Showing papers by "Karim Chamari published in 2019"

Italian consensus statement (2020) on return to play after lower limb muscle injury in football (soccer)

Abstract: Return to play (RTP) decisions in football are currently based on expert opinion. No consensus guideline has been published to demonstrate an evidence-based decision-making process in football (soccer). Our aim was to provide a framework for evidence-based decision-making in RTP following lower limb muscle injuries sustained in football. A 1-day consensus meeting was held in Milan, on 31 August 2018, involving 66 national and international experts from various academic backgrounds. A narrative review of the current evidence for RTP decision-making in football was provided to delegates. Assembled experts came to a consensus on the best practice for managing RTP following lower limb muscle injuries via the Delphi process. Consensus was reached on (1) the definitions of ‘return to training’ and ‘return to play’ in football. We agreed on ‘return to training’ and RTP in football, the appropriate use of clinical and imaging assessments, and laboratory and field tests for return to training following lower limb muscle injury, and identified objective criteria for RTP based on global positioning system technology. Level of evidence IV, grade of recommendation D.

Sleep deprivation affects post-lunch dip performances, biomarkers of muscle damage and antioxidant status.

Abstract: To compare the effects of two types of partial sleep deprivation (PSD) at the beginning (PSDBN) and the end (PSDEN) of the night on mood, cognitive performances, biomarkers of muscle damage, haematological status and antioxidant responses before and after repeated-sprint exercise in the post-lunch dip. Fourteen male athletes performed the Running-based Anaerobic Sprint Test following: (i) baseline normal sleep night, (ii) PSDBN, or (iii) PSDEN in a randomized and counter-balanced order. During each condition, participants performed simple and choice reaction time tests, the Profile of Mood States, subjective sleepiness, and the Running-based Anaerobic Sprint Test. Plasma biomarkers of muscle damage, total blood count, and antioxidant activities were measured at rest and after the repeated sprint in the three conditions. PSDEN decreased Pmax (p=0.008; d=1.12), Pmean (p=0.002; d=1.33) and Pmin (p=0.006; d=1.15), whilst PSDBN decreased Pmean (p=0.04; d=0.68) and Pmin (p=0.028; d=0.58), in comparison with baseline. PSDEN exerted stronger effects on Pmax (p=0.013; d=0.74) and Pmean (p=0.048; d=0.54) than PSDBN. Moreover, PSDEN increased subjective sleepiness (p<0.001; d=1.93), while PSDBN impaired choice reaction time (p<0.001, d=1.89). Both PSD types decreased resting glutathione peroxidase (p<0.001; d=5.43, d=3.86), and increased aspartate amino-transferase levels (p<0.001; d=1.36, d=1.37) respectively for PSDEN and PSDBN. PSDEN decreased repeated-sprint performances more than PSDBN in the post-lunch dip. This could be explained by the lowered mood and resting antioxidant status and the increased inflammatory profile after PSDEN. Repeated-sprint exercise resulted in greater inflammation after PSDEN, despite the decreased physical performance. The drop of resting antioxidant defence and haemoglobin concentration after PSDEN could explain the increased sleep drive at the post-lunch dip.

Match Fatigue Time-Course Assessment Over Four Days: Usefulness of the Hooper Index and Heart Rate Variability in Professional Soccer Players.

Abstract: The aims of the present study were to (a) examine recovery time-course and (b) analyze the usefulness of the Hooper-Index (wellness index) and resting heart rate variability (HRV) in professional soccer players during an in-season phase. The Hooper-Index and resting HRV were collected on matchday and on the four following days in three consecutive in-season weeks in nine players (25.2 ± 4.3-years). The usefulness of monitoring variables was assessed by (a) comparing noise (typical error, TE) to the smallest worthwhile change (SWC) (TE/SWC) and (b) comparing match-related changes (i.e., signal) to TE (i.e., signal-to-noise ratio). Between-days standardized differences in the changes of Hooper-Index and HRV were compared to the SWC using magnitude-based inferences. The magnitudes of TE were small and moderate for the Hooper-Index and HRV, respectively. The Hooper-Index showed to be more useful than HRV for monitoring match-induced fatigue as having a lower TE/SWC (3.1 versus 4.4) and a higher signal-to-noise ratio (5.5 versus 1.5). Small-to-very large [range of effect sizes, 0.48; 2.43, confidence limits (0.22; 2.91)] and moderate-to-large [-1.71; -0.61 (-2.44; -0.03)] detrimental changes in Hooper-Index and HRV, respectively, were observed on the days following matchday. While group analyses showed a similar pattern for recovery time-course, more individual players responded, similarly when tracked using the Hooper -Index compared to when they were tracked using HRV. An inverse moderate within-individual relationship was observed between changes in the Hooper index and HRV [r = -0.41, (-0.60, 0.18)]. The Hooper index is an easy-to-use, no-cost, and non-invasive monitoring tool and seems promising for tracking match-induced fatigue during in the season in professional soccer.

Inter-relationship between sleep quality, insomnia and sleep disorders in professional soccer players.

Abstract: Objective Insufficient sleep duration and quality has negative effects on athletic performance, injury susceptibility and athlete development. This study aimed to assess the sleep characteristics of professional Qatar Stars League (QSL) soccer players. Methods In a cross-sectional study, QSL players (n=111; 23.7±4.8 years) completed three questionnaires to screen sleep disorders: (1) Pittsburgh Sleep Quality Index (PSQI), (2) Insomnia Severity Index (ISI) and (3) Epworth Sleepiness Scale (ESS). Poor sleep quality was defined as PSQI≥5, excessive daytime sleepiness was defined by ESS>8 and insomnia was defined as ISI≥11. Results The prevalence of poor sleep quality (PSQI≥5) was 68.5%, with subthreshold insomnia (ISI≥11) 27.0% and daytime sleepiness 22.5% (ESS>8). Sleep quality was positively associated with insomnia (r=0.42, p Conclusion The prevalence of poor sleep quality (68.5%) reported should concern practitioners. Increasing awareness of the importance of sleep relative to athletic performance, recovery, injury and illness appears prudent. Further, regular qualitative/quantitative sleep monitoring may help target subsequent evidence-informed interventions to improve sleep in those demonstrating undesirable sleep traits.

Anterior cruciate ligament injury risk factors in football.

Abstract: Introduction Anterior cruciate ligament (ACL) lesion represents one of the most dramatic injuries in a football (soccer) player's career. There are many injury risk factors related to intrinsic (non-modifiable) and/or extrinsic (modifiable) factors of ACL injury. Evidence acquisition Research of the studies was conducted until September 2018 without publication data limitation or language restriction on the following databases: PubMed/MEDLINE, Scopus, ISI, EXCERPTA. Evidence synthesis To date, evidence from the literature suggests that the risk of ACL injury is multifactorial and involves biomechanical, anatomical, hormonal, and neuromuscular factors. Despite this relative complexity, the mechanisms of injury are well known and rationally classified into two categories: mechanisms of injury based on contact or on non-contact with another player, with the non-contact injury mechanisms clearly prevailing over the mechanisms of contact injury. One of the most frequent biomechanical risk factors, associated with ACL non-contact injury, is represented by the valgus knee in the pivoting and cutting movements and in the landing phase after jumping. Gender-related risk factors show female populations to have a higher predisposition to ACL injury than males However, there are still some theoretical and practical aspects that need further investigation such as; genetic risks together with the role of estrogen and progesterone receptors in female populations, and the in-vivo interaction shoe-playing surface. In particular, the genetic risk factors of ACL lesion seem to be an interesting and promising field of investigation, where considerable progress has still to be made. Conclusions This narrative review provides an insight into the risk factors of ACL injury that could be used by practitioners for preventing injury in football (soccer).

Involving research-invested clinicians in data collection affects injury incidence in youth football

Abstract: It is well established that differences in injury definition and recording methodology restrict comparisons between injury surveillance programmes. There is, however, little documentation of the variation that can exist between data recorders. The aim of this study was, therefore, to explore the effect on reported injuries when team recorders or supervisors are involved in research. Injury data collected prospectively over five seasons for the U16, U17, and U18 age groups in a youth football (soccer) academy were used to compare different recording settings based on the research involvement of the clinicians. A research-invested team physiotherapist reported an 8.8 times greater incidence (P < 0.001) of non-time-loss injuries and a 2.5 times greater incidence (P < 0.001) of minimal injuries (1-3 days lost) compared to a setting where neither the team physiotherapists nor the supervisor relied on the collected data for research purposes. When team physiotherapists were not invested in research themselves but were supervised by a researcher, the incidence of non-time-loss injuries and minimal injuries was 2.5 times (P < 0.001) and 2.0 times greater (P < 0.01) than in the non-invested setting, respectively. However, there were no differences between recording settings for overall incidence of time-loss injuries. The results from this study demonstrate that involving clinicians that are relying on the collected data for research purposes can significantly affect the reported rates of non-time-loss and minimal injuries. Time-loss injuries overall were not affected by research investment, and should therefore be preferred for comparisons between teams and seasons.

The acute effect of the tongue position in the mouth on knee isokinetic test performance: a highly surprising pilot study.

Abstract: The tongue involvement within the isokinetic knee extension/flexion exercises has been investigated. Eighteen participants randomly underwent isokinetic testing at 90 and 180°/s with three different tongue positions: middle position (MID, thrusting on the lingual surface of incisive teeth), lying on the lower arch of the mouth (LOW) and extended up to the palatine spot (UP). Statistical analysis of the data revealed an about 30% significant increase of knee flexion peak torque in UP with respect to MID at both angular speeds. Such a difference could have had a confounding effect on results from numerous past studies using isokinetic knee flexion testing. This study alerts future researchers about standardization of tongue position and warrants further investigations on the explicative processes of this phenomenon.

Soccer Footedness and Between-Limbs Muscle Strength: Systematic Review and Meta-Analysis

Abstract: Purpose: Limb dominance and consequent between-limbs muscle strength in soccer players should be explored to determine a standard musculoskeletal profile to maintain and establish during screening protocols and postinjury rehabilitation. The primary aim of this review was to identify dominant- vs non-dominant-lower-extremity muscle-strength characteristics of healthy soccer players, with secondary aims to consider available between-limbs outcome measures and directions for future research. Methods: Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Five electronic databases were used for study identification with guidance from a medical librarian. Inclusion criteria consisted of studies employing a cross-sectional design assessing soccer players of all ages, genders, and levels of play that identified limb dominance and associated lower-extremity muscle strength as a main purpose of the experiment. Results: The literature search identified 3471 articles. After screening titles, abstracts, and full texts, 17 articles were included in the review. Peak torques and hamstring-to-quadriceps ratios via isokinetic dynamometry were commonly used, and subsequent meta-analyses were conducted to yield remarkable between-limbs symmetry. Additional results of individual studies also demonstrate symmetry, except 1 article of velocity-dependent measures that reported greater strength in the dominant limb. Conclusions: In soccer, between-limbs muscle strength measured by maximal isokinetic dynamometry demonstrates symmetry across ages, genders, and levels of play. Future testing using alternative measures that more specifically replicate the movement demands of soccer players may further classify between-limbs characteristics.

Optimizing training and competition during the month of Ramadan: Recommendations for a holistic and personalized approach for the fasting athletes.

Abstract: During the month of Ramadan, Muslim believers of adult-aged and healthy, restrain themselves from food consumption and liquid intake from dawn to sunset (fasting duration varying according to the geographical location and time of the year). Differently from other fasting regimens such as caloric restriction, Ramadan fasting is a unique kind of fasting, being total (i.e., absolute abstain from food as well as fluid), time-restricted, intermittent, and circadian (following the circadian rhythm and the human biological clock). As such, the fasting athletes could potentially suffer from hypohydration, altered sleep pattern and architecture, sleep disturbances, mood swings, immunological alterations, impaired psychomotor performance and overall perceived physical and perhaps, mental fatigue, among others. Hence, Muslim athletes who continue to train and compete during Ramadan faced many challenges. Research has shown that depending on the level of effort, Ramadan fasting could have diverse effects on physical performance; from no effect to marked effects. The present review aims to provide practical recommendations based on an updated, evidence-based synthesis of the existing scholarly literature and/or experts opinions on the topic and subsequently, some useful tips for athletes, coaches, medical and scientific support, and sports managers, in order to guide them on how to promote appropriate behavioral, social and psychological strategies to cope with the changes and potential constraints induced by the observance of Ramadan fasting. These recommendations should be adjusted and coped with, utilizing a holistic approach, rather than focusing on the single alterations/perturbations. Moreover, the implemented strategies should not be "one size fits it all" approach, but should rather take into account the variability among athletes and their specific needs (biological, psychological, cognitive-behavioral), and their social and living environment; as it is clearly more challenging when the individual is performing the Ramadan fasting in a predominantly non-Muslim majority country.

Sport science applied to basketball refereeing: a narrative review.

Abstract: Objectives: The present review provides a summary of basketball referees’ game activities, fitness assessment, cognitive function, and energy expenditure (EE) during official games.Methods: Analyzi...

Multidirectional Plyometric Training: Very Efficient Way to Improve Vertical Jump Performance, Change of Direction Performance and Dynamic Postural Control in Young Soccer Players.

Abstract: The aim of the study was to assess the effects of multidirectional plyometric training (MPT) on vertical jump height, change of direction performance (CODP), and dynamic postural control (DPC) in young soccer players. Twenty-eight young male soccer players were randomly assigned to an experimental group (EG, n = 14; age: 11.8 ± 0.4 years) and a control group (CG, n = 14; age: 11.6 ± 0.5 years). The EG introduced 8-week MPT, two days per week into their in-season training, while CG continued training without change. Measurements of vertical jump height, CODP, and DPC were completed at the beginning and end of the 8-week MPT. A significant group × time interaction was observed for Squat-Jump (p 0.05). In conclusion, incorporating MPT into the in-season regimen of young male soccer players improved performance of various indices related to soccer activity (i.e., vertical jump height, CODP, and DPC). MPT has the potential to be appealing to coaches, as it requires little time while yielding valuable results in the physical preparation of young soccer players.

Hamstring Injuries Prevention in Soccer: A Narrative Review of Current Literature

Abstract: Hamstring injuries and reinjuries are one of the most important sport lesions in several sport activities including soccer, Australian football, track and field, rugby, and in general in all sport activities requiring sprinting and acceleration. However, it is important to distinguish between the lesions of the biceps femoris and semitendinosus and semimembranosus. Indeed, three muscles representing the hamstring complex have a very different injury etiology and consequently require different prevention strategies. This fact may explain, at least in part, the high incidence of reinjuries. In soccer, hamstring injuries cause an important rate of time loss (i.e., in average 15–21 matches missed per club per season). The hamstring injury risk factors may be subdivided in three categories: “primary injury risk factors” (i.e., the risk factors mainly causing a first lesion), “recurrent injury risk factors” (i.e., the risk that can cause a reinjury), and bivalent injury risk factors” (i.e., the risk factors that can cause both primary injuries and reinjuries). The high incidence of hamstring lesions caused consequently an important increase in hamstring injury research. However, although the prevention has increased paradoxically, epidemiological data do not show a loss in injuries and/or reinjuries but, on the contrary, they show an increase in hamstring injuries. This apparent paradox highlights the importance both of the improvement in the prevention programs quality and the criteria for return to play after hamstring injury.

A 12-Year Cohort Study of Doc-Stoppage in Professional Mixed Martial Arts.

Abstract: Purposes: To determine actions during bouts that generate serious enough injury to stop the bout; verifying the injury incidence, types, and prevalence of doctor stoppages (doc-stoppage); and ident...

Age, player position and 2 min suspensions were associated with match injuries during the 2017 Men's Handball World Championship (France)

Abstract: Aim To study the association between player characteristics, technical components of the game and the risk of match injuries during the 2017 Men’s Handball World Championship Methods Team physicians of the participating teams (n=24) were requested to provide injury report forms throughout the Men’s Handball World Championship (France, January 2017) The individual time played, age, number of international matches played and all technical and penalty variables for each player were extracted from the official International Handball Federation (IHF) online database and used as risk factors in a general logistic linear model analysis Results Of 387 players, 49 sustained one or more injuries (93 injuries in total) The total incidence of match injuries was 821 injuries per 1000 hours (95% CI 662 to 1005), non-time-loss injury incidence was 406 injuries per 1000 hours (95% CI 293 to 549), while time-loss injury incidence was 309 injuries per 1000 hours (95% CI 215 to 429) Multivariate analysis showed that age (OR 11, 95% CI 102 to 118, p=0011), player position (backs: OR 679, 95% CI 225 to 2054, p=0001; goalkeepers: OR 503, 95% CI 115 to 2194, p=0031) and 2 min suspensions (1–2 times: OR 277, 95% CI 127 to 604, p=0011; 3 or more times: OR 266, 95% CI 118 to 638, p=0029) were significant risk factors for getting injured during competition matches Conclusion Age, player position (backs, goalkeepers) and 2 min suspensions were associated with match injury Stricter rule enforcement should be considered to prevent match injuries in elite handball

Racial differences in hemoglobin and plasma volume variation: implications for muscle performance and recovery.

Abstract: Objective: To examine the effect of race differences on sprint performance, Hemoglobin (Hb), Hematocrit (Ht) and plasma volume (PV) variation in response to repeated sprint exercise.Design: Thirty-six healthy, moderately trained men and women (20.8 ± 0.2 year-old) volunteered to participate in this study. They were allocated to one of the four groups according to their gender and race: Black men’s group (BM, n = 9), White men’s group (WM, n = 9), Black women’s group (BW, n = 9) and White women’s group (WW, n = 9). All participants performed the running-based anaerobic sprint test (RAST), which consists of six 35-m sprints with 10 s of recovery in-between. Six venous blood samples were collected to determine Hb, Ht and PV levels at rest, after warm-up, immediately post- and at 5, 15 and 30 min post-RAST. Blood lactate is also sampled during the 3rd minutes of recovery.Results: The best running time was significantly shorter (P = .002) in BW compared to WW. We have observed significantly higher Hb (...

Effect of post-activation potentiation induced by one, two or three half-squats on repeated sprint acceleration performance

Abstract: 1 Tunisian Research Laboratory ‘‘Sport Performance Optimisation’’, National Center of Medicine and Science in Sports, Tunis, Tunisia 2 Department of Sports and Physical Activities, Higher Institute of Sport and Physical Education of Ksar Saïd, Manouba, Tunisia 3 School of Public Health, Department of Health Sciences (DISSAL), University of Genoa, Genoa, Italy 4 BenficaLAB, SL Benfica, Lisbon, Portugal. 5 Centre de Recherche et d’Innovation sur le Sport, Université Claude Bernard Lyon.1, Lyon, France. 6 Athlete Health and Performance Research Centre, ASPETAR, Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar 7 Sport Science Program, College of Arts and Sciences, Qatar University, Doha, Qatar

The Crucial Role of Elite Athletes and Expert Coaches With Academic Profiles in Developing Sound Sport Science

Abstract: Sport science and medicine are highly specialized fields, where many scientific disciplines can contribute to improving athletes’ health and performance. In that regard, having athletes, coaches, and scientists working side by side on scientific research projects can significantly improve the quality of the science. I can illustrate this by my own modest experience as a sport scientist and former elite athlete. Indeed, in many scientific articles that I have handled as an author or as International Journal of Sports Physiology and Performance (IJSPP) associate editor, I have noticed how deep “sportdiscipline knowledge” greatly improved the quality of publications. I hope that the recent call to reviewers in which we reminded all scientists about their roles in keeping science running had an impact. Indeed, without committed reviewers, the peer-review process would stop, and so would science. In this context, in the area of sport performance, I would like to highlight the fact that to obtain an optimal outcome of a sound and impactful paper, we need domain (sport) specialists’ input at 2 important steps: (1) study conception and article writing and (2) the manuscript peer-review process. To illustrate this point, I would highlight 2 recent articles, both being from the field of elite karate. In the first paper, I had the chance to work with 3 academics, 2 of whom were combat-sport specialists, with the leading author being an ex-world-class elite karateka. Without their input, the research would have been limited to practitioners in the field. Specifically, my biases and background would have pushed the study toward the viewpoint of an exercise physiologist with a different sport background. Most likely, the study would have been substantially different with a focus on classical physiological variables and concepts of internal and external load. The expert practitioners’ involvement instead took us down a previously unexplored but ultimately fruitful line of exploring what happens before and after the “decisive moment” in karate combat—the moment from which one of the 2 opponents uninterruptedly dominates the other until the end of the fight, in simple terms, “how the fight was won.” I like this paper not only because it clearly describes technical actions that lead to the decisive moment, and therefore, winning a karate combat, but also, and more important, because it could inspire other sport-scientific experts on this novel way of analyzing sport performance with regard to a crucial moment, when “victory has been definitely set.”Without the domain specialists, this project would have hadmuch less real-world impact. The second example is from the peer-review process of another original article on karate that I coauthored. One of the anonymous reviewers of this paper was clearly an expert in karate and greatly improved the final product. All the very detailed and constructive comments made on the manuscript clearly showcased the reviewer’s high level of expertise in this sport. As authors, we could not have been happier with this review process from such a rigorous, exigent, and competent reviewer. Among other things, the reviewer helped us better translate numbers in real sport actions to provide clear practical applications. Ultimately, the addition of this reviewer’s domain knowledge coupled with clear scientific knowledge greatly improved this paper for the readers. We believe that the outcome of the review process clearly brought relevant data/knowledge on the technical and tactical discriminatory factors between winners and defeated elite karate athletes, expressed in a much clearer way, thanks to both sport and scientific expertise of the reviewers. Reflecting on these specific papers, we suspect that their impact may go beyond karate and to inspire other sport scientists to investigate their sports regarding these crucial performance determinants. After all, isn’t winning or losing a central concern of all coaches and sport scientists? More broadly, these illustrations confirm a trend that I have noticed as associate editor while managing manuscript-review processes for IJSPP. Some reviewers are deep experts in their sports, and their influence undoubtedly enhances this quality and depth; on this much we can agree, as science always needs these attributes. Therefore, I call on academics who are sport specialists to maintain their efforts in improving sport science in their fields. We need these people, not only as authors of manuscripts, but also, and perhaps even more important, as reviewers. And again, I implore us, as a group, to work toward encouraging their participation and removing whatever barriers are currently in place making it difficult for them to be involved in the review process. Perhaps a fault lies in the actual situation, giving too much credit to manuscript authors, and surely not enough recognition to reviewers, who are indeed the “real unsung heroes in science.”

Risk diagnosis of minor muscle injuries in professional football players: when imaging cannot help out biology might.

Abstract: Muscle strain accounts for ~30% of all football injuries1 and engages medical staff in a complicated process of diagnostic and management. In 90% of the cases, muscle strains affect hamstrings, rectus femoris, adductors, soleus and gastrocnemius.2 3 In particular, into the group of the so-called minor muscle injuries, a subgroup defined ‘non-structural muscle injuries’ (NSI) has been identified.2 The NSIs do not present any visible muscle fibre lesion at MRI and ultrasound examination and are classified as grade 1a, 1b2 or zero3 according to the latest classifications.2 3 Moreover, they are fare from being rare as they account for 30% – 40% of all muscle lesions recorded by professional football clubs.1 Despite the fact that NSIs are not detected by imaging, they can have functional sequelae.2 3 The player affected by NSI generally loses between 1 and 7 days of training/match exposure, and the diagnosis of this type of injury can be challenging. Many medical centres are not adequately specialised in sports medicine injuries and the imaging exams may be negative or, at the very most, reveal an ill-defined oedematous area that may be difficult to interpret.2 3 In …