Showing papers in "Medicine and Science in Sports and Exercise in 2009"

Progressive Statistics for Studies in Sports Medicine and Exercise Science

Abstract: Statistical guidelines and expert statements are now available to assist in the analysis and reporting of studies in some biomedical disciplines. We present here a more progressive resource for sample-based studies, meta-analyses, and case studies in sports medicine and exercise science. We offer forthright advice on the following controversial or novel issues: using precision of estimation for inferences about population effects in preference to null-hypothesis testing, which is inadequate for assessing clinical or practical importance; justifying sample size via acceptable precision or confidence for clinical decisions rather than via adequate power for statistical significance; showing SD rather than SEM, to better communicate the magnitude of differences in means and nonuniformity of error; avoiding purely nonparametric analyses, which cannot provide inferences about magnitude and are unnecessary; using regression statistics in validity studies, in preference to the impractical and biased limits of agreement; making greater use of qualitative methods to enrich sample-based quantitative projects; and seeking ethics approval for public access to the depersonalized raw data of a study, to address the need for more scrutiny of research and better meta-analyses. Advice on less contentious issues includes the following: using covariates in linear models to adjust for confounders, to account for individual differences, and to identify potential mechanisms of an effect; using log transformation to deal with nonuniformity of effects and error; identifying and deleting outliers; presenting descriptive, effect, and inferential statistics in appropriate formats; and contending with bias arising from problems with sampling, assignment, blinding, measurement error, and researchers' prejudices. This article should advance the field by stimulating debate, promoting innovative approaches, and serving as a useful checklist for authors, reviewers, and editors.

Exercise and physical activity for older adults

Abstract: The purpose of this Position Stand is to provide an overview of issues critical to understanding the importance of exercise and physical activity in older adult populations. The Position Stand is divided into three sections: Section 1 briefly reviews the structural and functional changes that characterize normal human aging, Section 2 considers the extent to which exercise and physical activity can influence the aging process, and Section 3 summarizes the benefits of both long-term exercise and physical activity and shorter-duration exercise programs on health and functional capacity. Although no amount of physical activity can stop the biological aging process, there is evidence that regular exercise can minimize the physiological effects of an otherwise sedentary lifestyle and increase active life expectancy by limiting the development and progression of chronic disease and disabling conditions. There is also emerging evidence for significant psychological and cognitive benefits accruing from regular exercise participation by older adults. Ideally, exercise prescription for older adults should include aerobic exercise, muscle strengthening exercises, and flexibility exercises. The evidence reviewed in this Position Stand is generally consistent with prior American College of Sports Medicine statements on the types and amounts of physical activity recommended for older adults as well as the recently published 2008 Physical Activity Guidelines for Americans. All older adults should engage in regular physical activity and avoid an inactive lifestyle.

Progression Models in Resistance Training for Healthy Adults

Abstract: In order to stimulate further adaptation toward specific training goals, progressive resistance training (RT) protocols are necessary The optimal characteristics of strength-specific programs include the use of concentric (CON), eccentric (ECC), and isometric muscle actions and the performance of bilateral and unilateral single- and multiple-joint exercises In addition, it is recommended that strength programs sequence exercises to optimize the preservation of exercise intensity (large before small muscle group exercises, multiple-joint exercises before single-joint exercises, and higher-intensity before lower-intensity exercises) For novice (untrained individuals with no RT experience or who have not trained for several years) training, it is recommended that loads correspond to a repetition range of an 8-12 repetition maximum (RM) For intermediate (individuals with approximately 6 months of consistent RT experience) to advanced (individuals with years of RT experience) training, it is recommended that individuals use a wider loading range from 1 to 12 RM in a periodized fashion with eventual emphasis on heavy loading (1-6 RM) using 3- to 5-min rest periods between sets performed at a moderate contraction velocity (1-2 s CON; 1-2 s ECC) When training at a specific RM load, it is recommended that 2-10% increase in load be applied when the individual can perform the current workload for one to two repetitions over the desired number The recommendation for training frequency is 2-3 d·wk -1 for novice training, 3-4 d·wk -1 for intermediate training, and 4-5 d·wk -1 for advanced training Similar program designs are recommended for hypertrophy training with respect to exercise selection and frequency For loading, it is recommended that loads corresponding to 1-12 RM be used in periodized fashion with emphasis on the 6-12 RM zone using 1- to 2-min rest periods between sets at a moderate velocity Higher volume, multiple-set programs are recommended for maximizing hypertrophy Progression in power training entails two general loading strategies: 1) strength training and 2) use of light loads (0-60% of 1 RM for lower body exercises; 30-60% of 1 RM for upper body exercises) performed at a fast contraction velocity with 3-5 min of rest between sets for multiple sets per exercise (three to five sets) It is also recommended that emphasis be placed on multiple-joint exercises especially those involving the total body For local muscular endurance training, it is recommended that light to moderate loads (40-60% of 1 RM) be performed for high repetitions (>15) using short rest periods (<90 s) In the interpretation of this position stand as with prior ones, recommendations should be applied in context and should be contingent upon an individual's target goals, physical capacity, and training status

Appropriate Physical Activity Intervention Strategies for Weight Loss and Prevention of Weight Regain for Adults

Abstract: Overweight and obesity affects more than 66% of the adult population and is associated with a variety of chronic diseases. Weight reduction reduces health risks associated with chronic diseases and is therefore encouraged by major health agencies. Guidelines of the National Heart, Lung, and Blood Institute (NHLBI) encourage a 10% reduction in weight, although considerable literature indicates reduction in health risk with 3% to 5% reduction in weight. Physical activity (PA) is recommended as a component of weight management for prevention of weight gain, for weight loss, and for prevention of weight regain after weight loss. In 2001, the American College of Sports Medicine (ACSM) published a Position Stand that recommended a minimum of 150 min wk(-1) of moderate-intensity PA for overweight and obese adults to improve health; however, 200-300 min wk(-1) was recommended for long-term weight loss. More recent evidence has supported this recommendation and has indicated more PA may be necessary to prevent weight regain after weight loss. To this end, we have reexamined the evidence from 1999 to determine whether there is a level at which PA is effective for prevention of weight gain, for weight loss, and prevention of weight regain. Evidence supports moderate-intensity PA between 150 and 250 min wk(-1) to be effective to prevent weight gain. Moderate-intensity PA between 150 and 250 min wk(-1) will provide only modest weight loss. Greater amounts of PA (>250 min wk(-1)) have been associated with clinically significant weight loss. Moderate-intensity PA between 150 and 250 min wk(-1) will improve weight loss in studies that use moderate diet restriction but not severe diet restriction. Cross-sectional and prospective studies indicate that after weight loss, weight maintenance is improved with PA >250 min wk(-1). However, no evidence from well-designed randomized controlled trials exists to judge the effectiveness of PA for prevention of weight regain after weight loss. Resistance training does not enhance weight loss but may increase fat-free mass and increase loss of fat mass and is associated with reductions in health risk. Existing evidence indicates that endurance PA or resistance training without weight loss improves health risk. There is inadequate evidence to determine whether PA prevents or attenuates detrimental changes in chronic disease risk during weight gain.

Sitting time and mortality from all causes, cardiovascular disease, and cancer.

Abstract: KATZMARZYK, P. T., T. S. CHURCH, C. L. CRAIG, and C. BOUCHARD. Sitting Time and Mortality from All Causes, Cardiovascular Disease, and Cancer. Med. Sci. Sports Exerc., Vol. 41, No. 5, pp. 998–1005, 2009. Purpose: Although moderate-tovigorous physical activity is related to premature mortality, the relationship between sedentary behaviors and mortality has not been fully explored and may represent a different paradigm than that associated with lack of exercise. We prospectively examined sitting time and mortality in a representative sample of 17,013 Canadians 18–90 yr of age. Methods: Evaluation of daily sitting time (almost none of the time, one fourth of the time, half of the time, three fourths of the time, almost all of the time), leisure time physical activity, smoking status, and alcohol consumption was conducted at baseline. Participants were followed prospectively for an average of 12.0 yr for the ascertainment of mortality status. Results: There were 1832 deaths (759 of cardiovascular disease (CVD) and 547 of cancer) during 204,732 person-yr of follow-up. After adjustment for potential confounders, there was a progressively higher risk of mortality across higher levels of sitting time from all causes (hazard ratios (HR): 1.00, 1.00, 1.11, 1.36, 1.54; P for trend G0.0001) and CVD (HR: 1.00, 1.01, 1.22, 1.47, 1.54; P for trend G0.0001) but not cancer. Similar results were obtained when stratified by sex, age, smoking status, and body mass index. Age-adjusted all-cause mortality rates per 10,000 person-yr of follow-up were 87, 86, 105, 130, and 161 (P for trend G0.0001) in physically inactive participants and 75, 69, 76, 98, 105 (P for trend = 0.008) in active participants across sitting time categories. Conclusions: These data demonstrate a dose–response association between sitting time and mortality from all causes and CVD, independent of leisure time physical activity. In addition to the promotion of moderate-to-vigorous physical

American College of Sports Medicine position stand. Nutrition and athletic performance.

Abstract: It is the position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine that physical activity, athletic performance, and recovery from exercise are enhanced by optimal nutrition. These organizations recommend appropriate selection of foods and fluids, timing of intake, and supplement choices for optimal health and exercise performance. This updated position paper couples a rigorous, systematic, evidence-based analysis of nutrition and performance-specific literature with current scientific data related to energy needs, assessment of body composition, strategies for weight change, nutrient and fluid needs, special nutrient needs during training and competition, the use of supplements and ergogenic aids, nutrition recommendations for vegetarian athletes, and the roles and responsibilities of the sports dietitian. Energy and macronutrient needs, especially carbohydrate and protein, must be met during times of high physical activity to maintain body weight, replenish glycogen stores, and provide adequate protein to build and repair tissue. Fat intake should be sufficient to provide the essential fatty acids and fat-soluble vitamins and to contribute energy for weight maintenance. Although exercise performance can be affected by body weight and composition, these physical measures should not be a criterion for sports performance and daily weigh-ins are discouraged. Adequate food and fluid should be consumed before, during, and after exercise to help maintain blood glucose concentration during exercise, maximize exercise performance, and improve recovery time. Athletes should be well hydrated before exercise and drink enough fluid during and after exercise to balance fluid losses. Sports beverages containing carbohydrates and electrolytes may be consumed before, during, and after exercise to help maintain blood glucose concentration, provide fuel for muscles, and decrease risk of dehydration and hyponatremia. Vitamin and mineral supplements are not needed if adequate energy to maintain body weight is consumed from a variety of foods. However, athletes who restrict energy intake, use severe weight-loss practices, eliminate one or more food groups from their diet, or consume unbalanced diets with low micronutrient density may require supplements. Because regulations specific to nutritional ergogenic aids are poorly enforced, they should be used with caution and only after careful product evaluation for safety, efficacy, potency, and legality. A qualified sports dietitian and, in particular, the Board Certified Specialist in Sports Dietetics in the United States, should provide individualized nutrition direction and advice after a comprehensive nutrition assessment.

The Effect of Acute Aerobic and Resistance Exercise on Working Memory

Abstract: PONTIFEX, M. B., C. H. HILLMAN, B. FERNHALL, K. M. THOMPSON, and T. A. VALENTINI. The Effect of Acute Aerobic and Resistance Exercise on Working Memory. Med. Sci. Sports Exerc., Vol. 41, No. 4, pp. 927–934, 2009. Purpose: The goal of this investigation was to assess the influence of acute bouts of aerobic versus resistance exercise on the executive control of working memory. Methods: Twenty-one young adult participants completed a cardiorespiratory fitness test and maximal strength tests. On subsequent days, task performance measures of reaction time (RT) and accuracy were collected while participants completed a modified Sternberg working memory task before the start of, immediately after, and 30 min after an intervention consisting of 30 min of either resistance or aerobic exercise and a seated rest control. Results: Findings indicated shorter RT immediately and 30 min after acute aerobic exercise relative to the preexercise baseline with no such effects observed after resistance exercise or seated rest. Further, in the aerobic condition, a larger reduction in RT from the baseline occurred during task conditions requiring increased working memory capacity. Again, no effect was observed in the resistance exercise or the seated rest conditions. Conclusion: These data extend the current knowledge base by indicating that acute exercise-induced changes in cognition are disproportionately related to executive

Validity and reliability of short-term heart-rate variability from the Polar S810

Abstract: Purpose: To assess the validity and the reliability of short-term resting heart-rate variability (HRV) measures obtained using the Polar S810 heart-rate monitor and accompanying software. Methods: Measures of HRV were obtained from 5-min R to R wave (RR) interval data for 19 males and 14 females during 10 min of quiet rest on three separate occasions at 1-wk intervals using the Polar S8.10. Criterion measures of HRV were obtained simultaneously using the CardioPerfect (CP; Medical Graphics Corporation, St Paul, MN) 12-lead ECG module. Measures of validity of the Polar S810 were estimated by regression analysis, and measures of reliability of both. devices were estimated by analysis of change scores. Measures of the SD of normal-to-normal intervals (SDNN), the root mean square of successive differences (RMSSD), and the low-frequency (LF) and the high-frequency (HF) spectral power and their ratio (LF/HF) were analyzed after log transformation, whereas mean RR and LF and HF in normalized units were analyzed without transformation. Results: There were marginal differences between the Polar and the CP mean measures of HRV, and the uncertainty in the differences was small. The Polar S810 demonstrated high correlations (0.85-0.99) with CP for all measures of HRV indicating good to near-perfect validity. Except for the low- and the high-frequency normalized units, Polar S810 did not add any substantial technical error to the within-subject variability in the repeated measurements of HRV. Conclusion: HRV measures obtained with the Polar S810 and accompanying software have no appreciable bias or additional random error in comparison with criterion measures, but the measures are inherently unreliable over a 1-wk interval. Reliability of HRV from longer (e.g., 10 min) and/or consecutive 5-min RR recordings needs to be investigated with the Polar and criterion instruments. Copyright © 2008 by the American College of Sports Medicine.

Accelerometer-determined steps per day in US adults.

Abstract: Introduction: The 2005-2006 National Health and Nutrition Examination Survey (NHANES) released, for the first time, the ActiGraph AM-7164 accelerometer-defined step data in addition to time in intensity (defined by activity counts). This accelerometer is known to have a lower sensitivity threshold than accepted pedometers, leading to relatively higher step estimates. Purpose: The purpose of this analysis is to provide the population- and sex-specific epidemiology of accelerometer-determined steps per day with and without censoring steps detected at the lowest end of the activity spectrum (i.e., inactivity). Methods: The analysis sample represents 3744 participants >=20 yr who had at least one valid day (i.e., at least 10 h) of monitoring. Means (SE) for steps per day were computed using all steps (i.e., uncensored) and again after censoring those steps taken at an intensity <500 activity counts per minute (indicative of inactivity intensity). Results: On average, US adults took 9676 +/- 107 uncensored steps per day or 6540 +/- 106 censored steps per day. Conclusions: The results of this nationally representative survey indicate that US adults take approximately 10,000 uncensored accelerometer-determined steps per day, which is improbable considering other studies of free-living physical activity in the United States. Until a more valid conversion factor is ascertained for translating accelerometer and pedometer-determined steps, our use of the <500 activity count per minute threshold holds considerable merit.

Measuring total and domain-specific sitting: a study of reliability and validity.

Abstract: MARSHALL, A. L., Y. D. MILLER, N. W. BURTON, and W. J. BROWN. Measuring Total and Domain-Specific Sitting: A Study of Reliability and Validity. Med. Sci. Sports Exerc., Vol. 42, No. 6, pp. 1094-1102, 2010. Purpose: Although independent relationships between sitting behaviors (mainly television viewing) and health outcomes have been reported, few studies have examined the measurement properties of self-report sitting questions. This study assessed gender-specific test-retest reliability and validity of a questionnaire that assessed time spent sitting on weekdays and weekend days: 1) traveling to and from places, 2) at work, 3) watching television, 4) using a computer at home, and 5) for leisure, not including television. Methods: Test-retest reliability of domain-specific sitting time (min.d(-1)) on weekdays and weekend days was assessed using data collected on two occasions (median = 11 d apart). Validity of domain-specific self-reported sitting time on weekdays and weekend days was assessed against log data and sedentary accelerometer data. Results: Complete repeat questionnaire and log data were obtained from 157 women (aged 51-59 yr) and 96 men (aged 45-63 yr). Reliability coefficients were high for weekday sitting time at work, watching television, and using a computer at home (r = 0.84-0.78) but lower for weekend days across all domains (r = 0.23-0.74). Validity coefficients were highest for weekday sitting time at work and using a computer at home (r = 0.69-0.74). With the exception of computer use and watching television for women, validity of the weekend-day sitting time items was low. Conclusions: This study confirms the importance of measuring domain-and day-specific sitting time. The measurement properties of questions that assess structured domain-specific and weekday sitting time were acceptable and may be used in future studies that aim to elucidate associations between domain-specific sitting and health outcomes.

Ankle instability is associated with balance impairments: a meta-analysis.

Abstract: ARNOLD, B. L., S. DE LA MOTTE, S. LINENS and S. E. ROSS. Ankle Instability Is Associated with Balance Impairments: A Meta-Analysis. Med. Sci. Sports Exere., Vol: 41, No. 5, pp. 1048-1062, 2009. Purpose: Our primary purpose was to determine whether balance impairments were associated with functional ankle instability (FAI). Methods: Our literature search consisted of four parts: 1) an electronic search of PubMed, CINAHL, pre-CINAHL, and SPORTDiscus; 2) a forward search of articles selected from the electronic search using the Science Citation Index; 3) a hand search of the previously selected articles; and 4) a direct contact with corresponding authors of the previously selected articles. We initially identified 145 articles and narrowed these to 23 for inclusion in the metaanalysis. Identified outcomes were categorized by measurement units and balance task type (i.e., dynamic or static). Each study was coded based on whether inclusion or exclusion criteria were identified. Our statistical analysis included fixed, random, or mixed effect analyses based on the presence of within study heterogeneity and whether categories were being compared. Results: FAI was associated with poorer balance (standard difference of the mean [SDM] = 0.455, 95% confidence interval = 0.334-0.577, Z = 7.34, P < 0.001), but no difference existed between dynamic and static measure categories (Q = 3.44, P = 0.063). However, there was a significant difference between the dynamic measures (Q = 6.22, P = 0.0 13) with both time to stabilization and the Star Excursion Balance Test producing significant SDM and between static measures (Q = 13.00, P = 0.012). with the linear, time, velocity, and other measurement categories (but not area) producing significant SDM. Examination of individual outcomes revealed that time in balance and foot lifts produced very large SDM (3.3 and 4.8, respectively). Conclusion: FAI is associated with impaired balance. Due to the relatively large effect sizes

Detection of type, duration, and intensity of physical activity using an accelerometer.

Abstract: Objective: The aim of this study was to develop models for the detection of type, duration, and intensity of human physical activity using one triaxial accelerometer. Methods: Twenty subjects (age = 29 +/- 6 yr, BMI = 23.6 +/- 3.2 kg[middle dot]m-2) performed 20 selected activities, including walking, running, and cycling, wearing one triaxial accelerometer mounted on the lower back. Identification of activity type was based on a decision tree. The decision tree evaluated attributes (features) of the acceleration signal. The features were measured in intervals of defined duration (segments). Segment size determined the time resolution of the decision tree to assess activity duration. Decision trees with a time resolution of 0.4, 0.8, 1.6, 3.2, 6.4, and 12.8 s were developed, and the respective classification performances were evaluated. Multiple linear regression was used to estimate speed of walking, running, and cycling based on acceleration features. Results: Maximal accuracy for the classification of activity type (93%) was reached when the segment size of analysis was 6.4 or 12.8 s. The smaller the segment size, the lower the classification accuracy achieved. Segments of 6.4 s gave the highest time resolution for measuring activity duration without decreasing the classification accuracy. The developed models estimated walking, running, and cycling speeds with a standard error of 0.20, 1.26, and 1.36 km[middle dot]h-1, respectively. Conclusions: This study demonstrated the ability of a triaxial accelerometer in detecting type, duration, and intensity of physical activity using models based on acceleration features. Future studies are needed to validate the presented models in free-living conditions.

Athletic performance and vitamin D.

Abstract: CANNELL, J. J., B. W. HOLLIS, M. B. SORENSON, T. N. TAFT, and J. J. ANDERSON. Athletic Performance and Vitamin D. Med. Sci. Sports Exerc., Vol. 41, No. 5, pp. 1102–1110, 2009. Purpose: Activated vitamin D (calcitriol) is a pluripotent pleiotropic secosteroid hormone. As a steroid hormone, which regulates more than 1000 vitamin D–responsive human genes, calcitriol may influence athletic performance. Recent research indicates that intracellular calcitriol levels in numerous human tissues, including nerve and muscle tissue, are increased when inputs of its substrate, the prehormone vitamin D, are increased. Methods: We reviewed the world’s literature for evidence that vitamin D affects physical and athletic performance. Results: Numerous studies, particularly in the German literature in the 1950s, show vitamin D–producing ultraviolet light improves athletic performance. Furthermore, a consistent literature indicates physical and athletic performance is seasonal; it peaks when 25-hydroxy-vitamin D [25(OH)D] levels peak, declines as they decline, and reaches its nadir when 25(OH)D levels are at their lowest. Vitamin D also increases the size and number of Type II (fast twitch) muscle fibers. Most cross-sectional studies show that 25(OH)D levels are directly associated with musculoskeletal performance in older individuals. Most randomized controlled trials, again mostly in older individuals, show that vitamin D improves physical performance. Conclusions: Vitamin D may improve athletic performance in vitamin D–deficient athletes. Peak athletic performance may occur when 25(OH)D levels approach those obtained by natural, full-body, summer sun exposure, which is at least 50 ngImL j1 . Such 25(OH)D levels may also protect the athlete from several acute and chronic medical

Age differences in the relation of perceived neighborhood environment to walking.

Abstract: PURPOSE:: The strength of the relationship of environment to physical activity may differ by age group. Older adults were expected to be more affected by environmental attributes than younger adults. The present study examined age-related differences in associations between perceived neighborhood environment and physical activity. METHODS:: Participants were 1623 adults aged 20 to 97 yr divided into five groups: ages 20-39, 40-49, 50-65, 66-75, and 76+. They were recruited from King County/Seattle, WA, neighborhoods selected to vary in land use and median income. Participants completed questionnaires about neighborhood environment attributes and walking for transportation and for leisure purposes. Neighborhood environment, within a 15- to 20-min walk from home, was measured on nine attributes with the validated Neighborhood Environment Walkability Scale questionnaire: residential density, proximity to nonresidential land uses, ease of access to nonresidential uses, street connectivity, walking/cycling facilities, esthetics, pedestrian traffic safety, crime safety, and proximity to recreation facilities. Participants reported frequency and duration of walking using the validated International Physical Activity Questionnaire and the Community Healthy Activities Model Program for Seniors. Partial correlations were computed, adjusting for demographics. RESULTS:: Walking for transportation was significantly related to multiple perceived neighborhood attributes in all age groups, although walking for leisure was not. Walking for transportation was significantly related to almost all neighborhood environment variables in the youngest age group. In contrast, only two environmental attributes, proximity to nonresidential uses (like shops) and recreation facilities, were moderately correlated with walking for transportation in the two oldest groups. CONCLUSION:: Communities need to be designed with many favorable environmental attributes to support walking for transportation among younger adults. Having nonresidential destinations and recreation facilities within walking distance may be among the most important attributes to support older adults' physical activity. Language: en

Low Muscle Fitness Is Associated with Metabolic Risk in Youth

Abstract: STEENE-JOHANNESSEN, J., S. A. ANDERSSEN, E. KOLLE, and L. B. ANDERSEN. Low Muscle Fitness Is Associated withMetabolic Risk in Youth. Med. Sci. Sports Exerc., Vol. 41, No. 7, pp. 1361–1367, 2009. Purpose: To examine the independentassociations of muscle fitness and cardiorespiratory fitness with clustered metabolic risk in youth. Methods: In 2005–2006, a cohort of9- and 15-yr-olds (N = 2818) was randomly selected from all regions of Norway. The participation rate was 89% and 74% amongthe 9- and 15-yr-olds, respectively. We assessed muscular strength by measuring explosive, isometric, and endurance strength.Cardiorespiratory fitness was measured directly as peak oxygen uptake during a cycle ergometry test. Risk factors included in thecomposite risk factor score (sum of z-scores) were systolic blood pressure, triglyceride, high-density lipoprotein cholesterol, insulinresistance, and waist circumference. Results: Muscle fitness was negatively associated with clustered metabolic risk, independent ofcardiorespiratory fitness, and after adjustment for age, sex, and pubertal stage (A = j0.112, P G 0.001). Independent of muscle fitness,an inverse association was found between cardiorespiratory fitness and clustered metabolic risk (A = j0.337, P G 0.001). Moreover, theodds ratios for having clustered risk in the least fit quartile compared with the most fit quartile were 7.2 (95% confidence interval(CI) = 4.3–12.0) and 17.3 (95% CI = 9.2–32.7) for muscle fitness and cardiorespiratory fitness, respectively. Conclusions: Ourresults show that muscle fitness and cardiorespiratory fitness are independently associated with metabolic risk in youth.Key Words: CLUSTERED METABOLIC RISK, PHYSICAL FITNESS, CHILD, ADOLESCENT

Validity and reproducibility of motion sensors in youth: a systematic update.

Abstract: Purpose: To review recently published studies on the reproducibility, validity, and feasibility of motion sensors used to assess physical activity in healthy children and adolescents (2-18 yr). Methods: On October 2004, a systematic literature search in PubMed, EMBASE, and PsycINFO was performed. This search has been updated on October 2007. In this update, the clinimetric quality of three pedometers (Digi-Walker, Walk4Life, and Sun TrekLINQ) and nine accelerometers (ActiGraph, BioTrainer, StepWatch Activity Monitor, Actiwatch, Actical, Tritrac-R3D, RT3, ActivTracer, and Mini-Motionlogger) has been evaluated and compared using a checklist. Results: Thirty-two recently published clinimetric studies have been reviewed. All 12 motion sensors have been validated in youth in one or more studies. There is strong evidence for moderate validity of the StepWatch in children and adolescents (4-18 yr) and moderate to good validity of the ActiGraph in preschool children and young children (2-8 yr). There is less evidence for the reproducibility and feasibility of the 12 motion sensors. Strong evidence exists for good reproducibility of the ActiGraph in preschool children (2-4 yr). Conclusion: Compared to the review performed in 2004, there is increased evidence for the clinimetric quality of pedometers and accelerometers in youth. Most motion sensors seem reproducible, valid, and feasible in assessing physical activity in youth. © 2009 The American College of Sports Medicine.

A comparison of questionnaire, accelerometer, and pedometer: measures in older people.

Abstract: Purpose: To compare (i) the convergent validity of the self-report Zutphen Physical Activity Questionnaire with the 7-d objective physical activity (PA) measurement by accelerometers and pedometers and (ii) the construct validity of these measures by examining their associations with physical health and psychological and anthropometric variables. Methods: Five hundred and sixty community-dwelling people aged >=65 yr were invited from a UK primary care practice and 238 (43%) participated (mean age = 74, 53% male). PA was assessed subjectively by the Zutphen questionnaire (modified to include housework questions) and objectively by the 7-d accelerometer monitoring: a random half also had a pedometer. A questionnaire assessed health, disability, and psychological factors, and anthropometric assessment was performed. Results: Mean daily PA levels were as follows: Zutphen = 9.1 kcal[middle dot]kg-1[middle dot]d-1 (SD = 6.6 kcal[middle dot]kg-1[middle dot]d-1); accelerometer activity count = 226,648 (SD = 121,966); accelerometer step count = 6495 (SD = 3212); and pedometer step count = 6712 (SD = 3526). Zutphen score was moderately correlated with accelerometer activity count (R = 0.34, P < 0.001) and pedometer step count (R = 0.36, P < 0.001). Pedometer step count was highly correlated with accelerometer activity count (R = 0.82, P< 0.001) and accelerometer step count (R = 0.86, P < 0.001). Objective PA measures showed strong associations with health and anthropometric and psychological variables. Zutphen score was not significantly related to most health or anthropometric measures but was associated with psychological variables and provided information about activity type. Conclusions: Convergent validity was strong between accelerometers and pedometers but weaker between these and self-report Zutphen. Pedometers may be preferred to accelerometers for simple studies due to their lower cost. Objective measures had better construct validity, being more strongly associated with established PA determinants, and thus offered better value to researchers than the questionnaire, but the latter provided useful detail on activity type, so a combined approach to PA assessment may be preferable

A Randomized Trial to Increase Physical Activity in Breast Cancer Survivors

Abstract: Purpose:Interventions to increase physical activity among breast cancer survivors are needed to improve health and quality of life and possibly to reduce the risk of disease recurrence and early mortality. Therefore, we report the feasibility and preliminary outcomes of a pilot randomized tr

METs in adults while playing active video games: a metabolic chamber study.

Abstract: Purpose: Active video game systems controlled through arm gestures and motions (Nintendo Wii Sports) and video games controlled through force plate (Wii Fit Plus) are becoming increasingly popular. This study was performed to determine the energy expenditure (EE) during Wii Fit Plus and Wii Sports game activities. Methods: Twelve adult men and women performed all the activities of Wii Sports (five activities: golf, bowling, tennis, baseball, and boxing) and Wii Fit Plus (63 activities classified as yoga, resistance, balance, and aerobic exercises). Each activity was continued for at least 8 min to obtain a steady-state EE. Because EE was assessed in an open-circuit indirect metabolic chamber consisting of an airtight room (20,000 or 15,000 L), subjects were freed of apparatus to collect expired gas while playing the games. MET value was calculated from resting EE and steady-state EE during activity. Results: The mean MET values of all 68 activities were distributed over a wide range from 1.3 METs (Lotus Focus) to 5.6 METs (single-arm stand). The mean MET values in yoga, balance, resistance, and aerobic exercise of Wii Fit Plus and Wii Sports were 2.1, 2.0, 3.2, 3.4, and 3.0 METs, respectively. Forty-six activities (67%) were classified as light intensity ( 6.0 METs). Conclusions: Time spent playing one-third of the activities supplied by motion- and gesture-controlled video games can count toward the daily amount of exercise required according to the guidelines provided by the American College of Sports Medicine and the American Heart Association, which focus on 30 min of moderate-intensity daily physical activity 5 d[middle dot]wk-1.

Muscle Forces or Gravity: What Predominates Mechanical Loading on Bone?

Abstract: Most mechanical forces acting on the skeleton are generated either through impact with the ground (i.e., gravitational loading) or through muscle contractions (i.e., muscle loading). If one of these conduits for activating mechanotransduction in bone is more effective than the other with respect to developing or maintaining bone strength, this would have important clinical implications for prescribing physical activity for the prevention or treatment of osteoporosis. This section of the symposium considered whether there is evidence from studies of humans that the effectiveness of physical activity to preserve bone health is dependent on whether the activities stimulate the skeleton primarily through gravitational or muscle loading. Conclusive evidence is lacking, but several lines of research suggest that physical activities that involve impact forces, and therefore generate both gravitation and muscle loading, are most likely to have beneficial effects on bone metabolism and reduce fracture risk.

Validity and reliability of Omron pedometers for prescribed and self-paced walking.

Abstract: HOLBROOK, E. A., T. V. BARREIRA, and M. KANG. Validity and Reliability of Omron Pedometers for Prescribed and Self-Paced Walking. Med. Sci. Sports Exerc., Vol. 41, No. 3, pp. 669–673, 2009. Purpose: The purpose of this study was to examine the validity and reliability evidence for the Omron Healthcare HJ-151 and HJ-720ITC pedometers for prescribed and self-paced walking. Methods: A total of 47 adults (24 males, 23 females; age = 24 T 4.4 yr.; body mass index = 25.7 T 4.2 kgIm j2 ) participated in this study. Under prescribed walking conditions, 34 participants completed three randomized 100-m walking trials through a range of scripted walking speeds (slow, moderate, and very brisk) for each pedometer model. Under self-paced walking conditions, 31 participants completed one 1-mile walk on a standardized course for each model. HJ-151 pedometers were chosen at random from a pool of 54 devices and were worn along the waistband at the right hip, the left hip, and the midback, whereas HJ-720ITC pedometers were chosen from a pool of 24 devices and incorporated right pocket, left pocket, and backpack positions in addition to the three waist-mounted sites. Absolute percent error (APE) scores were calculated to examine pedometer accuracy between actual steps (a criterion measure) and pedometerdetermined steps. Coefficient of variation (CoV) was computed to describe interdevice reliability. Results: With the exception of the HJ-720ITC at the backpack position in the prescribed walking setting (mean APE = 3.4%), the HJ-151 and the HJ-720ITC accurately reported step counts under prescribed and self-paced conditions (all APE values G3.0%). Moreover, interdevice reliability evidence was established for the HJ-151 and the HJ-720ITC under prescribed and self-paced conditions (all CoV values G2.1%). Conclusions: The Omron HJ-151 and HJ-720ITC pedometers demonstrated validity and reliability at various mounting positions under prescribed and

Effects of stride length and running mileage on a probabilistic stress fracture model.

Abstract: Thefatiguelifeofboneisinverselyrelatedtost rainmagnitude.�Decreasingstridelengthisapoten tialmechanismof� strainreductionduringrunning.�Ifstridelengthi sdecreased,�thenumberofloadingcycleswillincr easeforagiven� mileage.�Itisunclearifincreasedloadingcycles� aredetrimentaltoskeletalhealthdespitereductio nsinstrain.� Purpose: �Todeterminetheeffectsofstridelengthandrunn ingmileageontheprobabilityoftibialstressfra cture.� Methods: �Tenmalesubjectsranovergroundattheirpreferre drunningvelocityduringtwoconditions:�preferred �stride� lengthand�10%�reductioninpreferredstridelength .�Forceplatformandkinematicdatawerecollected� concurrently.�A� combinationofexperimentalandmusculoskeletalmod elingtechniqueswasusedtodeterminejointcontac tforces� actingonthedistaltibia.�Peakinstantaneousjoin

Fatigue-Induced ACL Injury Risk Stems from a Degradation in Central Control

Abstract: Purpose:Fatigue contributes directly to anterior cruciate ligament (ACL) injury via promotion of high risk biomechanics. The potential for central fatigue to dominate this process, however, remains unclear. With centrally mediated movement behaviors being trainable, establishing this link se

Role of beta-alanine supplementation on muscle carnosine and exercise performance.

Abstract: In this narrative review, we present and discuss the current knowledge available on carnosine and beta-alanine metabolism as well as the effects of beta-alanine supplementation on exercise performance. Intramuscular acidosis has been attributed to be one of the main causes of fatigue during intense exercise. Carnosine has been shown to play a significant role in muscle pH regulation. Carnosine is synthesized in skeletal muscle from the amino acids l-histidine and beta-alanine. The rate-limiting factor of carnosine synthesis is beta-alanine availability. Supplementation with beta-alanine has been shown to increase muscle carnosine content and therefore total muscle buffer capacity, with the potential to elicit improvements in physical performance during high-intensity exercise. Studies on beta-alanine supplementation and exercise performance have demonstrated improvements in performance during multiple bouts of high-intensity exercise and in single bouts of exercise lasting more than 60 s. Similarly, beta-alanine supplementation has been shown to delay the onset of neuromuscular fatigue. Although beta-alanine does not improve maximal strength or VO2max, some aspects of endurance performance, such as anaerobic threshold and time to exhaustion, can be enhanced. Symptoms of paresthesia may be observed if a single dose higher than 800 mg is ingested. The symptoms, however, are transient and related to the increase in plasma concentration. They can be prevented by using controlled release capsules and smaller dosing strategies. No important side effect was related to the use of this amino acid so far. In conclusion, beta-alanine supplementation seems to be a safe nutritional strategy capable of improving high-intensity anaerobic performance.

Longitudinal study of physical activity and inactivity in preschoolers: the FLAME study.

Abstract: Purpose: To investigate patterns of activity and inactivity in a birth cohort of children followed from 3 to 5 yr and to investigate whether changes in activity occurred over time. Methods: Two hundred and forty-four children (44% female) were seen annually at 3, 4, and 5 yr. Physical activity and inactivity was measured by questionnaire (parent-proxy) and by Actical accelerometers for five consecutive days (24-h monitoring) each year in children and once in each parent for 7 d (69% with data). Results: Retention of participants was high (92%). Viable accelerometry data were obtained for 76-85% of children at each age. Reliability estimates ranged from 0.80 (3 yr) to 0.84 (5 yr). Day of the week, season, sex, hours of childcare, or birth order did not affect daily average accelerometry counts (AAC) at any age. Parental activity correlated weakly with the child's activity at 3 and 4 yr (r values = 0.17-0.28), but only the father's activity remained a significant predictor of the child's activity after adjustment for confounders. Children spent approximately 90 min[middle dot]d-1 in screen time (television, videos, DVD, and computers) with an additional 90 min in other sedentary activities (reading, drawing, and music). Physical activity was significantly reduced at 4 and 5 yr compared with 3 yr in both sexes, whether measured as AAC (24-h data, awake time only, weekend days, weekdays), time in moderate or vigorous activity, or from parental reports of activity. Conclusion: Levels of physical activity declined in boys and girls between the ages 3 and 4-5 yr, whether using objective measures or parental reports of activity

Brachial Artery Blood Flow Responses to Different Modalities of Lower Limb Exercise

Abstract: THIJSSEN, D. H. J., E. A. DAWSON, M. A. BLACK, M. T. E. HOPMAN, N. T. CABLE, and D. J. GREEN. Brachial Artery Blood Flow Responses to Different Modalities of Lower Limb Exercise. Med. Sci. Sports Exerc., Vol. 41, No. 5, pp. 1072-1079, 2009. Introduction/Purpose: Cycling is associated with a reproducible systolic anterograde and diastolic retrograde flow pattern in the brachial artery (BA) of the inactive upper limb, which results in endothelial nitric oxide (NO) release. The purpose of this study was to examine the impact of different types and intensities of lower limb exercise on the BA flow pattern. Methods: We examined BA blood flow and shear rate patterns during cycling, leg kicking, and walking exercise in 12 young subjects (24 T 3 yr). BA diameter, blood flow, and shear rate were assessed at baseline (1 min) and at three incremental intensity levels of cycling (60, 80, and 120 W), bilateral leg kicking (5, 7.5, and 10 kg), and walking (3, 4, and 5 kmIh j1 ), performed for 3 min each. Edge detection and wall tracking of high- resolution B-mode arterial ultrasound images, combined with synchronized Doppler waveform envelope analysis, were used to calculate conduit artery diameter and anterograde/retrograde blood flow and shear rate continuously across the cardiac cycle. Results: BA mean blood flow and shear rate increased significantly throughout each exercise protocol (P G 0.001), and BA anterograde blood flow and shear rate showed comparable increases throughout each protocol (P G 0.001). Retrograde blood flow and shear rate, however, demonstrated a significant increase during cycling and walking (P G 0.001) but not during leg kicking. Conclusion: Rhythmic lower limb exercise (cycling and walking) results in an increase in BA systolic anterograde blood flow and shear rate, directly followed by a large retrograde flow and shear rate. This typical pattern, previously linked with endothelial NO release, is not present during a different

The Western States 100-Mile Endurance Run: Participation and Performance Trends

Abstract: Purpose:Examine changes in demographics of participants and performance trends at the Western States 100-Mile Endurance Run (WSER) since its inception in 1974.Methods:Name, age, sex, and finish information was obtained on runners in the WSER from 1974 to 2007. Linear regression analyses, ANO

Body Composition and Strength Changes in Women with Milk and Resistance Exercise

Abstract: JOSSE, A. R., J. E. TANG, M. A. TARNOPOLSKY, and S. M. PHILLIPS. Body Composition and Strength Changes in Women with Milk and Resistance Exercise. Med. Sci. Sports Exerc., Vol. 42, No. 6, pp. 1122–1130, 2010. Purpose: We aimed to determine whether women consuming fat-free milk versus isoenergetic carbohydrate after resistance exercise would see augmented gains in lean mass and reductions in fat mass similar to what we observed in young men. Methods: Young women were randomized to drink either fat-free milk (MILK: n = 10; age (mean T SD) = 23.2 T 2.8 yr; BMI = 26.2 T 4.2 kgIm j2 ) or isoenergetic carbohydrate (CON: n =1 0; age =2 2.4T 2.4 yr; BMI = 25.2 T 3.8 kgIm j2 ) immediately after and 1 h after exercise (2 500 mL). Subjects exercised 5 dIwk j1 for 12 wk. Body composition changes were measured by dual-energy x-ray absorptiometry, and subjects’ strength and fasting blood were measured before and after training. Results: CON gained weight after training (CON: +0.86 T 0.4 kg, P G 0.05; MILK: +0.50 T 0.4 kg, P = 0.29). Lean mass increased with training in both groups (P G 0.01), with a greater net gain in MILK versus CON (1.9 T 0.2 vs 1.1 T 0.2 kg, respectively, P G 0.01). Fat mass decreased with training in MILK only (j1.6 T 0.4 kg, P G 0.01; CON: j0.3 T 0.3 kg, P = 0.41). Isotonic strength increased more in MILK than CON (P G 0.05) for some exercises. Serum 25-hydroxyvitamin D increased in both groups but to a greater extent in MILK than CON (+6.5 T 1.1 vs +2.8 T 1.3 nM, respectively, P G 0.05), and parathyroid hormone decreased only in MILK (j1.2 T 0.2 pM, P G 0.01). Conclusions: Heavy, whole-body resistance exercise with the consumption of milk versus carbohydrate in the early postexercise period resulted in greater muscle mass accretion, strength gains, fat mass loss, and a possible reduction in bone turnover in women after 12 wk. Our results, similar to those in men, highlight that milk is an effective drink to support favorable body composition

Physically Active Academic Lessons and Time on Task: The Moderating Effect of Body Mass Index

Abstract: GRIECO, L. A., E. M. JOWERS, and J. B. BARTHOLOMEW. Physically Active Academic Lessons and Time on Task: The Moderating Effect of Body Mass Index. Med. Sci. Sports Exerc., Vol. 41, No. 10, pp. 1921–1926, 2009. Physically active classroom lessons have been found to increase on-task behavior in children. Given that physical activity has been associated with an increased time on task (TOT) and that overweight children take fewer steps than normal weight children do, it was expected that benefits of the physical activity would differentially impact those children of higher weight status. Purpose: To examine the effects of a physically active classroom lesson and body mass index (BMI) category on TOT in a sample of elementary-aged children (N = 97). Methods: Behavior was assessed through direct observations before and after a physically active classroom lesson and before and after a traditional inactive classroom lesson. TOT was calculated through momentary time sampling for each student by dividing the number of on-task observations by the total number of observations per student (interrater reliability = 94%). Results: TOT decreased significantly from before to after the lesson for all BMI categories in the inactive control condition, with no change for the active condition. Post hoc analyses found a significant linear effect for the reduction in TOT with each level of BMI in the inactive condition, with the greatest magnitude of effect for the overweight group. Conclusions: Physically active classroom lessons provide a buffer to prevent the steep reduction in TOT experienced after a period of inactivity in all children, especially those who are overweight.

Change in parent and peer support across ages 9 to 15 yr and adolescent girls' physical activity.

Abstract: Purpose: To examine change in parent and peer support for girls' physical activity (PA) across ages 9 to 15 yr and assess if girls who remain active during adolescence are differentially exposed to support when compared with girls who do not remain active. Methods: Participants included 174 non-Hispanic white girls assessed at ages 9, 11, 13, and 15 yr. Parental modeling and logistic support for PA were assessed at all ages; peer support was assessed at ages 9, 11, and 13 yr. Minutes per day of moderate-to-vigorous PA (MVPA) was measured at ages 13 and 15 yr using 7-d accelerometry. Girls' body mass index and self-reported PA were measured at ages 9, 11, and 13 yr. Girls were classified as maintaining PA during adolescence if they recorded >=30 min[middle dot]d-1 of MVPA at ages 13 and 15 yr. Patterns of change in parent/peer support and differences in exposure to support for girls who maintained PA and those who did not maintain PA were assessed using individual growth curve modeling. Results: A linear decline was observed in parental modeling. A curvilinear pattern of change was observed for parental logistic support and peer support. Although the rate of change varied by age, logistic support generally decreased, and peer support increased across time. Girls who maintained PA had parents who reported higher modeling of PA across time and stable levels of logistic support. In contrast, girls who did not maintain PA had parents who reported lower modeling and declines in logistic support. Conclusions: Parental modeling of PA before adolescence and logistic support during adolescence could help girls establish early patterns of PA and social networks that facilitate maintained PA during adolescence.