Prolonged sedentary time and physical fitness among Canadian men and women aged 60 to 69
by Shilpa Dogra, Janine M. Clarke and Jennifer L. Copeland

Abstract
Background: Evidence for associations between prolonged sedentary time and breaks in sedentary time and tness is limited in older adults. This study examines associations between objectively measured and self-reported total sedentary time and breaks in sedentary time with cardiorespiratory and musculoskeletal tness among Canadian men and women aged 60 to 69.
Data and methods: Data from cycles 1 and 2 of the Canadian Health Measures Survey were used for analysis. This is a nationally representative survey with an overall response rate of 53.5%. Men (n = 564) and women (n = 593) aged 60 to 69 were selected for analysis. Sedentary time, breaks in sedentary time, and moderate-to-vigorous physical activity were objectively measured with accelerometers. Leisure sedentary time was self-reported. Cardiorespiratory tness was assessed with the modi ed Canadian Aerobic Fitness Test. Musculoskeletal tness was based on grip strength and exibility. Linear regression models were adjusted for age, sex, education, body mass index, smoking status and moderate-to-vigorous physical activity.
Results: The number of breaks in measured sedentary time (b:0.47, p = 0.02) and the percentage of measured sedentary time spent in bouts lasting at least 20 minutes (b:-0.53, p = 0.01) were associated with cardiorespiratory tness. For men, grip strength was negatively associated with measured total sedentary time (b:-0.03, p = 0.03), and sit-and-reach was positively associated with breaks in measured sedentary time (b:0.15, p = 0.02). Self-reported sedentary time was not associated with any of the tness outcomes.
Interpretation: Among Canadians aged 60 to 69, tness may be in uenced not only by total sedentary time, but also by patterns of sedentary time.

Key words: Aging, exercise, exibility, functional autonomy, hand strength, physical activity, sitting

Cardiorespiratory tness is a predictor of morbidity and all-

1,2 cause mortality among middle-aged and older adults.

Musculoskeletal tness, particularly grip strength, is also a predictor of cardiovascular mortality and all-cause mortality— an even stronger predictor than systolic blood pressure3—and is critical to functional autonomy and quality of life.4

Fitness is in uenced by a combination of age, genetics and physical activity. Aging is associated with a decline in both cardiorespiratory and musculoskeletal tness, but some of these changes can be attributed to decreased physical activity.5 In fact, multicomponent exercise programs that include strengthening, balance and/or exibility have been shown to signi cantly affect the physical and cognitive function of older adults.6 However, objectively measured data reveal that only 4.5% of Canadians aged 60 to 79 accumulate 30 minutes per day of physical activity in the recommended 10-minute bouts.7 More than 90% of men and women older than age 60 are seden- tary for at least 8 hours a day.8

Even when physical activity levels are taken into account, sedentary time may in uence health.9 Among older adults, the amount of time spent sitting is associated with impaired glucose tolerance, dyslipidemia, high-risk waist circumference, cor- onary heart disease and poor perceived health.8,10 Less is known about associations with measures of tness, especially cardio- respiratory tness.

In addition to total sedentary time, patterns of sedentary time may in uence health outcomes. Prolonged sitting with few interruptions is associated with greater metabolic health risks

compared with more fragmented sedentary periods.11 Frequent interruptions may also positively in uence lower extremity function and body composition in older adults.12,13 However, little evidence is available on associations between patterns of sedentary time and cardiorespiratory and musculoskeletal tness among older men and women.

Examining relationships between sedentary time and cardio- respiratory and musculoskeletal tness, while accounting for physical activity levels, is critical for understanding the conse- quences of prolonged sitting for the health and autonomy of the older population. These associations are particularly important for people in their sixties, as targeted interventions may be able to slow declines in tness. Based on data for 2007 through 2011 from the Canadian Health Measures Survey, this study ana- lyzes associations between total sedentary time (self-reported and objectively measured) and breaks in sedentary time (object- ively measured) and cardiorespiratory and musculoskeletal tness among men and women aged 60 to 69.

Data and methods

Data from cycles 1 and 2 of the Canadian Health Measures Survey (CHMS) were used for analysis. The CHMS covers the Canadian population aged 3 to 79 living in private dwellings. Approximately 96% of the population is represented; residents of reserves, institutions and certain remote regions, and full- time members of the Canadian Forces are excluded.

Authors: Shilpa Dogra (Shilpa.Dogra@uoit.ca) is with the Faculty of Health Sciences, Kinesiology at the University of Ontario Institute of Technology in Oshawa, Ontario. Janine M. Clarke is with the Health Statistics Division at Statistics Canada, Ottawa, Ontario. Jennifer L. Copeland is with the Department of Kinesiology and Physical Education at the University of Lethbridge in Lethbridge, Alberta

4

Health Reports, Vol. 28, no. 2, pp. 3-9, February 2017 • Statistics Canada, Catalogue no. 82-003-X

Prolonged sedentary time and physical fitness among Canadian men and women aged 60 to 69 • Research Article

Data were collected from March 2007 through February 2009 (cycle 1) and from August 2009 through November 2011 (cycle 2). Data collection occurred in two phases: a questionnaire on socio-demographic characteristics and health behaviours administered at the respondent’s home, and a series of physical measurements, including tness tests, during a subsequent visit to a mobile examination centre.

Of the households selected across both survey cycles, 72.7% provided the sex and date of birth of all house- hold members. Within each responding household, one or two members were chosen to participate in the survey. Of these, 89.3% completed the household questionnaire, of whom 83.3% visited the mobile examination centre. The nal response rate for the combined cycles, after adjusting for the sampling strategy, was 53.5% (53.2% for males and 53.8% for females).14

Ethics approval for the CHMS was obtained from the Research Ethics Board for Health Canada and the Public Health Agency of Canada, and informed, written consent was obtained from adult participants.15

After their mobile examination centre visit, ambulatory respondents received an Actical accelerometer to wear on an elasticized belt over their right hip during waking hours for seven days.16,17 The Actical measures acceleration of movement in all directions. Movement is captured and recorded as a digitized value summed over one-minute inter- vals, resulting in a count per minute (cpm). Accelerometer data reduction fol- lowed published guidelines to identify and remove invalid data.18 Total daily accelerometer wear time was deter- mined by identifying non-wear time and subtracting it from 24 hours. Non-wear time was de ned as periods of at least 60 consecutive minutes of zero counts, with allowance for 1 or 2 minutes of counts between 0 and 100 cpm.18 A valid day was de ned as at least 10 hours of wear time; only participants with at least four valid days were included in this analysis.

Total daily measured time (minutes) spent in sedentary and moderate-to-vig- orous physical activity (MVPA) was determined based on values of 100 cpm or less and more than 1,535 cpm, respectively, on each valid day.19,20 Daily average sedentary time and time spent in MVPA were calcu- lated as the total number of minutes for all valid days, divided by the number of valid days. Daily average sedentary time spent in bouts of at least 20 minutes and the average number of bouts were deter- mined. A bout was a continuous period of at least 20 minutes with 100 cpm or less (allowing for interruptions up to 2 minutes with cpm greater than 100).21 The daily average number of breaks in sedentary time was determined. A break was any interruption (activity counts more than 100 cpm) of sedentary time lasting at least 1 minute. The percentage of total sedentary time spent in bouts of at least 20 minutes was calculated as average sedentary time in bouts divided by average sedentary time.13

Self-reported sedentary time was based on the combined number of hours per week respondents said they typ- ically spent watching TV, playing video games, using computers and reading. In cycle 1, respondents selected from a list of pre-determined durations (none, lessthan1hour,1to2hours,3to5 hours, 6 to 10 hours, 11 to 14 hours, 15 to 20 hours, or more than 20 hours). The derived variable for the total number of self-reported sedentary hours per week was the sum of the mid-point of the answer category for each question, which was grouped into the following categories (in hours): less than 5, 5 to less than 10, 10 to less than 15, 15 to less than 20, 20 to less than 25, 25 to less than 30, 30 to less than 35, 35 to less than 40, 40 to less than 45, or more than 45. In cycle 2, respondents provided an exact dur- ation (to the nearest half hour) for each question. The derived variable for the total number of self-reported sedentary hours per week was the sum of all four responses. To allow for comparability between cycles, the derived variable in cycle 2 was grouped into the cycle 1 cat-

egories. The mid-point of each category was used to calculate average self-re- ported sedentary minutes per day.

Detailed descriptions of the eligibility criteria and measurement procedures for each CHMS tness test are available elsewhere.16,17,22 Brie y, at the begin- ning of the mobile examination centre visit, respondents answered a series of screening questions (including com- pleting the Physical Activity Readiness Questionnaire (PAR-Q))22 and had their resting blood pressure and heart rate measured to assess their risk of engaging in the tests.

The modi ed Canadian Aerobic Fitness Test (mCAFT) is a multi-stage sub-maximal test used to assess aerobic tness. Stepping stages were completed until the respondent’s heart rate reached 85% of maximum at the end of a stage (or until the respondent could no longer continue). Heart rate, the oxygen cost of the last stepping stage, and weight were used to calculate cardiorespiratory tness.22

Sit-and-reach was measured with a exometer (Fit Systems Inc., Calgary, Canada). Each respondent completed two trials; the best score (centimetres) was used.22

Grip strength was measured with a Smedley III dynamometer (Takei Scien- ti c Instruments, Japan). Respondents completed two trials with each hand; the best scores from each hand were summed to calculate total grip strength (kilograms).

Covariates in the analysis were age, sex, education (postsecondary gradu- ation, yes/no), body mass index, and smoking (smoker, yes/no).

The total sample consisted of 1,405 respondents aged 60 to 69. Of these, 14 were excluded from this analysis because they were screened out of the grip strength test (owing to an acute con- dition, a positive response to the PAR-Q or an unspeci ed reason). Another 234 were excluded because of incomplete grip strength or covariate data. The nal study sample numbered 1,157, of whom 1,109 had complete sit-and-reach data, and 616 had complete mCAFT

Statistics Canada, Catalogue no. 82-003-X • Health Reports, Vol. 28, no. 2, pp. 3-9, February 2017

5

Prolonged sedentary time and physical fitness among Canadian men and women aged 60 to 69 • Research Article

data. A total of 48 and 576 respondents were screened out of sit-and-reach and mCAFT, respectively, mainly because of medication use or a positive response to the PAR-Q.

Statistical analysis

Basic descriptive statistics were used to present characteristics of the sample, tness scores, sedentary time (meas- ured and self-reported), and physical activity levels by sex. Linear regression models were used to evaluate associ- ations between the tness outcomes and self-reported and measured sedentary time. Beta estimates, 95% con dence intervals, and p-values were calculated. Linear regression was also used to

evaluate adjusted associations between tness and the percentage of sedentary time spent in intervals lasting at least 20 minutes and the daily number of breaks in sedentary time. All models were adjusted for age, sex, education, body mass index and smoking. To evaluate independent associations with tness, models were further adjusted for total MVPA. Statistical signi cance was set at?<0.05.

Analyses were completed using SAS v9.2 and SUDAAN v10. Results were weighted using the activity monitor subsample weights. Standard errors, coef cients of variation and 95% CI were calculated with the bootstrap technique. The CHMS combined cycle 1 and 2

study design requires that 24 degrees of freedom be speci ed in the software.14

Results

Characteristics of sample

The average age of respondents was 64 (Table 1). Three-quarters (74%) were married/common-law, and 55% were postsecondary graduates. According to accelerometer data, they accumulated a daily average of 595 minutes (95% CI: 589 to 601) of sedentary time, most of which (83% or 501 minutes, 95% CI: 491 to 510) were in bouts lasting at least 20 minutes. An estimated 12% of respondents aged 60 to 69 met the Canadian Physical Activity Guidelines of 150 minutes per week of MVPA.

Table 1
Characteristics of Canadian Health Measures Survey sample aged 60 to 69, by sex, Canada, 2007-to-2009 and 2009-to-2011 combined

Total (n = 1,157)

95% con dence interval

Men (n = 564)

95% con dence interval

Women (n = 593)

95% con dence interval

estimate from to

64 64 64

67.2* 60.8 73.0 26.7* 22.3 31.7 6.1E 3.8 9.5

52.8 45.8 59.7 47.2 40.3 54.2 27.9 27.2 28.6 31.7* 25.7 38.3 37.9 32.5 43.6 30.4 24.7 36.8

24.1* 23.6 24.7 48* 46 49 26.8* 25.7 27.9

220 210 231 600* 588 611 501 482 521

8* 8 9 44 42 46 82.7 80.7 84.6 218 205 231 13* 11 15 10.9 7.9 14.9

Characteristic

Average age (years)
Marital status (%)
Married or common-law Widowed, separated or divorced Single, never married Education (%)

Postsecondary graduation Less than postsecondary Body mass index (kg/m2) Normal weight (%) Overweight (%)

Obese (%)

Fitness outcomes

Aerobic score (cardiorespiratory tness; ml/kg/min) Grip strength (kg)
Sit-and-reach (cm)
Physical activity

Average daily leisure sedentary time† – self-reported (minutes) Average daily sedentary time – measured (minutes)
Average daily sedentary time in bouts – measured (minutes) Average daily number of sedentary bouts of at least 20 minutes Average daily number of breaks (at least 1 minute) in sedentary time Average daily sedentary time in bouts (%)

Average daily TPA – measured (minutes)
Average daily MVPA – measured (minutes)
Physical Activity Guidelines for Older Adults (% meeting)

E use with caution
* signi cantly different from men (p < 0.05)
† watching TV, playing video games, using computer and reading
TPA = total physical activity (light and moderate-to-vigorous)
MVPA = moderate-to-vigorous physical activity
Note: A sedentary “break” was any movement above the sedentary threshold lasting at least 1 minute. Source: 2007-to-2009 and 2009-to-2011 Canadian Health Measures Survey (combined).

estimate from

64 64

74.1 69.9 20.6 17.5 5.3E 3.7

55.1 49.7 44.9 39.6 28.3 27.8 27.8 22.9 40.1 35.2 32.1 27.5

25.5 25.1 64 62 22.1 21.4

221 209 595 589 501 491

9 8 44 43 83.2 82.2 224 216 15 13 12.0 9.0

to

64

77.9 24.0 7.6

60.4 50.3 28.8 33.3 45.3 37.0

26.0 66 22.9

233 601 510

9 45 84.3 232 18 16.0

estimate from

64 64

to

64

86.2 19.6 6.8

64.0 49.3 29.4 30.9 50.8 41.0

28.0 83 18.2

238 600 515

9 45 85.3 241 21 18.7

81.5 14.0E 4.5E

57.5 42.5 28.6 23.6 42.5 33.9

27.1 81 17.4

222 590 500

75.7 9.8 3.0

50.7 36.0 27.9 17.6 34.7 27.4

26.3 79 16.6

207 580 485

9 44 83.8 231 18

8 43 82.4 220 14 13.2E 9.2

6

Health Reports, Vol. 28, no. 2, pp. 3-9, February 2017 • Statistics Canada, Catalogue no. 82-003-X

Prolonged sedentary time and physical fitness among Canadian men and women aged 60 to 69 • Research Article

Sedentary time and tness

In the fully adjusted models, no tness measures were associated with the amount of self-reported TV/video game/ computer/reading time among men or women (Table 2).

For measured total sedentary time, a signi cant and negative association was noted for cardiorespiratory tness in the combined sample of men and women in the fully adjusted model b (?:-0.1283, p < 0.01). The association between grip strength and measured sedentary time was also signi cant in the combined sample of men and women in the fully adjusted model (?: -0.017, p = 0.03) (Table 2).

In the combined sample of men and women, cardiorespiratory tness was signi cantly and negatively associated with the percentage of sedentary time spent in bouts lasting at least 20 minutes (?:-0.581, p < 0.01) (Table 3). After

adjustment for total MVPA, the rela- tionship remained signi cant (?:-0.529, p = 0.01). No signi cant associations were evident between sedentary time in bouts of at least 20 minutes and grip strength or sit-and-reach.

The association between the number of breaks in sedentary time and cardio- respiratory tness was positive and signi cant in the combined sample of men and women, even when adjusted for MVPA (?:0.468, p = 0.02) (Table 4). However, the association re ected the situation among women; the number of breaks in sedentary time was not signi cantly related to men’s cardiores- piratory tness. The number of breaks in sedentary time was positively and sig- ni cantly associated with sit-and-reach among men (?:0.145, p = 0.02). Breaks in sedentary time were not associated with the grip strength of either sex.

Discussion

This study examined associations between sedentary time and tness among Canadians in their sixties. The main ndings were that, after adjusting for MVPA: 1) objectively measured sed- entary time was inversely associated with cardiorespiratory tness and grip strength; 2) the number of breaks in sed- entary time was positively associated with cardiorespiratory tness; 3) the per- centage of sedentary time spent in bouts of at least 20 minutes was inversely asso- ciated with cardiorespiratory tness; 4) associations between sedentary time in bouts of at least 20 minutes and breaks in sedentary time and cardiorespira- tory tness were not consistent between sexes, nor were associations between sedentary time and grip strength; and 5) self-reported sedentary time was not related to any tness variable. The last

Table 2
Association of self-reported and measured sedentary time with selected tness outcomes, by sex, Canada, 2007-to-2009 and 2009-to-2011 combined

Type of sedentary time, tness outcome and sex

con dence interval

con dence interval

? estimate‡ from to p-value

-0.014 -0.061 0.034 0.56 -0.018 -0.101 0.066 0.66 -0.001 -0.043 0.041 0.96

-0.009 -0.022 0.004 0.15 -0.008 -0.029 0.013 0.43 -0.010 -0.022 0.003 0.12

-0.003 -0.012 0.005 0.43 -0.001 -0.014 0.012 0.88 -0.004 -0.015 0.006 0.40

-0.128 -0.185 -0.072 0.00 -0.134 -0.244 -0.024 0.02 -0.108 -0.174 -0.043 0.00

-0.017 -0.032 -0.002 0.03 -0.031 -0.058 -0.003 0.03 -0.007 -0.026 0.012 0.47

-0.009 -0.028 0.010 0.35 -0.016 -0.037 0.006 0.14 -0.001 -0.023 0.021 0.90

95% 95%

Self-reported leisure sedentary time§
Cardiorespiratory tness
Total 616 Men 294 Women 322 Grip strength
Total 1,157 Men 564 Women 593 Sit-and-reach
Total 1,106

Men

Women

Measured sedentary time Cardiorespiratory tness Total
Men

Women

Grip strength

541 558

616 294 322

Total 1,157 Men 564 Women 593 Sit-and-reach

Total 1,106 Men 541 Women 558

Number

? estimate†

-0.014 -0.018 -0.016

-0.009 -0.008 -0.010

-0.003 -0.001 -0.005

-0.135 -0.119 -0.150

-0.014 -0.025 -0.007

-0.008 -0.011 -0.002

from

-0.063 -0.100 -0.061

-0.022 -0.029 -0.022

-0.012 -0.014 -0.016

-0.184 -0.224 -0.224

-0.028 -0.049 -0.027

-0.024 -0.028 -0.025

to p-value

0.035 0.57 0.064 0.66 0.028 0.45

0.004 0.15 0.013 0.44 0.002 0.10

0.005 0.43 0.011 0.86 0.007 0.41

-0.086 <0.01 -0.013 0.03 -0.075 0.00

-0.000 0.04 -0.001 0.04 0.012 0.44

0.009 0.36 0.006 0.19 0.020 0.83

† adjusted for age, sex, education, body mass index, smoking status and accelerometer wear time.
‡ adjusted for age, sex, education, body mass index, smoking status, accelerometer wear-time and measured moderate-to-vigorous physical activity § watching TV, playing video games, using computer and reading
Source: 2007-to-2009 and 2009-to-2011 Canadian Health Measures Survey (combined).

Statistics Canada, Catalogue no. 82-003-X • Health Reports, Vol. 28, no. 2, pp. 3-9, February 2017

7

Prolonged sedentary time and physical fitness among Canadian men and women aged 60 to 69 • Research Article

Table 3
Association of percentage of total sedentary time spent in bouts of at least 20 minutes with selected tness outcomes, by sex, Canada, 2007-to-2009 and 2009-to-2011 combined

95% con dence interval

95% con dence interval

from to p-value

-0.938 -0.120 0.01 -1.298 0.230 0.16 -0.904 -0.055 0.03

-0.153 0.021 0.13 -0.278 0.050 0.16 -0.149 0.036 0.22

-0.163 0.050 0.28 -0.239 0.036 0.14 -0.136 0.104 0.79

95% con dence interval

from to p-value

0.098 0.838 0.02 -0.214 1.294 0.15 0.076 0.770 0.02

-0.023 0.136 0.16 -0.056 0.195 0.27 -0.020 0.177 0.11

-0.031 0.160 0.17 0.025 0.266 0.02 -0.122 0.102 0.86

Fitness outcome and sex number

Cardiorespiratory tness

Total 616 Men 294 Women 322 Grip strength

Total 1,157 Men 564 Women 593 Sit-and-reach

Total 1,106 Men 541 Women 558

? estimate†

-0.581 -0.534 -0.625

-0.064 -0.111 -0.059

-0.056 -0.097 -0.019

from

-0.965 -1.277 -1.088

-0.148 -0.266 -0.157

-0.159 -0.226 -0.146

to p-value

-0.198 0.00 0.210 0.15 -0.161 0.01

0.021 0.13 0.045 0.16 0.038 0.22

0.048 0.28 0.031 0.13 0.108 0.76

? estimate‡

-0.529 -0.534 -0.479

-0.066 -0.114 -0.057

-0.057 -0.101 -0.016

† adjusted for age, sex, education, body mass index and smoking status
‡ adjusted for age, sex, education, body mass index, smoking status and total minutes of measured moderate-to-vigorous physical activity Source: 2007-to-2009 and 2009-to-2011 Canadian Health Measures Survey (combined).

Table 4
Association of number of breaks in sedentary time with selected tness outcomes, by sex, Canada, 2007-to-2009 and 2009-to-2011, combined

95% con dence interval

from to p-value

0.196 0.898 0.00 -0.112 1.331 0.09 0.175 0.920 0.01

-0.011 0.147 0.09 -0.035 0.240 0.14 -0.034 0.168 0.18

-0.035 0.161 0.20 0.020 0.258 0.02 -0.111 0.108 0.97

Fitness outcome and sex

Cardiorespiratory tness

number

? estimate†

0.547 0.609 0.547

0.068 0.103 0.067

0.063

0.139 -0.002

? estimate‡

0.468 0.540 0.423

0.056 0.069 0.078

0.065

0.145 -0.010

Total 616 Men 294 Women 322 Grip strength

Total 1,157 Men 564 Women 593 Sit-and-reach

Total 1,106 Men 541 Women 558

† adjusted for age, sex, education, body mass index and smoking status
‡ adjusted for age, sex, education, body mass index, smoking status, total measured sedentary time and total minutes of measured moderate-to-vigorous physical activity Note: A sedentary “break” was any movement above the sedentary threshold lasting at least 1 minute.
Source: 2007-to-2009 and 2009-to-2011 Canadian Health Measures Survey (combined).

conforms with previous work showing measured sedentary time to be more con- sistently related to health outcomes than are self-reported measures.8 Together, these results indicate that prolonged sed- entary time may affect age-related losses in cardiorespiratory and musculoskeletal tness, and that breaking it up with with light-intensity activity could positively in uence tness levels in older adults, regardless of moderate-to-vigorous physical activity levels.

Earlier research indicates that seden- tary time and patterns of sedentary time

are associated with older adults’ health and functional tness.8,10,23 In the present study, the percentage of total sedentary time spent in bouts of at least 20 minutes was inversely associated with cardiores- piratory tness, and a greater number of breaks in sedentary time was associ- ated with better cardiorespiratory tness. These ndings are important because cardiorespiratory tness is a strong predictor of morbidity and all-cause mortality.2 In 2015, Oudegeest-Sander et al. demonstrated that non-exercising older adults with higher cardiorespira-

tory tness have better vascular function and lower cardiovascular risk.24 They suggested that greater amounts of non-exercise activity, such as activities of daily living, may partly explain the tness and vascular health of some older individuals who do not engage in pur- poseful physical actvity.24 It is possible that adaptations in the vasculature, and likely other components such as muscle oxidative capacity, are stimulated by light intensity activities. While mech- anistic studies are required, the present results support the potential importance

8

Health Reports, Vol. 28, no. 2, pp. 3-9, February 2017 • Statistics Canada, Catalogue no. 82-003-X

Prolonged sedentary time and physical fitness among Canadian men and women aged 60 to 69 • Research Article

of non-exercise activity by demon- strating that breaks in prolonged sitting may in uence cardiorespiratory tness in older adults. Frequent interruptions of sedentary periods may be particularly important for older adults, who tend to accumulate considerable daily seden- tary time.7,8 However, the CHMS data are cross-sectional, so it is possible that older adults with lower cardiorespira- tory tness nd it more dif cult to break up their sedentary time. Intervention research is needed to determine the impact that breaking up sedentary time has on cardiorespiratory tness.

Total sedentary time was inversely related to grip strength in men and women, even after adjusting for MVPA. As well, the association between breaks in sedentary time and sit-and-reach scores was positive among men. Therefore, sedentary time may also in uence mus- culoskeletal tness, which is crucial for independent living and autonomy.

A study by Santos et al. found that sedentary time was signi cantly related to functional tness in older adults.23 Similarly, Davis et al. reported that more breaks in sedentary time were asso- ciated with better physical function.12 Both of these studies used functional performance tests to measure tness in contrast to the more traditional tness tests employed in the CHMS. It is pos- sible that, similar to cardiorespiratory tness, breaking up sedentary time with light-intensity weight-bearing activities provides a stimulus for adaptations in the working muscle. However, the CHMS does not include a lower body measure of muscular strength or endurance. Research is needed to assess associ- ations between breaks in sedentary time and measures of lower body strength at older ages.

The two studies mentioned above12,23 examined participants who were sig- ni cantly older and had lower tness than the CHMS sample. This makes the present ndings noteworthy, as even among the sample, who were younger and healthier, an inverse association was apparent between both cardiorespiratory tness and musculoskeletal tness and sedentary time.

Relationships between the sedentary variables and cardiorespiratory tness and musculoskeletal tness were not consistent for men and women. Among women, the percentage of sedentary time spent in bouts of at least 20 minutes and breaks in sedentary time were asso- ciated with cardiorespiratory tness; no signi cant associations were found among men. By contrast, for men, asso- ciations were noted between measured sedentary time and grip strength, and between breaks in sedentary time and sit-and-reach; similar associations were not observed for women.

At any given age, men’s cardiores- piratory tness exceeds that of women. For example, in this sample, according to the mCAFT score, which was used to estimate cardiorespiratory tness in ml/kg/min, the cardiorespiratory tness for men was 27.1, compared with 24.1 for women (Table 1). Moreover, at ages 60 to 70, women fall in a critical range (15 to 20 ml/kg/min), where functional autonomy may become compromised.25 It is possible that sedentary time in u- ences cardiorespiratory tness once it falls below a certain level. Due to screening restrictions placed on per- forming the aerobic test, the CHMS sample was also tter and healthier than the general population. Thus, the asso- ciation between patterns of sedentary time and cardiorespiratory tness may be stronger in less t women. Similarly, with regard to the differences in associ- ations with sit-and-reach, it is possible that because women tend to have better exibility than men,26,27 men are more susceptible to the effects of sedentary time on exibility, as prolonged sitting is associated with muscle stiffness.28

The results for patterns of seden- tary time are of particular interest as they suggest that breaking up sedentary time may positively in uence cardio- respiratory tness among women but not men, while such breaks affect ex- ibility in men but not in women. This may indicate that in household, leisure, transportation and occupation domains, men and women interrupt their seden- tary time with different types of activity. It is clear that sex needs to be considered

when assessing associations between sedentary time and tness among older adults, as they point to a possible need for differences in intervention strategies.

Strengths and limitations

The strengths of the current analysis are the use of a large, nationally representa- tive sample, and standardized, objective measurements of sedentary time, cardio- respiratory tness and musculoskeletal tness. However, the results should be interpreted in the context of several limitations. First, as a result of rigorous screening for CHMS tness testing, the

Statistics Canada, Catalogue no. 82-003-X • Health Reports, Vol. 28, no. 2, pp. 3-9, February 2017

9

Prolonged sedentary time and physical fitness among Canadian men and women aged 60 to 69 • Research Article

nal sample was tter and healthier than the population overall. Consequently, the ndings may not be generalizable to all people in their sixties. In fact, associations between sedentary time and tness might be even stronger among those with functional restric- tions or chronic conditions. Second, the cross-sectional study design precludes drawing conclusions about the direction of observed relationships. Less- t people

References

1. Fowles J, Roy J, Clarke J, Dogra S. Are thefittest Canadian adults the healthiest? Health Reports 2014; 25(5): 13-8.
2. Kodama S, Saito K, Tanaka S, et al. Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis. Journal of the American Medical Association 2009; 301(19): 2024-35.
3. Leong DP, Teo KK, Rangarajan S, et al. Prognostic value of grip strength: findings from the Prospective Urban Rural Epidemiology (PURE) study. Lancet 2015; 386(9990): 266-73.
4. Kell RT, Bell G, Quinney A. Musculoskeletal fitness, health outcomes and quality of life. Sports Medicine 2001; 31(12): 863-73.
5. Trappe S, Hayes E, Galpin A, et al. New records in aerobic power among octogenarian lifelong endurance athletes. Journal of Applied Physiology 2013; 114(1): 3-10.
6. Bouaziz W, Lang PO, Schmitt E, et al. Health benefits of multicomponent training programmes in seniors: a systematic review. International Journal of Clinical Practice 2016; 70(7): 520-36.
7. Colley RC, Garriguet D, Janssen I, et al. Physical activity of Canadian adults: Accelerometer results from the 2007 to 2009 Canadian Health Measures Survey. Health Reports 2011; 22(1): 7-14.
8. Copeland JL, Clarke J, Dogra S. Objectively measured and self-reported sedentary time in older Canadians. Preventive Medicine Reports 2015; 2: 90-5.
9. Katzmarzyk PT, Church TS, Craig CL, Bouchard C. Sitting time and mortality from all causes, cardiovascular disease, and cancer. Medicine and Science in Sports and Exercise 2009; 41(5): 998-1005.

may spend more time in sedentary activ- ities, a possibility that could be explored in future studies.

Conclusion

These data demonstrate a signi cant relationship between directly measured sedentary time, breaks in sedentary time, and tness among Canadians in their sixties. Given the long-established

10. Gardiner PA, Healy GN, Eakin EG, et al. Associations between television viewing time and overall sitting time with the metabolic syndrome in older men and women: the Australian Diabetes, Obesity and Lifestyle study. Journal of the American Geriatric Society 2011; 59(5): 788-96.

11. Dunstan DW, Kingwell BA, Larsen R, et al. Breaking up prolonged sitting reduces postprandial glucose and insulin responses. Diabetes Care 2012; 35(5): 976-83.

12. Davis MG, Fox KR, Stathi A, et al. Objectively measured sedentary time and its association with physical function in older adults. Journal of Aging and Physical Activity 2014; 22(4): 474-81.

13. Chastin SF, Ferriolli E, Stephens NA, et al. Relationship between sedentary behaviour, physical activity, muscle quality and body composition in healthy older adults. Age and Ageing 2012; 41(1): 111-4.

14. Statistics Canada. Instructions for Combining Multiple Cycles of Canadian Health Measures Survey (CHMS) Data, Ottawa: Statistics Canada, 2013.

15. Day B, Langlois R, Tremblay M, Knoppers B. Canadian Health Measures Survey: Ethical, legal and social issues. Health Reports 2007; 18(S): 37-52.

16. Statistics Canada. Canadian Health Measures Survey (CHMS) Data User Guide. Ottawa: Statistics Canada, 2010.

17. Statistics Canada. Canadian Health Measures Survey (CHMS) Data User Guide (Cycle 2). Ottawa: Statistics Canada, 2012.

18. Colley R, Connor Gorber S, Tremblay MS. Quality control and data reduction procedures for accelerometry-derived measures of physical activity. Health Reports 2010; 21(1): 63-9.

19. Colley RC, Tremblay MS. Moderate and vigorous physical activity intensity cut-points for the Actical accelerometer. Journal of Sports Science 2011; 29(8): 783-9.

associations between tness and both health and functional autonomy for older adults, this study underscores the importance of minimizing total sed- entary time and breaking up sedentary time, in addition to increasing physical activity. Differences in the results for men and women suggest that sex is a factor to consider when developing and evaluating intervention studies of older adults. ?

20. Wong SL, Colley R, Gorber SC, Tremblay MS. Actical accelerometer sedentary activity thresholds for adults. Journal of Physical Activity and Health 2011; 8(4): 587-91.

21. Carson V, Janssen I. Volume, patterns, and types of sedentary behavior and cardio-metabolic health in children and adolescents: a cross-sectional study. BMC Public Health 2011; 11(274).

22. Canadian Society for Exercise Physiology.

Canadian Physical Activity, Fitness and Lifestyle Appraisal, Third Edition. Ottawa: Canadian Society for Exercise Physiology, 2004.

23. Santos DA, Silva AM, Baptista F, et al. Sedentary behavior and physical activity are independently related to functional fitness in older adults. Experimental Gerontology 2012; 47(12): 908-12.

24. Oudegeest-Sander MH, Thijssen DHJ, Smits P, et al. Association of fitness level with cardiovascular risk and vascular function in older non-exercising individuals. Journal of Aging and Physical Activity 2015; 23(3): 417-24.

25. Fleg JL, Morrell CH, Bos AG, et al. Accelerated longitudinal decline of aerobic capacity in healthy older adults. Circulation 2005; 112(5): 674-82.

26. Shields M, Tremblay MS, Laviolette M, et al. Fitness of Canadian adults: Results from the 2007-2009 Canadian Health Measures Survey. Health Reports 2010; 21(1): 21-35.

27. Hoge KM, Ryan ED, Costa PB, et al. Gender differences in musculotendinous stiffness and range of motion after an acute bout of stretching. Journal of Strength and Conditioning Research 2010; 24(10): 2618-26.

28. Beach TA, Parkinson RJ, Stothart JP, Callaghan JP. Effects of prolonged sitting on the passive flexion stiffness of the in vivo lumbar spine. Spine Journal 2005; 5(2): 145-54.