Latest research in football - week 44 - 2016

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

Following studies were retrieved for this week:

#1 Test-Retest Reliability of Physiological and Performance Responses to 120 Minutes of Simulated Soccer Match Play
Reference: J Strength Cond Res. 2016 Nov;30(11):3178-3186.
Author: Harper LD, Hunter R, Parker P, Goodall S, Thomas K, Howatson G, West DJ, Stevenson E, Russell M
Summary: This study investigated the test-retest reliability of physiological and performance responses to 120 minutes (90 minutes plus 30 minutes extra-time [ET]) of the soccer match simulation (SMS). Ten university-standard soccer players completed the SMS on 2 occasions under standardized conditions. Capillary and venous blood was taken pre-exercise, at half-time, and at 90 and 120 minutes, with further capillary samples taken every 15 minutes throughout the exercise. Core temperature (Tcore), physical (20- and 15-m sprint speeds and countermovement jump height), and technical (soccer dribbling) performance was also assessed during each trial. All variables except blood lactate demonstrated no systematic bias between trials (p > 0.05). During the last 15 minutes of ET, test-rest reliability (coefficient of variation %, Pearson's r, respectively) was moderate to strong for 20-m sprint speed (3.5%, 0.71), countermovement jump height (4.9%, 0.90), dribble speed (2.8%, 0.90), and blood glucose (7.1%, 0.93), and very strong for Tcore (1.2%, 0.99). Moderate reliability was demonstrated for 15-m sprint speed (4.6%, 0.36), dribble precision (11.5%, 0.30), plasma insulin (10.3%, 0.96), creatine kinase ([CK] 28.1%, 0.38), interleukin-6 (24%, 0.99), nonesterified fatty acids ([NEFA] 13.2%, 0.73), glycerol (12.5%, 0.86), and blood lactate (18.6%, 0.79). In the last 15 minutes of ET, concentrations of blood glucose and lactate and sprint and jump performances were reduced, whereas Tcore, NEFA, glycerol, and CK concentrations were elevated (p ≤ 0.05). The SMS is a reliable protocol for measuring responses across the full 120 minutes of soccer-specific exercise. Deleterious effects on performance and physiological responses occur during ET.

#2 Failure of Internal Fixation for Painful Bipartite Navicular in Two Adolescent Soccer Players: A Report of Two Cases
Reference: J Foot Ankle Surg. 2016 Nov - Dec;55(6):1323-1326. doi: 10.1053/j.jfas.2016.01.015. Epub 2016 Feb 6.
Authors: Yamaguchi S, Niki H, Akagi R, Yamamoto Y, Sasho T
Summary: Bipartite navicular bone is an uncommon condition that can cause midfoot pain in children and adolescents. No treatment methods, other than conservative management, have been reported. We report the cases of 2 adolescent soccer players who underwent internal fixation of the painful bipartite fragments, resulting in nonunion. After failure of conservative management, the patients underwent surgery. Curettage of the junction between the 2 bone fragments was performed, and autologous cancellous bone was grafted. Next, the fragments were fixed with variable-threaded screws. Bone union of the bipartite fragments was once achieved on computed tomography in both cases at 3 and 5 months after surgery, respectively. However, separation of the fragment occurred in both cases after the patients had returned to sports. Although the patients were able to return to sports activities, they still had mild midfoot pain 3 and 2 years after surgery, respectively. Internal fixation using screws and an autologous bone graft for painful bipartite navicular bone in adolescent athletes is not recommended, and other surgeries should be considered to achieve bony union.

#3 Effects of the FIFA 11 training program on injury prevention and performance in football players: A systematic review and meta-analysis
Reference: Clin Rehabil. 2016 Nov 2. pii: 0269215516675906. [Epub ahead of print]
Authors: Gomes Neto M, Conceição CS, de Lima Brasileiro AJ, de Sousa CS, Carvalho VO, de Jesus FL
Summary: The purpose was to investigate the effects of FIFA 11 training on injury prevention and performance in football players. We conducted a systematic search using four databases (CINAHL, Cochrane Library, EMBASE, and PubMed) to find controlled trials evaluating the effects of FIFA 11 on injury prevention and performance among football players. Weighted mean differences, standard mean differences, risk ratios, and 95% confidence intervals were calculated, and heterogeneity was assessed using the I2 test. We analyzed 11 trials, including 4700 participants. FIFA 11 resulted in a significant reduction in injury risk (risk ratio = 0.69; 95% confidence interval, 0.49-0.98; P = 0.02) and improvements in dynamic balance (weighted mean difference = 2.68; 95% confidence interval, 0.44-4.92; P = 0.02) and agility (standard mean difference = -0.36; 95% confidence interval, 0.70-0.02; P = 0.04). The meta-analysis indicated a non-significant improvement in jump height (standard mean difference = 0.25; 95% confidence interval, 0.08-0.59; P = 0.14) and running sprint (standard mean difference = -0.24; 95% confidence interval, 0.58-0.10; P = 0.17) in the FIFA 11 group. FIFA 11 can be considered as a tool to reduce the risk of injury. It may improve dynamic balance and agility and can be considered for inclusion in the training of football players.

#4 Recreational football training improved health-related physical fitness in 9- to 10-year-old boys
Reference: J Sports Med Phys Fitness. 2016 Oct 28. [Epub ahead of print]
Authors: Wang J, Cao L, Xie P, Wang J
Summary: Recreational football is an aerobic/anaerobic intermittent sport with altering exercise periods at high or low intensity. Various football drills and body movement in this exercise may easily attract children to take part in. The purpose of this study was to test the hypothesis that recreational football training would improve the health-related physical fitness in healthy 9- to 10-year-old boys, compared to the outcome from non-exercise boys. Forty boys were randomly allocated into the football and control groups. Body composition, predicted maximal oxygen uptake, heart rate responses during submaximal exercise, running ability, muscle strengths, and body balance and flexibility were measured before and after the experimental period. No dietary modification was suggested to the boys in this study. Following 10 weeks of recreational football training, the football group achieved significant improvements in body fat% (-2.42%), fat mass (-0.93kg), abdominal fat (-0.06kg), 50-meter run (-0.9s), long jump (+7.6cm), core muscle strengths (front bridge increased 10.9s and side bridge increased 5.6s), and body balance (single-leg standing time increased 5.2s). The heart function during submaximal exercise and predicted maximal oxygen uptake were also significantly improved in the trained boys. There were no changes in these variables of the control group. There was no sport injury occurred during the training program. The daily energy intake was not changed for all boys before and after the interventions. the 10-week recreational football training is an effective method to improve the health-related physical fitness in 9- to 10-year-old boys.

#5 Foot and Ankle Kinematics and Dynamic Electromyography: Quantitative Analysis of Recovery From Peroneal Neuropathy in a Professional Football Player
Reference: J Surg Orthop Adv. 2016 Fall;25(3):180-186.
Authors: Prasad NK, Coleman Wood KA, Spinner RJ, Kaufman KR
Summary: The assessment of neuromuscular recovery after peripheral nerve surgery has typically been a subjective physical examination. The purpose of this report was to assess the value of gait analysis in documenting recovery quantitatively. A professional football player underwent gait analysis before and after surgery for a peroneal intraneural ganglion cyst causing a left-sided foot drop. Surface electromyography (SEMG) recording from surface electrodes and motion parameter acquisition from a computerized motion capture system consisting of 10 infrared cameras were performed simultaneously. A comparison between SEMG recordings before and after surgery showed a progression from disorganized activation in the left tibialis anterior and peroneus longus muscles to temporally appropriate activation for the phase of the gait cycle. Kinematic analysis of ankle motion planes showed resolution from a complete foot drop preoperatively to phase-appropriate dorsiflexion postoperatively. Gait analysis with dynamic SEMG and motion capture complements physical examination when assessing postoperative recovery in athletes.

#6 Training loads and injury risk in Australian football-differing acute: chronic workload ratios influence match injury risk
Reference: Br J Sports Med. 2016 Oct 27. pii: bjsports-2016-096309. doi: 10.1136/bjsports-2016-096309. [Epub ahead of print]
Authors: Carey DL, Blanch P, Ong KL, Crossley KM, Crow J, Morris ME
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Summary: The purpose was to investigate whether a daily acute:chronic workload ratio informs injury risk in Australian football players; (2) to identify which combination of workload variable, acute and chronic time window best explains injury likelihood. Workload and injury data were collected from 53 athletes over 2 seasons in a professional Australian football club. Acute:chronic workload ratios were calculated daily for each athlete, and modelled against non-contact injury likelihood using a quadratic relationship. 6 workload variables, 8 acute time windows (2-9 days) and 7 chronic time windows (14-35 days) were considered (336 combinations). Each parameter combination was compared for injury likelihood fit (using R2). The ratio of moderate speed running workload (18-24 km/h) in the previous 3 days (acute time window) compared with the previous 21 days (chronic time window) best explained the injury likelihood in matches (R2=0.79) and in the immediate 2 or 5 days following matches (R2=0.76-0.82). The 3:21 acute:chronic workload ratio discriminated between high-risk and low-risk athletes (relative risk=1.98-2.43). Using the previous 6 days to calculate the acute workload time window yielded similar results. The choice of acute time window significantly influenced model performance and appeared to reflect the competition and training schedule. Daily workload ratios can inform injury risk in Australian football. Clinicians and conditioning coaches should consider the sport-specific schedule of competition and training when choosing acute and chronic time windows. For Australian football, the ratio of moderate speed running in a 3-day or 6-day acute time window and a 21-day chronic time window best explained injury risk.

#7 Physical and Physiological Responses of Amateur Football Players on Third-Generation Artificial Turf Systems During Simulated Game Situations
Reference: J Strength Cond Res. 2016 Nov;30(11):3165-3177
Authors: Sánchez-Sánchez J, García-Unanue J, Felipe JL, Jiménez-Reyes P, Viejo-Romero D, Gómez-López M, Hernando E, Burillo P, Gallardo L
Summary: The aim of this study is to evaluate the physical and physiological load imposed on amateur football players in a simulated game situation on different artificial turf systems. For that purpose, 20 football players (21.65 ± 3.10 year old) were monitored with Global Positioning Systems and heart rate bands during 45-minutes games on 4 selected artificial turf systems. The results show more covered distance in high-intensity ranges on the system with lower levels of damping and higher rates of rotational traction (p ≤ 0.05). Likewise, this system of artificial turf demonstrated a high number of sprints (12.65 ± 5.67) and more elevated maximum speed peaks during the last part of the game (28.16 ± 2.90 km·h) in contrast to the systems with better damping capacity (p ≤ 0.05). On the other hand, the physiological load was similar across the 4 artificial turf systems (p > 0.05). Finally, the regression analysis demonstrated a significant influence of the mechanical properties of the surface on global distance (15.4%), number (12.6%), and maximum speed (16.6%) of the sprints. To conclude, the mechanical variability of the artificial turf systems resulted in differences in the activity profiles and the players' perceptions during simulated football games.

#8 Factors associated with playing football after anterior cruciate ligament reconstruction in female football players
Reference: Scand J Med Sci Sports. 2016 Nov;26(11):1343-1352. doi: 10.1111/sms.12588. Epub 2015 Nov 21.
Authors: Fältström A, Hägglund M, Kvist J
Summary: This study investigated whether player-related factors (demographic, personality, or psychological factors) or the characteristics of the anterior cruciate ligament (ACL) injury were associated with the return to playing football in females after ACL reconstruction (ACLR). We also compared current knee function, knee related quality of life and readiness to return to sport between females who returned to football and those who had not returned. Females who sustained a primary ACL rupture while playing football and underwent ACLR 6-36 months ago were eligible. Of the 460 contacted, 274 (60%) completed a battery of questionnaires, and 182 were included a median of 18 months (IQR 13) after ACLR. Of these, 94 (52%) returned to football and were currently playing, and 88 (48%) had not returned. Multiple logistic regression analysis identified two factors associated with returning to football: short time between injury and ACLR (0-3 months, OR 5.6; 3-12 months OR 4.7 vs reference group > 12 months) and high motivation. Current players showed higher ratings for current knee function, knee-related quality of life, and psychological readiness to return to sport (P < 0.001). Undergoing ACLR sooner after injury and high motivation to return to sports may impact a player's return to football after ACLR.

#9 Large eccentric strength increase using the Copenhagen Adduction exercise in football: A randomized controlled trial
Reference: Scand J Med Sci Sports. 2016 Nov;26(11):1334-1342. doi: 10.1111/sms.12585. Epub 2015 Nov 21.
Authors: Ishøi L, Sørensen CN, Kaae NM, Jørgensen LB, Hölmich P, Serner A
Summary: Hip adductor injuries are frequent in football, and players with low adductor strength appear to be at increased risk of injury. High adductor muscle activity has been shown in the Copenhagen Adduction exercise (CA); however, an associated strength gain has not been investigated. This study aims to examine the eccentric hip adduction strength (EHAD) gain using the CA in-season. Two U-19 sub-elite football teams, including 24 football players, were randomized to either an 8-week supervised progressive training program in addition to the usual training (intervention) or to continue training as usual (control). EHAD, eccentric hip abduction strength (EHAB), and side-bridge endurance were measured using reliable test procedures at baseline and follow-up by a blinded tester. There was a significant interaction between group and time on EHAD, EHAB, and EHAD/EHAB ratio (P < 0.025). The intervention group demonstrated a 35.7% increase in EHAD (P < 0.001); a 20.3% increase in EHAB (P = 0.003), and 12.3% increase in EHAD/EHAB ratio (P = 0.019). No significant within-group differences were found in the control group (P > 0.335). Compliance was 91.25%, and median muscle soreness ranged from 0 to 2. The CA implemented in-season with an 8-week progressive training program elicited a large significant increase in EHAD, EHAB, and EHAD/EHAB ratio.

#10 Economic impact study: neuromuscular training reduces the burden of injuries and costs compared to standard warm-up in youth soccer
Reference: Br J Sports Med. 2016 Nov;50(22):1388-1393. doi: 10.1136/bjsports-2015-095666. Epub 2016 Mar 31.
Authors: Marshall DA, Lopatina E, Lacny S, Emery CA
Summary: There is randomised controlled trial (RCT) evidence that neuromuscular training (NMT) programmes can reduce the risk of injury in youth soccer. We evaluated the cost-effectiveness of such an NMT prevention strategy compared to a standard of practice warm-up. A cost-effectiveness analysis was conducted alongside a cluster RCT. Injury incidence rates were adjusted for cluster using Poisson regression analyses. Direct healthcare costs and injury incidence proportions were adjusted for cluster using bootstrapping. The joint uncertainty surrounding the cost and injury rate and proportion differences was estimated using bootstrapping with 10 000 replicates. Along with a 38% reduction in injury risk (rate difference=-1.27/1000 player hours (95% CI -0.33 to -2.2)), healthcare costs were reduced by 43% in the NMT group (-$689/1000 player hours (95% CI -$1741 to $234)) compared with the control group. 90% of the bootstrapped ratios were in the south-west quadrant of the cost-effectiveness plane, showing that the NMT programme was dominant (more effective and less costly) over standard warm-up. Projecting results onto 58 100 Alberta youth soccer players, an estimated 4965 injuries and over $2.7 million in healthcare costs would be conservatively avoided in one season with implementation of a neuromuscular training prevention programme. Implementation of an NMT prevention programme in youth soccer is effective in reducing the burden of injury and leads to considerable reduction in costs. These findings inform practice and policy supporting the implementation of NMT prevention strategies in youth soccer nationally and internationally.

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