Latest research in football - week 40 - 2014

Latest research in football

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 Determinant Factors of Repeat Sprint Sequences in Young Soccer Players
Reference: Int J Sports Med. 2014 Sep 26. [Epub ahead of print]
Authors: López-Segovia M, Pareja-Blanco F, Jiménez-Reyes P, González-Badillo JJ
Summary: The aim of this study was to investigate the relationships between repeated explosive effort sequences (20+20 m shuttle sprint with change of direction, kicking and jumping), metabolic response (lactate and ammonia), and fitness qualities (strength and endurance) in under-19 soccer players. 21 players completed: 1) sprint test: 30 m (T30) and 40 m (20+20 m) shuttle sprints; 2) countermovement jumps (CMJ); 3) maximal kicking; and 4) 9 repeated-explosive effort sequences (RES); 4) a progressive isoinertial loading test in full squat to determine the load which subjects achieved ~1 m · s-1 (V1-load); 6) Yo-Yo Intermittent Recovery Test Level 1 (YYIRT-1). Mean sprint time of the 9 repeated sprints (RSAmean1-9) showed correlation with V1-load (r=- 0.52 [- 0.79, - 0.25]) metabolic response (lactate, r=0.67 [0.47, 0.87] and ammonia, r=0.53 [0.27, 0.79]). YYIRT-1 correlated with RSAmean1-9 (rw=- 0.78 [- 0.92, - 0.64]) when the body weight was controlled. Furthermore, the 3 first sprints (RSAmean1-3) correlated with RSAbest (r=0.93 [0.88, 0.98]), V1-load (r=- 0.64 [-0.86, - 0.42]), and T30 (r=0.63 [0.41, 0.85]). These results suggest that the soccer player's lower body strength (V1-load, jumping and sprinting) explains a large part of the performance in the first sequences, whereas the aerobic capacity, estimated through YYIRT-1, becomes more important to performance as the number of sprints is increases.

#2 Endoscopic Repair of Posterior Ankle Impingement Syndrome Due to Os Trigonum in Soccer Players
Reference: Foot Ankle Int. 2014 Sep 23. pii: 1071100714552078. [Epub ahead of print]
Authors: López Valerio V, Seijas R, Alvarez P, Ares O, Steinbacher G, Sallent A, Cugat R
Summary: An os trigonum may cause posterior ankle impingement syndrome (PAIS), which may lead to poor sports performance, especially in soccer players. The aim of the present study was to analyze the outcomes of endoscopic repaired posterior ankle impingement (PAI) secondary to os trigonum syndrome within a group of soccer players as well as their return to play time. A retrospective review of 20 soccer players with Tegner activity level 9 was performed. All players were diagnosed of PAIS due to os trigonum. Chief complaint was pain produced with forced plantarflexion when kicking the ball. Conservative treatment was first performed during a 6-week rehabilitation program. When conservative treatment failed, arthroscopic surgical resection of the os trigonum was proposed. Visual analogue scale (VAS) was used to measure pain before and after surgery as well as time until their return to previous sports level. VAS showed a mean preoperative pain score of 7.5 (SD = 0.9), whereas postoperative VAS at 1 month after surgery decreased to 0.8 (SD = 1.36). Mean symptomatic period was 8.5 months (SD = 4.3), from the beginning of symptoms up to the surgery day. Once patients had undergone surgery, mean time until their return to previous level of sports was 46.9 days (SD = 25.96), reaching the same pre-lesion Tegner level. Endoscopic treatment of posterior ankle impingement syndrome due to os trigonum showed excellent results. Hindfoot endoscopy with a posterior approach was an effective treatment and allowed for a prompt return to play in soccer players with a high activity level.

#3 Effects of anterior cruciate ligament injury on neuromuscular tensiomyographic characteristics of the lower extremity in competitive male soccer players
Reference: Knee Surg Sports Traumatol Arthrosc. 2014 Sep 25. [Epub ahead of print]
Authors: Alvarez-Diaz P, Alentorn-Geli E, Ramon S, Marin M, Steinbacher G, Boffa JJ, Cuscó X, Ares O, Ballester J, Cugat R.
Summary: The purpose was to investigate the effects of anterior cruciate ligament injury on mechanical and contractile characteristics of the skeletal muscles of the lower extremity in competitive soccer players through tensiomyography (TMG). All competitive male soccer players with confirmed acute anterior cruciate ligament tear included underwent resting TMG assessment of muscles of both lower extremities before anterior cruciate ligament reconstruction. The same values were obtained from a sex- and sports level-matched control group. The maximal displacement, delay time, contraction time, sustained time, and half-relaxation time were obtained for the following muscles in all subjects: vastus medialis, vastus laterals, rectus femoris, semitendinosus, biceps femoris, gastrocnemius medialis, and gastrocnemius lateralis. The majority of TMG parameters were higher in the injured compared to the control group. The contraction time of the vastus medialis, vastus lateralis, and rectus femoris was significantly higher in the injured compared to the control group (p = 0.003, p = 0.001, and p < 0.001, respectively). The biceps femoris was the only hamstring muscle with significant differences between groups, with increased contraction time and maximal displacement in the injured compared to the control group (p = 0.002 and p < 0.001, respectively). The gastrocnemius medialis was clearly more affected than the gastrocnemius lateralis, with contraction time, half-relaxation time, and maximal displacement significantly higher (p = 0.01, p = 0.03, and p < 0.001, respectively), and the sustained time significantly lower (p = 0.01), in the injured compared to the control group. The contraction time of the vastus medialis, vastus lateralis, rectus femoris, semitendinosus, and biceps femoris was significantly higher in the injured compared to non-injured side in the anterior cruciate ligament-injured group (p = 0.007, p = 0.04, p = 0.004, p = 0.02, and p = 0.02, respectively). Anterior cruciate ligament injury caused a decrease in contraction velocity (in quadriceps, hamstrings and gastrocnemius medialis), resistance to fatigue (in quadriceps and gastrocnemius medialis), and muscle tone/stiffness (in hamstrings and gastrocnemius medialis). Overall, it was demonstrated that these effects were worst in the quadriceps and gastrocnemius medialis compared to the hamstring and gastrocnemius lateralis. These findings may contribute to a better design of rehabilitation programs in order to optimize the recovery and potentially increase sport performance at return to sport.

#4 Modeling heading in adult soccer players
Reference: IEEE Comput Graph Appl. 2014 Sep-Oct;34(5):8-13. doi: 10.1109/MCG.2014.96.
Authors: Ponce E, Ponce D, Andresen M.
Summary: Heading soccer balls can generate mild brain injuries and in the long run can lead to difficulty in solving problems, memory deficits, and language difficulties. Researchers evaluated the effects on the head for both correct and incorrect heading techniques. They based the head's geometry on medical images. They determined the injury's magnitude by comparing the neurological tissue's resistance with predictions of the generated stresses. The evaluation examined fast playing conditions in adult soccer, taking into account the ball's speed and the type of impact. Mathematical simulations using the finite element method indicated that correctly heading balls arriving at moderate speed presents a low risk of brain injury. However, damage can happen around the third cervical vertebra. These results coincide with medical studies. Incorrect heading greatly increases the brain injury risk and can alter the parietal area.

#5 Impact of sports on health of former professional soccer players in Brazil
Reference: Acta Ortop Bras. 2014;22(4):188-90. doi: 10.1590/1413-78522014220400954.
Authors: Arliani GG, Lara PS, Astur DC, Cohen M, Gonçalves JP, Ferretti M.
Download link:
Summary: The purpose of the study was to evaluate the social, economic and health aspects related to former professional soccer players in Brazil.
This was a cross-sectional study with the participation of 100 male Brazilian former professional soccer players. For characterization of the sample variables such as age, current and past weight, height, BMI (Body Mass Index) and player position were evaluated. In all analyzes it was considered P <0.05. In the group of former players evaluated, 78% were overweight and 4% were considered obese. During their careers, 54% of now ex-soccer players underwent drugs infiltration in the knee. Currently, former athletes presented on average 5.4 points on the VAS pain scale, with 97% of ex-players complaining of knee pain. The results of this study show that these individuals had large weight gain after retirement, high frequency of drug injections in the knee during their careers and chronic pain in this joint after retirement. Level of Evidence III, Cross-Sectional Study.

#6 Comparison of tensiomyographic neuromuscular characteristics between muscles of the dominant and non-dominant lower extremity in male soccer players
Reference: Knee Surg Sports Traumatol Arthrosc. 2014 Sep 19. [Epub ahead of print]
Authors: Alvarez-Diaz P, Alentorn-Geli E, Ramon S, Marin M, Steinbacher G, Rius M, Seijas R, Ballester J, Cugat R.
Summary: Tensiomyography (TMG) has been used to assess neuromuscular characteristics of muscles of the lower extremity in soccer players. However, the effects of lower extremity dominance on TMG characteristics in this population have not been reported to date. The purpose of this study was to compare the TMG neuromuscular characteristics between the dominant and non-dominant lower extremity in male soccer players. Thirty-eight consecutive healthy male soccer players underwent resting TMG assessment of vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF), semitendinosus (ST), biceps femoris (BF), gastrocnemius medialis (GM), and gastrocnemius lateralis (GL) in both lower extremities. The maximal displacement, delay time, contraction time, sustained time, and half-relaxation time were obtained and compared between both sides. There were no significant differences in the vast majority of the TMG parameters between both lower extremities. The dominant side demonstrated higher VM contraction time (p = 0.008), RF sustained time (p = 0.009), RF half-relaxation time (p = 0.01), and BF sustained time (p = 0.04), but lower VL contraction time (p = 0.03) and VL delay time (p = 0.02) compared to the non-dominant side. In general, TMG-assessed neuromuscular characteristics of the VM, VL, RF, ST, BF, GM, and GL were not affected by lower extremity dominance in male soccer players. Therefore, there is no need to assess both sides when using TMG to monitor the response to training or muscles at risk of injury in soccer players unless there is a specific reason.

#7 Age determination using ultrasonography in young football players
Reference: Adv Biomed Res. 2014 Aug 19;3:174. doi: 10.4103/2277-9175.139192. eCollection 2014.
Authors: Karami M, Moshirfatemi A, Daneshvar P
Download link:
Summary: Increasing of age cheating in sports makes problems to athletes comparable to taking illegal substances. Current method used by AFC and FIFA is applying MRI of growth plate of distal of radius to determine the bone age. This study was designed to evaluate the diagnostic accuracy of ultrasonography in bone age determination by measuring the width of growth plate in distal of radius, and comparing it with identity documents. The study was conducted from September to December 2009 in the Department of Radiology at Al-Zahra University Hospital, Isfahan, Iran. Ultrasonography was done for 82 (15-20 years old) young professional football players and results were compared with identity documents (such as National ID card). Young football players were divided into three age categories: < 16 and > 16 years old, < 17 and > 17 years old, and < 18 and > 18 years old. Receiver Operator Characteristics (ROC) curves for discriminant values and sensitivity and specificity were analyzed. Cut-off point was set for each group, based on the width of the growth plate, and negative test was defined as subjects < cut-off point, showing subjects over the defined age in each group. ROC curve analysis demonstrates consistently acceptable diagnostic sensitivity and specificity values in age determination of each group. The overall predictive accuracy of ultrasonography, as described by the area under the ROC curve, was high for determination of bone age. It has an acceptable sensitivity and specificity to use for determination of age in sport competitions, and has the capability to become the screening test for age determination, especially because it is inexpensive and without any risk of radiation. It seems to be comparable with MRI in age determination.

The Training Manager -