Managing Free-Living Hyperglycemia with Exercise or Interrupted Sitting in Type 2 Diabetes.

Breaking up sitting with light physical activity (PA) is effective in reducing hyperglycemia in the laboratory. Whether the same effects are observed in the free-living environment remains unknown.  Aim: We evaluated how daily and postprandial glycemia are impacted by 20, 40 or 60 minutes of activity performed as either breaks from sitting after each meal (BR) or as one continuous walk after breakfast (WALK). Methods: Thirty individuals with type 2 diabetes completed 3 experimental conditions (BR, WALK and control) in a randomized crossover design. Conditions were performed in a free-living environment with strict dietary control over 7 days. Participants increased PA in BR and WALK by 20, 40 or 60 minutes (n=10 in each group) and maintained habitual levels of PA during CON. A continuous glucose monitor (iPro2) and activPAL activity monitor were worn to quantify glycemic control and PA. Using linear mixed models with repeated measures we (1) compared postprandial glucose (PPG) across conditions and (2) assessed the relationship between activity volume and glucose responses. Results:  While WALK tended to shorten the duration of daily duration of hyperglycemia compared to CON (p=0.05), BR was not different from CON.BR and WALK significantly attenuated the breakfast PPG vs. CON (p≤0.05), but lunch and dinner PPG were unaffected by BR and WALK.  Conclusions: Continuous walking was more effective than breaks from sitting to lower daily hyperglycemia for the group, but, both conditions lowered breakfast PPG. In contrast to tightly controlled laboratory studies, breaks from sitting did not lower hyperglycemia in the free-living environment.