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  • Author: Meredith C. Peddie x
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Meredith C. Peddie, Claire Cameron, Nancy Rehrer and Tracy Perry

Background:

Interrupting sedentary time induces improvements in glucose metabolism; however, it is unclear how much activity is required to reduce the negative effects of prolonged sitting.

Methods:

Sixty-six participants sat continuously for 9 hours except for required bathroom breaks. Participants were fed meal replacement beverages at 60, 240 and 420 min. Blood samples were obtained hourly for 9 hours, with additional samples collected 30 and 45 min after each feeding. Responses were calculated as incremental area under the curve (iAUC) for plasma glucose, insulin and triglyceride. Participants wore a triaxial accelerometer and a heart rate monitor. Energy expenditure was estimated using indirect calorimetry.

Results:

After controlling for age, sex and BMI, every 100 count increase in accelerometer derived total movement was associated with a 0.06 mmol·L-1·9 hours decrease in glucose iAUC (95% CI 0.004–0.1; P = .035), but not associated with changes in insulin or triglyceride iAUC. Every 1 bpm increase in mean heart rate was associated with a 0.76 mmol·L-1·9 hours increase in triglyceride iAUC (95% CI 0.13–1.38).

Conclusion:

Accelerometer measured movement during periods of prolonged sitting can result in minor improvements in postprandial glucose metabolism, but not lipid metabolism.

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Meredith C. Peddie, Matthew Reeves, Millie K. Keown, Tracy L. Perry and C. Murray Skeaff

Background: Regular activity breaks positively impact markers of cardiometabolic health when performed in a laboratory. However, identifying compliance to a free-living regular activity breaks intervention is challenging, particularly if intensity is prescribed. Methods: This study had two parts. In Part A, 20 participants performed activity breaks similar to those shown to impart health benefits while wearing an ActiGraph and activPAL accelerometer, and a heart rate monitor. In Part B, the threshold found to identify these activities was used to identify the activity breaks performed by 78 sedentary, university employees wearing an ActiGraph accelerometer for seven days. Results: A cut-point of 1,000 vector magnitude counts per minute accurately identified activity breaks performed in the laboratory. Applying this cut-point to data collected in free living, sedentary participants identified, on average, seven activity breaks were being performed during work-hours. Conclusions: Using a cut-point of 1,000 vector magnitude counts per minute will identify activity breaks of a similar intensity to those found to elicit acute cardiometabolic benefit. Sedentary university employees may benefit from interventions to increase the number of activity breaks performed across their entire day.