Background: Moderate-to-vigorous physical activity (MVPA) is an important treatment in type 2 diabetes (T2D). Few studies examine the timing of MVPA, as there are no established methods to characterize the MVPA bout timing throughout the day. We determined the timing of MVPA bouts in adults with T2D, and examined whether cardiorespiratory fitness and odds of cardiovascular disease (CVD) history relate to timing of MVPA bouts in men and women.

Methods: Baseline data from Look AHEAD participants (n=2153, 57% women) were analyzed. Cardiorespiratory fitness assessed by VO2max test was expressed as METs. MVPA bouts (≥3METs in ≥10mins bouts) were determined using the hip-worn RT3 accelerometer for 7 days. Participants were categorized into six groups based on the time of day with the major amount of MVPA bouts (MET-min): ≥50% of MVPA bouts during the same time window (Early morning, Late morning, Afternoon, or Evening, N=214-280/group), <50% of MVPA bouts in any time category (Mixed; reference group, N=436), and ≤1 day with MVPA bouts per week (Inactive, N=624).

Results: Cardiorespiratory fitness differed by timing of MVPA bout category (P<0.0001). In a multivariate adjusted model, the association of timing of MVPA bouts with fitness varied by sex (P=0.002). In women, the evening group had higher fitness (β 0.35 [0.04, 0.66] METs). After further adjustment for individual total bout-MVPA (MET-min) per week, in men, the early morning group was associated with higher fitness (β 0.46 [0.06, 0.85] METs). Interestingly, in men, but not in women, the early morning group also had higher odds of CVD history (OR 2.4 [1.38, 4.21]).

Conclusion: Higher cardiorespiratory fitness associated with evening MVPA bouts in women, and with early morning MVPA bouts in men independent of total amount of bout-MVPA. Prospective studies are needed to investigate the relationship between timing of MVPA and cardiovascular outcomes to optimize MVPA benefits in adults with T2D.


J. Qian: None. M.P. Walkup: None. S. Chen: None. P.H. Brubaker: None. D. Bond: None. P.A. Richey: None. J.M. Jakicic: Advisory Panel; Self; Weight Watchers International, Inc. K. Hu: None. F.A. Scheer: None. R. Middelbeek: None.

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