Latest research in football - week 37 - 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 Daily Distribution of Carbohydrate, Protein and Fat Intake in Elite Youth Academy Soccer Players Over a 7-day Training Period
Reference: Int J Sport Nutr Exerc Metab. 2016 Aug 24:1-20. [Epub ahead of print]
Authors: Naughton RJ, Drust B, O'Boyle A, Morgans R, Abayomi J, Davies IG, Morton JP, Mahon E
Summary: While traditional approaches to dietary analysis in athletes have focused on total daily energy and macronutrient intake, it is now thought that daily distribution of these parameters can also influence training adaptations. Using seven-day food diaries, we quantified the total daily macronutrient intake and distribution in elite youth soccer players from the English Premier League in U18 (n=13), U15/16 (n=25) and U13/14 squads (n=21). Total energy (43.1±10.3, 32.6±7.9, 28.1±6.8 kcal·kg-1·day-1), CHO (6±1.2, 4.7±1.4, 3.2±1.3 g·kg-1·day-1) and fat (1.3±0.5, 0.9±0.3, 0.9±0.3 g·kg-1·day-1) intake exhibited hierarchical differences (P<0.05) such that U13/14>U15/16>U18. Additionally, CHO intake in U18s was lower (P<0.05) at breakfast, dinner and snacks when compared with both squads but no differences were apparent at lunch. Furthermore, the U15/16s reported lower relative daily protein intake than the U13/14s and U18s (1.6±0.3 vs. 2.2±0.5, 2.0±0.3 g·kg-1). A skewed distribution (p<0.05) of daily protein intake was observed in all squads, with a hierarchical order of dinner (~0.6 g·kg-1) > lunch (~0.5 g·kg-1) > breakfast (~0.3 g·kg-1). We conclude elite youth soccer players do not meet current CHO guidelines. Although daily protein targets are achieved, we report a skewed daily distribution in all ages such that dinner>lunch>breakfast. Our data suggest that dietary advice for elite youth players should focus on both total daily macronutrient intake and optimal daily distribution patterns.

#2 Vitamin D in relation to bone health and muscle function in young female soccer players
Reference: Eur J Sport Sci. 2016 Sep 15:1-8. [Epub ahead of print]
Authors: Brännström A, Yu JG, Jonsson P, Åkerfeldt T, Stridsberg M, Svensson M
Summary: The present work investigated serum vitamin D (25(OH)D) status in relation to bone and muscle qualities and functions in 19 female soccer players (13-16 years) resident at northern latitude with very low sun exposure (∼32-36 h/month) during winter season (late January to early March). Serum 25(OH)D, parathyroid hormone and bone turnover markers osteocalcin (OC) and beta carboxy-terminal collagen cross-links (β-Ctx), as well as body composition and muscle performance were examined. Hormones were tested using routine laboratory methods. Fat mass, lean mass, and bone mineral density in whole body, as well as femur and lumbar spine were evaluated with dual-energy X-ray absorptiometry. Muscle performance was assessed through isokinetic knee extension and flexion, countermovement jump, and sprint running. 25(OH)D was low (50.5 ±   12.8 nmol l-1), whereas the values of bone turnover markers were markedly high (OC: 59.4 ±   18.6 µg l-1; β-Ctx: 1075 ±   408 ng l-1). All bone and muscle measurements were normal or above normal. 25(OH)D was not significantly correlated with most of the parameters of bone and muscle quality or function, except the knee extension time to peak torque (r   =   -0.50, p =   .03). In conclusion, the level of vitamin D is markedly low in adolescent female soccer players during the winter in Sweden. However, vitamin D levels did not significantly correlate with measures of bone and muscle except a moderate correlation in time to peak torque in the knee extensors. The practical implication of low vitamin D levels in young growing female athletes remains unclear.

#3 Associations between Functional and Isolated Performance Measures in Collegiate Women's Soccer Players
Reference: J Sport Rehabil. 2016 Aug 24:1-29. [Epub ahead of print]
Authors: McCann RS, Kosik KB, Terada M, Beard MQ, Buskirk GE, Gribble PA
Summary: The Star Excursion Balance Test (SEBT) and Functional Movement Screen (FMS) are functional performance measures capable of predicting lower extremity injury risk. While suboptimal SEBT and FMS performances are influenced by multiple factors, the contribution of hip strength and flexibility to these tests is mostly unknown. Examination of hip strength and flexibility influences on the SEBT and FMS may direct clinicians to better methods of correcting functional deficits. The objective of the study was to determine the relationships of isometric hip strength and hip passive range of motion (PROM) with functional performance measures. Forty-three NCAA Division I women's soccer players (19.65±1.12yrs; 166.93±3.84cm; 60.99±4.31kg) volunteered. All participants were tested bilaterally in the SEBT; the deep squat, in-line lunge, hurdle step, and straight leg raise, comprising a lower extremity FMS (FMS-LE); hip internal and external rotation PROM; and isometric hip extension strength (HEXT). The mean of the three averaged, normalized SEBT scores was used as a composite score. Pearson product moment correlations assessed relationships of SEBT and FMS-LE scores with PROM and HEXT. Significance was set a priori at P<0.05. Pearson correlations revealed anterior (ANT) SEBT scores had a low negative association with HEXT (r=-0.33,P=0.004) and a low positive association with hip internal rotation PROM (PROM-IR) (r=0.43,P=0.0032). All other correlations were negligible. Flexibility training aimed at PROM-IR may contribute to improved ANT scores. Targeting HEXT and hip external rotation PROM are likely not preferred means of correcting deficits in SEBT and FMS-LE performance.

#4 Longitudinal Changes in Hip Strength and Range of Motion in Female Youth Soccer Players: Implications for ACL Injury. A Pilot Study
Reference: J Sport Rehabil. 2016 Aug 24:1-23. [Epub ahead of print]
Authors: Nguyena AD, Zuka EF, Baellowa AL, Pfileb KR, DiStefanoc LJ, Bolingd MC
Summary: Risk of ACL injuries in young female athletes increases with age, appearing to peak during maturation. Changes in hip muscle strength and range of motion (ROM) during this time may contribute to altered dynamic movement patterns that are known to increase risk of ACL injuries. Understanding the longitudinal changes in hip strength and ROM is needed in order to develop appropriate interventions to reduce the risk of ACL injuries. The objective was to examine the longitudinal changes in hip strength and ROM in female youth soccer players. Fourteen female youth soccer athletes (14.1± 1.1yrs, 165.8± 5.3cm, 57.5± 9.9kg) volunteered as part of a multi-year risk factor screening project. Clinical measures of hip strength and ROM were collected annually over three consecutive years. Passive hip internal rotation (IR), external rotation (ER), abduction (ABD), and adduction (ADD) ROM were measured with a digital inclinometer. Isometric hip ABD and extension (EXT) strength were evaluated using a hand-held dynamometer. Separate repeated measures ANOVAs compared hip strength and ROM values across 3 consecutive years (P<0.05). As youth female soccer players increased in age, there were no changes in normalized hip ABD (P=0.830) or EXT strength (P=0.062) across three consecutive years. Longitudinal changes in hip ROM were observed with increases in hip IR (P=0.001) and ABD (P<0.001), while hip ADD (P=0.009) and ER (P<0.001) decreased. Anatomical changes at the hip occur as youth female soccer players increase in age. While there are no changes in hip strength, there is an increase in hip IR and ABD ROM with a concomitant decrease in hip ER and ADD ROM. The resulting asymmetries in hip ROM may decrease the activation and force producing capabilities of the hip muscles during dynamic activities, contributing to altered lower extremity mechanics known to increase the risk of ACL injuries.

#5 Eccentric Exercises Reduce Hamstring Strains in Elite Adult Male Soccer Players: A Critically Appraised Topic
Reference: J Sport Rehabil. 2016 Aug 24:1-11. [Epub ahead of print]
Authors: Shadle IB, Cacolice PA

#6 Soccer helps in controlling the development of psoriasis in Italian second league players
Reference: J Eur Acad Dermatol Venereol. 2016 Sep 15. doi: 10.1111/jdv.13971. [Epub ahead of print]
Authors: Megna M, Lobasso A, Napolitano M, Rossi FW, Balato A, Matucci-Cerinic C, Braconaro F, Prignano F, Monfrecola G, Balato N, Paulis A
Summary: Psoriasis is a systemic disease linked to a general state of inflammation and increased risk to develop metabolic and cardiovascular diseases such as obesity, diabetes, and hypertension.1,2 Physical activity, a vital component in prevention and management of these diseases, is reported to be potentially associated in a negative way with psoriasis, since the latter often cause significant restriction of social activities.3 The interest in the relationship between exercise and psoriasis is constantly growing. Recently, we have shown that regular physical activity may lower the risk of psoriasis and have a beneficial effect on the natural course of the disease.

#7 Comparison of the Kinematic Patterns of Kick Between Brazilian and Japanese Young Soccer Players
Reference: Asian J Sports Med. 2016 Jun 1;7(2):e33645. doi: 10.5812/asjsm.33645. eCollection 2016.
Authors: Pereira Santiago PR, Palucci Vieira LH, Barbieri FA, Moura FA, Exel Santana J, de Andrade VL, de Souza Bedo BL, Cunha SA
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Summary: Kicking performance is the most studied technical action in soccer and lower limbs kinematics is closely related to success in kicking, mainly because they are essential in imparting high velocity to the ball. Previous studies demonstrated that soccer leagues in different countries exhibit different physical demands and technical requirements during the matches. However, evidencewhether nationality has any influence in the kinematics of soccer-related skills has not yet been reported. The nationality of the players is an aspect that might be also relevant to the performance in kicking. The aim of this study was to compare the lower limbs kinematic patterns during kicking, between Brazilian and Japanese young top soccer players. Seven Brazilian (GA) and seven Japanese (GB) U-17 players performed 15 side-foot kicks each, with a distance of 20 m away from the goal, aiming a target of 1 × 1 m in upper corner, constrained by a defensive wall (1.8 × 2 m). Four digital video cameras (120 Hz) recorded the performance for further 3D reconstruction of thigh, shank and foot segments of both kicking and support limbs. The selected kicking cycle was characterized by the toe-off of the kicking limb to the end of the kicking foot when it came in contact with the ball. Stereographical projection of each segment was applied to obtain the representative curves of kicking as function of time for each participant in each trial. Cluster analysis was performed to identify the mean GA and GB curves for each segment. Silhouette coefficient (SC) was calculated, in order to determine the degree of separation between the two groups' curves. Comparison between the median confidence intervals of the SC showed no differences between groups as regards lower limb patterns of movements. Task accuracy was determined by the relative frequency that the ball reached the target for all attempts and no differences were found (GA: 10.48 ± 14.33%; GB: 9.52 ± 6.51%; P = 0.88). We conclude that lower limb kinematic patterns, in support and ball contact phases, are similar in young Brazilian and Japanese soccer players during free kicks when adopting the side-foot kick style.

#8 Asymmetry of the Modified Illinois Change of Direction Test Impacts Young Elite Soccer Players' Performance
Reference: Asian J Sports Med. 2016 Jun 11;7(2):e33598. doi: 10.5812/asjsm.33598. eCollection 2016.
Authors: Rouissi M, Chtara M, Berriri A, Owen A, Chamari K
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Summary: The modified Illinois change of direction test (MICODT) is an asymmetrical test because the numbers of changes of direction performed to the right and to the left are unequal. Therefore, it is possible that the asymmetry of this test may influence agility performance testing. The aim of this study was to compare two opposite/mirrored versions of the modified Illinois change of direction test. Forty-six right-footed soccer players (17.2 ± 1.6 years-old) participated in the study. Players performed a modified Illinois change of direction test and a mirrored version of this test "inverted modified Illinois change of direction test" (I/MICODT) in a randomized and counter-balanced order. Paired t-test was used to determine whether significant differences existed between time performances of the tests as a within-subjects measure. Players were thereafter stratified into MICODT group or I/MICODT group according to their best performance and independent t-tests were used to determine differences between groups. The analysis revealed no significant difference in time performance between the two versions of test as a within-subjects measure (P > 0.05, ES = 0.05). However, significant better time performances among inverted modified Illinois change of direction group (52% of players) were found when compared to the modified Illinois change of direction group (48% of players) (P < 0.04, ES = 0.66). The modified Illinois change of direction test must be considered as an asymmetrical test because it underestimates more than half of the players' agility performances. Therefore, fitness coaches should take these results into account when using this test.

#9 The hydration status of elite youth female soccer players during an official tournament
Reference: J Sports Med Phys Fitness. 2016 Sep 13. [Epub ahead of print]
Authors: Chapelle L, Tassignon B, Aerenhouts D, Mullie P, Clarys P
Summary: The hydration status of elite female soccer players is a concern, especially during high-volume training periods or tournaments. Furthermore, scientific literature on this topic is scarce to non-existent. Therefore, the primary aim of this study was to evaluate the hydration status in elite youth female soccer players during an official tournament. The secondary aim was to identify a possible relationship between pre-training hydration status and fluid intake. Eighteen players were followed during eight consecutive days. Urine specific gravity was used to assess hydration status. Body weight was monitored before and after every training and match, whilst individual fluid intake was only registered during training. The players were informed about their hydration status on day 5. On days 1 to 4, the percentage of players who were at least minimally hypohydrated ranged between 44% and 78%. On day 5 (rest day), all the players were at least minimally hypohydrated. After the information session on day 5, the relative number of euhydrated players increased to 89% on both day 6 (training day) and day 7 (match day). On the final day (rest day), all players were either minimally hypohydrated or hypohydrated. Furthermore, a moderate and significant negative correlation (r = -0.44; N = 54; p = 0.01) was found between fluid intake during and USG value before the training sessions. The data illustrates that the hydration status of this population of elite youth female soccer players may be suboptimal and is of substantial concern on rest days during this tournament under temperate conditions. Receiving personal advice about rehydration seems to have a positive effect.

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