evidence that women meeting physical activity guidelines do not sit less: An observational inclinometry study

Lynette L Craft14*, Theodore W Zderic2, Susan M Gapstur3, Erik H VanIterson1, Danielle M Thomas1, Juned Siddique1 and Marc T Hamilton2

Author Affiliations

1 Feinberg School of Medicine, Northwestern University, 680 N Lake Shore Drive, Suite 1400, Chicago, IL, 60611, USA

2 Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA

3 American Cancer Society, 250 Williams Street, Atlanta, GA, 30303, USA

4 Department of Preventive Medicine, Northwestern University, 680 N. Lake Shore Drive, Suite 1400, Chicago, IL, 60611, USA

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International Journal of Behavioral Nutrition and Physical Activity 2012, 9:122  doi:10.1186/1479-5868-9-122

Published: 4 October 2012

Abstract

Background

The inactivity physiology paradigm proposes that sedentary behaviors, including sitting too much, are independent of the type of physical activity delineated for health in the Physical Activity Guidelines for Americans. Thus, we hypothesized that, when accounting for behaviors across the entire day, variability in the amount of time spent sitting would be independent of the inter-and intra-individual time engaged in sustained moderate-to-vigorous physical activity (MVPA).

Methods

Ninety-one healthy women, aged 40–75 years, completed a demographic questionnaire and assessment of height and weight. Participants wore the activPAL activity monitor for one week and time (minutes/day) spent sitting, standing, stepping, and in sustained bouts (bouts ≥10 minutes) of MVPA were quantified. The women were then stratified into groups based on weekly sustained MVPA. Additionally, each day of data collection for each participant was classified as either a “sufficient” MVPA day (≥ 30 min of MVPA) or an “insufficient” MVPA day for within-participant analyses.

Results

Time spent sitting, standing, and in incidental non-exercise stepping averaged 64, 28, and 11 hrs/week, respectively, and did not differ between groups with individuals meeting/exceeding the current exercise recommendation of 150 min/week of sustained MVPA in ≥10 minutes bouts (M = 294 min/week, SD = 22) compared to those with none or minimal levels (M= 20min/week, SD = 4). Time spent sitting (M = 9.1 hr/day, SD = 0.19 vs. M = 8.8 hr/day, SD = 0.22), standing (M = 3.9 hr/day, SD = 0.16 vs. M = 3.9 hr/day, SD = 0.15), and in intermittent stepping (M = 1.6 hr/day, SD = 0.07 vs. M = 1.6 hr/day, SD = 0.06) did not differ between days with (~55 min/day) and without recommended MVPA.

Conclusions

This study provides the first objective evidence that participation in sustained MVPA is unrelated to daily sitting duration in relatively healthy, middle and older-aged women. More research is needed to extend these findings to other populations and to inform distinct behavioral recommendations focused on sedentary time.

Keywords:
Inactivity physiology; Walking; Stepping; Standing; Non-exercise physical activity; Sedentary behavior