Health Reports
Accelerometer-measured moderate-to-vigorous physical activity of Canadian adults, 2007 to 2017

by Janine Clarke, Rachel Colley, Ian Janssen and Mark S. Tremblay

DOI: https://www.doi.org/10.25318/82-003-x201900800001-eng

Physical inactivity is associated with an increased risk of several chronic diseases and premature mortality.^{Note 1Note 2} It is estimated that physical inactivity is responsible for 3.7% of total direct and indirect health care costs in Canada ($6.8 billion/year).^{Note 3} The current Canadian Physical Activity Guidelines recommend that adults accumulate at least 150 minutes of moderate-to-vigorous physical activity (MVPA) per week in bouts of at least 10 minutes, in addition to engaging in muscle and bone strengthening activities at least twice a week.^{Note 4Note 5Note 6} Before accelerometers were adopted for use in the Canadian Health Measures Survey (CHMS) in 2007, physical activity prevalence and trend data in Canada were assessed using self-reported and pedometer-measured data only.

From 2007 to 2009, the first nationally representative accelerometer-measured physical activity data were collected as part of the CHMS. Results showed that 15% of adults were getting enough MVPA to meet physical activity guidelines.^{Note 7} This was significantly lower than previous national estimates based on self-reported data, which indicated that nearly two-thirds of Canadian adults were meeting physical activity guidelines in 2007.^{Note 8} That same study reported that physical activity in Canada had increased between 1994 and 2007.^{Note 8} An increase in physical activity in Canadian adults between 2003 and 2013 was also reported by the Canadian Fitness and Lifestyle Research Institute,^{Note 9} although a more recent report suggests that physical activity levels have stabilized in recent years.^{Note 10} Now that additional cycles of CHMS data (2009 to 2017) are available, it is possible to examine whether the trend over time using accelerometer-measured data provides clarity on the inconsistent trends observed using self-reported data.

Canadian guidelines recommend that Canadians accumulate MVPA in bouts of at least 10 minutes.^{Note 5Note 6} The stipulation for 10-minute bouts was added to the most recent guidelines because there was insufficient evidence to indicate substantial health benefits from physical activity accumulated in periods < 10 minutes.^{Note 2Note 4} More recent evidence suggests that MVPA does not need to be accumulated in 10-minute bouts and that sporadic physical activity (i.e., accumulated in bouts of less than 10 minutes) is also associated with health benefits.^{Note 11Note 12Note 13Note 14} This type of sporadic or incidental activity is difficult to capture through questionnaires and represents one of the key advantages of accelerometry.^{Note 4Note 15} The minute-by-minute resolution of the CHMS accelerometer data allows for the quantification of MVPA accumulated in bouts of any duration.

The purpose of this paper is to present an overview of the accelerometer-measured MVPA levels of Canadian adults by age and sex, and adherence to physical activity guidelines from 2007 through 2017. A secondary purpose is to examine how the 10-minute bout stipulation affects levels of MVPA and adherence to the current physical activity guidelines.

Methods

Data source

Data are from the CHMS, a nationally representative repeated cross-sectional survey at Statistics Canada that collects self-reported and directly measured health information from the Canadian population aged 3 to 79 living in private dwellings. Approximately 96% of the Canadian population is represented in each cycle. Residents of Aboriginal reserves or Crown lands, institutions and certain remote regions, as well as full-time members of the Canadian Forces, are excluded. Data were collected from March 2007 to February 2009 (Cycle 1), August 2009 to November 2011 (Cycle 2), January 2012 to December 2013 (Cycle 3), January 2014 to December 2015 (Cycle 4) and January 2016 to December 2017 (Cycle 5). Data collection in each cycle occurred in two parts. First, a questionnaire on sociodemographic characteristics and health behaviours was administered at the respondent’s home. This was followed by an appointment at a mobile examination centre, where a series of physical measurements (e.g., height, weight, blood pressure) were administered and the accelerometers were provided to participants. Ethics approval for the CHMS was obtained from Health Canada’s Research Ethics Board.^{Note 16Note 17Note 18Note 19Note 20Note 21} More information about the CHMS is available elsewhere.^{Note 17Note 18Note 19Note 20Note 21Note 22}

The study sample included respondents aged 18 to 79 from all survey cycles with valid accelerometer data (Cycle 1: n = 2,952; Cycle 2: n = 2,959; Cycle 3: n = 2,517; Cycle 4: n = 2,390; Cycle 5: n = 2,355).

Measurement of physical activity

All ambulatory respondents were provided with an Actical accelerometer (Philips Respironics, Oregon, United States) to wear on an elasticized belt over the right hip during their waking hours for seven consecutive days. The Actical accelerometer measures acceleration of movement in all directions. Movement was captured and recorded as a digitized value that was summed over one-minute intervals, resulting in 10,080 measures (activity counts per minute [cpm]) per person across seven days. Published guidelines were followed to identify and remove invalid data during accelerometer data reduction.^{Note 23} Total daily accelerometer wear time was determined by identifying non-wear time and subtracting it from 24 hours. Non-wear time was defined as periods of at least 60 consecutive minutes of zero counts, with an allowance for one or two minutes of counts between 0 and 100 cpm.^{Note 23} A valid day was defined as having at least 10 hours of wear time, and only participants with at least four valid days of data were included in this analysis.^{Note 23}

Total measured time on each valid day (bouts + sporadic) spent in moderate physical activity (MPA_ALL), vigorous physical activity (VPA_ALL) and moderate-to-vigorous physical activity (MVPA_ALL) was determined based on the following intensity cut points: moderate (1,535 to 3,961 cpm) and vigorous (≥3,962 cpm).^{Note 24Note 25} The daily average times spent in MPA, VPA and MVPA_ALL were calculated as the total number of minutes for all valid days, divided by the number of valid days. For MVPA, this was also calculated for minutes accumulated in bouts of at least 10 minutes (MVPA_BOUTS), where a bout was defined analytically as a period of at least 10 consecutive minutes above the moderate intensity cut point. To count as a 10-minute bout, 80% of the minutes within a 10-minute block (i.e., 8 out of 10 minutes) had to be above the moderate intensity cut point.^{Note 26} This is consistent with previous accelerometer analyses of the CHMS and other datasets.^{Note 7Note 11Note 12Note 13Note 26}

Adherence to the Canadian Physical Activity Guidelines was assessed based on respondents with a weekly sum of at least 150 minutes of MVPA accumulated in bouts of at least 10 minutes (MVPA_BOUTS).^{Note 4Note 5Note 6} If respondents had fewer than seven valid days of accelerometer data, then their average daily MVPA_BOUTS was multiplied by seven to obtain a weekly sum. The same approach was taken to assess the proportion of adults with a weekly sum of at least 150 minutes of MVPA_ALL.

Statistical analysis

Descriptive statistics were used to calculate means or proportions and 95% confidence intervals overall and by age group and sex. Pairwise contrasts were used to compare results by age group and sex. Significance was set at p < 0.05.

A trend analysis was performed on average daily minutes of MVPA_ALL, allowing for linear, square and cubic effects of time (survey cycle). Linear regression analysis was performed on average daily minutes of MVPA_ALL, controlling for several covariates, including age, sex, body mass index, quintiles of household income adjusted for household size, highest level of education in the household (postsecondary graduate: yes/no), season of data collection, and time (survey cycle).

Activity monitor subsample weights for each individual cycle were used for analyses to present individual cycle estimates.^{Note 17Note 18Note 19Note 20Note 21} The activity monitor subsample data from CHMS cycles 1 to 4 were also stacked and weighted using combined activity monitor subsample weights generated by Statistics Canada to present combined cycle estimates.^{Note 27} Detailed information on creating the activity monitor subsample and associated survey weights is available elsewhere. Briefly, the subsample included only respondents with a sufficient amount of data over the seven days. In adults, this included those who wore the accelerometer for a minimum of 10 hours on at least four days.^{Note 16Note 17Note 18Note 19Note 20Note 21Note 23} Approximately 40% of CHMS respondents in each cycle had sufficient accelerometer data to be included in the analysis.^{Note 21}

All analyses were completed using SAS 9.3 (SAS Institute, North Carolina, United States) and SUDAAN 11.0, using the appropriate number of degrees of freedom for combined^{Note 27} or individual cycle analysis.^{Note 16Note 17Note 18Note 19Note 20Note 21} Survey and bootstrap weights were used in the variance estimations and in the confidence interval calculations to account for survey design and to adjust for non-response.

Results

From 2016 to 2017, Canadian adults accumulated an average of 26 minutes of MVPA_ALL per day (Table 1, Figure 1). Less than half of the daily MVPA_ALL accumulated was performed in bouts of at least 10 minutes (MVPA_BOUTS: 12 minutes per day, on average) (Figure 1). Average daily VPA was less than five minutes, which indicates that the majority of MVPA accumulated was at a moderate intensity (Figure 2). About 3% of Canadian adults accumulated no MVPA at all, while nearly 36% did not accumulate any MVPA in bouts of at least 10 minutes (Figure 3).

MVPA_ALL was higher among men compared with women, and among younger adults compared with older adults. Average daily MVPA_BOUTS was not significantly different by age group or sex (p > 0.05). VPA_ALL was slightly higher among younger adults (four minutes) compared with older adults (two minutes), and among men (four minutes) compared with women (two minutes).

In 2016 and 2017, 16% of Canadian adults met the Canadian Physical Activity Guidelines of 150 minutes of MVPA_BOUTS per week (Figure 3). Nearly triple the percentage of Canadian adults met the guideline when MVPA_ALL was used instead of MVPA_BOUTS (45% versus 16%).

Trends over time

No significant linear trend in average daily minutes of MVPA_ALL was evident across CHMS cycles (Table 1). The same trend was observed for MVPA_BOUTS (Table 2). Finally, the percentage of adults who meet the guidelines has not changed significantly since the first cycle (2007 to 2009) of the CHMS (Table 3).

In a linear regression model that controlled for season, age, sex, body mass index, household income and education, there was no significant effect of time (survey cycle) or season (data not shown).

Discussion

This study provides an overview of MVPA among Canadian adults across five CHMS cycles spanning the years 2007 to 2017. There were no significant temporal trends observed over the five cycles. The most recent results (2016 and 2017) indicate that Canadian adults accumulated a daily average of 26 minutes of MVPA_ALL, less than half of which was accumulated in bouts of at least 10 minutes. Less than one in five Canadian adults met the current Canadian Physical Activity Guidelines, which recommend a minimum of 150 minutes of MVPA per week, accumulated in bouts of 10 minutes or more.^{Note 4Note 5Note 6}

This is the first study to assess physical activity trends in a nationally representative sample of Canadian adults by using accelerometer-measured physical activity data. The results contradict previous reports based on self-reported physical activity in Canada, which suggested that physical activity levels in Canadian adults had increased in recent decades.^{Note 8Note 9Note 28Note 29Note 30} However, caution is recommended in using self-reported and accelerometer-measured physical activity data interchangeably since these data capture different aspects of the same behaviour: perceived time spent active versus actual movement above a set intensity threshold.^{Note 31}

Adherence to the Canadian Physical Activity Guidelines is based on MVPA accumulated in bouts of at least 10 minutes. In the current analysis, about one in five Canadian adults met this recommendation, in part because MVPA accumulated in bouts (12 minutes on average per day from 2016 to 2017) represented less than half of total accumulated MVPA (26 minutes on average per day from 2016 to 2017). However, certain research has shown that, for an equivalent volume, there is no significant difference in health benefits between MVPA accumulated in any time increment compared with MVPA accumulated in bouts.^{Note 11Note 12Note 13Note 32} Further, based on this and other recent evidence, the 2018 Physical Activity Guidelines Advisory Committee Scientific Report in the United States concluded that MVPA of any duration contributes to the health benefits associated with the accumulated weekly volume of MVPA.^{Note 14} As a result, the recently updated Physical Activity Guidelines for Americans no longer stipulate that MVPA should be accumulated in bouts.^{Note 14} Results from the CHMS suggest that, if the guidelines did not stipulate the 10-minute bout requirement, the percentage of Canadian adults meeting physical activity guidelines would almost triple to 45%. Results also showed that over half of Canadian adults not meeting the guidelines are getting at least some MVPA_ALL per week (i.e., between 1 and 149 minutes per week), including one-quarter of adults who are getting between 75 and 149 minutes. This latter group is important for public health messaging because these people are close to meeting the guideline, and a small shift in the distribution could have a meaningful impact on the percentage of the population surpassing the target of 150 minutes per week. Furthermore, it is well established that any physical activity is better than none and, in fact, the greatest health benefits occur when physical activity is increased at the lowest end of the physical activity scale (i.e., going from none to some, or from some to a bit more).^{Note 1Note 2Note 14}

The results demonstrated that Canadian adults accumulate the vast majority of their MVPA_ALL as MPA_ALL. In fact, of the average 26 minutes per day of MVPA_ALL, only four minutes were of a vigorous intensity. Although the current Canadian guidelines do not specifically prescribe VPA, other international guidelines stipulate that adults can accumulate either 150 minutes of MPA or 75 minutes of VPA, or some equivalent combination of the two (e.g., 100 minutes of MPA and 25 minutes of VPA).^{Note 14Note 33Note 34Note 35Note 36Note 37} Although this differentiation was made as a way for people to accumulate a healthy dose of physical activity in less time, at least one study found that objectively measured VPA had a greater influence on cardiometabolic risk factors than an equivalent energy expenditure dose of MPA.^{Note 38} Furthermore, it is well established that VPA leads to greater improvements in cardiorespiratory fitness,^{Note 39} which in turn is associated with improvements in many health outcomes and a decreased risk for premature death.^{Note 40Note 41}

Strengths and limitations

The examination of MVPA_BOUTS, as stipulated in physical activity guidelines, and MVPA_ALL is a strength of this analysis. This examination provides information about physical activity levels for the entire population, not just the percentage who meet the guidelines. This information may be useful to governments and other organizations in improving physical activity in Canada—physical inactivity and sedentary living have been identified as critical issues in Canada and internationally. For example, A Common Vision for Increasing Physical Activity and Reducing Sedentary Living in Canada: Let’s Get Moving is a policy in Canada that strives for “a Canada where all Canadians move more and sit less, more often.”^{Note 42} Internationally, the World Health Organization’s global action plan on physical activity calls for a 15% relative reduction in the global prevalence of physical inactivity in adults and adolescents by 2030.^{Note 41}

With CHMS accelerometer data (the only nationally representative Canadian dataset with direct measures of physical activity), it is possible to track changes in physical activity over time. Accelerometers yield objective information about movement intensity and, thus, overcome some of the limitations associated with self-reporting. However, accelerometers may underestimate MVPA since they do not accurately measure the intensity of movement from activities such as swimming or cycling, and they do not take into account the additional energy expenditure from any load-bearing movement. Furthermore, using one set of cut points to determine the intensity of physical activity in adults may overestimate or underestimate physical activity levels in certain subpopulations. For example, at a given accelerometer count-per-minute value, energy expenditure may be higher for those who are obese compared with those at a normal weight.^{Note 43}

Finally, the overall response rate to the accelerometer measurement across the five CHMS cycles was about 40%. Despite adjustments to the sampling weights to compensate, estimates may be biased by systematic differences between respondents and non-respondents.

Conclusion

Results from the 2016 to 2017 CHMS showed that less than one in five Canadian adults met the Canadian Physical Activity Guidelines. Results also showed that Canadian adults accumulated the majority of their MVPA in periods < 10 minutes in duration and at a moderate intensity. This information may be important to governments and other organizations to increase physical activity levels in Canadian adults, which, according to accelerometer data, have not changed between 2007 and 2017.