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1.
The Effect of Exercise Training on the Energetic Cost of Cycling.
Montero, D, Lundby, C
Sports medicine (Auckland, N.Z.). 2015;(11):1603-18
Abstract
BACKGROUND AND OBJECTIVE The energetic cost of cycling (CE) is a major contributor to cycling performance but whether CE can be improved by exercise intervention remains uncertain. Here, we sought to systematically review and determine the effect of exercise training on CE in healthy humans. METHODS MEDLINE, Scopus, and Web of Science were searched since their inceptions up until December 2014 for articles assessing the effect of exercise training in healthy subjects on CE, as determined by cycling economy or efficiency. Meta-analyses were performed to determine the standardized mean difference (SMD) in CE between post- and pre-training measurements. Subgroup and meta-regression analyses were used to evaluate potential moderating/confounding factors. RESULTS Fifty-one studies were included after systematic review, comprising a total of 531 healthy subjects (mean age = 20-66 years). Exercise interventions primarily consisted of endurance and/or strength training ranging from 4 to 34 weeks of duration. After data pooling, the meta-analysis revealed that CE was improved with strength training alone or along with endurance training (n = 16, SMD = -0.50, P < 0.0001) but not with endurance training alone (n = 33, SMD = -0.18, P = 0.08). In further subgroup analyses, endurance training alone was effective in improving CE in previously untrained (n = 20, SMD = -0.21, P = 0.04) but not in trained (n = 6, SMD = 0.09, P = 0.75) subjects. The SMD in CE was associated with the duration of training (n = 51, B = -0.03, P = 0.0002). CONCLUSION The current meta-analysis provides evidence that CE is improved by exercise training, particularly when strength training or untrained subjects are included.
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2.
Trends in Physical Activity and Sedentary Behaviors of United States Youth.
Bassett, DR, John, D, Conger, SA, Fitzhugh, EC, Coe, DP
Journal of physical activity & health. 2015;(8):1102-11
Abstract
BACKGROUND Increases in childhood and adolescent obesity are a growing concern in the United States (U.S.), and in most countries throughout the world. Declines in physical activity are often postulated to have contributed to the rise in obesity rates during the past 40 years. METHODS We searched for studies of trends in physical activity and sedentary behaviors of U.S. youth, using nontraditional data sources. Literature searches were conducted for active commuting, physical education, high-school sports, and outdoor play. In addition, trends in sedentary behaviors were examined. RESULTS Data from the Youth Risk Behavior Surveillance System (YRBSS) and other national surveys, as well as longitudinal studies in the transportation, education, electronic media, and recreation sectors showed evidence of changes in several indicators. Active commuting, high school physical education, and outdoor play (in 3- to 12-year-olds) declined over time, while sports participation in high school girls increased from 1971 to 2012. In addition, electronic entertainment and computer use increased during the first decade of the 21st century. CONCLUSIONS Technological and societal changes have impacted the types of physical activities performed by U.S. youth. These data are helpful in understanding the factors associated with the rise in obesity, and in proposing potential solutions.
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3.
Strategies to improve running economy.
Barnes, KR, Kilding, AE
Sports medicine (Auckland, N.Z.). 2015;(1):37-56
Abstract
Running economy (RE) represents a complex interplay of physiological and biomechanical factors that is typically defined as the energy demand for a given velocity of submaximal running and expressed as the submaximal oxygen uptake (VO2) at a given running velocity. This review considered a wide range of acute and chronic interventions that have been investigated with respect to improving economy by augmenting one or more components of the metabolic, cardiorespiratory, biomechanical or neuromuscular systems. Improvements in RE have traditionally been achieved through endurance training. Endurance training in runners leads to a wide range of physiological responses, and it is very likely that these characteristics of running training will influence RE. Training history and training volume have been suggested to be important factors in improving RE, while uphill and level-ground high-intensity interval training represent frequently prescribed forms of training that may elicit further enhancements in economy. More recently, research has demonstrated short-term resistance and plyometric training has resulted in enhanced RE. This improvement in RE has been hypothesized to be a result of enhanced neuromuscular characteristics. Altitude acclimatization results in both central and peripheral adaptations that improve oxygen delivery and utilization, mechanisms that potentially could improve RE. Other strategies, such as stretching should not be discounted as a training modality in order to prevent injuries; however, it appears that there is an optimal degree of flexibility and stiffness required to maximize RE. Several nutritional interventions have also received attention for their effects on reducing oxygen demand during exercise, most notably dietary nitrates and caffeine. It is clear that a range of training and passive interventions may improve RE, and researchers should concentrate their investigative efforts on more fully understanding the types and mechanisms that affect RE and the practicality and extent to which RE can be improved outside the laboratory.
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4.
Physiological and health-related adaptations to low-volume interval training: influences of nutrition and sex.
Gibala, MJ, Gillen, JB, Percival, ME
Sports medicine (Auckland, N.Z.). 2014;(Suppl 2):S127-37
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Abstract
Interval training refers to the basic concept of alternating periods of relatively intense exercise with periods of lower-intensity effort or complete rest for recovery. Low-volume interval training refers to sessions that involve a relatively small total amount of exercise (i.e. ≤10 min of intense exercise), compared with traditional moderate-intensity continuous training (MICT) protocols that are generally reflected in public health guidelines. In an effort to standardize terminology, a classification scheme was recently proposed in which the term 'high-intensity interval training' (HIIT) be used to describe protocols in which the training stimulus is 'near maximal' or the target intensity is between 80 and 100 % of maximal heart rate, and 'sprint interval training' (SIT) be used for protocols that involve 'all out' or 'supramaximal' efforts, in which target intensities correspond to workloads greater than what is required to elicit 100 % of maximal oxygen uptake (VO2max). Both low-volume SIT and HIIT constitute relatively time-efficient training strategies to rapidly enhance the capacity for aerobic energy metabolism and elicit physiological remodeling that resembles changes normally associated with high-volume MICT. Short-term SIT and HIIT protocols have also been shown to improve health-related indices, including cardiorespiratory fitness and markers of glycemic control in both healthy individuals and those at risk for, or afflicted by, cardiometabolic diseases. Recent evidence from a limited number of studies has highlighted potential sex-based differences in the adaptive response to SIT in particular. It has also been suggested that specific nutritional interventions, in particular those that can augment muscle buffering capacity, such as sodium bicarbonate, may enhance the adaptive response to low-volume interval training.
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5.
School-based programs aimed at the prevention and treatment of obesity: evidence-based interventions for youth in Latin America.
Lobelo, F, Garcia de Quevedo, I, Holub, CK, Nagle, BJ, Arredondo, EM, Barquera, S, Elder, JP
The Journal of school health. 2013;(9):668-77
Abstract
BACKGROUND Rapidly rising childhood obesity rates constitute a public health priority in Latin America which makes it imperative to develop evidence-based strategies. Schools are a promising setting but to date it is unclear how many school-based obesity interventions have been documented in Latin America and what level of evidence can be gathered from such interventions. METHODS We performed a systematic review of papers published between 1965 and December 2010. Interventions were considered eligible if they had a school-based component, were done in Latin America, evaluated an obesity related outcome (body mass index [BMI], weight, %body fat, waist circumference, BMI z-score), and compared youth exposed vs not exposed. RESULTS Ten studies were identified as having a school-based component. Most interventions had a sample of normal and overweight children. The most successful interventions focused on prevention rather than treatment, had longer follow-ups, a multidisciplinary team, and fewer limitations in execution. Three prevention and 2 treatment interventions found sufficient improvements in obesity-related outcomes. CONCLUSIONS We found sufficient evidence to recommend school-based interventions to prevent obesity among youth in Latin America. Evidence-based interventions in the school setting should be promoted as an important component for integrated programs, policies, and monitoring frameworks designed to reverse the childhood obesity in the region.
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6.
Respiratory dysfunction in ventilated patients: can inspiratory muscle training help?
Bissett, B, Leditschke, IA, Paratz, JD, Boots, RJ
Anaesthesia and intensive care. 2012;(2):236-46
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Abstract
Respiratory muscle dysfunction is associated with prolonged and difficult weaning from mechanical ventilation. This dysfunction in ventilator-dependent patients is multifactorial: there is evidence that inspiratory muscle weakness is partially explained by disuse atrophy secondary to ventilation, and positive end-expiratory pressure can further reduce muscle strength by negatively shifting the length-tension curve of the diaphragm. Polyneuropathy is also likely to contribute to apparent muscle weakness in critically ill patients, and nutritional and pharmaceutical effects may further compound muscle weakness. Moreover, psychological influences, including anxiety, may contribute to difficulty in weaning. There is recent evidence that inspiratory muscle training is safe and feasible in selected ventilator-dependent patients, and that this training can reduce the weaning period and improve overall weaning success rates. Extrapolating from evidence in sports medicine, as well as the known effects of inspiratory muscle training in chronic lung disease, a theoretical model is proposed to describe how inspiratory muscle training enhances weaning and recovery from mechanical ventilation. Possible mechanisms include increased protein synthesis (both Type 1 and Type 2 muscle fibres), enhanced limb perfusion via dampening of a sympathetically-mediated metaboreflex, reduced lactate levels and modulation of the perception of exertion, resulting in less dyspnoea and enhanced exercise capacity.
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Survey of antiobesity legislation: are these laws working?
Downey, M, Still, C
Current opinion in endocrinology, diabetes, and obesity. 2012;(5):375-80
Abstract
PURPOSE OF REVIEW Obesity is well recognized as a major public health crisis throughout the USA. In recent years, governmental bodies at the federal, state and local levels have enacted policies intended to prevent the transition to obesity. Researchers have had the opportunity to study these policies and evaluate their impact on prevention of obesity. RECENT FINDINGS Most public policies have been directed principally, but not exclusively, to the prevention of obesity in school-age children. Interventions have been directed to encouraging breast-feeding, to changing school lunches, limiting access to sugar-sweetened beverages, encouraging physical activity, changing the composition of competitive foods and affecting food advertising directed at children as well as collecting BMI information. Efforts more directed at adults include encouraging workplace wellness programs and improving the nutrition label on packaged foods with front-of-package labels and caloric information on restaurant menus. SUMMARY For the most part, evaluations of the interventions reveal weak or modest benefits. The actual picture might be less positive due to the poor quality of research and publication bias. Push back by industry and others will require higher quality experimental and real world studies. All interventions fail to accommodate the multifactorial aspects of obesity.
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[High intensity training (HIT) for the improvement of endurance capacity of recreationally active people and in prevention & rehabilitation].
Wahl, P, Hägele, M, Zinner, C, Bloch, W, Mester, J
Wiener medizinische Wochenschrift (1946). 2010;(23-24):627-36
Abstract
Although intensive exercise protocols are commonly used in practical training and scientific studies, there is recently a great scientific discussion about "high intensity (interval) training" (HIT). New are the large amounts of studies and the more detailed knowledge about the physiological responses and adaptations to HIT in comparison to the classic high volume, low intensity endurance training. The present article summarizes the current knowledge about HIT in endurance exercise for clinical applications. In the first part, molecular and cellular adaptations to HIT are discussed in comparison to low intensity high volume training. Furthermore, studies are summarized which compare HIT vs. HVT in the field of prevention and rehabilitation. Terminally the differences in physiological stimuli of both training interventions are considered.
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Maximising performance in triathlon: applied physiological and nutritional aspects of elite and non-elite competitions.
Bentley, DJ, Cox, GR, Green, D, Laursen, PB
Journal of science and medicine in sport. 2008;(4):407-16
Abstract
Triathlon is a sport consisting of sequential swimming, cycling and running. The main diversity within the sport of triathlon resides in the varying event distances, which creates specific technical, physiological and nutritional considerations for athlete and practitioner alike. The purpose of this article is to review physiological as well as nutritional aspects of triathlon and to make recommendations on ways to enhance performance. Aside from progressive conditioning and training, areas that have shown potential to improve triathlon performance include drafting when possible during both the swim and cycle phase, wearing a wetsuit, and selecting a lower cadence (60-80 rpm) in the final stages of the cycle phase. Adoption of a more even racing pace during cycling may optimise cycling performance and induce a "metabolic reserve" necessary for elevated running performance in longer distance triathlon events. In contrast, drafting in swimming and cycling may result a better tactical approach to increase overall performance in elite Olympic distance triathlons. Daily energy intake should be modified to reflect daily training demands to assist triathletes in achieving body weight and body composition targets. Carbohydrate loading strategies and within exercise carbohydrate intake should reflect the specific requirements of the triathlon event contested. Development of an individualised fluid plan based on previous fluid balance observations may assist to avoid both dehydration and hyponatremia during prolonged triathlon racing.
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Physical education and sport in schools: a review of benefits and outcomes.
Bailey, R
The Journal of school health. 2006;(8):397-401
Abstract
This paper explores the scientific evidence that has been gathered on the contributions and benefits of physical education and sport (PES) in schools for both children and for educational systems. Research evidence is presented in terms of children's development in a number of domains: physical, lifestyle, affective, social, and cognitive. The review suggests that PES have the potential to make significant and distinctive contributions to development in each of these domains. It is suggested that PES have the potential to make distinctive contributions to the development of children's fundamental movement skills and physical competences, which are necessary precursors of participation in later lifestyle and sporting physical activities. They also, when appropriately presented, can support the development of social skills and social behaviors, self-esteem and proschool attitudes, and, in certain circumstances, academic and cognitive development. The review also stresses that many of these benefits will not necessarily result from participation, per se; the effects are likely to be mediated by the nature of the interactions between students and their teachers, parents, and coaches who work with them. Contexts that emphasize positive experiences, characterized by enjoyment, diversity, and the engagement of all, and that are managed by committed and trained teachers and coaches, and supportive and informed parents, significantly influence the character of these physical activities and increase the likelihood of realizing the potential benefits of participation.