Author
Alun G. Williams
Other affiliations: Sheffield Hallam University, Staffordshire University, University College London
Bio: Alun G. Williams is an academic researcher from Manchester Metropolitan University. The author has contributed to research in topics: Skeletal muscle & Medicine. The author has an hindex of 34, co-authored 107 publications receiving 5347 citations. Previous affiliations of Alun G. Williams include Sheffield Hallam University & Staffordshire University.
Topics: Skeletal muscle, Medicine, Genetic testing, Population, Athletes
Papers published on a yearly basis
Papers
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TL;DR: The gains in strength with HRST are undoubtedly due to a wide combination of neurological and morphological factors, although there is contrary evidence suggesting no change in cortical or corticospinal excitability.
Abstract: High-resistance strength training (HRST) is one of the most widely practiced forms of physical activity, which is used to enhance athletic performance, augment musculo-skeletal health and alter body aesthetics. Chronic exposure to this type of activity produces marked increases in muscular strength, which are attributed to a range of neurological and morphological adaptations. This review assesses the evidence for these adaptations, their interplay and contribution to enhanced strength and the methodologies employed. The primary morphological adaptations involve an increase in the cross-sectional area of the whole muscle and individual muscle fibres, which is due to an increase in myofibrillar size and number. Satellite cells are activated in the very early stages of training; their proliferation and later fusion with existing fibres appears to be intimately involved in the hypertrophy response. Other possible morphological adaptations include hyperplasia, changes in fibre type, muscle architecture, myofilament density and the structure of connective tissue and tendons. Indirect evidence for neurological adaptations, which encompasses learning and coordination, comes from the specificity of the training adaptation, transfer of unilateral training to the contralateral limb and imagined contractions. The apparent rise in whole-muscle specific tension has been primarily used as evidence for neurological adaptations; however, morphological factors (e.g. preferential hypertrophy of type 2 fibres, increased angle of fibre pennation, increase in radiological density) are also likely to contribute to this phenomenon. Changes in inter-muscular coordination appear critical. Adaptations in agonist muscle activation, as assessed by electromyography, tetanic stimulation and the twitch interpolation technique, suggest small, but significant increases. Enhanced firing frequency and spinal reflexes most likely explain this improvement, although there is contrary evidence suggesting no change in cortical or corticospinal excitability. The gains in strength with HRST are undoubtedly due to a wide combination of neurological and morphological factors. Whilst the neurological factors may make their greatest contribution during the early stages of a training programme, hypertrophic processes also commence at the onset of training.
1,086 citations
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TL;DR: It was concluded that acceleration, maximum speed, and agility are specific qualities and relatively unrelated to one another and suggest that specific testing and training procedures for each speed component should be utilized when working with elite players.
Abstract: High-speed actions
are known to impact soccer performance and can be categorized
into actions requiring maximal speed, acceleration, or
agility. Contradictory findings have been reported as to the extent
of the relationship between the different speed components.
This study comprised 106 professional soccer players who were
assessed for 10-m sprint (acceleration), flying 20-m sprint (maximum
speed), and zigzag agility performance. Although performances
in the three tests were all significantly correlated (p ,
0.0005), coefficients of determination (r2) between the tests were
just 39, 12, and 21% for acceleration and maximum speed, acceleration
and agility, and maximum speed and agility, respectively.
Based on the low coefficients of determination, it was concluded
that acceleration, maximum speed, and agility are specific
qualities and relatively unrelated to one another. The findings
suggest that specific testing and training procedures for
each speed component should be utilized when working with
elite players.
574 citations
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Haramaya University1, Université de Moncton2, Université de Montréal3, University of Ibadan4, National Heart Foundation of Australia5, University of La Frontera6, University of Cuenca7, University of Waterloo8, University of the Republic9, Ghent University10, National Taiwan University11, University of Ottawa12, Karolinska Institutet13, Technische Universität München14, University of the Witwatersrand15, University of Cape Town16, Swansea University17, Lithuanian Sports University18, Emory University19, University of Los Andes20, Central University of Venezuela21, Hong Kong Baptist University22, Qatar Airways23, University of Tartu24, University of Regina25, The Chinese University of Hong Kong26, Mahidol University27, Pennington Biomedical Research Center28, University of Queensland29, Seoul National University30, Queen's University31, Linköping University32, University of Medicine and Health Sciences33, University of Guadalajara34, Shanghai University of Sport35, National University of Science and Technology36, University of Primorska37, University of Porto38, University of Ghana39, University of Strathclyde40, Carlos III Health Institute41, University of Girona42, Universidade Federal de Santa Catarina43, Katholieke Universiteit Leuven44, University of South Australia45, University of Southern Denmark46, University of Auckland47, Bath Spa University48, University of Ljubljana49, Tribhuvan University50, Utrecht University51, J. F. Oberlin University52, University of Botswana53, Stamford University Bangladesh54, National Chung Hsing University55, University of Warsaw56
TL;DR: The present study provides rich new evidence showing that the situation regarding the physical activity of children and youth is a concern worldwide and strategic public investments to implement effective interventions to increase physical activity opportunities are needed.
Abstract: Background: Accumulating sufficient moderate to vigorous physical activity is recognized as a key determinant of physical, physiological, developmental, mental, cognitive, and social health among children and youth (aged 5–17 y). The Global Matrix 3.0ofReportCardgradesonphysicalactivitywasdevelopedtoachieveabetterunderstandingoftheglobalvariationinchildand youth physical activity and associated supports. Methods: Work groups from 49 countries followed harmonized procedures to develop their Report Cards by grading 10 common indicators using the best available data. The participating countries were divided into 3 categories using the United Nations’ human development index (HDI) classification (low or medium, high, and very high HDI). Results: A total of 490 grades, including 369 letter grades and 121 incomplete grades, were assigned by the 49 work groups. Overall, an average grade of “C−,”“D+,” and “C−” was obtained for the low and medium HDI countries, high HDI countries, and very high HDI countries, respectively. Conclusions: The present study provides rich new evidence showing that the situation regarding the physical activity of children and youth is a concern worldwide. Strategic public investments to implement effective interventions to increase physical activity opportunities are needed.
502 citations
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TL;DR: Examining the effects of different modes of stretching within a pre-exercise warm-up on high-speed motor capacities important to soccer performance found dynamic stretching during the warm up was most effective as preparation for subsequent high- speed performance.
Abstract: The purpose of this study was to examine the effects of different modes of stretching within a pre-exercise warm-up on high-speed motor capacities important to soccer performance. Eighteen professional soccer players were tested for countermovement vertical jump, stationary 10-m sprint, flying 20-m sprint, and agility performance after different warm-ups consisting of static stretching, dynamic stretching, or no stretching. There was no significant difference among warm-ups for the vertical jump: mean +/- SD data were 40.4 +/- 4.9 cm (no stretch), 39.4 +/- 4.5 cm (static), and 40.2 +/- 4.5 cm (dynamic). The dynamic-stretch protocol produced significantly faster 10-m sprint times than did the no-stretch protocol: 1.83 +/- 0.08 seconds (no stretch), 1.85 +/- 0.08 seconds (static), and 1.87 +/- 0.09 seconds (dynamic). The dynamic- and static-stretch protocols produced significantly faster flying 20-m sprint times than did the no-stretch protocol: 2.41 +/- 0.13 seconds (no stretch), 2.37 +/- 0.12 seconds (static), and 2.37 +/- 0.13 seconds (dynamic). The dynamic-stretch protocol produced significantly faster agility performance than did both the no-stretch protocol and the static-stretch protocol: 5.20 +/- 0.16 seconds (no stretch), 5.22 +/- 0.18 seconds (static), and 5.14 +/- 0.17 seconds (dynamic). Static stretching does not appear to be detrimental to high-speed performance when included in a warm-up for professional soccer players. However, dynamic stretching during the warm-up was most effective as preparation for subsequent high-speed performance.
364 citations
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TL;DR: In this article, training-related changes in the mechanical efficiency of human skeletal muscle (energy used per unit power output) were examined, and the presence of this ACE allele confers an enhanced mechanical efficiency in trained muscle.
Abstract: Angiotensin-converting enzyme in human skeletal muscle1 can be encoded by either of two variants of the ACE gene2, one of which carries an insertion of 287 base pairs. This longer allele gives rise to lower enzyme activity2, and is associated with enhanced endurance performance3 and an anabolic response to intense exercise training4. Here we examine training-related changes in the mechanical efficiency of human skeletal muscle (energy used per unit power output) and find that the presence of this ACE allele confers an enhanced mechanical efficiency in trained muscle.
287 citations
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TL;DR: An update on the physiology of soccer players and referees, and relevant physiological tests is provided, and examples of effective strength- and endurance-training programmes to improve on-field performance are given.
Abstract: Soccer is the most popular sport in the world and is performed by men and women, children and adults with different levels of expertise. Soccer performance depends upon a myriad of factors such as technical/biomechanical, tactical, mental and physiological areas. One of the reasons that soccer is so popular worldwide is that players may not need to have an extraordinary capacity within any of these performance areas, but possess a reasonable level within all areas. However, there are trends towards more systematic training and selection influencing the anthropometric profiles of players who compete at the highest level. As with other activities, soccer is not a science, but science may help improve performance. Efforts to improve soccer performance often focus on technique and tactics at the expense of physical fitness. During a 90-minute game, elite-level players run about 10 km at an average intensity close to the anaerobic threshold (80-90% of maximal heart rate). Within this endurance context, numerous explosive bursts of activity are required, including jumping, kicking, tackling, turning, sprinting, changing pace, and sustaining forceful contractions to maintain balance and control of the ball against defensive pressure. The best teams continue to increase their physical capacities, whilst the less well ranked have similar values as reported 30 years ago. Whether this is a result of fewer assessments and training resources, selling the best players, and/or knowledge of how to perform effective exercise training regimens in less well ranked teams, is not known. As there do exist teams from lower divisions with as high aerobic capacity as professional teams, the latter factor probably plays an important role. This article provides an update on the physiology of soccer players and referees, and relevant physiological tests. It also gives examples of effective strength- and endurance-training programmes to improve on-field performance. The cited literature has been accumulated by computer searching of relevant databases and a review of the authors' extensive files. From a total of 9893 papers covering topics discussed in this article, 843 were selected for closer scrutiny, excluding studies where information was redundant, insufficient or the experimental design was inadequate. In this article, 181 were selected and discussed. The information may have important implications for the safety and success of soccer players and hopefully it should be understood and acted upon by coaches and individual soccer players.
1,841 citations
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TL;DR: The metabolic responses and molecular mechanisms that underpin the adaptatation of skeletal muscle to acute exercise and exercise training are reviewed.
1,505 citations
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TL;DR: This eighth edition of exercise physiology is updated with the latest research in the field to give you easy to understand up to date coverage of how nutrition energy transfer and exercise training affect human performance.
1,328 citations
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TL;DR: Current prevalence and trends of insufficient physical activity among school-going adolescents aged 11–17 years by country, region, and globally are described and urgent scaling up of implementation of known effective policies and programmes is needed.
1,293 citations
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TL;DR: The epidemiological distinction between the generic term "physical activity" and the specific category of "exercise", which implies activity for a specific purpose such as improvement of physical condition or competition is recognised.
Abstract: An ever-growing volume of peer-reviewed publications speaks to the recent and rapid growth in both scope and understanding of exercise immunology. Indeed, more than 95% of all peer-reviewed publications in exercise immunology (currently >2, 200 publications using search terms "exercise" and "immune") have been published since the formation of the International Society of Exercise and Immunology (ISEI) in 1989 (ISI Web of Knowledge). We recognise the epidemiological distinction between the generic term "physical activity" and the specific category of "exercise", which implies activity for a specific purpose such as improvement of physical condition or competition. Extreme physical activity of any type may have implications for the immune system. However, because of its emotive component, exercise is likely to have a larger effect, and to date the great majority of our knowledge on this subject comes from exercise studies.
1,260 citations