Biomedical subjects

Mark S Tremblay

Publications and source records attributed to Mark S Tremblay.

13 recordsLinked to original sources

PubMed2006

Technical reliability assessment of three accelerometer models in a mechanical setup.

PURPOSE: To determine which of the three most commonly used accelerometer models has the best intra- and interinstrument reliability using a mechanical laboratory setup. Secondly, to determine the effects that acceleration and frequency have on these reliability measures. METHODS: Three experiments were performed. In the first, five each of the Actical, Actigraph, and RT3 accelerometers were placed on a hydraulic shaker plate and simultaneously accelerated in the vertical plane at varying accelerations and frequencies. Six different conditions of varying intensity were used to produce a range of accelerometer counts. Reliability was calculated using standard deviation, standard error of the measurement, coefficient of variation, and intraclass correlation coefficients. In the second and third experiments, 39 Actical and 50 Actigraph accelerometers were put through the same six conditions. RESULTS: Experiment 1 showed poor reliability in the RT3 (intra- and interinstrument CV > 40%). Experiments 2 and 3 clearly indicated that the Actical (CVintra = 0.5%, CVinter = 5.4%) was more reliable than the Actigraph (CVintra = 3.2%, CVinter = 8.6%). Variability in the Actical was negatively related to the acceleration of the condition, whereas no relationship was found between acceleration and reliability in the Actigraph. Variability in the Actigraph was negatively related to the frequency of the condition, whereas no relationship was found between frequency and reliability in the Actical. CONCLUSION: Of the three accelerometer models measured in this study, the Actical had the best intra- and interinstrument reliability. However, discrepant trends in the variability of Actical and Actigraph counts across accelerations and frequencies preclude the selection of a superior model. More work is needed to understand why accelerometers designed to measure the same thing behave so differently.

Acceleration↗

PubMed2005

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.

Adaptation, Physiological↗

PubMed2005

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.

Adolescent↗

PubMed2005

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.

Adult↗

PubMed2004

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.

Dehydroepiandrosterone↗

PubMed2004

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.

Aging↗

PubMed2003

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.

Adolescent↗

PubMed2003

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.

Adolescent↗

PubMed2002

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.

Adult↗

PubMed2002

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.

Adaptation, Physiological↗

PubMed2002

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.

Adult↗

PubMedDate not supplied

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.

Adult↗

PubMedDate not supplied

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.

Adult↗