Conquering Childhood Inactivity: Is the Answer in the Past?

PURPOSE

The primary purpose of this study was to compare the health-related physical fitness and physical activity behaviors of Old Order Mennonite children to both rural and urban-dwelling children living a contemporary Canadian lifestyle.

METHODS

A cross-sectional study design was used to compare the physical fitness and physical activity characteristics of three groups of children between the ages of 8-13 yr. A total of 124 Old Order Mennonite children (OOM) from Ontario, Canada, were compared with contemporary living children from urban (USK, N = 110) and rural (RSK, N = 165) Saskatchewan, Canada. Fitness was assessed using measures of height, weight, triceps skinfold, grip strength, push-ups, partial curl-ups, and aerobic fitness. Physical activity levels were directly measured for seven consecutive days using a MTI Actigraph accelerometer model 7164.

RESULTS

After controlling for maturational age, analyses revealed that OOM children had a smaller triceps skinfold than USK children (P < 0.01), a greater aerobic fitness score than RSK children (P < 0.05), and greater grip strength than both RSK and USK children (P < 0.001). The OOM children also accumulated more minutes of MVPA per day than RSK or USK groups (P < 0.001).

CONCLUSION

This research demonstrates that OOM children tend to be leaner, stronger and more active than urban and rural dwelling children living a contemporary Canadian lifestyle despite having no physical education, no institutionalized sport, and low socioeconomic status. These findings support the notion that that contemporary living may facilitate a decline in fitness and physical activity among some Canadian children.

Influence of exercise duration on post-exercise steroid hormone responses in trained males

The purpose of this study was to systematically evaluate the effect of endurance exercise duration on hormone concentrations in male subjects while controlling for exercise intensity and training status. Eight endurance-trained males (19-49 years) completed a resting control session and three treadmill runs of 40, 80, and 120 min at 55% of VO2max . Blood samples were drawn before the session and then 1, 2, 3 and 4 h after the start of the run. Plasma was analyzed for luteinizing hormone (LH), dehydroepiandrosterone sulfate (DHEAS), cortisol, and free and total testosterone. LH was significantly greater at rest compared to the running sessions. Both free and total testosterone generally increased in the first hour of the 80 and 120 min runs and then showed a trend for a steady decline for the next 3 h of recovery. Dehydroepiandrosterone sulfate increased in a dose-response manner with the greatest increases observed during the 120-min run, followed by the 80-min run. Cortisol only increased in response to the 120-min run and showed a decline across time in all other sessions. The ratios of anabolic hormones (testosterone and DHEAS) to cortisol were greater during the resting session and the 40-min run compared to the longer runs. The results indicate that exercise duration has independent effects on the hormonal response to endurance exercise. At a low intensity, longer duration runs are necessary to stimulate increased levels of testosterone, DHEAS and cortisol and beyond 80 min of running there is a shift to a more catabolic hormonal environment.

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.

Effect of HRT on hormone responses to resistance exercise in post-menopausal women

PURPOSE

The purpose of this study was to evaluate the effect of hormone replacement therapy (HRT) on the acute and chronic hormonal responses to resistance exercise in post-menopausal women.

METHODS

Thirty-two post-menopausal women were recruited for this study; 16 who were currently using HRT and 16 who were not using HRT. Subjects in both the HRT and NHRT groups were randomly assigned to either a resistance training group (N = 16; 8 HRT and 8 NHRT) or a control group (N = 16; 8 HRT and 8 NHRT). The training group completed a supervised resistance training program three times a week for 12 weeks. To evaluate changes in hormone levels, resting blood samples were drawn at weeks 0, 4, and 13 of the program. In addition, at weeks 0 and 13, post-exercise blood samples were drawn in order to examine the hormone response to an acute bout of resistance exercise. Samples were analyzed for serum growth hormone (GH), insulin-like growth factor-1 (IGF-1), testosterone, estradiol, dehydroepiandrosterone (DHEA), and cortisol.

RESULTS

There were no significant changes in resting hormone levels between weeks 0, 4, and 13 of the training program. There was a significant week-by-group interaction for DHEA (P < 0.05 ) and cortisol (P < 0.05 ) with the NHRT-training group having a greater post-exercise increase in DHEA and cortisol after training. Overall, the post-exercise GH levels were significantly greater than pre-exercise (P < 0.05 ) or recovery levels (P < 0.01). There were no significant differences between HRT and NHRT groups in the acute hormone response to exercise.

CONCLUSION

These results indicate that HRT will not have an effect on the acute or chronic hormone response to a recreational resistance training program in post-menopausal women.

Effect of training status and exercise mode on endogenous steroid hormones in men

The purpose of this study was to determine the acute anabolic and catabolic hormone response to endurance and resistance exercise bouts of equal volume in subjects with differing training status. Twenty-two healthy men were recruited who were either resistance trained ( n = 7), endurance trained ( n = 8), or sedentary ( n = 7). Three sessions were completed: a resting session, a 40-min run at 50-55% maximal oxygen consumption, and a resistance exercise session. Expired gases were monitored continuously during exercise, and the endurance and resistance exercise sessions were individually matched for caloric expenditure. Blood samples were drawn before exercise and 1, 2, 3, and 4 h after the start of the exercise. Plasma was analyzed for luteinizing hormone, dehydroepiandrosterone sulfate, cortisol, and free and total testosterone. Androgens increased in response to exercise, particularly resistance exercise, whereas cortisol only increased after resistance exercise. Dehydroepiandrosterone sulfate levels increased during the resistance exercise session and remained elevated during recovery in the resistance-trained subjects. Endurance-trained subjects displayed less pronounced changes in hormone concentrations in response to exercise than resistance-trained subjects. After an initial postexercise increase, there was a significant decline in free and total testosterone during recovery from resistance exercise ( P < 0.05), particularly in resistance-trained subjects. On the basis of the results of this study, it appears that the endogenous hormone profile of men is more dependent on exercise mode or intensity than exercise volume as measured by caloric expenditure. The relatively catabolic environment observed during the resistance session may indicate an intensity-rather than a mode-dependent response.

Exercise Endocrinology in Women: Issues Across the Lifespan Symposium Introduction

Recent concerns over the risks of hormone replacement therapy in postmenopausal women have increased interest in assessing alternative therapies to preserve the health and well-being of women as they age. Because of the dramatic changes observed in the endocrine system as women age, particularly with anabolic hormones, there is interest in the potential for exercise to promote a hormonal milieu that preserves or enhances physiological function, especially muscle and bone mass, and healthy aging. To examine this potential, the papers from this symposium assessed different but related areas of exercise endocrinology in women. The symposium addressed important work on energy balance and reproductive function, exercise and estrogen interactions on health in postmenopausal women, and how age affects hormonal responses to exercise in women. Methodological inconsistencies make it difficult to draw definitive conclusions, which highlights the need for additional, carefully controlled work in this area. Key words: hormones, physical activity, female, methodological issues

Aging, Physical Activity, and Hormones in Women—A Review

Women experience significant changes in endocrine function during aging. Decreasing levels of anabolic hormones may be associated with musculoskeletal atrophy and decrease in function that is observed in older women and, as a result, there has been an increase in the use of pharmacological hormone therapies. It is difficult to distinguish, however, between physiological changes that are truly age related and those that are associated with lifestyle factors such as physical activity participation. Some research has shown that circulating levels of anabolic hormones such as DHEA(S) and IGF-I in older women are related to physical activity, muscle function, and aerobic power. Exercise-intervention studies have generally shown that increasing age blunts the acute hormonal response to exercise, although this might be explained by a lower exercise intensity in older women. There have been relatively few studies that examine hormonal adaptations to exercise training. Physical activity might have an effect on hormone action as a result of changes in protein carriers and receptors, and future research needs to clarify the effect of age and exercise on these other components of the endocrine system. The value and safety of hormone supplements must be examined, especially when used in combination with an exercise program.

Is the Canadian childhood obesity epidemic related to physical inactivity?

OBJECTIVE

This study examined the relation among children's physical activity, sedentary behaviours, and body mass index (BMI), while controlling for sex, family structure, and socioeconomic status.

DESIGN

Epidemiological study examining the relations among physical activity participation, sedentary behaviour (video game use and television (TV)/video watching), and BMI on a nationally representative sample of Canadian children.

SUBJECTS

A representative sample of Canadian children aged 7-11 (N=7216) from the 1994 National Longitudinal Survey of Children and Youth was used in the analysis.

MEASUREMENTS

Physical activity and sport participation, sedentary behaviour (video game use and TV/video watching), and BMI measured by parental report.

RESULTS

Both organized and unorganized sport and physical activity are negatively associated with being overweight (10-24% reduced risk) or obese (23-43% reduced risk), while TV watching and video game use are risk factors for being overweight (17-44% increased risk) or obese (10-61% increased risk). Physical activity and sedentary behaviour partially account for the association of high socioeconomic status and two-parent family structure with the likelihood of being overweight or obese.

CONCLUSION

This study provides evidence supporting the link between physical inactivity and obesity of Canadian children.

Geographic and demographic variation in the prevalence of overweight Canadian children

OBJECTIVE

To examine the geographic and demographic variation in the prevalence of overweight Canadian children.

RESEARCH METHODS AND PROCEDURES

Using BMI data from the 1981 Canada Fitness Survey and the 1996 National Longitudinal Survey of Children and Youth, this study assessed: 1). the prevalence of overweight and obesity among Canadian boys and girls ages 7 to 13 years; 2). secular trends in the prevalence of overweight from 1981 to 1996, by province and adjusted for age and sex; and 3). provincial variation in the prevalence of overweight, before and after adjusting for socioeconomic and demographic characteristics.

RESULTS

The prevalence of boys and girls classified as overweight in 1996 was 33% and 26%, respectively. The corresponding figures for obesity were 10% for boys and 9% for girls. Provincial variation was observed with a trend of increasing risk of being overweight from west to east. Socioeconomic status was inversely related to the prevalence of overweight regardless of geographic region. The risk of being overweight was more related to geography (province) than demographic variables (income and family background); however, the effect of secular trends (1981 to 1996) exceeded the effect of geographic or demographic variables.

DISCUSSION

The prevalence of childhood overweight and obesity is increasing in all areas of Canada and can be explained only partially by geographic or demographic characteristics.

Temporal trends in overweight and obesity in Canada, 1981-1996

OBJECTIVE

To assess changes in the prevalence of overweight and obesity among Canadian children and adults between 1981 and 1996 using recent recommendations for the classification of overweight and obesity.

DESIGN

Epidemiological study comparing the prevalence of overweight and obesity from the 1981 Canada Fitness Survey (CFS) to the 1996 National Longitudinal Survey of Children and Youth (NLSCY) and the 1996 National Population Health Survey (NPHS).

SUBJECTS

Adults 20-64 y of age and children 7-13 y of age from the CFS, NLSCY and NPHS.

MEASUREMENTS

BMI was calculated from directly measured or self-reported body mass and height. For adults 20-64 y of age, overweight and obesity were defined as BMI > or = 25 kg/m2 and BMI > or = 30 kg/m2, respectively. Age- and sex-specific cut-off points for children that correspond to the adulthood categories were used to define overweight and obesity for children 7-13 y of age.

RESULTS

The prevalence of overweight increased from 48 to 57% among men and from 30 to 35% among women, while the prevalence of obesity increased from 9 to 14% in men and from 8 to 12% in women. The corresponding increases were from 11 to 33% in boys and from 13 to 27% in girls for overweight and from 2 to 10% in boys and from 2 to 9% in girls for obesity.

CONCLUSION

The results indicate dramatic increases in the prevalence of both overweight and obesity in Canada over the last 15 y, and the problem is particularly pronounced among children.

Hormonal responses to endurance and resistance exercise in females aged 19-69 years

Thirty cross-trained, female subjects (19-69 years) completed an endurance exercise session (ES), a resistance exercise session (RS), and a control session (CS) in a randomized, balanced design. The ES consisted of 40 minutes of cycling at 75% maximum heart rate, and the RS consisted of 3 sets of 10 repetitions of eight exercises. During the CS, subjects performed no exercise. Before and after exercise, and after 30 minutes of recovery, blood samples were analyzed for plasma lactate and serum growth hormone, insulin-like growth factor 1, testosterone, estradiol, dehydroepiandrosterone, and cortisol. Samples were taken during the CS at the same intervals as during the exercise sessions. There were no age-related differences in intensity measures during exercise. Absolute change from baseline in testosterone (p <.001), estradiol (p <.05), and growth hormone (p <.01) was significantly greater in the ES and RS compared with that in the CS. Absolute change in dehydroepiandrosterone was significantly greater in the RS only (p <.05). Results indicate that an acute bout of exercise can increase concentrations of anabolic hormones in females across a wide age range.

Endogenous anabolic hormone responses to endurance versus resistance exercise and training in women

Research in exercise endocrinology has flourished over the past few decades. In general, research examining short- and long-term hormone responses to endurance exercise preceded studies on resistance exercise, and research on women lagged behind research on men. Sufficient data are now available to allow a comparison of endogenous anabolic hormone responses to endurance versus resistance exercise and training in women. Circulating levels of testosterone, dehydroepiandrosterone, dehydroepiandrosterone sulphate, estradiol, growth hormone and cortisol have been shown to increase in response to an acute bout of endurance exercise in women. However, only growth hormone, estradiol and cortisol have been reported to increase following resistance exercise. Hormone changes following training, either endurance or resistance, have been variable, probably because of differences in experimental design and major differences in the length, intensity and volume of training programmes. With the notable exception of growth hormone, the anabolic hormones reviewed here appear to decline with endurance training. Resistance training has little effect on resting hormone levels, except insulin-like growth factor-I, which has been shown to increase following a training programme. These hormone changes potentially have both metabolic and hypertrophic implications, and future research needs to focus on the biological significance of these adaptations.

Effects of a sports nutrition bar on endurance running performance

The Access bar claims to contain adenosine antagonists and a precise mixture of macronutrients that are purported to improve aerobic performance by increasing fat metabolism and providing sustained exogenous energy. The purpose of this research was to examine the effect of the Access bar on endurance running performance. Twelve active, healthy runners completed 5 sessions: a V(O)2 max test, a 30-minute familiarization session, and 3 experimental sessions. During each experimental session subjects ran a self-paced, simulated race on a treadmill (approximately 55 minutes) until they had completed a set energy expenditure target (0.8368 kJ x 60 minutes x body mass). Fifteen minutes before exercise subjects received either the Access bar and water, Uncle Tobys Peanut Butter Muesli Bar and water, or Crystal Light, using a randomized, double-blind design. Heart rate, oxygen consumption, respiratory exchange ratio, and running speed were measured every minute during testing. Blood lactate and rating of perceived exertion were assessed at selected intervals; time to finish was also recorded. Analysis of variance showed no significant difference between the 3 treatments in any of the measures. These results do not support the use of the Access Sports Nutrition Bar to enhance endurance running performance of approximately one hour.

Hormone responses to resistance vs. endurance exercise in premenopausal females

Sixteen, cross-trained, premenopausal women participated in an endurance, resistance, and control session to compare hormone responses. The resistance session included 3 sets of eight exercises at 10 RM intensity. The endurance session consisted of a 40-min cycling protocol at 75% of maximal heart rate. During the control session, subjects rested for 35 min. Serum DHEA, estradiol, testosterone, growth hormone, IGF-I, cortisol, and plasma lactate concentrations were measured pre-exercise, post-exercise, and 30 min into recovery. Differences in intensity variables existed between the three sessions. Endurance exercise elicited increases in growth hormone, estradiol, and testosterone compared to the control session, and growth hormone increased after the resistance compared to the control session. The exercise protocols used in this study indicate that an acute bout of exercise can stimulate the endocrine system in premenopausal females. In addition, these results indicate that differences exist between these two exercise protocols when compared to a control session.

Preliminary evaluation of a video questionnaire to assess activity levels of children

PURPOSE

The purpose of this study was to explore the validity of the Assessment of Young Children's Activity Using Video Technology (ACTIVITY) self-report instrument in assessing previous-day physical activity.

METHODS

Forty-seven third-grade children (mean age 7.72 +/- 0.45, 41% female) from one elementary school completed the ACTIVITY on one weekday. To evaluate concurrent validity, children wore a Caltrac accelerometer and a Polar Vantage XL heart rate monitor on the day before completing the ACTIVITY. An ACTIVITY score from six time-anchored questions was obtained from the ACTIVITY. Mean Caltrac counts per minute (CNTSMIN), average activity heart rates, and cumulative minutes at or above 50% of heart rate reserve (50% HRR) were calculated for the entire day (7:00 a.m. to 7:00 p.m.).

RESULTS

Significant Pearson product-moment correlations were observed between the ACTIVITY score and CNTSMIN (r = 0.40, P < 0.001) and 50% HRR (r = 0.50, P < 0.001). Answers from four of six time-anchored questions correlated significantly with heart rate scores during those time periods (r = 0.30-0.49).

CONCLUSIONS

This exploratory study suggests that the ACTIVITY self-report instrument is a moderately valid instrument for measuring general activity levels of young children during the school year, including during specified periods of time. The potential for video technology to facilitate accurate physical activity recall in young children warrants further study.

Physical activity assessment options within the context of the Canadian Physical Activity, Fitness, and Lifestyle Appraisal

The Canadian Physical Activity, Fitness, and Lifestyle Appraisal (CPAFLA) is a standardized battery of tests that is commonly used to assess asymptomatic individuals. This paper reviews evidence concerning the reliability, validity, and utility of the procedure currently used to assess habitual physical activity in the CPAFLA and surveys available physical activity assessment options. Special considerations related to age, gender, ethnicity, seasonal variations, and within-week variance are discussed. The potential assessment options are discussed with consideration given to the logistical and pragmatic constraints inherent in the CPAFLA. New technologies for future assessment of physical activity are briefly presented and recommendations for future research forwarded.

Secular trends in the body mass index of Canadian children

BACKGROUND

Various changes in society have created the opportunity for more sedentary behaviour and the consumption of food that is high in kilojoules, which may lead to a progressive increase in body mass over time. The purpose of this study was to examine secular changes in the body mass index (BMI) of Canadian children between 1981 and 1996.

METHODS

Nationally representative data from the 1981 Canada Fitness Survey, the 1988 Campbell's Survey on the Well-being of Canadians and the 1996 National Longitudinal Survey of Children and Youth were used in the analysis. Regression analyses were used to assess population changes in BMI from 1981 to 1996 for children aged 7-13 years. Changes in the distribution of BMI results were evaluated by plotting the residuals from regression analyses of BMI on age, assessed separately by sex, using the 1981 data as baseline. The proportions of children exceeding the 85th and 95th age- and sex-specific percentiles from the 1981 (baseline) data were also calculated.

RESULTS

Since 1981, BMI has increased at the rate of nearly 0.1 kg/m2 per year for both sexes at most ages, indicating a clear secular trend toward an increase in BMI of Canadian children. The prevalence of overweight among boys increased from 15% in 1981 to 28.8% in 1996 and among girls from 15% to 23.6%. The prevalence of obesity in children more than doubled over that period, from 5% to 13.5% for boys and 11.8% for girls.

INTERPRETATION

Secular trends indicate that Canadian children aged 7-13 years are becoming progressively overweight and obese.

The effects of acute phosphate supplementation in subjects of different aerobic fitness levels

Six trained cyclists (high-fitness group) and six untrained individuals (low-fitness group), performed a 20-min cycle ergometer exercise test at 70% of maximum oxygen consumption (VO2max) followed by a 30-min rest period and then an incremental ride to exhaustion on two occasions, 1 week apart. Ninety minutes prior to exercise subjects consumed a drink containing either 22.2 g dibasic calcium phosphate (DCP; treatment) or calcium carbonate (placebo). Blood was drawn prior to drink ingestion, during submaximal exercise, during recovery and at exhaustion for determination of blood 2,3-DPG, blood ATP, plasma lactate, plasma phosphate, haemoglobin and haematocrit. Throughout exercise, cardiorespiratory variables [oxygen uptake (VO2), minute ventilation, (VE), respiratory exchange ratio, heart rate and oxygen pulse] were monitored, and ratings of perceived exertion obtained. Although there was a trend for the low-fitness group to have a higher plasma phosphate concentration prior to treatment ingestion, no treatment effects on plasma phosphate were noted at any sample time in either group. 2,3-DPG, VO2, oxygen pulse, VE, time to exhaustion and VO2max were significantly higher in the high-fitness group; however, no differences in these variables were observed as a result of phosphate ingestion. Plasma lactate was significantly lower in the high-fitness group during the submaximal exercise and the recovery period, but again phosphate ingestion had no effect. These results suggest that acute DCP supplementation is not effective as an ergogenic aid and that aerobic fitness level does not affect the response to phosphate supplementation.