Objective: Moderate-to-vigorous physical activity (MVPA) improves cardiovascular health.
Few studies have examined MVPA timing. We examined the associations of timing
of bout-related MVPA with cardiorespiratory fitness and cardiovascular risk in
adults with type 2 diabetes.
Methods: Baseline
7-day hip-worn accelerometry data from Look AHEAD participants (n=2,153, 57% women) were analyzed to identify
bout-related MVPA (≥3 metabolic
equivalent tasks (MET)/min
for ≥10mins). Cardiorespiratory fitness was assessed by maximal graded exercise
test. Participants were categorized into six groups based on the time of day
with the majority of bout-related MVPA (MET×min): ≥50% of bout-related MVPA
during the same time window (Morning, Midday, Afternoon, or Evening), <50%
bout-related MVPA in any time category (Mixed; the reference group), and ≤1 day
with bout-related MVPA per week (Inactive).
Results:
Cardiorespiratory fitness was highly associated with timing of bout-related MVPA (P=0.0005), independent of weekly bout-related MVPA volume
and intensity. Importantly, this association varied by sex (P=0.02). In men,
the midday group had the lowest fitness (β -0.46 [95%CI -0.87, -0.06]), while the mixed
group in women was the least fit. Framingham risk score (FRS) was associated
with timing of bout-related MVPA (P=0.02), which also differed by sex (P=0.0007).
The male morning group had highest 4-year FRS (2.18% [0.70%, 3.65%]), but no association
was observed in women.
Conclusions:
Timing of bout-related
MVPA is associated with
cardiorespiratory
fitness and cardiovascular risk in men with type 2 diabetes, independent of
bout-related MVPA volume and intensity. Prospective studies are needed to
determine the impacts of MVPA timing on cardiovascular health.
Funding
This study was supported by National Heart, Lung, and Blood Institute (K99HL148500, Qian, PI). The Look AHEAD trial was supported by the Department of Health and Human Services through the following cooperative agreements from the National Institutes of Health: DK57136, DK57149, DK56990, DK57177, DK57171, DK57151, DK57182, DK57131, DK57002, DK57078, DK57154, DK57178, DK57219, DK57008, DK57135, and DK56992. The following federal agencies have contributed support: National Institute of Diabetes and Digestive and Kidney Diseases; National Heart, Lung, and Blood Institute; National Institute of Nursing Research; National Center on Minority Health and Health Disparities; Office of Research on Women’s Health; and the Centers for Disease Control and Prevention. This research was supported in part by the Intramural Research Program of the National Institute of Diabetes and Digestive and Kidney Diseases. The Indian Health Service (I.H.S.) provided personnel, medical oversight, and use of facilities. The opinions expressed in this paper are those of the authors and do not necessarily reflect the views of the I.H.S. or other funding sources. Additional support was received from The Johns Hopkins Medical Institutions Bayview General Clinical Research Center (M01RR02719); the Johns Hopkins-University of Maryland Diabetes Research and Training Center (P60DK079637); the Massachusetts General Hospital Mallinckrodt General Clinical Research Center (M01RR01066); the University of Colorado Health Sciences Center General Clinical Research Center (M01RR00051) and Clinical Nutrition Research Unit (P30 DK48520); the University of Tennessee at Memphis General Clinical Research Center (M01RR0021140); the University of Pittsburgh General Clinical Research Center (M01RR000056 44) and NIH grant (DK 046204); and the University of Washington / VA Puget Sound Health Care System Medical Research Service, Department of Veterans Affairs; Frederic C. Bartter General Clinical Research Center (M01R
