An Intervention to Reduce Sitting Time at Work: Effects on Metabolic Health and Inactivity

The Effects of Short, Frequent Breaks in Sitting Versus Longer, Planned Breaks in Sitting on Sedentary Behavior and Metabolic Health Among Inactive Females Working Sedentary Jobs

The purpose of this study is to determine whether varying the frequency and length of activity breaks during the workday will differentially impact sedentary behavior and health outcomes. Participants will be randomly assigned to take short, frequent breaks (i.e., 1 minute every half hour) or longer, planned breaks (i.e., two 15-minute walks) from sitting during the workday. They will be instructed to follow the assigned protocols for an 8-week intervention and the effects of their participation on sedentary behavior and a variety of health outcomes will be assessed. The investigators anticipate participants in both intervention arms will demonstrate significant reductions in daily sitting time, bit do not have an a priori hypothesis regarding the relative effectiveness of each approach.

The purpose of this study is to determine whether varying the frequency and length of activity breaks during the workday will differentially impact sedentary behavior and health outcomes. Women aged 25-50 who work full-time in sedentary jobs and participate in less than 60 minutes of overall physical activity per week will be recruited. At the beginning of the study participants will visit the laboratory to complete baseline health assessments and meet with a research assistant to outline their plan for reducing sitting time at work. At this time they will be randomly assigned to one of two groups: 1) Group A will be asked to take two 15-minute walks during each workday, or 2) Group B will be asked to stand up and move around for 1-2 minutes every half hour throughout the workday. The total duration of this program will be eight weeks. During this time participants will be asked to keep a brief daily log of their activity breaks during the workday. At the end of the 8-week program participants will return to the laboratory to repeat the health assessments.

ASSESSMENTS:

All participants will complete the following tests and procedures:

• Metabolic blood panel. Blood will be drawn from a quick finger stick to assess total cholesterol, triglycerides, LDL, HDL, and fasting glucose.
• DEXA scan. Participants will lie down on a body scanner for about 10 minutes to assess body composition.
• Body measurements. A trained research assistant will measure height, weight, and waist circumference.
• Blood pressure. A trained research assistant will measure blood pressure using an automated blood pressure cuff.

In addition, participants will complete the following assessments outside of the laboratory:

• Questionnaires: Participants will be asked to complete a series of questionnaires. This should take 15-20 minutes.
• Accelerometer: Participants will be asked to wear a motion sensor for a total of 21 days (three 7-day periods). This small apparatus is worn around the waist during the day. Participants will complete a log indicating when they were wearing the accelerometer each day.
• Food diary: Participants will be asked to record their food intake for a total of 9 days (three 3-day periods).

Inclusion Criteria:

1. Work at least 35 hours per week
2. Spend at least 80% of working hours sitting (self-reported)
3. Engage in less than 60 minutes per week of leisure-time exercise (self-reported)
4. Not pregnant or planning to become pregnant in the next 3 months
5. Not currently trying to change weight
6. Speak English
7. Able to attend assessments
8. Willing to wear accelerometer
9. No anticipated significant conflicts during 8-week intervention

Exclusion Criteria:

1. Male
2. Working less than 35 hours per week
3. Spend >25% of working hours standing or active
4. Engage in more than 60 minutes per week of leisure-time exercise
5. Pregnant
6. Actively dieting or attempting to change weight