Head Injury in Soccer: From Science to the Field; summary of the head injury summit held in April 2017 in New York City, New York.

There has been an increased focus and awareness of head injury and sport-related concussion (SRC) across all sports from the medical and scientific communities, sports organisations, legislators, the media and the general population. Soccer, in particular, has been a focus of attention due to the popularity of the game, the frequency of SRC and the hypothesised effects of repetitive heading of the ball. Major League Soccer, US Soccer and the National Women's Soccer League jointly hosted a conference entitled, 'Head Injury in Soccer: From Science to the Field', on 21-22 April 2017 in New York City, New York. The mission of this conference was to identify, discuss and disseminate evidence-based science related to the findings and conclusions of the fifth International Conference on Concussion in Sport held by the Concussion in Sport Group and apply them to the sport of soccer. In addition, we reviewed information regarding the epidemiology and mechanism of head injuries in soccer at all levels of play, data regarding the biomechanics and effects of repetitive head impacts and other soccer-specific considerations. We discussed how to release the information raised during the summit to key stakeholders including athletes, parents, coaches and healthcare providers. We identified future areas for research and collaboration to enhance the health and safety of soccer (football) players.

Relative age effect: beyond the youth phenomenon.

INTRODUCTION: Initially described in a sports context in ice hockey in 1985, the relative age effect (RAE) refers to the performance advantages of youth born in the first quarter of the birth year when trying-out for select, age-restricted sports. The competitive advantage bestowed to the relatively older athlete in their age band is the result of the older athlete being more physically and emotionally mature. These more mature players will likely go on to be exposed to better coaching, competition, teammates and facilities in their respective sport. OBJECTIVES: Our study sought to characterise the ubiquity of this effect by examining the birth distribution of some of the world's most elite athletes, Olympians. METHODS: We extended the exploration of the RAE beyond specific sports by examining the birth quarter of over 44 000 Olympic athlete's birthdates, born between 1964 and 1996. Our hypothesis was that the RAE would be prominent in both Olympic athletes as a whole and in selected subcategories of athletes. RESULTS AND CONCLUSION: The fractions of births in the first versus the fourth quarter were significantly different (p<0.001) from each other for the summer and winter Olympians, ball and non-ball sports, and team as well as individual sports. This significant difference was not gender specific. We found the general existence of the RAE in Olympic athletes regardless of global classification. Our findings suggest that coaching staff should be cognisant of the RAE when working with young athletes and should take relative age into consideration when evaluating a burgeoning athlete's abilities.

The impact of specific high-intensity training sessions on football referees' fitness levels.

BACKGROUND: In comparison to the amount of literature that has examined the match demands of football refereeing, there has been little attempt to assess the impact of high-intensity training. PURPOSE: The main goals were to get a better understanding of the long-term effect of specific intermittent training. STUDY DESIGN: The authors examined the cardiovascular strain of specific high-intensity training sessions and also their impact on referees' fitness levels. METHODS: To examine the physical workload during intensive intermittent training sessions, heart rates were recorded and analyzed relative to the referees' maximum heart rate (HR(max)). To assess the referees' fitness levels, the Yo-Yo intermittent recovery test was used. RESULTS: Both the pitch- and track-training sessions were successful in imposing an appropriate high intensity load on the referees, at 86.4 +/- 2.9% and 88.2 +/- 2.4% HR(max), respectively. Following 16 months of intermittent high-intensity training, referees improved their performance on the Yo-Yo intermittent recovery test by 46.5%, to a level that is comparable with professional players. CONCLUSIONS: As match officials are subjected to a high physical load during matches, they should follow structured weekly training plans that have an emphasis on intensive, intermittent training sessions.

Electromyographic Analysis of Single-Leg, Closed Chain Exercises: Implications for Rehabilitation After Anterior Cruciate Ligament Reconstruction.

OBJECTIVE: Many knee rehabilitation studies have examined open and closed kinetic chain exercises. However, most studies focus on 2-legged, closed chain exercise. The purpose of our study was to characterize 1-legged, closed chain exercise in young, healthy subjects. SUBJECTS: Eighteen normal subjects (11 men, 7 women; age, 24.6 +/- 1.6 years) performed unsupported, 1-legged squats and step-ups to approximately tibial height. MEASUREMENTS: Knee angle data and surface electromyographic activity from the thigh muscles were recorded. RESULTS: The maximum angle of knee flexion was 111 +/- 23 degrees for squats and 101 +/- 16 degrees for step-ups. The peak quadriceps activation was 201 +/- 66% maximum voluntary isometric contraction, occurring at an angle of 96 +/- 16 degrees for squats. Peak quadriceps activation was 207 +/- 50% maximum voluntary isometric contraction and occurred at 83 +/- 12 degrees for step-ups. CONCLUSIONS: The high and sustained levels of quadriceps activation indicate that 1-legged squats and step-ups would be effective in muscle rehabilitation. As functional, closed chain activities, they may also be protective of anterior cruciate ligament grafts. Because these exercises involve no weights or training equipment, they may prove more cost effective than traditional modes of rehabilitation.