Patterns and trends in walking behaviour among Canadian adults.

OBJECTIVES: Regular walking is associated with many health benefits and is of particular interest for the promotion of daily physical activity. The purpose of this study is to describe the epidemiology of walking for exercise among Canadian adults aged 18-55 years. METHODS: Nationally representative cross-sectional data from the National Population Health Survey and Canadian Community Health Survey from 1994/95 to 2007 were used for this study. The weighted and age-standardized prevalence of walking for exercise, walking duration, regular walking (at least 4 times a week) and deriving 100% of the total leisure-time physical activity energy expenditure (LTPAEE) from walking were calculated. RESULTS: Overall, 70% of Canadian adults walked for exercise at least once during the previous three months; however, only 30% of the population reported walking regularly, a figure that has remained relatively stable since 2001. Women, older adults, those with lower body mass index (BMI) and those with lower total household income reported regular walking more often than their counterparts. Women, older adults and lower-income Canadians also tended to derive 100% of their total LTPAEE from walking more often than men, young adults and those in higher-income groups. CONCLUSION: Walking is a popular physical activity for Canadian adults, regardless of age, sex, BMI or income group, however, the prevalence of regular walking varies between demographic subgroups. Public health strategies that focus on promoting walking for exercise should consider these results when defining target audiences and designing interventions.

Physical activity and ethnicity: evidence from the Canadian Community Health Survey.

BACKGROUND: A large proportion of the Canadian population lives a sedentary lifestyle. Few data are available describing the physical activity behaviours among specific ethnic groups in Canada, so the purpose of this study is to examine the relationship between ethnicity and the level of self-reported physical activity. METHODS: Pooled data from cycles 1.1 (2000/01) and 2.1 (2003) of the cross-sectional Canadian Community Health Survey (ages 20-64 yrs; N = 171,513) were used for this study. Weighted prevalences of self-reported leisure-time moderate (> or = 1.5 kcal x kg(-1) day(-1) (kkd)); moderate to high (> or = 3 kkd) and high physical activity (> or = 6 kkd) were calculated, and multiple logistic regression models were used to quantify the odds of being physically active across ethnic groups, after adjustment for several covariates (White referent group). RESULTS: The rank order of prevalence of being moderately physically active by ethnicity was: White (49%), Other (48%), NA Aboriginal (47%), Latin American (40%), East/Southeast Asian (39%), Black (38%), West Asian/Arab (36%), South Asian (34%). Aboriginal men and women had the highest prevalences of being physically active at > or = 3 kkd (M = 32%, F = 22%) while East/Southeast Asian (19%) and East Asian/Arab men (19%), and South Asian women (12%) had the lowest prevalences. After accounting for covariates, Aboriginal men were at elevated odds of being physically active compared to Whites (> or = 3 kkd, OR=1.6, p < 0.05; > or = 6 kkd, OR = 2.7, p < 0.05). Only 7% and 3% of Canadian men and women, respectively, were active at > or = 6 kkd. CONCLUSION: These results suggest that the prevalence of physically active Canadian adults varies by ethnicity. Strategies to promote physical activity and prevent physical inactivity should consider these findings.

Physical activity and immigrant status: evidence from the Canadian Community Health Survey.

BACKGROUND: The immigrant population in Canada is diverse and growing, yet little is known about their physical activity behaviour and how it changes as they adapt to a Canadian lifestyle. This study extends the surveillance of physical activity in Canada to include the influence of time since immigration within and between ethnic groups. METHODS: Pooled data from cycles 1.1 (2000/01) and 2.1 (2003) of the cross-sectional Canadian Community Health Survey (ages 20-64 y; N = 171,513) were used for this study. Weighted prevalences of self-reported leisure-time physical activity (> or = 3 kcal x kg(-1) x day(-1) (kkd)) were calculated, and unadjusted and adjusted (age, income, education, BMI) multiple logistic regression models were used to quantify the odds of being physically active (PA) (> or = 3 kkd) by time since immigration (recent immigrant < or = 10 yrs, immigrant >10 yrs, non-immigrant) within and between ethnic groups (White referent group). RESULTS: The prevalence of recent immigrants (< or = 10 yrs) being PA (> or = 3 kkd) by ethnicity was: White (21%), Other (19%), Black (19%), Latin American (17%), West Asian/Arab (16%), East/Southeast Asian (14%), South Asian (11%). Recent immigrant Black men and White women had the highest prevalence of being PA (M = 27%, F = 18%) while South Asian men and women had the lowest prevalence (M = 14%, F = 9%). There is a gradient in the prevalence of being PA with recent immigrants (16%) < immigrants (20%) < non-immigrants (24%). Ethnic differences in the prevalence of being PA by time since immigration show similar patterns for men and women. Controlling for age, income, education and BMI had only small effects on the odds of being physical active across ethnicities and immigrant status. CONCLUSION: These results suggest that physical activity levels vary according to immigrant status and self-ascribed ethnicity in Canadian adults. Strategies to promote physical activity and prevent physical inactivity should consider both ethnicity and time since immigration.

The association between meeting physical activity guidelines and chronic diseases among Canadian adults.

BACKGROUND: Physical activity is associated with a reduced risk of chronic disease. This study describes the relationship between meeting the guidelines for physical activity described in Canada's Physical Activity Guide and heart disease, type 2 diabetes, hypertension, obesity, and low levels of general health. METHODS: Leisure-time energy expenditure (LTEE) was calculated from leisure-time physical activities reported by adults who participated in the 2007 Canadian Community Health Survey. Respondents were classified as meeting the guidelines for physical activity or not, and were stratified by sex into quartiles of LTEE. Logistic regression was used to determine the odds for all conditions associated with not meeting the guidelines and by quartile of LTEE, adjusting for covariates. RESULTS: The odds of type 2 diabetes, obesity, and fair/poor health were significantly higher among those not meeting the guidelines for both sexes and for high blood pressure among women. Significantly higher odds were seen between the lowest and highest quartiles of LTEE for type 2 diabetes and high blood pressure and across all quartiles for obesity and fair/poor health for both sexes. CONCLUSIONS: Canadian adults meeting the physical activity guidelines have lower odds of chronic diseases and fair/poor health than those not meeting the guidelines.

Estimating leisure-time physical activity energy expenditure in the Canadian population: a comparison of 2 methods.

The purpose of this study was to determine the impact of 2 different calculation methods for total leisure-time physical activity energy expenditure (LTPAEE) and LTPAEE from different intensity activities on the classification of level of physical activity in the population. Nationally representative cross-sectional data from the Canadian Community Health Survey Cycle 4.1 (2007) were used for this study (N = 64, 397). LTPAEE was calculated using a metabolic equivalent (MET) value of 4.0 for all activities in the "other activity" category for method 1 (currently employed by Statistics Canada) and using activity-specific MET values for method 2. The weighted prevalence and 95% confidence intervals of active (> or =3 kcal.kg-1.day-1 (kkd)), moderately active (1.5-2.9 kkd), and inactive (<1.5 kkd) were determined for each method by demographic characteristics. The agreement between the 2 methods was assessed overall, and for light, moderate, and vigorous activities. There was no difference between methods in the proportion classified as active, moderately active, or inactive for any of the subgroups studied and there was no difference in the distribution or mean LTPAEE between methods. However, assessment of the agreement showed a large number of outliers and a tendency to underestimate LTPAEE from light and vigorous activities while overestimating LTPAEE from moderate activities at the individual level. The results of this study should be considered when performing inferential statistics on the relationship between physical activity and health outcomes.

Are Canadians meeting the guidelines for moderate and vigorous leisure-time physical activity?

The purpose of this study was to determine the proportion of Canadian adults (aged 18-55 years) who met the guidelines for moderate and vigorous physical activity set out in Canada's Physical Activity Guide to Healthy Active Living. Leisure-time physical activity energy expenditure from moderate- and vigorous-intensity activities was calculated using data from the National Population Health Surveys (1994-1998) and the Canadian Community Health Surveys (2001-2007). The prevalence was estimated for no leisure-time physical activity, meeting only the moderate guideline, meeting both the moderate and vigorous guidelines, and meeting the guidelines through a combination of moderate and vigorous activities. Logistic regression was used to determine the odds of meeting the guidelines by various demographic characteristics. The prevalence of no activity did not change appreciably over time, ranging from 6.5% to 10%, depending on the survey year. Reporting of no activity was more prevalent among older adults, those in lower income groups, and those with a body mass index (BMI) > or =30 kg.m-2. Overall, 65% of adults met the guidelines for physical activity in 2007, which has increased from 54% in 1994-1995. Men, younger adults, those with a higher income, and those with a lower BMI more often met the guidelines. Among all subgroups, meeting the guidelines was most often accomplished through participation in moderate-intensity activities. These findings should be considered when designing and implementing public health interventions that promote participation in daily physical activity.

Obesity, overweight and ethnicity.

OBJECTIVES: This article describes the prevalence of self-reported overweight and obesity, based on body mass index (BMI), by ethnicity and examines the influence of time since immigration within and between ethnic groups. DATA SOURCES: Results are based on data from two cycles of Statistics Canada's Canadian Community Health Survey, conducted in 2000/01 and 2003. ANALYTICAL TECHNIQUES: Weighted prevalences of overweight (BMI > or =25) and obesity (BMI > or =30) were calculated by sex and ethnicity for the population aged 20 to 64. Multiple logistic regression models were used to examine associations between overweight/obesity and ethnicity, and within and between ethnic groups based on time since immigration, controlling for age, household income, education and physical activity. MAIN RESULTS: Aboriginal men and women had the highest prevalences of overweight and obesity; East/Southeast Asians, the lowest. Independent of age, household income, education and physical activity, Aboriginal people had elevated odds of overweight and obesity, compared with Whites; South Asians and East/Southeast Asians had significantly lower odds. Recent immigrants (10 years or less) had significantly lower prevalences of overweight, compared with non-immigrants, but this difference tended to disappear over time.

Potentiation of shortening and velocity of shortening during repeated isotonic tetanic contractions in mammalian skeletal muscle.

The purpose of this study was to investigate the enhancement of shortening and of the velocity of shortening during repeated incompletely fused isotonic tetanic contractions. The medial gastrocnemius muscle of anesthetized rats was isolated in situ and the motor nerve stimulated with supramaximal pulses, 50 micros duration, at optimal length. Estimated maximal velocity of shortening (V(max)) was 210 +/- 6 mm x s(-1) (mean +/- SEM). Repeated incompletely fused tetanic contractions (three pulses at 80 Hz) resulted in initial shortening which was 1.5 +/- 0.1 mm, and this increased to 2.7 +/- 0.2 mm after 7 s of 4 s(-1) contractions. Peak velocity of shortening for intermittent 80 Hz stimulation increased from 60.5 +/- 4 mm x s(-1) to 91.8 +/- plus minus 6 mm x s(-1). The initial velocity of shortening for 80 Hz stimulation was substantially less than the velocity of shortening observed with 200 Hz stimulation, but increased to 72 +/- 3% of the load-specific value for 200 Hz stimulation. Myosin regulatory light chain phosphorylation increased from 11.1 +/- 1.5% at rest to 32.9 +/- 5.4% after 4 s of intermittent 80 Hz stimulation and 50.4 +/- 8.8% after 7 s ( P<0.01). The ascending limb of the length-force relationship was determined with tetanic contractions, 200 Hz for 100 ms. At the length corresponding to peak shortening after 7 s of repeated 80 Hz contractions, the maximal isometric force was five times greater than the isotonic load. The rate of phosphorylation was sustained from 4 to 7 s, but the rate of increase in shortening and velocity decreased. The slower rate of change in shortening and velocity may be due to approaching maximal velocity for this short duration of contraction, but is not due to slowing of the rate of phosphorylation of the myosin regulatory light chains.