The Relationship Between Different Patterns of Weekly Physical Activity Accumulation and the Metabolic Syndrome in Canadian Adults
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Total weekly moderate-to-vigorous (MVPA) accumulated in different patterns has not been well studied: it is not yet known whether sporadic MVPA (periods of <10 consecutive minutes) or whether the weekly frequency of MVPA is associated with health benefits in adults. For this reason, the physical activity guidelines recommend that adults aged 18 to 64 years accumulate at least 150 minutes of MVPA per week in bouts of at least 10 minutes. The overall objective of this thesis was therefore to study the relationships between different patterns of MVPA and the metabolic syndrome (MetS) – a clustering of risk factors that increases the risk of developing cardiovascular disease and type 2 diabetes in adults. Both manuscripts in this thesis used data from the Canadian Health Measures Survey (CHMS), a nationally-representative sample of Canadians. The MetS was determined from direct physical measurements and blood samples, while physical activity levels were assessed by accelerometers (also known as activity monitors). Complex statistical models were used to determine the relationship between patterns of MVPA and the MetS. The first study assessed whether bouted MVPA was associated with lower odds for MetS than an equal volume of sporadic MVPA. Results showed that both bouted and sporadic MVPA were equally related to the MetS; even small bursts of sporadic MVPA <3 minutes in length were meaningful when predicting the MetS. The second study evaluated whether more frequent weekly MVPA was associated with lower odds for the MetS in physically active adults. Among those who were considered physically active, there was no difference in the odds of the MetS between those who were infrequently or frequently active. Together, the results of this thesis suggest that the pattern in which weekly MVPA is accumulated is unimportant, provided that sufficient energy is expended.