Latest research in football - week 1 - 2015

As previous literature updates, we have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Early repolarization in soccer players' ECG. Prevalence, characteristics and evolution
Reference: Medicina (B Aires). 2014;74(6):443-447.
Authors: Peidro RM, Brión GB, Bruzzese M, Castiello G.
Summary: Early repolarization (RP) on the electrocardiogram (ECG) of the athlete has been considered a benign finding. In some publications it has been associated with increased risk of sudden death. The objectives of this study were to evaluate the prevalence of infero-lateral RP in a population of trained players, to describe variables associated with this pattern and investigate the occurrence of events in the follow up. ECG of players with a normal cardiovascular physical examination and without family and personal history of heart disease, were analyzed. RP was considered the J-point elevation = 0.1 mV over baseline in at least 2 inferior and / or lateral precordial leads, associated or not with positive deflection or notch in the end of the QRS. RP is related to the voltage of R in V5 or V6, the PR interval, heart rate (HR) and age. They were contacted at 60 ± 5 months after the initial assessment ECG. Statistics: chi square and t test for unpaired data. We evaluated ECG of 210 soccer players, of European-South American origin, with high intensity training. Age: 18 ± 4.6 years. The RP ECG was present in 86 (40.9%), including the lower subtype in 17 (8.1%). One ECG showed PR in lower face in isolation. RP footballers were older, with less FC, prolonged PR and lower voltage of R. None of the players presented cardiovascular events in a 5 years follow up after this evaluation.

#2 Heterotopic ossification in a recreational soccer player
Reference: J Orthop Sports Phys Ther. 2015 Jan;45(1):45. doi: 10.2519/jospt.2015.0401.
Authors: Hando B, Flottmann J, Tuli R.
Summary: The patient was a 44-year-old man who was evaluated by a physical therapist in a direct-access capacity for a chief complaint of intermittent right hip pain that began 6 months prior while playing soccer. After discussing the patient's presentation with an orthopaedic surgeon, the physical therapist ordered magnetic resonance imaging, which revealed an avulsion tear of rectus femoris tendon from the anterior inferior iliac spine, with surrounding soft tissue edema and heterotopic ossification.

#3 Meniscal allograft transplant in a 16-year-old male soccer player: A case report
Reference: J Can Chiropr Assoc. 2014 Dec;58(4):436-43.
Authors: Menta R, Howitt S
Summary: Meniscal allograft transplantation (MAT) is a relatively new procedure that has gained popularity in the last couple of decades as a possible alternative to a meniscectomy to provide significant pain relief, improve function, and prevent the early onset of degenerative joint disease (DJD). As of present, evidence is limited and conflicting on the success of such procedures. In this case, a 16-year old male athlete underwent numerous surgical procedures to correct a left anterior cruciate ligament (ACL) rupture with associated medial and lateral meniscal damage that occurred as a result of a non-contact mechanism of injury. Following multiple procedures, including repair of both menisci and follow-up partial meniscectomy of the lateral meniscus, the patient continued to experience symptoms on the left lateral knee, making him a candidate for MAT. This case is used to highlight what a MAT is, what makes someone a candidate for this type of procedure, the current evidence surrounding the success of this intervention, and some rehabilitation considerations following surgery. The role of chiropractors and primary clinicians is to ensure that young athletes undergo early intervention to offset any degenerative changes that would be associated with sustained meniscal lesions.

#4 A four year prospective study of injuries in elite Ontario youth provincial and national soccer players during training and matchplay
Reference: J Can Chiropr Assoc. 2014 Dec;58(4):369-76.
Authors: Mohib M, Moser N, Kim R, Thillai M, Gringmuth R
Summary: With over 200 million amateur players worldwide, soccer is one of the most popular and internationally recognized sports today. By understanding how and why soccer injuries occur we hope to reduce prevalent injuries amongst elite soccer athletes. Via a prospective cohort, we examined both male and female soccer players eligible to train with the Ontario Soccer Association provincial program between the ages of 13 to 17 during the period of October 10, 2008 and April 20, 2012. Data collection occurred during all player exposures to potential injury. Exposures occurred at the Soccer Centre, Ontario Training grounds and various other venues on multiple playing surfaces. A total number of 733 injuries were recorded. Muscle strain, pull or tightness was responsible for 45.6% of all injuries and ranked as the most prevalent injury. As anticipated, the highest injury reported was muscular strain, which warrants more suitable preventive programs aimed at strengthening and properly warming up the players' muscles.

#5 Heart rate' based training intensity and its impact on injury incidence amongst elite level professional soccer players
Reference: J Strength Cond Res. 2014 Dec 24. [Epub ahead of print]
Authors: Owen AL, Forsyth JJ, Wong DP, Dellal A, Connelly S, Chamari K.
Summary: Elite level professional soccer players are suggested to have increased physical, technical, tactical and psychological capabilities when compared to their sub-elite counterparts. Ensuring these players remain at the elite level generally involves training many different bodily systems to a high intensity or level within a short duration. This study aimed to examine whether an increase in training volume at high intensity levels were related to injury incidence, or increased the odds of sustaining an injury. Training intensity was monitored through time spent in high- (T-HI) and very high- (T-VHI) intensity zones of 85-<90% and ≥90% of maximal heart rate (HRmax), and all injuries were recorded over two consecutive seasons. Twenty-three elite professional male soccer players (mean±SD age 25.6±4.6 years, stature 181.8±6.8 cm, and body mass of 79.3±8.1 kg) were studied throughout the 2-yrs span of the investigation. The results showed a mean total injury incidence of 18.8 (95% CI 14.7 to 22.9) injuries per 1000 h of exposure. Significant correlations were found between training volume at T-HI and injury incidence (r=0.57, p=0.005). Further analysis revealed how players achieving more time in the T-VHI zone during training increased the odds of sustaining a match injury (odds ratio=1.87, 95% CI 1.12 to 3.12, p=0.02), but did not increase the odds of sustaining a training injury. Reducing the number of competitive match injuries amongst elite professional level players may be possible if greater focus is placed on the training intensity and volume over a period of time ensuring the potential reduction of fatigue or overuse injuries. In addition, it is important to understand the optimal training load at which adaptation occurs without raising the risk of injury.

#6 Testing Strength and Power in soccer players: The application of conventional and traditional methods of assessment
Reference: J Strength Cond Res. 2014 Dec 24. [Epub ahead of print]
Authors: Paul DJ, Nassis GP
Summary: Soccer is a highly complex sport influenced by many physical, psychological, tactical and technical factors. In terms of basic physical components, strength and power are considered requisites for many important actions such as tackling, jumping and shooting. Hence, assessment of strength and power are commonly performed within a soccer club's test battery. The objective is to use valid and reliable measures that allow for trustworthy analysis of the physical characteristics of players. Before any credence can be placed in test results, test's validity and reliability needs to be established. This will allow practitioners to make informed decisions about test selection. This review examines the reliability and validity of different strength and power assessments. The suitability of conventional and functional tests is detailed and the strengths and weaknesses of isokinetic dynamometry, hand-held dynamometry, repetition maximum and power testing are also addressed. Generally, the tests considered in this review provide moderate to high reliability in soccer players of different training level. Similarly, the consensus demonstrates test methods to be sensitive to training interventions. In comparison, test validity seems less established. Isokinetic dynamometry has often been recognized as a gold standard measure of testing strength. Other methods of assessment are emerging as viable options (e.g. hand-held dynamometry), likely due to functionality and suitability of testing. Given the demands within a soccer club setting, practitioners should endeavour to utilise testing procedures that are informative yet not time consuming or labour intensive. By providing this, practitioners may have the option to perform more regular monitoring throughout the season rather than a limited number of specific time periods.

#7 Constraints on dynamic stability during forward, backward and lateral locomotion in skilled football players
Reference: Eur J Sport Sci. 2015 Jan 2:1-9. [Epub ahead of print]
Authors: Mehdizadeh S, Arshi AR, Davids K
Summary: The aim of this study was to investigate effects of speed and plane of motion on stability during locomotion in skilled football players. Ten male national-level football players participated in this study to run forward, backward and in lateral directions on a treadmill at 80%, 100% and 120% of their preferred running speeds. The coordinate data of passive reflective markers attached to body segments were recorded using motion capture systems. Time series data obtained from the ankle marker were used for further analyses. The largest finite-time Lyapunov exponent and maximum Floquet multiplier were adopted to quantify local and orbital dynamic stabilities, respectively. Results showed that speed did not significantly change local and orbital dynamic stabilities in any of running patterns. However, both local and orbital dynamic stability were significantly higher in the secondary plane of progression. Data revealed that in running, unlike walking, stability in the direction perpendicular to the direction of running is significantly higher, implying that less active control is required in the secondary plane of progression. The results of this study could be useful in sports training and rehabilitation programmes where development of fundamental exercise programmes that challenge both speed and the ability to maintain stability might produce a tangible enhancement of athletic skill level.

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