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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Kinesiology

Year Degree Awarded

2017

Month Degree Awarded

February

First Advisor

Patty S. Freedson

Second Advisor

Barry Braun

Third Advisor

Stuart Chipkin

Fourth Advisor

John Staudenmayer

Subject Categories

Exercise Science

Abstract

Physical activity is a cornerstone in the management of hyperglycemia and risk of cardiovascular disease in type 2 diabetes (T2D). However, the dose response relationship between physical activity and glucose regulation is not well defined. The overall goal of this dissertation was to assess the magnitude and timing of changes of daily glucose concentrations in response to continuous and intermittent light physical activity in T2D. Through utilizing continuous glucose monitors (CGM) and physical activity monitoring concurrently, we were able to assess the glycemic impact of physical activity and sedentary behavior in the free-living environment.

Study 1 aimed to examine the effect of regularly interrupting 7-h of prolonged sitting (SIT) with brief bouts of light walking (LW) or simple resistance activities (SRA) on 22-h glucose homeostasis in adults with T2D. Twenty-four individuals with T2D completed 3 conditions (SIT, LW and SRA) in the laboratory. A CGM was worn during the laboratory conditions and in the free-living environment through next morning. Compared to SIT, both LW and SRA reduced mean 22-h glucose concentrations (SIT: 11.5±0.3, LW: 8.7±0.3 and SRA: 8.8±0.3 mmol.L-1), daily duration of hyperglycemia (SIT: 14.7±0.9, LW: 6.3±0.8 and SRA: 6.3±0.9 hours), and mean glucose concentrations through to the next morning.

Study 2 compared the effect of increasing physical activity by breaking up sitting time after meals (BR) or by a continuous bout of morning walking (EX) on daily and postprandial glucose (PPG) concentrations (measured by CGM). Thirty individuals with T2D completed EX, BR and a control condition (normal behavior [CON]) in their free-living environment over 1 week. Participants increased their total physical activity in EX and BR by 20, 40 or 60 minutes. Overall, EX was the only condition to significantly lower duration of postprandial glycemia (↓11.4 ± 4.0%) and the 40-minute dose of activity lowered mean PPG. In a subset of participants with high postprandial hyperglycemia at CON (n=9): (1) both EX and BR significantly shortened duration of hyperglycemia and (2) the 40 and 60-minute doses of activity significantly lowered mean PPG.

Study 3 evaluated the sex differences in the glucose response to the EX and BR conditions described in Study 2. We found that men had a significant glucose lowering effect of EX and BR compared to control, whereas women’s level of glycemia was unchanged with the activity conditions. This sex difference was driven by higher levels of hyperglycemia in men during the CON condition.

This dissertation utilized CGM and physical activity monitors to identify effective interventions to manage hyperglycemia in T2D. The combination of studies performed in the laboratory and free-living environment in this dissertation have potential to better inform physical activity guidelines for the management of T2D.

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