Introduction: Trail running is an increasing popular endurance discipline. Thegoal of the present study was to investigate long range correlations in strideintervals during a full trail running time trial.Methods: Adopting an exploratory approach, it was hypothesized that thestrength of such correlations would differ between uphill and downhill sectionsand between the initial and final stage of the race (incline and stage asindependent variables). Twenty participants were recruited to run a solo all-outtime trial equipped with inertial sensors to calculate stride intervals. Thestrength of long range correlations in stride intervals was quantified by meansof Detrended Fluctuations Analysis alpha exponents (DFA-alpha). Differencesacross conditions were tested by means of linear mixed effect models.Results and discussion: A significant main effect for incline was found, withhigher values of DFA-alpha in downhill sections (resulting from less tightcontrol) with respect to uphill. This is likely due to the higher technicaldifficulty running at high speed on an uneven surface. A significant maineffect was found for race stage, with stronger correlations in the second racehalf as compared to the first one, most likely resulting from the difficulty toregulate running cadence in presence of acute fatigue. A significantinteraction between incline and race stage was found as well, indicating thatthe strength of long range correlations in the second half of the raceincreased in both uphill and downhill sections, but the increase wassignificantly larger in uphill sections. This is likely due to the increase inphysical fatigue which is prevalent in uphill sections, whilst the technicaldifficulty of downhill section remains constant. The present study shows thatDFA-alpha is a sensitive quantity to discriminate between more and lesschallenging motor control scenarios. Incorporating such DFA-alpha amongthe metrics provided by wearables may aid runners in choosing a pacingstrategy aiming to minimize fall and injury risks.
Introduction: In male team handball, different playing positions have differentdemands due to their tactical roles. However, if the game-based physicalperformance differs across playing positions has not been analyzed, althoughthis is crucial for training young elite players to reach a world-class levelbased on their specific positions. Consequently, the aim of this study was toanalyze game-based performance in young elite male team handball playersbased on their playing positions.Methods: Forty-eight young elite male team handball players (age: 17.5 ± 1.9years, body weight: 82.5 ± 9.9 kg, body height: 1.86 ± 0.05 m), including 23backs, 17 wings and 8 pivots participated in the study. All players trained 7–8sessions per week at an elite team handball academy and competed at thehighest international level for their age group. To determine specific physicalperformance, all participants performed the team handball game-basedperformance test. A one-way ANOVA was used to compare the performancedifferences among backs, wings and pivots.Results: Significant differences between playing positions (P < 0.05) were foundin peak oxygen uptake, heart rate, fast break and offense time, jump heightduring the jump shot, and body mass. Wings showed the best performancein fast break (1.78 ± 0.08 s), offense time (5.74 ± 0.19 s), jump height duringthe jump shot (0.39 ± 0.06 m), and peak oxygen uptake (72.4 ± 8.4 ml/kg/min). Backs performed best in ball velocity during the jump shot(25.1 ± 1.5 m/s), while pivots had the highest body weight (90.5 ± 14.1 kg).Discussion: As expected, pivots were the heaviest due to facing the mostphysical contact with defenders during matches. Wings were the fastest onthe court and jumped the highest, while backs demonstrated the highestthrowing velocities, as they frequently perform long-distance throws duringgames. However, the high levels of peak oxygen uptake for wings and backs(around 70 ml/kg/min) and pivots (around 60 ml/kg/min), along with nosignificant differences in defense time between positions, highlight theimportance of both aerobic and anaerobic performance for all players tomaintain an active and dynamic performance throughout the entire match.
POINT-COUNTERPOINTCounterpoint: The interpolated twitch does not provide a valid measure of the voluntary activation of muscleA. de Haan, K. H. L. Gerrits, and C. J. de RuiterA. de Haan, K. H. L. Gerrits, and C. J. de RuiterPublished Online:01 Jul 2009https://doi.org/10.1152/japplphysiol.91220.2008aMoreSectionsPDF (105 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations The interpolated twitch technique (ITT) was first used by Merton (17) who superimposed an evoked stimulation on a voluntary contraction to detect muscle fibers not activated by the voluntary effort. The method has since been applied, mainly during isometric contractions, to determine how much of the muscles' potential can be used voluntarily. When no extra force is produced on a superimposed stimulus, this is usually taken as sign that "full activation" was achieved. Different methodological issues related to the measurement of voluntary activation have been addressed in the past, such as timing of, potentiation of, and type (single, doublet, multiple pulses) of the superimposed stimulus (6, 12, 18, 19), intermuscular differences (5), the method of extrapolation used to determine maximal muscle capacity (linear or curvilinear (4, 12), the influence of series elastic structures, synergistic and antagonist activation (2, 16), etc. Overall, these methodological reports indicate that the method can provide a valid estimation of voluntary activation, but that it should be used with care. In this Point:Counterpoint, we want to point out some major limitations of the ITT technique. The main issue addressed in this Counterpoint is what "full activation" signifies.The first point is the low sensitivity of the ITT method at near maximal contraction intensities (13). It should be noted that in accordance with the s-shaped stimulation frequency-force relation, the superimposed stimulus leads to relatively large increases in isometric force during submaximal contractions (with nonsaturating intracellular calcium concentrations, [Ca2+]i), but that only very small increases can be expected when maximal effort is approached. Clearly there is a low sensitivity of the ITT method at near maximal contraction intensities (13). "Full activation" in relation to the ITT method thus seems defined as the level of excitation ([Ca2+]i) needed to produce maximal force under the given contractile conditions. Surface EMG data show that for many subjects the EMG-force relationship is linear up to the near maximal voluntary isometric force (23). However, subjects with a high ability to "voluntarily activate" their muscles (e.g., with a high neural drive) show steep increases in EMG during contractions >80% of their maximal force, illustrating that much more extra excitation ([Ca2+]i ) is needed to completely use the force generating potential of the muscle (1, 14). Therefore, it can be expected that under those conditions (>80% maximal force capacity) in many experimental set ups a single superimposed twitch does not result in a measurable force increase. Consequently the force at which "full activation" is obtained is substantially underestimated in many studies.The second point is that it is not allowed to generalize findings based on a specific measurement of voluntary activation. Usually, measurements of voluntary activation have been carried out under isometric conditions and at a single specific joint angle. Such data cannot be extrapolated to other conditions. For instance, voluntary activation at one joint angle can be different from other angles, especially at angles where muscle length is short. The stimulation frequency-force relation shifts to the right at shorter muscle lengths (8), consequently higher levels of excitation are needed to obtain maximal force. It will therefore probably be more difficult to reach high levels of voluntary activation at shorter muscle lengths. Indeed, voluntary activation was measured to be lower at shorter muscle length in large muscle groups, such as the quadriceps femoris, which are relatively difficult to activate (3, 15). The poor ability to generalize voluntary activation established under isometric conditions is also illustrated by data during rapid fast "explosive" force attempts. Muscle excitation, inferred from surface EMG, is very short and much higher during jumping (10) and during fast isometric force rise (9, 22), compared with excitation at the plateau of an isometric contraction. The capacity to voluntarily activate muscles during explosive isometric contractions can be measured by comparing the initial fast-increasing force response during voluntary and electrically evoked contractions. In subjects who all had "high" voluntary activation, as established with ITT at the isometric force plateau during MVCs of the quadriceps muscles (96.5 ± 2.9%), large variations were seen in the capacity of initial activation during maximal fast contractions (9). The observed variation in this capacity was highly correlated with the initial EMG, indicating that differences in neural drive underlie this variation (9). Moreover, these findings show that the level of excitation, high enough for a near 100% activation at the plateau of an isometric contraction (full activation), is far from "full" under other conditions.The third point is that the implicit consequence of the measurement of voluntary activation is that maximal capacity is obtained at 100% voluntary activation. For the estimation of the maximal capacity, linear and curvilinear extrapolations of the superimposed force-voluntary force relation are used (7, 11). The differences in optimal curve fitting may be a consequence of variation in the ability of subject groups to "voluntarily activate" their muscles, leading to linear or curvilinear EMG-force relationships (1, 14). In almost all reports, curve fitting is performed for data of whole groups of subjects, which may mask relationships for individual subjects. Data from Kooistra et al. (14) indicate that for single subjects there might be a linear phase in the relationship between superimposed and voluntary torque, which in subjects with a very high neural drive is followed by a second (linear) phase (14 resp. Fig. 1), during which increases in EMG are much steeper than increases in voluntary force. For subjects with a very high neural drive, high voluntary activation levels (>95%) can be calculated using linear extrapolations from submaximal contraction levels, resulting in maximal capacity estimations, which are far below their real maximal capacity. From the inset in Fig. 2 it can be seen that the (very small) superimposed forces decline linearly and similarly with increasing voluntary forces on two different days. The consequence of the data for the subject displayed in Fig. 2 is that for the measurement with a torque of ∼150 Nm and extrapolating the linear relation between voluntary and superimposed torque below 150 Nm, a voluntary activation level of ∼96% is calculated, whereas in reality 150 Nm is only ∼75% of the measured maximal torque, which would indicate a voluntary activation level of ∼75%. Clearly, there is a mismatch between calculated voluntary activation levels and maximal torque capacity. Thus, even at the isometric force plateau, an almost full activation may be far from complete, at least in some subjects and in large muscle groups. In the scarce reports that show examples of data for individual subjects, linear relationships can be seen for the submaximal contractions, but there are additional data points having a low superimposed force at near maximal voluntary forces. The voluntary forces of these latter data points seem to be higher than the maximal force capacity calculated from the submaximal data (2, 19–21). Although only for subjects who are consistently very well able to activate their muscles, overestimation of voluntary activation can be demonstrated, it is conceivable that this in fact occurs for all subjects. Many subjects will not be able to further increase muscle excitation and despite measured levels of voluntary activation of ∼95% most of them do not approach their real maximal force capacity. The ITT method clearly overestimates the true voluntary activation and therewith underestimates maximal force capacity in many subjects. Fig. 2.Schematic illustration of the relationship between the amplitude of the superimposed twitch evoked by twitch interpolation and contraction strength. An inverse linear relationship is ideal. Nonlinearity can be introduced by various methodological and physiological factors.Download figureDownload PowerPointREFERENCES1 Alkner BA, Tesch PA, Berg HE. Quadriceps EMG/force relationship in knee extension and leg press. Med Sci Sports Exerc 32: 459–463, 2000.Crossref | PubMed | ISI | Google Scholar2 Allen GM, McKenzie DK, Gandevia SC. Twitch interpolation of the elbow flexor muscles at high forces. Muscle Nerve 21: 318–328, 1998.Crossref | PubMed | ISI | Google Scholar3 Becker R, Awiszus F. Physiological alterations of maximal voluntary quadriceps activation by changes of knee joint angle. 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Novel Perspectives from Mechanomyographic Data27 October 2022 | Medicine & Science in Sports & Exercise, Vol. 55, No. 3The effect of constant load cycling at extreme- and severe-intensity domains on performance fatigability and its determinants in young femaleScience & Sports, Vol. 74Determining voluntary activation in synergistic muscles: a novel mechanomyographic approach24 May 2022 | European Journal of Applied Physiology, Vol. 122, No. 8Acute Neuromuscular and Hormonal Responses to Power, Strength, and Hypertrophic Protocols and Training Background14 July 2022 | Frontiers in Sports and Active Living, Vol. 4Increase in Volitional Muscle Activation from Childhood to Adulthood: A Systematic Review and Meta-analysis30 December 2021 | Medicine & Science in Sports & Exercise, Vol. 54, No. 5A voluntary activation deficit in m. abductor hallucis exists in asymptomatic feetJournal of Biomechanics, Vol. 130Quantification of central fatigue: a central debate15 May 2021 | European Journal of Applied Physiology, Vol. 121, No. 9Comparison Between Isometric and Concentric Motor Fatigability in Persons With Multiple Sclerosis and Healthy Controls – exploring central and peripheral contributions of motor fatigability22 May 2021 | Neurorehabilitation and Neural Repair, Vol. 35, No. 7Specific motor cortex hypoexcitability and hypoactivation in COPD patients with peripheral muscle weakness3 January 2020 | BMC Pulmonary Medicine, Vol. 20, No. 1Peripheral Electrical Stimulation Paired With Movement-Related Cortical Potentials Improves Isometric Muscle Strength and Voluntary Activation Following Stroke15 May 2020 | Frontiers in Human Neuroscience, Vol. 14Quantification of Neuromuscular Fatigue: What Do We Do Wrong and Why?12 November 2019 | Sports Medicine, Vol. 50, No. 3Neuromuscular Factors Contributing to Reductions in Muscle Force After Repeated, High-Intensity Muscular Efforts24 June 2019 | Frontiers in Physiology, Vol. 10Neural Adaptations to Endurance Training1 November 2018Neural and Muscular Function in the Heat7 March 2019The role of the nervous system in neuromuscular fatigue induced by ultra-endurance exerciseApplied Physiology, Nutrition, and Metabolism, Vol. 43, No. 11Estimating Voluntary Activation Of The Elbow And Wrist Muscles In Chronic Hemiparetic Stroke Using Twitch Interpolation MethodologyPlasticity in central neural drive with short-term disuse and recovery - effects on muscle strength and influence of agingExperimental Gerontology, Vol. 106The Effects of Sex and Motoneuron Pool on Central FatigueMedicine & Science in Sports & Exercise, Vol. 50, No. 5Neurophysiological Mechanisms Underpinning Stretch-Induced Force Loss24 January 2017 | Sports Medicine, Vol. 47, No. 8Voluntary activation of biceps-to-triceps and deltoid-to-triceps transfers in quadriplegia2 March 2017 | PLOS ONE, Vol. 12, No. 3Original Research: Central and peripheral quadriceps fatigue in young and middle-aged untrained and endurance-trained men: A comparative study24 July 2016 | Experimental Biology and Medicine, Vol. 241, No. 16Voluntary muscle activation improves with power training and is associated with changes in gait speed in mobility-limited older adults — A randomized controlled trialExperimental Gerontology, Vol. 80Muscle Fatigue Affects the Interpolated Twitch Technique When Assessed Using Electrically-Induced Contractions in Human and Rat Muscles28 June 2016 | Frontiers in Physiology, Vol. 7Is the notion of central fatigue based on a solid foundation?Paola Contessa, Alessio Puleo, and Carlo J. De Luca16 February 2016 | Journal of Neurophysiology, Vol. 115, No. 2Task-specific neural adaptations to isoinertial resistance training31 July 2014 | Scandinavian Journal of Medicine & Science in Sports, Vol. 25, No. 5Children have a reduced maximal voluntary activation level of the adductor pollicis muscle compared to adults19 February 2015 | European Journal of Applied Physiology, Vol. 115, No. 7Evaluation of Central and Peripheral Fatigue in the Quadriceps Using Fractal Dimension and Conduction Velocity in Young Females16 April 2015 | PLOS ONE, Vol. 10, No. 4Activation deficit correlates with weakness in chronic stroke: Evidence from evoked and voluntary EMG recordingsClinical Neurophysiology, Vol. 125, No. 12The influence of strength training on muscle activation in elderly persons: A systematic review and meta-analysisExperimental Gerontology, Vol. 58Time Course of Central and Peripheral Alterations after Isometric Neuromuscular Electrical Stimulation-Induced Muscle Damage12 September 2014 | PLoS ONE, Vol. 9, No. 9Combining heat stress and moderate hypoxia reduces cycling time to exhaustion without modifying neuromuscular fatigue characteristics19 April 2014 | European Journal of Applied Physiology, Vol. 114, No. 7Insights into the neural control of eccentric contractionsJacques Duchateau, and Stéphane Baudry1 June 2014 | Journal of Applied Physiology, Vol. 116, No. 11Neuromuscular Adjustments of the Quadriceps Muscle after Repeated Cycling Sprints1 May 2013 | PLoS ONE, Vol. 8, No. 5Hot conditions improve power output during repeated cycling sprints without modifying neuromuscular fatigue characteristics29 June 2012 | European Journal of Applied Physiology, Vol. 113, No. 2Potential interests and limits of magnetic and electrical stimulation techniques to assess neuromuscular fatigueNeuromuscular Disorders, Vol. 22Distinct profiles of neuromuscular fatigue during muscle contractions below and above the critical torque in humansMark Burnley, Anni Vanhatalo, and Andrew M. Jones15 July 2012 | Journal of Applied Physiology, Vol. 113, No. 2Effect of stimulation intensity on assessment of voluntary activation10 May 2012 | Muscle & Nerve, Vol. 45, No. 6Dynapenia and Aging: An Update28 March 2011 | The Journals of Gerontology: Series A, Vol. 67A, No. 1Neuromuscular Contributions to Age-Related Weakness17 March 2011 | The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol. 67A, No. 1Fatigue Perceived by Multiple Sclerosis Patients Is Associated With Muscle Fatigue19 August 2011 | Neurorehabilitation and Neural Repair, Vol. 26, No. 1Exercise and Osteoarthritis: Cause and Effects1 October 2011Electrical stimulation for testing neuromuscular function: from sport to pathology18 May 2011 | European Journal of Applied Physiology, Vol. 111, No. 10Neural adaptations to electrical stimulation strength training4 June 2011 | European Journal of Applied Physiology, Vol. 111, No. 10Short-term unilateral resistance training affects the agonist-antagonist but not the force-agonist activation relationship11 February 2011 | Muscle & Nerve, Vol. 43, No. 3Training Adaptation of the Neuromuscular System9 November 2010Muscle torque in total knee arthroplasty: comparison of subvastus and midvastus approaches11 February 2010 | Knee Surgery, Sports Traumatology, Arthroscopy, Vol. 18, No. 7The repeated bout effect of eccentric exercise is not associated with changes in voluntary activation15 December 2009 | European Journal of Applied Physiology, Vol. 108, No. 6Comments on Point:Counterpoint: The interpolated twitch does/does not provide a valid measure of the voluntary activation of muscleAstrid M. Horstman1 July 2009 | Journal of Applied Physiology, Vol. 107, No. 1Last Word on Point:Counterpoint: The interpolated twitch does/does not provide a valid measure of the voluntary activation of muscleA. de Haan, K. H. L. Gerrits, and C. J. de Ruiter1 July 2009 | Journal of Applied Physiology, Vol. 107, No. 1 More from this issue > Volume 107Issue 1July 2009Pages 355-357 Copyright & PermissionsCopyright © 2009 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.91220.2008aPubMed19567806History Published online 1 July 2009 Published in print 1 July 2009 Metrics
Imagine a parent telling their child to come inside to practice their video games in hopes of getting a scholarship to college. This is the new and quickly evolving reality of eSport. There are currently 22 colleges that recognize eSport as a collegiate varsity team. Five of these 22 offered eSport scholarships for the 2015 to 2016 academic year. Robert Morris University was the first school to sanction eSport as a varsity sport and 17 of their eSport athletes are on 70% scholarship (1). The popularity of eSports is growing at a rapid pace. However, like many individuals in the health profession, you might lack familiarity of this new phenomena. eSports is electronic gaming, also referred to as programing or competitive video gaming. Competitive video gaming has a global audience of more than 320 million, and it is being included in the 2022 Asian Games. It is being considered by the International Olympic Committee to be included in the Paris 2024 Olympic Games. eSports broadcasts games via the internet on a social platform through Twitch.tv. More people watched the League of Legends World Championship (32 million) than the Major League World Series (14.9 million) and the NCAA Basketball Final Four (15.7 million) (2,3). In 2017, it generated more than 400 million dollars in revenue (4). Goldman Sachs valued eSports at US $500 million in 2016, and by 2020 predicts it to generate more than US $1 billion (4). The grand prize for winning the championship can go as high as US $20 million. Smaller schools are starting to take notice and jump on board as a way to increase enrollment numbers. It brings new attention to colleges and a new type of student to enhance college recognition. The New York Institute of Technology created an eSport team in January 2017 with 8 players. Within one competitive season, it has grown to 37 players. “This will be the first full year that the team competes. I expect them to compete at the highest level possible, just the same as I expect from the traditional sports teams. They are a part of our department and my expectation of them is the same as the rest of our programs,” says Daniel Vélez, director of Intercollegiate Athletics at the New York Institute of Technology. However, when most people think of the word “sport,” computer games is the last thing that comes to mind. When we hear the word “student-athlete” on campus, we do not envision someone sitting in front of a computer playing a video game. In fact, the exact activity of sitting in front of a computer game for hours is the opposite of what we perceive as an athlete. The National Association of Intercollegiate Athletics (NAIA) recognizes eSport as a sport, but it is not yet sanctioned by the National Collegiate Athletic Association (NCAA). However, in December 2017, the NCAA reached out to Chicago-based Intersport, a sports and marketing firm to help explore its options, and is now investigating them as a “sport.” Because both men and women can play together, it can fall under the category of emerging sports for women. You will find many articles on the Web supporting eSport. The Oxford dictionary definition of a sport is “An activity involving physical exertion and skill in which an individual or team competes against another or others for entertainment” (5). In an article by Kane et al. (2), the authors make the argument that eSport has been studied and that it fits the criteria for the physical exertion category. The one study they referenced is from 2010 that compared oxygen consumption (V˙O2) to three different gaming conditions. One game was played sitting, one was played standing and bowling, the third was what is considered a high-intensity game with abrupt arm movements while standing. The high-intensity game produced the greatest change in V˙O2 reserve. However, when we examine the V˙O2 level, the highest V˙O2 attained was comparative to the activity of raking leaves. The American College of Sports Medicine (ACSM) recommends moderate exercise to be between 40% and 60% of heart rate reserve (HRR) (6). The highest-intensity game studied while standing which produced the highest V˙O2 was still lower than 40% of HRR. At best, it can be argued that only while standing does gaming produce low-level cardiovascular conditions similar to activities of daily living. ACSM recommends that individuals should exercise at greater than 40% of HRR to induce health benefits. The U.S. Centers for Disease Control and Prevention guidelines state that for substantial health benefits, adults should do at least 150 min (2 h and 30 min) a week of moderate-intensity, or 75 min (1 h and 15 min) a week of vigorous-intensity aerobic activity, or an equivalence combination of moderate- and vigorous-intensity aerobic activity. The intensity levels attained at the highest level game playing was below the minimum requirements to be classified as moderate intensity. Recently, we surveyed more than 40 eSport team players from five different universities (data collection ongoing). The average eSport player logs approximately 3 to 4 h·d−1 of practice. The serious competitors can go as high as more than 10 h·d−1 to prepare for competition. The most frequently reported complaint from the players we surveyed was eye fatigue (45%). Thirty-four percent of the players surveyed complained of back and neck pain. Another 27% reported having wrist and hand injuries. Additionally, 24% said they do not do any form of exercise, 30% said they try to do 30 to 60 min of exercise a few times per week. As we try to promote fitness and health on college campuses and in children, we need to find ways to support these players. Like most college sports, overuse injuries are inevitable. Also, like many sports, using stimulants is not uncommon. Staying focused for competition is key, and it has been reported that these players use excessive caffeine and Ritalin to stay focused. The debate whether eSport players fit the criteria of an athlete goes beyond the scope of this article. Much in the way of exercise specialists trying to incorporate exercise onto college campuses, how do health professionals integrate themselves with such an activity as eSport? Although we may not all agree on the concept of eSport being a sport, it is important for ACSM to start making college campuses and health professionals aware of this rapidly growing competition and potential ways to keep players healthy and fit. In addition, we need to be prepared to deal with the medical consequences of this new activity. How Do We Integrate the Health Professions Into the eSport Community? Perhaps we should see how we, as health professionals, can accommodate these athletes. Should college eSport athletes have their physical activity levels assessed? Teams use cardiovascular and strength training to improve performance of their athletes to keep them fit and to reduce overuse injuries. If eSport is to be included as a college sport, perhaps eSport coaches should be required to physically train their players away from the computer for the same purpose as other teams. Should athletic trainers and exercise specialists dedicate time to incorporate more activity into the daily lives of these students? The University of California, Irvine, has incorporated individual exercise prescriptions for their eSport athletes. Should all schools start to incorporate physical training and rehabilitation services into the eSport programs? The average eSport athlete can conduct more than 400 movements per minute using a mouse or a keyboard (1). Perhaps physical therapists and occupational therapists can understand the common overuse injuries and offer ergonomically efficient ways to train. Physicians can be more sympathetic to the demands of this sport while assessing physical activity, diet, and the danger of excessive ergogenic aids. Like many individuals in health professions, it is difficult to understand an activity that promotes being sedentary. We as health care professionals need to get actively involved. Where is our role in this new phenomena? Where should ACSM stand on eSport? That is a question that will likely be debated in the near future. However, the growth of eSports on college campuses cannot be understated, and it is not just a passing fad. We as health professionals have a wide open platform to research and to try to integrate our expertise into this new expanding frontier.
Beginning in 2019, the world experienced an extraordinary, transformative challenge due to the COVID-19 pandemic. The pandemic revealed how a single highly infectious virus can overburden the healthcare systems of even economically developed nations (1,2). Worldwide there has been >775 million reported cases and >7 million deaths from COVID-19 (3). The overall impact of COVID-19 took many additional forms, including physical, emotional, and economic. In addition to mortality, the consequences of ongoing illnesses, hospitalizations, longterm health complications, and loss of income or employment have been enormous, and far too challenging to quantify with precision.One of the fundamental lessons that emerged from the COVID-19 pandemic was the fact that individuals with fewer cardiovascular disease (CVD) risk factors, healthier lifestyles, or both, had lower risks for severe COVID-19 outcomes, including mortality, admission to the ICU, and need for mechanical ventilation (4)(5)(6). In contrast, the most severe COVID-19 outcomes were most commonly associated with comorbidities that included obesity, hypertension, cardiovascular disease, smoking, and type 2 diabetes mellitus (4-7). A particular health behavior which has been associated with worse COVID-19 outcomes is physical inactivity (8). Potential mechanisms for better outcomes among individuals who acquired COVID-19 and were regularly physically active include better immune function, reduced systemic inflammation, improved cardiovascular health, improved muscle strength, and a better ability to withstand internal and external stressors, such as surgery or severe illness (9,10). Overall, individuals who are more physically active or with greater cardiorespiratory fitness appear to be better equipped to withstand the physical and mental health challenges imposed by COVID-19 (4,5,(9)(10)(11).Cardiorespiratory fitness is in part a consequence of regular physical activity (12). In recent years, cardiorespiratory fitness has been demonstrated to be a powerful predictor of risk for mortality and other adverse health outcomes (5,(11)(12)(13). A growing body of research has demonstrated that higher levels of cardiorespiratory fitness reduce the risk of many highly prevalent noncommunicable diseases, including CVD, diabetes, and several site-specific cancers. The fact that cardiorespiratory fitness reflects the integrity of numerous systems at least partially explains the growing recognition that cardiorespiratory fitness predicts morbidity and mortality risk beyond commonly obtained risk factors. Higher cardiorespiratory fitness or regular moderate intensity physical activity has long been proposed to lower the risk of respiratory tract infections or improve vaccination responses due to immunomodulatory effects (14,15). Skeletal muscle itself is recognized as an endocrine organ, whereby IL-6 -the first coined 'myokine'-is one of several immune mediators released upon muscle contraction and considered to be a key driver of the anti-inflammatory effects of regular physical activity (16).Such anti-inflammatory mechanisms underlie the benefits of high cardiorespiratory fitness and regular physical activity in lowering chronic low-grade inflammation or improving immune and inflammatory markers in several diseases including cancers, cardiovascular diseases, diabetes, and cognitive impairment (17,18).It has become clear from recent studies that lifestyle factors, including physical activity patterns and level of cardiorespiratory fitness, have had a clear relationship with health outcomes during acute COVID-19 infection and post COVID-19 conditions. This Research Topic of Frontiers in Sports and Active Living presents original research in these areas, including the impact of mild to moderate COVID-19 infection on cardiorespiratory fitness among firefighters.In those who were hospitalized with acute COVID-19 infection, this Research Topic reports the prevalence of systemic inflammation and low functional exercise capacity in people who selfreported symptoms with or without pulmonary lesions 6-12 months after hospital discharge. Furthermore, the physical and cognitive impairments with post-COVID-19 may be associated with reduced quality of life. We also learn that infection control measures such as lockdowns introduced in response to the COVID-19 pandemic affected mobility trends and resulted in a rise in population-level physical inactivity, particularly in older (ages 75+) and Black and Asian minority ethnicity (BAME) individuals. Clearly, an important public health lesson from the COVID-19 pandemic was that it provided yet another reason for promoting regular physical activity to the public. The COVID-19 pandemic led to trends in specific types of physical activity, and this Research Topic reports on a comparison of different group exercise formats whereby streaming and on demand group fitness are viable options for sustaining physical activity but physiological intensity and psychological perceptions may be greater during live class formats.The articles in this Research Topic highlight the important role of physical activity and cardiorespiratory fitness during a global pandemic. Their findings will remain important with evolving SARS-CoV-2 variants and in preparedness for future viral pandemics, particularly in high-risk individuals.
In ergonomics, considering a worker's movement is important for assessing the risks of musculoskeletal disorders, among many other factors. Several commercial motion capture systems are available, mostly based on monocular or multi RGB (THEIA system www.theiamarkerless.com) or RGB-D videos (Microsoft Kinect system). Hybrid systems combining computer vision and Inertial Measurement Units (IMUs) have been introduced, such as the KIMEA (1 RGB-D+4 IMUs) and the KIMEA Cloud (1 RGB+4 IMUs) solutions (www.Moovency.com). Although previous works analyzed the accuracy of some of these systems, the relevance of coupling computer vision and IMU has not been studied. Hence, we tested the performance of these systems in measuring bimanual handling tasks, which lead to partial occlusions of the body in the images. As in previous works, the Xsens (www.movella.com) system was used as a reference (Kim et al., 2021), because it is not affected by such occlusions. Three Orbbec depth cameras were installed around the participant with different viewpoints. Six RGB cameras were also placed around the subject. Additional inertial (IMU) sensors were placed over both arms and the forearms, as recommended by the KIMEA and KIMEA Cloud systems. Testing several camera viewpoints makes sense in real industrial conditions where the camera placement is generally strongly constrained. 12 participants, 3 women and 9 men (age: 32.6 +/- 10 years, height: 1.73 +/- 0.079 m, mass: 76 +/- 16 kg) performed the following task: removing an empty cardboard box (size: 39x29.5x19cm, weight: 250g) from a three-tier shelf and transferring it to another one, repeated five times. A reference pose (corresponding to 0 value for each degree of freedom) was preliminary performed for each subject. It enabled us to estimate the same angular offsets for each pose, compared to this reference pose. As a results, angles measured by the various systems have similar definitions and can be compared. This study was approved by the Operational Committee for the Evaluation of Legal and Ethical Risks (COERLE) No. 2021-32.Results for the computer vision methods only are similar to those reported in Kim et al. (2021) and Lakhar et al. (2022). The THEIA system exhibits an average of 11.1° error for all the joints, with larger Root Mean Square errors on the wrists and the shoulder (&#62;14° error). KIMEA Cloud with IMU obtained similar global RMS error (10.3 ° to 10.9° depending on the viewpoint), but with obviously better results for the wrists (3.9 ° to 4.3°). The impact of coupling RGB-D images and IMU data is even bigger: the RMS error of the Kinect decreased from 17.2° to 8.9° when adding the IMUs information (KIMEA system). This difference is even bigger for the wrists: 28.3° to 38.5° for the Kinect, and 3.8 ° to 4° for KIMEA. When studying the Mean Absolute Error, or the Spearman’s correlation coefficient, these statements are consistent. These results confirm the advantage of introducing a few IMU sensors, especially for the wrists which are badly tracked in the images: often occluded and consisting in a little number of pixels in the image. We also show that it leads to more robust measurement for various points of views, including from the back. The information provided by the IMU, not impacted by the occlusions, seems to help the computer vision system to reconstruct the whole-body posture. However, adding IMUs also introduces some experimental constraints compared to simply placing one camera. THEIA obtained the best results for the whole-body reconstruction, but still had difficulties to correctly reconstruct the wrists angles. On the one hand, THEIA does not involve to add sensors. On the other hand, it involves the calibration of a multi-camera system, which might be difficult to place in real industrial environment. References Kim, W., Sung, J., Saakes, D., Huang, C., Xiong, S., 2021. Ergonomic postural assessment using a new open-source human pose estimationtechnology (openpose). International Journal of Industrial Ergonomics 84, 103164. doi:https://doi.org/10.1016/j.ergon.2021.103164Lahkar, B.K., Muller, A., Dumas, R., Reveret, L., Robert, T., 2022. Accuracy of a markerless motion capture system in estimating upper extremitykinematics during boxing. Frontiers in Sports and Active Living 4, 939980. doi:https://doi.org/10.3389/fspor.2022.939980.
The human ageing process is universal, ubiquitous and inevitable. Every physiological function is being continuously diminished. There is a range between two distinct phenotypes of ageing, shaped by patterns of living - experiences and behaviours, and in particular by the presence or absence of physical activity (PA) and structured exercise (i.e., a sedentary lifestyle). Ageing and a sedentary lifestyle are associated with declines in muscle function and cardiorespiratory fitness, resulting in an impaired capacity to perform daily activities and maintain independent functioning. However, in the presence of adequate exercise/PA these changes in muscular and aerobic capacity with age are substantially attenuated. Additionally, both structured exercise and overall PA play important roles as preventive strategies for many chronic diseases, including cardiovascular disease, stroke, diabetes, osteoporosis, and obesity; improvement of mobility, mental health, and quality of life; and reduction in mortality, among other benefits. Notably, exercise intervention programmes improve the hallmarks of frailty (low body mass, strength, mobility, PA level, energy) and cognition, thus optimising functional capacity during ageing. In these pathological conditions exercise is used as a therapeutic agent and follows the precepts of identifying the cause of a disease and then using an agent in an evidence-based dose to eliminate or moderate the disease. Prescription of PA/structured exercise should therefore be based on the intended outcome (e.g., primary prevention, improvement in fitness or functional status or disease treatment), and individualised, adjusted and controlled like any other medical treatment. In addition, in line with other therapeutic agents, exercise shows a dose-response effect and can be individualised using different modalities, volumes and/or intensities as appropriate to the health state or medical condition. Importantly, exercise therapy is often directed at several physiological systems simultaneously, rather than targeted to a single outcome as is generally the case with pharmacological approaches to disease management. There are diseases for which exercise is an alternative to pharmacological treatment (such as depression), thus contributing to the goal of deprescribing of potentially inappropriate medications (PIMS). There are other conditions where no effective drug therapy is currently available (such as sarcopenia or dementia), where it may serve a primary role in prevention and treatment. Therefore, this consensus statement provides an evidence-based rationale for using exercise and PA for health promotion and disease prevention and treatment in older adults. Exercise prescription is discussed in terms of the specific modalities and doses that have been studied in randomised controlled trials for their effectiveness in attenuating physiological changes of ageing, disease prevention, and/or improvement of older adults with chronic disease and disability. Recommendations are proposed to bridge gaps in the current literature and to optimise the use of exercise/PA both as a preventative medicine and as a therapeutic agent.
Changing demographics make it ever more important to understand the modifiable risk factors for disability and loss of independence with advancing age. For more than two decades there has been increasing interest in the role of sarcopenia, the age-related loss of muscle or lean mass, in curtailing active and healthy aging. There is now evidence to suggest that lack of strength, or dynapenia, is a more constant factor in compromised wellbeing in old age and it is apparent that the decline in muscle mass and the decline in strength can take quite different trajectories. This demands recognition of the concept of muscle quality; that is the force generating per capacity per unit cross-sectional area (CSA). An understanding of the impact of aging on skeletal muscle will require attention to both the changes in muscle size and the changes in muscle quality. The aim of this review is to present current knowledge of the decline in human muscle mass and strength with advancing age and the associated risk to health and survival and to review the underlying changes in muscle characteristics and the etiology of sarcopenia. Cross-sectional studies comparing young (18-45 years) and old (>65 years) samples show dramatic variation based on the technique used and population studied. The median of values of rate of loss reported across studies is 0.47% per year in men and 0.37% per year in women. Longitudinal studies show that in people aged 75 years, muscle mass is lost at a rate of 0.64-0.70% per year in women and 0.80-00.98% per year in men. Strength is lost more rapidly. Longitudinal studies show that at age 75 years, strength is lost at a rate of 3-4% per year in men and 2.5-3% per year in women. Studies that assessed changes in mass and strength in the same sample report a loss of strength 2-5 times faster than loss of mass. Loss of strength is a more consistent risk for disability and death than is loss of muscle mass.
Positive effects from sports are achieved primarily through physical activity, but secondary effects bring health benefits such as psychosocial and personal development and less alcohol consumption. Negative effects, such as the risk of failure, injuries, eating disorders, and burnout, are also apparent. Because physical activity is increasingly conducted in an organized manner, sport's role in society has become increasingly important over the years, not only for the individual but also for public health. In this paper, we intend to describe sport's physiological and psychosocial health benefits, stemming both from physical activity and from sport participation per se. This narrative review summarizes research and presents health-related data from Swedish authorities. It is discussed that our daily lives are becoming less physically active, while organized exercise and training increases. Average energy intake is increasing, creating an energy surplus, and thus, we are seeing an increasing number of people who are overweight, which is a strong contributor to health problems. Physical activity and exercise have significant positive effects in preventing or alleviating mental illness, including depressive symptoms and anxiety- or stress-related disease. In conclusion, sports can be evolving, if personal capacities, social situation, and biological and psychological maturation are taken into account. Evidence suggests a dose-response relationship such that being active, even to a modest level, is superior to being inactive or sedentary. Recommendations for healthy sports are summarized.
With minimal costs and travel constraints for athletes, the "living low-training high" (LLTH) approach is becoming an important intervention for modern sport. The popularity of the LLTH model of altitude training is also associated with the fact that it only causes a slight disturbance to athletes' usual daily routine, allowing them to maintain their regular lifestyle in their home environment. In this perspective article, we discuss the evolving boundaries of the LLTH paradigm and its practical applications for athletes. Passive modalities include intermittent hypoxic exposure at rest (IHE) and Ischemic preconditioning (IPC). Active modalities use either local [blood flow restricted (BFR) exercise] and/or systemic hypoxia [continuous low-intensity training in hypoxia (CHT), interval hypoxic training (IHT), repeated-sprint training in hypoxia (RSH), sprint interval training in hypoxia (SIH) and resistance training in hypoxia (RTH)]. A combination of hypoxic methods targeting different attributes also represents an attractive solution. In conclusion, a growing number of LLTH altitude training methods exists that include the application of systemic and local hypoxia stimuli, or a combination of both, for performance enhancement in many disciplines.
1. Time and energy are key currencies in animal ecology, and judicious management of these is a primary focus for natural selection. At present, however, there are only two main methods for estimation of rate of energy expenditure in the field, heart rate and doubly labelled water, both of which have been used with success; but both also have their limitations. 2. The deployment of data loggers that measure acceleration is emerging as a powerful tool for quantifying the behaviour of free-living animals. Given that animal movement requires the use of energy, the accelerometry technique potentially has application in the quantification of rate of energy expenditure during activity. 3. In the present study, we test the hypothesis that acceleration can serve as a proxy for rate of energy expenditure in free-living animals. We measured rate of energy expenditure as rates of O2 consumption (VO2) and CO2 production (VCO2) in great cormorants (Phalacrocorax carbo) at rest and during pedestrian exercise. VO2 and VCO2 were then related to overall dynamic body acceleration (ODBA) measured with an externally attached three-axis accelerometer. 4. Both VO2 and VCO2 were significantly positively associated with ODBA in great cormorants. This suggests that accelerometric measurements of ODBA can be used to estimate VO2 and VCO2 and, with some additional assumptions regarding metabolic substrate use and the energy equivalence of O2 and CO2, that ODBA can be used to estimate the activity specific rate of energy expenditure of free-living cormorants. 5. To verify that the approach identifies expected trends in from situations with variable power requirements, we measured ODBA in free-living imperial cormorants (Phalacrocorax atriceps) during foraging trips. We compared ODBA during return and outward foraging flights, when birds are expected to be laden and not laden with captured fish, respectively. We also examined changes in ODBA during the descent phase of diving, when power requirements are predicted to decrease with depth due to changes in buoyancy associated with compression of plumage and respiratory air. 6. In free-living imperial cormorants, ODBA, and hence estimated VO2, was higher during the return flight of a foraging bout, and decreased with depth during the descent phase of a dive, supporting the use of accelerometry for the determination of activity-specific rate of energy expenditure.
BACKGROUND: Physical activity is associated with many physical and mental health benefits, however many children do not meet the national physical activity guidelines. While schools provide an ideal setting to promote children's physical activity, adding physical activity to the school day can be difficult given time constraints often imposed by competing key learning areas. Classroom-based physical activity may provide an opportunity to increase school-based physical activity while concurrently improving academic-related outcomes. The primary aim of this systematic review and meta-analysis was to evaluate the impact of classroom-based physical activity interventions on academic-related outcomes. A secondary aim was to evaluate the impact of these lessons on physical activity levels over the study duration. METHODS: A systematic search of electronic databases (PubMed, ERIC, SPORTDiscus, PsycINFO) was performed in January 2016 and updated in January 2017. Studies that investigated the association between classroom-based physical activity interventions and academic-related outcomes in primary (elementary) school-aged children were included. Meta-analyses were conducted in Review Manager, with effect sizes calculated separately for each outcome assessed. RESULTS: Thirty-nine articles met the inclusion criteria for the review, and 16 provided sufficient data and appropriate design for inclusion in the meta-analyses. Studies investigated a range of academic-related outcomes including classroom behaviour (e.g. on-task behaviour), cognitive functions (e.g. executive function), and academic achievement (e.g. standardised test scores). Results of the meta-analyses showed classroom-based physical activity had a positive effect on improving on-task and reducing off-task classroom behaviour (standardised mean difference = 0.60 (95% CI: 0.20,1.00)), and led to improvements in academic achievement when a progress monitoring tool was used (standardised mean difference = 1.03 (95% CI: 0.22,1.84)). However, no effect was found for cognitive functions (standardised mean difference = 0.33 (95% CI: -0.11,0.77)) or physical activity (standardised mean difference = 0.40 (95% CI: -1.15,0.95)). CONCLUSIONS: Results suggest classroom-based physical activity may have a positive impact on academic-related outcomes. However, it is not possible to draw definitive conclusions due to the level of heterogeneity in intervention components and academic-related outcomes assessed. Future studies should consider the intervention period when selecting academic-related outcome measures, and use an objective measure of physical activity to determine intervention fidelity and effects on overall physical activity levels.
Objective: Numerous reports advocate that training of the proprioceptive sense is a viable behavioral therapy for improving impaired motor function. However, there is little agreement of what constitutes proprioceptive training and how effective it is. We therefore conducted a comprehensive, systematic review of the available literature in order to provide clarity to the notion of training the proprioceptive system. Methods: Four major scientific databases were searched. The following criteria were subsequently applied: 1) A quantified pre and post-treatment measure of proprioceptive function. 2) An intervention or training program believed to influence or enhance proprioceptive function. 3) Contained at least one form of treatment or outcome measure that is indicative of somatosensory function. From a total of 1284 articles, 51 studies fulfilled all criteria and were selected for further review. Results: Overall, proprioceptive training resulted in an average improvement of 52% across all outcome measures. Applying muscle vibration above 30Hz for longer durations (i.e., min vs. sec) induced outcome improvements of up to 60%. Joint position and target reaching training consistently enhanced joint position sense (up to 109%) showing an average improvement of 48%. Cortical stroke was the most studied disease entity but no clear evidence indicated that proprioceptive training is differentially beneficial across the reported diseases. Conclusions: There is converging evidence that proprioceptive training can yield meaningful improvements in somatosensory and sensorimotor function. However, there is a clear need for further work. Those forms of training utilizing both passive and active movements with and without visual feedback tended to be most beneficial. There is also initial evidence suggesting that proprioceptive training induces cortical reorganization, reinforcing the notion that proprioceptive training is a viable method for improving sensorimotor function.
The Bundesliga made headlines for becoming the first major sports league to return to sport worldwide following COVID-19 lockdown. To-date, there lacks retrospective studies on longitudinal injury rates to elucidate the effect isolation measures had on the health and safety of professional athletes. This study sought to compare injury rates experienced by Bundesliga athletes before and after the COVID-19 lockdown. Data was collected from public injury and player reports regarding the Bundesliga, with injury defined as trauma resulting in loss of game time. Descriptive statistics were used to present differences in injury incidence between all Bundesliga Match days pre- and post-lockdown. Between the league's resumption and completion on May 16 and June 27, 2020, injuries occurred in 21 forwards (FW), 11 central midfielders (CM), 12 wide midfielders (WM), 16 central defenders (CD), 6 fullbacks (FB), and 2 goalkeepers. Players had 1.13 (95% CI 0.78, 1.64) times the odds of being injured following the COVID-19 lockdown, with a 3.12 times higher rate of injury when controlling for games played compared to injury rates pre-lockdown (0.84 injuries per game vs. 0.27 injuries per game). The most frequent injury group was muscular injuries with 23 injuries total, with 17% of athletes experiencing injury during their first competitive match following lockdown. Injury rate increased over 3-fold following COVID-19 lockdown. Athletes did not experience an increased rate of injury with more cumulative competitive matches played. High injury incidence for players yet to complete their first competitive match may imply suboptimal sport readiness following home confinement.
The Canadian Society for Exercise Physiology (CSEP), in partnership with the Healthy Active Living and Obesity Research Group (HALO) at the Children's Hospital of Eastern Ontario Research Institute, and in collaboration with ParticipACTION, and others, has developed the Canadian Sedentary Behaviour Guidelines for Children (aged 5-11 years) and Youth (aged 12-17 years). The guidelines include a preamble to provide context, followed by the specific recommendations for sedentary behaviour. The entire development process was guided by the Appraisal of Guidelines for Research Evaluation (AGREE) II instrument, which is the international standard for clinical practice guideline development. Thus, the guidelines have gone through a rigorous and transparent developmental process and the recommendations are based on evidence from a systematic review and interpretation of the research evidence. The final guidelines benefitted from an extensive online consultation process with 230 domestic and international stakeholders and key informants. The final guideline recommendations state that for health benefits, children (aged 5-11 years) and youth (aged 12-17 years) should minimize the time that they spend being sedentary each day. This may be achieved by (i) limiting recreational screen time to no more than 2 h per day - lower levels are associated with additional health benefits; and (ii) limiting sedentary (motorized) transport, extended sitting time, and time spent indoors throughout the day. These are the first evidence-based Canadian Sedentary Behaviour Guidelines for Children and Youth and provide important and timely recommendations for the advancement of public health based on a systematic synthesis, interpretation, and application of the current scientific evidence.
Since the mid-2000s, perturbation-based balance training has been gaining interest as an efficient and effective way to prevent falls in older adults. It has been suggested that this task-specific training approach may present a paradigm shift in fall prevention. In this review, we discuss key concepts and common issues and questions regarding perturbation-based balance training. In doing so, we aim to provide a comprehensive synthesis of the current evidence on the mechanisms, feasibility and efficacy of perturbation-based balance training for researchers and practitioners. We address this in two sections: "Principles and Mechanisms" and "Implementation in Practice." In the first section, definitions, task-specificity, adaptation and retention mechanisms and the dose-response relationship are discussed. In the second section, issues related to safety, anxiety, evidence in clinical populations (e.g., Parkinson's disease, stroke), technology and training devices are discussed. Perturbation-based balance training is a promising approach to fall prevention. However, several fundamental and applied aspects of the approach need to be further investigated before it can be widely implemented in clinical practice.
Background: Patients with a chronic disease may have an increased risk of non-adherence to prescribed home-based exercise therapy. We performed a systematic review with the aim to identify variables associated with adherence to home-based exercise therapy in patients with chronic diseases and to grade the quality of evidence for the association between these prognostic factors and adherence. Methods: Cohort studies, cross-sectional studies and the experimental arm of randomized trials were identified using a search strategy applied to PubMed, Embase, PsychINFO and CINAHL from inception until August 1, 2022. We included studies with participants ≥18 years with a chronic disease as an indication for home-based exercise therapy and providing data on prognostic factors of adherence to home-based exercise. To structure the data, we categorized the identified prognostic factors into the five WHO-domains; (1) Patient-related, (2) Social/economic, (3) Therapy-related, (4) Condition-related, and (5) Health system factors. Risk of bias was assessed using the Quality in Prognostic Studies (QUIPS) tool. Prognostic factors of adherence were identified and the quality of the evidence between the prognostic factors and adherence were graded using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework for predictor studies. We performed a meta-analysis of the obtained information. Results: A total of 57 studies were included. Within patient-related factors moderate- and high-quality evidence suggested that more self-efficacy, exercise history, motivation and perceived behavioral control predicted higher adherence. Within social-economic factors moderate-quality evidence suggested more education and physical health to be predictive of higher adherence and within condition-related factors moderate- and low-quality evidence suggested that less comorbidities, depression and fatigue predicted higher adherence. For the domains therapy-related and health-system factors there was not enough information to determine the quality evidence of the prognostic factors. Conclusion: These findings might aid the development of future home-based exercise programs as well as the identification of individuals who may require extra support to benefit from prescribed home-based exercise therapy. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=277003, identifier PROSPERO CRD42021277003.
The Internet of Things (IoT)-centric concepts like augmented reality, high-resolution video streaming, self-driven cars, smart environment, e-health care, etc. have a ubiquitous presence now. These applications require higher data-rates, large bandwidth, increased capacity, low latency and high throughput. In light of these emerging concepts, IoT has revolutionized the world by providing seamless connectivity between heterogeneous networks (HetNets). The eventual aim of IoT is to introduce the plug and play technology providing the end-user, ease of operation, remotely access control and configurability. This paper presents the IoT technology from a bird's eye view covering its statistical/architectural trends, use cases, challenges and future prospects. The paper also presents a detailed and extensive overview of the emerging 5G-IoT scenario. Fifth Generation (5G) cellular networks provide key enabling technologies for ubiquitous deployment of the IoT technology. These include carrier aggregation, multiple-input multiple-output (MIMO), massive-MIMO (M-MIMO), coordinated multipoint processing (CoMP), device-to-device (D2D) communications, centralized radio access network (CRAN), software-defined wireless sensor networking (SD-WSN), network function virtualization (NFV) and cognitive radios (CRs). This paper presents an exhaustive review for these key enabling technologies and also discusses the new emerging use cases of 5G-IoT driven by the advances in artificial intelligence, machine and deep learning, ongoing 5G initiatives, quality of service (QoS) requirements in 5G and its standardization issues. Finally, the paper discusses challenges in the implementation of 5G-IoT due to high data-rates requiring both cloud-based platforms and IoT devices based edge computing.
In this paper, we explore the costs and benefits of hosting the Olympic Games. On the cost side, there are three major categories: general infrastructure such as transportation and housing to accommodate athletes and fans; specific sports infrastructure required for competition venues; and operational costs, including general administration as well as the opening and closing ceremony and security. Three major categories of benefits also exist: the short-run benefits of tourist spending during the Games; the long-run benefits or the “Olympic legacy” which might include improvements in infrastructure and increased trade, foreign investment, or tourism after the Games; and intangible benefits such as the “feel-good effect” or civic pride. Each of these costs and benefits will be addressed in turn, but the overwhelming conclusion is that in most cases the Olympics are a money-losing proposition for host cities; they result in positive net benefits only under very specific and unusual circumstances. Furthermore, the cost–benefit proposition is worse for cities in developing countries than for those in the industrialized world. In closing, we discuss why what looks like an increasingly poor investment decision on the part of cities still receives significant bidding interest and whether changes in the bidding process of the International Olympic Committee (IOC) will improve outcomes for potential hosts.
The movement of undulatory underwater swimming (UUS), a swimming technique adapted from whales, is mainly limited by human anatomy. A greater ankle joint flexibility could improve the imitation of the whale's flap of the fin and therefore enhance USS performance. The aim of this study was to investigate the impact of ankle joint flexibility on swimming velocity and kick efficiency during UUS by comparing kinematics of swimming trials with reduced, normal, and enhanced maximum angles of plantar flexion. Ten well trained swimmers (5m and 5f; 22 ± 4years; 177 ± 7cm; 74 ± 15kg), performed multiple trials of UUS with normal, restricted, and increased ankle joint flexibility on two separate days in randomized order. Kick frequency was controlled by a metronome. Plantar flexion (PF) was restricted by tape application on both feet and increased by passive-dynamic stretching. All trials were filmed. Kinematics were obtained with two-dimensional motion analysis. Tape application restricted maximum PF by 10.42% while stretching increased PF by 6.87% compared to normal PF. Swimming velocity and kick efficiency significantly decreased during swimming with restricted PF (1.13 ± 0.13m<sup>*</sup>s<sup>-1</sup>; 0.69 ± 0.09m) compared to normal (1.20 ± 0.14 m<sup>*</sup>s<sup>-1</sup>; 0.72 ± 0.10m) and increased (1.22 ± 0.15m<sup>*</sup>s<sup>-1</sup>; 0.73 ± 0.10m) PF. Swimming velocity and kick efficiency did not differ between normal and increased PF. Body height normalized swimming velocity correlated significantly with PF angle (<i>r</i> = 0.538). The results suggest that UUS velocity is affected by impaired PF. Particularly swimmers with low or average maximum PF angles may benefit from a long-term ankle joint flexibility program to improve their UUS performance.