Showing papers in "Medicine and Science in Sports and Exercise in 2010"

American College of Sports Medicine roundtable on exercise guidelines for cancer survivors.

Abstract: to physical functioning and quality of life are sufficient for the recommendation that cancer survivors follow the 2008 Physical Activity Guidelines for Americans, with specific exercise programming adaptations based on disease and treatment-related adverse effects. The advice to ‘‘avoid inactivity,’’ even in cancer patients with existing disease or undergoing difficult treatments, is likely helpful.

Energy cost and metabolic power in elite soccer: a new match analysis approach.

Abstract: Purpose:Video match analysis is used for the assessment of physical performances of professional soccer players, particularly for the identification of "high intensities" considered as "high running speeds." However, accelerations are also essential elements setting metabolic loads, even whe

Exercise and type 2 diabetes: American College of Sports Medicine and the American Diabetes Association: joint position statement. Exercise and type 2 diabetes.

Abstract: Although physical activity (PA) is a key element in the prevention and management of type 2 diabetes mellitus (T2DM), many with this chronic disease do not become or remain regularly active. High-quality studies establishing the importance of exercise and fitness in diabetes were lacking until recently, but it is now well established that participation in regular PA improves blood glucose control and can prevent or delay T2DM, along with positively affecting lipids, blood pressure, cardiovascular events, mortality, and quality of life. Structured interventions combining PA and modest weight loss have been shown to lower T2DM risk by up to 58% in high-risk populations. Most benefits of PA on diabetes management are realized through acute and chronic improvements in insulin action, accomplished with both aerobic and resistance training. The benefits of physical training are discussed, along with recommendations for varying activities, PA-associated blood glucose management, diabetes prevention, gestational diabetes, and safe and effective practices for PA with diabetes-related complications.

Sedentary behaviors increase risk of cardiovascular disease mortality in men.

Abstract: Purpose:The purpose of this study was to examine the relationship between two sedentary behaviors (riding in a car and watching TV) and cardiovascular disease (CVD) mortality in men in the Aerobics Center Longitudinal Study.Methods:Participants were 7744 men (20-89 yr) initially free of CVD

Accuracy of Armband Monitors for Measuring Daily Energy Expenditure in Healthy Adults

Abstract: Introduction:There is a need to develop accurate devices for measuring daily energy expenditure under free-living conditions, particularly given our current obesity epidemic.Purpose:The purpose of the present study was to evaluate the validity of energy expenditure estimates from two portabl

Critical Power: Implications for Determination of V˙O2max and Exercise Tolerance

Abstract: For high-intensity muscular exercise, the time-to-exhaustion (t) increases as a predictable and hyperbolic function of decreasing power (P) or velocity (V ). This relationship is highly conserved across diverse species and different modes of exercise and is well described by two parameters: the "critical power" (CP or CV), which is the asymptote for power or velocity, and the curvature constant (W') of the relationship such that t = W'/(P - CP). CP represents the highest rate of energy transduction (oxidative ATP production, V˙O2) that can be sustained without continuously drawing on the energy store W' (composed in part of anaerobic energy sources and expressed in kilojoules). The limit of tolerance (time t) occurs when W' is depleted. The CP concept constitutes a practical framework in which to explore mechanisms of fatigue and help resolve crucial questions regarding the plasticity of exercise performance and muscular systems physiology. This brief review presents the practical and theoretical foundations for the CP concept, explores rigorous alternative mathematical approaches, and highlights exciting new evidence regarding its mechanistic bases and its broad applicability to human athletic performance.

Adaptations in athletic performance after ballistic power versus strength training.

Abstract: Purpose: To determine whether the magnitude of improvement in athletic performance and the mechanisms driving these adaptations differ in relatively weak individuals exposed to either ballistic power training or heavy strength training. Methods: Relatively weak men (n = 24) who could perform the back squat with proficient technique were randomized into three groups: strength training (n = 8; ST), power training (n = 8; PT), or control (n = 8). Training involved three sessions per week for 10 wk in which subjects performed back squats with 75%-90% of one-repetition maximum (1RM; ST) or maximal-effort jump squats with 0%-30% 1RM (PT). Jump and sprint performances were assessed as well as measures of the force-velocity relationship, jumping mechanics, muscle architecture, and neural drive. Results: Both experimental groups showed significant (P <= 0.05) improvements in jump and sprint performances after training with no significant between-group differences evident in either jump (peak power: ST = 17.7% +/- 9.3%, PT = 17.6% +/- 4.5%) or sprint performance (40-m sprint: ST = 2.2% +/- 1.9%, PT = 3.6% +/- 2.3%). ST also displayed a significant increase in maximal strength that was significantly greater than the PT group (squat 1RM: ST = 31.2% +/- 11.3%, PT = 4.5% +/- 7.1%). The mechanisms driving these improvements included significant (P <= 0.05) changes in the force-velocity relationship, jump mechanics, muscle architecture, and neural activation that showed a degree of specificity to the different training stimuli. Conclusions: Improvements in athletic performance were similar in relatively weak individuals exposed to either ballistic power training or heavy strength training for 10 wk. These performance improvements were mediated through neuromuscular adaptations specific to the training stimulus. The ability of strength training to render similar short-term improvements in athletic performance as ballistic power training, coupled with the potential long-term benefits of improved maximal strength, makes strength training a more effective training modality for relatively weak individuals

High-intensity training versus traditional exercise interventions for promoting health.

Abstract: NYBO, L., E. SUNDSTRUP, M. D. JAKOBSEN, M. MOHR, T. HORNSTRUP, L. SIMONSEN, J. BULOW, M. B. RANDERS, J. J. NIELSEN, P. AAGAARD, and P. KRUSTRUP. High-Intensity Training versus Traditional Exercise Interventions for Pro- moting Health. Med. Sci. Sports Exerc., Vol. 42, No. 10, pp. 1951-1958, 2010. Purpose: The purpose of this study was to deter- mine the effectiveness of brief intense interval training as exercise intervention for promoting health and to evaluate potential benefits about common interventions, that is, prolonged exercise and strength training. Methods: Thirty-six untrained men were divided into groups that completed 12 wk of intense interval running (INT; total training time 40 minIwk j1 ), prolonged running (E150 minIwk j1 ), and strength training (E150 minIwk j1 ) or continued their habitual lifestyle without participation in physical training. Results: The improvement in cardiorespiratory fitness was superior in the INT (14% T 2% increase in VO2max) compared with the other two exercise interventions (7% T 2% and 3% T 2% increases). The blood glucose concentration 2 h after oral ingestion of 75 g of glucose was lowered to a similar extent after training in the INT (from 6.1 T 0.6 to 5.1 T 0.4 mM, P G 0.05) and the prolonged running group (from 5.6 T 1.5 to 4.9 T 1.1 mM, P G 0.05). In contrast, INT was less efficient than prolonged running for lowering the subjects' resting HR, fat percentage, and reducing the ratio between total and HDL plasma cholesterol. Furthermore, total bone mass and lean body mass remained unchanged in the INT group, whereas both these parameters were increased by the strength-training intervention. Conclusions: INT for 12 wk is an effective training stimulus for improvement of cardiorespiratory fitness and glucose tolerance, but in relation to the treatment of hyperlipidemia and obesity, it is less effective than prolonged training. Furthermore and in contrast

Inclusion criteria when investigating insufficiencies in chronic ankle instability.

Abstract: DELAHUNT, E., G. F. COUGHLAN, B. CAULFIELD, E. J. NIGHTINGALE, C.-W. C. LIN, and C. E. HILLER. Inclusion CriteriaWhen Investigating Insufficiencies in Chronic Ankle Instability. Med. Sci. Sports Exerc., Vol. 42, No. 11, pp. 2106–2121, 2010.Introduction: The development of chronic ankle instability (CAI) is the primary residual deficit after ankle joint sprain. It has beenproposed that CAI is characterized by two entities, namely, mechanical instability and functional instability. Each of these entities inturn is composed of various insufficiencies. Research of functional insufficiencies to date has shown large variances in results. Oneparticular reason for this could be discrepancies in inclusion criteria and definitions between CAI, mechanical instability, and functionalinstability used in the literature. Thus, we endeavored to undertake a systematic investigation of those studies published in the area ofCAI to identify if there is a large discrepancy in inclusion criteria across studies. Methods: A systematic search of the followingdatabases was undertaken to identify relevant studies: Cochrane Central Register of Controlled Trials, PubMed, CINAHL, SportDiscus,PEDro, and AMED. Results: The results of this study indicate that there is a lack of consensus across studies regarding what actuallyconstitutes ankle instability. Furthermore, it is evident that the majority of studies use very different inclusion criteria, which leads to anonhomogenous population and to difficulties when comparing results across studies. Conclusions: Future studies should endeavor tobe specific with regard to the exact inclusion criteria being used. Particular emphasis should be given to issues such as the number ofprevious ankle sprains reported by each subject and how often and during which activities episodes of ‘‘giving way’’ occur as well asthe presence of concomitant symptoms such as pain and weakness. We recommend that authors use one of the validated tools fordiscriminating the severity of CAI. Furthermore, we have provided a list of operational definitions and key criteria to be specified whenreporting on studies with CAI subjects. Key Words: ANKLE SPRAIN, INJURY, SYSTEMATIC INVESTIGATION, FUNCTIONALINSTABILITY, MECHANICAL INSTABILITY

Prevalence of chondral defects in athletes' knees: a systematic review.

Abstract: Purpose: To determine the prevalence of full-thickness focal chondral defects in the athlete's knee. Methods: We conducted a systematic review of multiple databases, evaluating studies of the prevalence of articular cartilage defects in athletes. Because of the heterogeneity of data, a meta-analysis could not be performed. Results: Eleven studies were identified for inclusion (931 subjects). All studies were level 4 evidence. Defects were diagnosed via magnetic resonance imaging, arthroscopy, or both. Forty percent of athletes were professionals (NBA and NFL). The overall prevalence of full-thickness focal chondral defects in athletes was 36% (range = 2.4%-75% between all studies). Fourteen percent of athletes were asymptomatic at the time of diagnosis. Patellofemoral defects (37%) were more common than femoral condyle (35%) and tibial plateau defects (25%). Medial condyle defects were more common than lateral (68% vs 32%), and patella defects were more common than trochlea (64% vs 36%). Meniscal tear (47%) was the most common concomitant knee pathological finding, followed by anterior cruciate ligament tear (30%) and then medial collateral ligament or lateral collateral ligament tear (14%). Conclusions: Full-thickness focal chondral defects in the knee are more common in athletes than among the general population. More than one-half of asymptomatic athletes have a full-thickness defect. Further study is needed to define more precisely the prevalence of these lesions in this population

Dose-Response Relationship of Resistance Training in Older Adults: A Meta-Analysis

Abstract: Purpose:The purpose of this study was to determine the dose-response relationship of resistance training (RT) to improve strength and function in older adults.Methods:A systematic literature search was performed in relevant databases and study reference lists to identify randomized controlle

Neuromuscular training for sports injury prevention: a systematic review.

Abstract: Purpose: The aim of this systematic review was to assess the effectiveness of proprioceptive/neuromuscular training in preventing sports injuries by using the best available evidence from methodologically well-conducted randomized controlled trials and controlled clinical trials without randomization. Methods: Two independent researchers performed a literature search in various electronic databases and reference lists. The reviewers independently assessed trials for inclusion criteria and methodological quality and extracted the data. Focusing on studies of high methodological quality, relative risks (RR) and 95% confidence intervals (CI) were used to estimate treatment effects. Results: From a total of 32 relevant studies, 7 methodologically well-conducted studies were considered for this review. Pooled analysis revealed that multi-intervention training was effective in reducing the risk of lower limb injuries (RR = 0.61, 95% CI = 0.49-0.77, P < 0.01), acute knee injuries (RR = 0.46, 95% CI = 0.28-0.76, P < 0.01), and ankle sprain injuries (RR = 0.50, 95% CI = 0.31-0.79, P < 0.01). Balance training alone resulted in a significant risk reduction of ankle sprain injuries (RR = 0.64, 95% CI = 0.46-0.9, P < 0.01) and a nonsignificant risk reduction for injuries overall (RR = 0.49, 95% CI = 0.13-1.8, P = 0.28). Exercise interventions were more effective in athletes with a history of sports injury than in those without. Conclusion: On the basis of the results of seven high-quality studies, this review showed evidence for the effectiveness of proprioceptive/neuromuscular training in reducing the incidence of certain types of sports injuries among adolescent and young adult athletes during pivoting sports. Future research should focus on the conduct of comparative trials to identify the most appropriate and effective training components for preventing injuries in specific sports and populations

Pedometer-measured physical activity and health behaviors in U.S. adults.

Abstract: U.S. adults may have lower levels of ambulatory physical activity compared with adults living in other countries. Purpose: The purpose of this study was to provide descriptive, epidemiological data on the average number of steps per day estimated to be taken by U.S. adults and to identify predictors of pedometer-measured physical activity on the basis of demographic characteristics and self-reported behavioral characteristics. Methods: The America On the Move study was conducted in 2003. Individuals (N = 2522) aged 13 yr and older consented to fill out a survey, including 1921 adults aged 18 yr and older. Valid pedometer data were collected on 1136 adults with Accusplit AE120 pedometers. Data were weighted to reflect the general U.S. population according to several variables (age, gender, race/ethnicity, education, income, level of physical activity, and number of 5- to 17-yr-old children in the household). Differences in steps per day between subgroups were analyzed using unpaired t-tests when only two subgroups were involved or one-way ANOVA if multiple subgroups were involved. Results: Adults reported taking an average of 5117 steps per day. Male gender, younger age, higher education level, single marital status, and lower body mass index were all positively associated with steps per day. Steps per day were positively related to other self-reported measures of physical activity and negatively related to self-reported measures on physical inactivity. Living environment (urban, suburban, or rural) and eating habits were not associated with steps per day. Conclusions: In the current study, men and women living in the United States took fewer steps per day than those living in Switzerland, Australia, and Japan. We conclude that low levels of ambulatory physical activity are contributing to the high prevalence of adult obesity in the United States.

Physical Activity in US Youth: Effect of Race/Ethnicity, Age, Gender, and Weight Status

Abstract: BELCHER, B. R., D. BERRIGAN, K. W. DODD, B. A EMKEN, C.-P. CHOU, and D. SPRUIJT-METZ. Physical Activity in US Youth: Effect of Race/Ethnicity, Age, Gender, and Weight Status. Med. Sci. Sports Exerc., Vol. 42, No. 12, pp. 2211–2221, 2010. Purpose: To describe physical activity (PA) levels by race/ethnicity, age, gender, and weight status in a representative sample of US youth. Methods: Cross-sectional data from the 2003–2004 and 2005–2006 National Health and Nutrition Examination Survey were combined and analyzed. Youth aged 6–19 yr with at least four 10-h days of PA measured by accelerometry were included (n = 3106). Outcomes included mean counts per minute and minutes spent in moderate-to-vigorous PA (MVPA). Results: Among the groups, the 6- to 11-yr-olds spent more time (88 minId j1 ) in MVPA than the 12- to 15-yr-olds (33 minId j1 ) and 16- to 19-yr-olds (26 minId j1 ; P G 0.001 for both). Females spent fewer minutes per day in MVPA than males (P G 0.001). Overall, obese youth spent 16 fewer minutes per day in MVPA than normal-weight youth. However, non-Hispanic white males spent three to four fewer minutes per day in vigorous PA than Mexican American (MA; P = 0.004) and non-Hispanic black (P G 0.001) males but had lower obesity rates and obese 12- to 15-yr-old MA recorded similar minutes in MVPA per day as normal-weight MA (P 9 0.050). There was a significant three-way age–body mass index–race/ethnicity interaction for mean minutes per day in MVPA (P G 0.001). Adjustment for total energy intake did not qualitatively alter these results. Conclusions: Females and older youth were the least active groups. Obese youth were generally less active, but this did not hold uniformly across race/ethnic groups. Cultural or biological factors could moderate the association between

Biomechanical properties of concussions in high school football

Abstract: BROGLIO, S. P., B. SCHNEBEL, J. J. SOSNOFF, S. SHIN, X. FENG, X. HE, and J. ZIMMERMAN. Biomechanical Properties of Concussions in High School Football. Med. Sci. Sports Exerc., Vol. 42, No. 11, pp. 2064–2071, 2010. Introduction: Sport concussion represents the majority of brain injuries occurring in the United States with 1.6–3.8 million cases annually. Understanding the biomechanical properties of this injury will support the development of better diagnostics and preventative techniques. Methods :W e monitored all football related head impacts in 78 high school athletes (mean age = 16.7 yr) from 2005 to 2008 to better understand the biomechanical characteristics of concussive impacts. Results: Using the Head Impact Telemetry System, a total of 54,247 impacts were recorded, and 13 concussive episodes were captured for analysis. A classification and regression tree analysis of impacts indicated that rotational acceleration (95582.3 radIs j2 ), linear acceleration (996.1g), and impact location (front, top, and back) yielded the highest predictive value of concussion. Conclusions: These threshold values are nearly identical with those reported at the collegiate and professional level. If the Head Impact Telemetry System were implemented for medical use, sideline personnel can expect to diagnose one of every five athletes with a concussion when the impact exceeds these tolerance levels. Why all athletes did not sustain a concussion when the impacts generated variables in excess of our threshold criteria is not entirely clear, although individual differences between participants may play a role. A similar threshold to concussion in adolescent athletes compared with their collegiate and

Advances in exercise, fitness, and performance genomics.

Abstract: An annual review publication of the most significant articles in exercise, fitness, and performance genomics begins with this article, which covers 2 yr, 2008 and 2009. The review emphasizes the strongest articles as defined by sample size, quality of phenotype measurements, quality of the exercise program or physical activity exposure, study design, adjustment for multiple testing, quality of genotyping, and other related study characteristics. With this avowed focus on the highest quality articles, only a small number of published articles are reviewed. Among the most significant findings reported here are a brief overview of the first genome-wide association study of the genetic differences between exercisers and nonexercisers. In addition, the latest results on the actinin alpha 3 (ACTN3) R577X nonsense polymorphism are reviewed, emphasizing that no definitive conclusion can be reached at this time. Recent studies that have dealt with mitochondrial DNA haplogroups and endurance performance are described. Published reports indicating that physical activity may attenuate the effect of the fat mass and obesity associated (FTO) gene risk allele on body mass index are reviewed. Articles that have tested the contributions of specific genes to the response of glucose and insulin metabolism traits to regular exercise or physical activity level are considered and found to be generally inconclusive at this stage. Studies examining ethnic differences in the response of blood lipids and lipoproteins to exercise training cannot unequivocally relate these to apolipoprotein E (APOE) genotypes. Hemodynamic changes with exercise training were reported to be associated to sequence variation in kinesin heavy chain (KIF5B), but no replication study is available as of yet. We conclude from this first installment that exercise scientists need to prioritize high-quality research designs and that replication studies with large sample sizes are urgently needed.

Effects of resistance or aerobic exercise training on interleukin-6, C-reactive protein, and body composition.

Abstract: Purpose: To determine the effects of 10 wk of resistance or aerobic exercise training on interleukin-6 (IL-6) and C-reactive protein (CRP). Further, to determine pretraining and posttraining associations between alterations of IL-6 and CRP and alterations of total body fat mass (TB-FM), intra-abdominal fat mass (IA-FM), and total body lean mass (TB-LM). Methods: A sample of 102 sedentary subjects were assigned to a resistance group (n = 35), an aerobic group (n = 41), or a control group (n = 26). Before and after intervention, subjects were involved in dual-energy x-ray absorptiometry, muscular strength and aerobic fitness, measurements and further provided a resting fasted venous blood sample for measures of IL-6, CRP, cholesterol profile, triglycerides, glucose, insulin, and glycosylated hemoglobin. The resistance and the aerobic groups completed a respective 10-wk supervised and periodized training program, whereas the control group maintained sedentary lifestyle and dietary patterns. Results: Both exercise training programs did not reduce IL-6; however, the resistance and the aerobic groups reduced CRP by 32.8% (P = -0.24). Compared with the resistance and the control groups, the aerobic group exhibited significant (P < 0.05) improvements in all aerobic fitness measures and significant reductions in IA-FM (7.4%) and body mass (1.1%). Compared with the aerobic and the control groups, the resistance group significantly (P < 0.05) improved TB-FM (3.7%) and upper (46.3%) and lower (56.6%) body strength. Conclusion: Despite no alteration in baseline IL-6 and significantly smaller reductions in measures of adipose tissue as compared with the aerobic training group, only resistance exercise training resulted in significant attenuation of CRP concentration

Longitudinal Sex Differences during Landing in Knee Abduction in Young Athletes

Abstract: Purpose: The objective of this study was to determine whether biomechanical and neuromuscular risk factors related to abnormal movement patterns increased in females, but not males, during the adolescent growth spurt. Methods: A total of 315 subjects participated in two testing sessions approximately 1 yr apart. Male and female subjects were classified on the basis of their maturation status as pubertal or postpubertal. Three trials of a drop vertical jump (DVJ) were collected. Maximum knee abduction angle and external moments were calculated during the DVJ deceleration phase using a three-dimensional motion analysis system. Changes in knee abduction from the first to second year were compared among four subject groups (female pubertal, female postpubertal, male pubertal, and male postpubertal). Results: There were no sex differences in peak knee abduction angle or moment during DVJ between pubertal males and females (P > 0.05). However, pubertal females increased peak abduction angle from first to second year (P < 0.001), whereas males demonstrated no similar change (P = 0.90) in the matched developmental stages. After puberty, the peak abduction angle and moment were greater in females relative to males (angle: female -9.3[degrees] +/- 5.7[degrees], male -3.6[degrees] +/- 4.6[degrees], P < 0.001; moment: female -21.9 +/- 13.5 N[middle dot]m, male -13.0 +/- 12.0 N[middle dot]m, P = 0.017). Conclusions: This study identified, through longitudinal analyses, that knee abduction angle was significantly increased in pubertal females during rapid adolescent growth, whereas males showed no similar change. In addition, knee abduction motion and moments were significantly greater for the subsequent year in young female athletes, after rapid adolescent growth, compared with males. The combination of longitudinal, sex, and maturational group differences indicates that early puberty seems to be a critical phase related to the divergence of increased anterior cruciate ligament injury risk factors

Increased protein intake reduces lean body mass loss during weight loss in athletes.

Abstract: Purpose: To examine the influence of dietary protein on lean body mass loss and performance during short-term hypoenergetic weight loss in athletes. Methods: In a parallel design, 20 young healthy resistance-trained athletes were examined for energy expenditure for 1 wk and fed a mixed diet (15% protein, 100% energy) in the second week followed by a hypoenergetic diet (60% of the habitual energy intake), containing either 15% (~1.0 g[middle dot]kg-1) protein (control group, n = 10; CP) or 35% (~2.3 g[middle dot]kg-1) protein (high-protein group, n = 10; HP) for 2 wk. Subjects continued their habitual training throughout the study. Total, lean body, and fat mass, performance (squat jump, maximal isometric leg extension, one-repetition maximum (1RM) bench press, muscle endurance bench press, and 30-s Wingate test) and fasting blood samples (glucose, nonesterified fatty acids (NEFA), glycerol, urea, cortisol, free testosterone, free Insulin-like growth factor-1 (IGF-1), and growth hormone), and psychologic measures were examined at the end of each of the 4 wk. Results: Total (-3.0 +/- 0.4 and -1.5 +/- 0.3 kg for the CP and HP, respectively, P = 0.036) and lean body mass loss (-1.6 +/- 0.3 and -0.3 +/- 0.3 kg, P = 0.006) were significantly larger in the CP compared with those in the HP. Fat loss, performance, and most blood parameters were not influenced by the diet. Urea was higher in HP, and NEFA and urea showed a group x time interaction. Fatigue ratings and "worse than normal" scores on the Daily Analysis of Life Demands for Athletes were higher in HP. Conclusions: These results indicate that ~2.3 g[middle dot]kg-1 or ~35% protein was significantly superior to ~1.0 g[middle dot]kg-1 or ~15% energy protein for maintenance of lean body mass in young healthy athletes during short-term hypoenergetic weight loss

Effect of caffeine ingestion on muscular strength and endurance: a meta-analysis.

Abstract: Purpose:Our objective was to perform a systematic review and meta-analysis of the research literature assessing the effect of caffeine ingestion on maximal voluntary contraction (MVC) strength and muscular endurance.Methods:Thirty-four relevant studies between 1939 and 2008 were included in

Behavior mapping: a method for linking preschool physical activity and outdoor design.

Abstract: COSCO, N. G., R. C. MOORE, and M. Z. ISLAM. Behavior Mapping: A Method for Linking Preschool Physical Activity and Outdoor Design. Med. Sci. Sports Exerc., Vol. 42, No. 3, pp. 513–519, 2010. The preschool that children attend has been shown to be a significant but variable predictor of physical activity of 3- to 5-yr-olds, whereas the time outdoors has been found to be a strong correlate of physical activity. Researchers speculate that variations in preschool physical activity may be attributed to variations in preschool policies and practices, including the form and content of outdoor physical environments. However, assessment methods linking them to physical activity are limited. Improved understanding of links between environment and activity could be used to influence childcare policy, which is highly regulated, usually at state level, to create outdoor environments more conducive to children’s informal play and physical activity. The purpose of this article was to introduce behavior mapping as a direct observation method on the basis of the theories of behavior setting and affordance and to demonstrate its sensitivity to gathering physical activity and associated environmental data at a sufficiently detailed level to affect built environment design policy. Methods: Behavior mapping data, including outdoor environmental characteristics and children’s physical activity levels, were obtained in two preschool centers at the Research Triangle region, NC. Results: Physical activity levels at the two centers varied across different types of behavior settings, including pathways, play structures, and open areas. The same type of setting with different attributes, such as circular versus straight pathways, and open areas with different ground surfaces, such as asphalt, compacted soil, woodchips, and sand, attracted different levels of physical activity. Conclusions: Behavior mapping provides a promising method for objectively measuring relationships between

Low levels of objectively measured physical activity in preschoolers in child care.

Abstract: Background: Physical activity (PA) undertaken at child care could assist in the achievement of PA recommendations across a large proportion of the population in early childhood. Purpose: To review recent evidence on volume of PA and amount of moderate- to vigorous-intensity PA (MVPA) in preschool children within child care centers. Methods: Literature search for studies published in 2000-2008 in which objective methods (accelerometry, direct observation, pedometers, HR monitoring) were used to measure typical levels of PA and MVPA of preschool children while within child care. Results: Twelve eligible articles were identified, describing 13 studies, involving 96 different child care centers and >1900 children. In all six of the accelerometry studies that quantified MVPA and in three of the four studies that used direct observation to quantify MVPA, typical levels of PA within the child care center would have led to the accumulation of <60 min·d−1 MVPA during a full 8-h child care day. Conclusions: A body of high-quality evidence is consistent in suggesting that PA levels within child care centers are typically very low, and levels of sedentary behavior are typically high.

Measurement of physical activity in preschool children.

Abstract: Purpose: To provide an overview of the methods that have been developed for measurement of physical activity in children of preschool age. Emphasis will be given to direct observation and accelerometry, but pedometry, HR monitoring, and proxy reports will be reviewed as well. Method: Research articles detailing the measurement properties of direct observational systems, accelerometry, pedometry, HR monitoring, and proxy reporting specifically in children of preschool age were selected and reviewed. Results: Systems for direct observation of physical activity and accelerometry are valid and reliable measures of physical activity in young children. Direct observation, which can provide information on type and context of physical activity, is an excellent complement to accelerometry, which provides detailed information on the intensity and duration of physical activity but no contextual information. Conclusions: Direct observation systems and accelerometry have become well-established measurements of physical activity in young children as well as older groups. Pedometry and HR monitoring have been shown to be applicable, but these methods have been studied less extensively than direct observation and accelerometry. Proxy reports of physical activity are attractive because of low burden, but they have limited validity

Prevalence, Magnitude, and Methods of Rapid Weight Loss among Judo Competitors

Abstract: Purpose: To identify the prevalence, magnitude, and methods of rapid weight loss among judo competitors. Methods: Athletes (607 males and 215 females; age = 19.3 +/- 5.3 yr, weight = 70 +/- 7.5 kg, height = 170.6 +/- 9.8 cm) completed a previously validated questionnaire developed to evaluate rapid weight loss in judo athletes, which provides a score. The higher the score obtained, the more aggressive the weight loss behaviors. Data were analyzed using descriptive statistics and frequency analyses. Mean scores obtained in the questionnaire were used to compare specific groups of athletes using, when appropriate, Mann-Whitney U-test or general linear model one-way ANOVA followed by Tamhane post hoc test. Results: Eighty-six percent of athletes reported that have already lost weight to compete. When heavyweights are excluded, this percentage rises to 89%. Most athletes reported reductions of up to 5% of body weight (mean +/- SD: 2.5 +/- 2.3%). The most weight ever lost was 2%-5%, whereas a great part of athletes reported reductions of 5%-10% (mean +/- SD: 6 +/- 4%). The number of reductions underwent in a season was 3 +/- 5. The reductions usually occurred within 7 +/- 7 d. Athletes began cutting weight at 12.6 +/- 6.1 yr. No significant differences were found in the score obtained by male versus female athletes as well as by athletes from different weight classes. Elite athletes scored significantly higher in the questionnaire than nonelite. Athletes who began cutting weight earlier also scored higher than those who began later. Conclusions: Rapid weight loss is highly prevalent in judo competitors. The level of aggressiveness in weight management behaviors seems to not be influenced by the gender or by the weight class, but it seems to be influenced by competitive level and by the age at which athletes began cutting weight.

Neuromuscular Performance of Explosive Power Athletes versus Untrained Individuals

Abstract: Purpose: Electromechanical delay (EMD) and rate of force development (RFD) are determinants of explosive neuromuscular performance. We may expect a contrast in EMD and RFD between explosive power athletes, who have a demonstrable ability for explosive contractions, and untrained individuals. However, this comparison, and the neuromuscular mechanisms for any differences, has not been studied. Methods: The neuromuscular performance of explosive power athletes (n = 9) and untrained controls (n = 10) was assessed during a series of twitch, tetanic, explosive and maximum voluntary, isometric knee extensions. Knee extension force and EMG of the superficial quadriceps was measured in three 50 ms time windows from their onset, and normalised to strength and maximal M-wave (Mmax), respectively. Involuntary and voluntary EMD were determined from twitch and explosive voluntary contractions, respectively, and were similar for both groups. Results: The athletes were 28% stronger and their absolute RFD in the first 50 ms was 2-fold that of controls. Athletes had greater normalised RFD (4.86 ± 1.46 vs. 2.81 ± 1.20 MVC.s -1 ) and neural activation (mean quadriceps, 0.26 ± 0.07 vs. 0.15 ± 0.06 Mmax) during the first 50 ms of explosive voluntary contractions. Surprisingly the controls had a greater normalised RFD in the second 50 ms (6.68 ± 0.92 vs. 7.93 ± 1.11 MVC.s -1 ) and a greater change in EMG preceding this period. However, there were no differences in the twitch response or normalised tetanic RFD between groups. Conclusion: The differences in voluntary normalised RFD between athletes and controls were explained by agonist muscle neural activation, and not the similar intrinsic contractile properties of the groups.

Influence of Strength on Magnitude and Mechanisms of Adaptation to Power Training

Abstract: Purpose: To determine whether the magnitude of performance improvements and the mechanisms driving adaptation to ballistic power training differ between strong and weak individuals. Methods: Twenty-four men were divided into three groups on the basis of their strength level: stronger (n = 8, one-repetition maximum-to-body mass ratio (1RM/BM) = 1.97 +/- 0.08), weaker (n = 8, 1RM/BM = 1.32 +/- 0.14), or control (n = 8, 1RM/BM = 1.37 +/- 0.13). The stronger and weaker groups trained three times per week for 10 wk. During these sessions, subjects performed maximal-effort jump squats with 0%-30% 1RM. The impact of training on athletic performance was assessed using a 2-d testing battery that involved evaluation of jump and sprint performance as well as measures of the force-velocity relationship, jumping mechanics, muscle architecture, and neural drive. Results: Both experimental groups showed significant (P <= 0.05) improvements in jump (stronger: peak power = 10.0 +/- 5.2 W[middle dot]kg-1, jump height = 0.07 +/- 0.04 m; weaker: peak power = 9.1 +/- 2.3 W[middle dot]kg-1, jump height = 0.06 +/- 0.04 m) and sprint performance after training (stronger: 40-m time = -2.2% +/- 2.0%; weaker: 40-m time = -3.6% +/- 2.3%). Effect size analyses revealed a tendency toward practically relevant differences existing between stronger and weaker individuals in the magnitude of improvements in jump performance (effect size: stronger: peak power = 1.55, jump height = 1.46; weaker: peak power = 1.03, jump height = 0.95) and especially after 5 wk of training (effect size: stronger: peak power = 1.60, jump height = 1.59; weaker: peak power = 0.95, jump height = 0.61). The mechanisms driving these improvements included significant (P <= 0.05) changes in the force-velocity relationship, jump mechanics, and neural activation, with no changes to muscle architecture observed. Conclusions: The magnitude of improvements after ballistic power training was not significantly influenced by strength level. However, the training had a tendency toward eliciting a more pronounced effect on jump performance in the stronger group. The neuromuscular and biomechanical mechanisms driving performance improvements were very similar for both strong and weak individuals

Myostatin Decreases with Aerobic Exercise and Associates with Insulin Resistance

Abstract: Purpose: There is mounting evidence that skeletal muscle produces and secretes biologically active proteins or "myokines" that facilitate metabolic cross talk between organ systems. The increased expression of myostatin, a secreted anabolic inhibitor of muscle growth and development, has been associated with obesity and insulin resistance. Despite these intriguing findings, there have been few studies linking myostatin and insulin resistance. Methods: To explore this relationship in more detail, we quantified myostatin protein in muscle and plasma from 10 insulin-resistant, middle-aged (53.1 ± 5.5 yr) men before and after 6 months of moderate aerobic exercise training (1200 kcal·wk at 40%-55% V?O ). To establish a cause-effect relationship, we also injected C57/Bl6 male mice with high physiological levels of recombinant myostatin protein. Results: Myostatin protein levels were shown to decrease in muscle (37%, = 0.042, = 10) and matching plasma samples (from 28.7 ng·mL pretraining to 22.8 ng·mL posttraining, = 0.003, = 9) with aerobic exercise. Furthermore, the strong correlation between plasma myostatin levels and insulin sensitivity ( = 0.82, < 0.001, = 9) suggested a cause-effect relationship that was subsequently confirmed by inducing insulin resistance in myostatin-injected mice. A modest increase (44%) in plasma myostatin levels was also associated with significant reductions in the insulin-stimulated phosphorylation of Akt (Thr ) in both muscle and liver of myostatin-treated animals. Conclusions: These findings indicate that both muscle and plasma myostatin protein levels are regulated by aerobic exercise and, furthermore, that myostatin is in the causal pathway of acquired insulin resistance with physical inactivity.

Time Course of Leukocyte Accumulation in Human Muscle after Eccentric Exercise

Abstract: Purpose: To investigate the time course of leukocyte accumulation in eccentric exercised human muscles and its relation to recovery of muscle function and soreness. Methods: Eleven young males performed 300 unilateral, maximal voluntary, eccentric actions with the musculus quadriceps femoris (30[degrees][middle dot]s-1). Before and at regular intervals for 7 d after exercise, force-generating capacity was measured with maximal concentric knee extensions (60[degrees][middle dot]s-1). Accumulation of radiolabeled (autologous) leukocytes was measured with scintigraphy. Biopsies from musculus vastus lateralis were obtained 0.5, 4, 8, 24, 96, and 168 h after exercise from both the exercised leg and the control leg. Muscle cross-sections were stained with antibodies against leukocytes (CD16 and CD68). Muscle soreness was rated on a visual analog scale. Results: Immediately after exercise, the subjects' ability to generate force was reduced by 47 +/- 5%. Muscle function recovered slowly and was not fully restored after 1 wk. Radiolabeled leukocytes accumulated in the muscles during the first hour (3-24 h) after exercise, and leukocytes were at the same time observed histologically, primarily in the endomysium and perimysium. A part of the accumulated radiolabeled leukocytes appeared to be located within local blood vessels. The highest numbers of CD16+ and CD68+ cells were found 4 and 7 d after exercise. There was a positive correlation between accumulation of radiolabeled leukocytes and muscle weakness measured 1-3 d after exercise (r = 0.8, P < 0.05) and, surprisingly, a negative correlation between radiolabeled leukocyte accumulation and muscle soreness (r = -0.96, P < 0.01). Conclusion: Exercise-induced muscle damage initiated a rapid local inflammatory response that gradually increased over the next days. Halted recovery of muscle function was associated with local accumulation of leukocytes, whereas muscle soreness could not be explained by the presence of leukocytes

Changes in the eccentric phase contribute to improved stretch-shorten cycle performance after training

Abstract: Purpose: To determine whether ballistic power training and strength training result in specific changes in stretch-shorten cycle (SSC) function during the eccentric (ECC) phase and, if so, whether these changes are influenced by the individual's strength level. Methods: Thirty-two male subjects were divided into four groups: stronger power training group (SP, n = 8, squat one-repetition maximum-to-body mass ratio (1RM/BM) = 1.97 ± 0.08), weaker power training group (WP, n = 8, 1RM/BM = 1.32 ± 0.14), weaker strength training group (WS, n = 8, 1RM/BM = 1.28 ± 0.17), or control group (C, n = 8, 1RM/BM = 1.37 ± 0.13). Training involved three sessions per week for 10 wk. The SP and WP groups performed maximal-effort jump squats with 0%-30% 1RM, and the WS group performed back squats at 75%-90% 1RM. Maximal strength, jump performance, musculotendinous stiffness, and neural activation were assessed before training and after 5 and 10 wk of training. Results: Both power and strength training elicited significant changes in a multitude of ECC variables that were significantly associated with improvements in concentric (CON) performance. Enhancements in CON performance were theorized to be driven by the development of a strategy to better use the ECC phase during jumping (i.e., greater unloading allowed for increased negative acceleration and thus velocity during the countermovement and improved musculotendinous stiffness resulted in an enhanced ability to translate the momentum developed during the ECC phase into force). Although a significant improvement in maximal strength resulted in changes to SSC function during the ECC phase, the initial strength level did not significantly affect the ECC variables before training or the magnitude of adaptations in individuals exposed to ballistic power training. Conclusions: Training-induced alterations in SSC function during the ECC phase contributes to improvements in jump performance after both ballistic power training and heavy strength training.

Interventions for increasing physical activity at child care.

Abstract: Experts agree that physical activity is critical to children's health and development. Child care is an ideal setting that could be used to increase physical activity given the large number of young children enrolled. To effectively address physical activity at child care, it is necessary to understand what strategies are most effective. This article reviews existing intervention studies targeting physical activity conducted within a child care setting (including preschools, nursery schools, and day care). Given the limited work in this setting, liberal criteria were used that allowed for inclusion of studies with diverse outcomes (physical activity, physical activity-related, motor skills) and a variety of research designs (randomized control, quasi-experimental, single group). Searching six databases, 1355 studies were located, and 19 met inclusion criteria. Half of the studies that assessed intervention impact on physical activity reported significant findings. All five studies measuring motor skills and eight assessing physical activity-related outcomes demonstrated generally positive findings. Although the variety of outcome measures and research quality made it difficult to draw conclusions, findings do provide encouragement that regularly provided, structured physical activity programs can increase the amount and intensity of physical activity that children receive and improve children's motor skills. These studies also demonstrate that the organized child care setting provides multiple targets for intervention beyond structured activity programs; however, additional studies are needed to explore such opportunities.