Differences in sole arch indices in various sports

Background: There are controversial data about the relation between foot morphology and athletic injuries of the lower extremity. Studies in soldiers have shown some relationship, whereas those involving athletes have not shown any significant relationship. The reason for these differences is not clear.

Objective: To determine the effect of various sports on sole arch indices (AIs).

Method: A total of 116 elite male athletes (24 soccer players, 23 wrestlers, 19 weightlifters, 30 handball players, and 20 gymnasts) and 30 non-athletic men were included in this cross sectional study. Images of both soles were taken in a podoscope and transferred to a computer using a digital still camera. AIs were calculated from the stored images.

Results: The AI of the right sole of the gymnasts was significantly lower than that of the soccer players, wrestlers, and non-athletic controls (p<0.01). The AI of the right sole of the wrestlers was significantly higher than that of the soccer players, handball players, weightlifters, gymnasts, and non-athletic controls (p<0.03). The AI of the left sole of the gymnasts was significantly lower than that of the wrestlers and non-athletic controls (p<0.001). The AI of the left sole of the wrestlers was significantly higher than that of the soccer players, handball players, and gymnasts (p<0.007). The AI of both soles in handball players was significantly lower than those of the non-athletic subjects (p = 0.049). The correlation between the AI of the left and right foot was poor in the soccer players, handball players, and wrestlers (r = 0.31, 0.69, and 0.56 respectively), but was high in the gymnasts, weightlifters, and non-athletic controls (r = 0.96, 0.88, and 0.80 respectively).

Conclusion: The AIs of the gymnasts and wrestlers were significantly different from those of other sportsmen studied, and those of the gymnasts and handball players were significantly different from those of non-athletic controls.

     

Qt dispersion in soccer players during exercise testing

Screening for cardiac health should involve relevant parameters or indices that are easy and inexpensive to obtain. Various cardiac adaptation mechanisms develop during regular exercise that are affected by many factors, and these are reflected on a surface electrocardiogram. QT dispersion has been considered a surrogate for heterogeneity of repolarization, leading to ventricular arrhythmias. We compared QT parameters between athletes and sedentary subjects. A total of 225 men were assessed, comprising a group of professional soccer players and sedentaries. Each subject underwent supine 12-lead electrocardiographic examinations and exercise testing by ergospirometry. QT parameters were taken at rest and at peak exercise. Peak oxygen consumption was considerably higher in the athletes than in the controls (59.3 +/- 5.6 vs. 44.3 +/- 2.4 ml/kg/min, mean +/- SD, p < 0.001). QT parameters at rest: There were significant differences in heart-rate-corrected rest maximal QT duration (413.9 +/- 50.5 vs. 445.3 +/- 45.7 ms, p < 0.001) and in heart-rate-corrected rest minimum QT duration (380.5 +/- 51.2 vs. 409.5 +/- 46.7 ms, p < 0.001). QT parameters at peak exercise: maximal QT duration at peak exercise (253.9 +/- 20.8 vs. 261.7 +/- 26.2, p = 0.02), QT dispersion at peak exercise (25.2 +/- 9.1 vs. 29.5 +/- 15.8 ms, p = 0.04), heart-rate-corrected QT dispersion at peak exercise (44.6 +/- 16.4 vs. 52.6 +/- 28.3 ms, p = 0.03) differed significantly between professional soccer players and controls. QT dispersion and corrected QT dispersion at peak exercise are lower in athletes than in controls. Athletes and other subjects identified with a long QT interval should be examined at regular intervals.     

Validation of a soccer skill test for use with females

The aim of this study was to validate the Loughborough Soccer Passing Test (LSPT) for use with female players. Nineteen Premier Division (elite) and 16 Reserve team players (nonelite) volunteered for this study. The LSPT requires players to complete 16 passes against coloured target areas as fast and as accurately as possible. Participants completed an initial familiarisation trial followed by two main trials, each separated by at least one week. During both trials participants were given two practice efforts before recording the mean of the next two attempts as the performance score. All trials were performed inside a sports hall, using an indoor soccer ball, and following a standardised 10-min warm-up. The mean time taken (54.6 +/- 5.3 s vs. 61.6 +/- 6.5 s, p = 0.002), added penalty time (22.8 +/- 7.2 s vs. 35.9 +/- 11.5 s, p < 0.001) and overall performance time (77.4 +/- 11.6 s vs. 97.5 +/- 17.2 s, p < 0.001) were lower for elite players. Due to the lower agreement ratio, LSPT performance was more repeatable in the elite (x//1.39) relative to nonelite (x//1.45) group. In conclusion, the LSPT is a valid and reliable protocol to assess differences in soccer skill performance using female players.     

Postural balance asymmetry and subsequent noncontact lower extremity musculoskeletal injuries among Tunisian soccer players with groin pain: A prospective case control study

BackgroundRecent studies reported postural balance disorders in patients and soccer players with groin pain (GP) compared to controls. Since postural balance asymmetry identified after an initial injury contributes for subsequent injuries, identification of this asymmetry in soccer players with GP may highlight the risk of sustaining subsequent noncontact lower extremity musculoskeletal injuries in these players. Therefore, the aims of this study were to (i) examine static and dynamic unipedal postural balance asymmetry in soccer players with GP compared to healthy ones, and (ii) quantify the risk of subsequent noncontact lower extremity injuries in these players.Research questionDo soccer players with GP exhibit higher static and dynamic unipedal postural balance asymmetry, and higher risk of sustaining subsequent injuries compared to controls?MethodsIn this prospective case control study, 27 soccer players with non-time loss GP (GP group: GPG), and 27 healthy ones (control group: CG) were enrolled. Static and dynamic unipedal postural balance asymmetry were evaluated with a force platform using symmetry index (SI), and Y-balance test (Y-BT), respectively. Additionally, subsequent noncontact lower extremity musculoskeletal injuries were tracked for 10 months.ResultsThe GPG revealed higher (p < 0.01) SI in eyes closed condition, higher (p < 0.001) side-to-side asymmetry in anterior, posteromedial and posterolateral reach distances and in composite Y-BT score compared to CG. They showed lower (p < 0.001) composite score for injured limb and higher (p < 0.001) side-to-side asymmetry in posteromedial reach distance compared to the cut-off values of 89.6 % and 4 cm, respectively. Moreover, GPG exhibited higher odds (OR= 7.48; 95 % CI = 2.15, 26.00; p < 0.01) of sustaining subsequent injuries compared to CG.SignificanceThe Y-BT should be instituted into existing pre-participation physical examinations to screen for soccer players with non-time loss GP at an elevated risk of sustaining subsequent injuries. This could help coaches and clinicians make valid return to play decisions.     

Do elite athletes exhibit enhanced proprioceptive acuity,range and strength of knee rotation compared with non‐athletes?

The aims of this study were to compare proprioception in knee rotation in Olympic-level soccer players ( N =18) with non-athletes ( N =18), to explore between-limb differences in soccer players, and examine correlations between proprioception and years of playing, function, physical measures and skill level. The knee rotatory kinaesthetic device was used to present stimuli of different magnitudes to determine proprioceptive acuity for internal and external active rotation, and to measure active and passive rotation range of motion (ROM). Knee rotation strength was measured using a dynamometer. Proprioceptive acuity of the athletes was significantly ( P =0.004) better than that of the non-athletes. Athletes displayed significantly less passive ROM ( P =0.001), higher isometric muscle strength ( P =0.006) and greater hop for distance ( P =0.001) than non-athletes. No significant between-limb differences were found in the athletes in any objective outcome measure. Internal rotation proprioceptive acuity was negatively correlated with coach-rated ball skill ( r =−0.52) and positively correlated with internal rotation ROM ( r =0.59). Our findings suggest that highly trained athletes possess enhanced proprioceptive acuity and muscle strength that may be inherent, or may develop as a result of long-term athletic training.     

A cross-sectional analysis of sagittal knee laxity and isokinetic muscle strength in soccer players

In this cross-sectional study, sagittal knee laxity and isokinetic strength of knee extensor and flexor muscle groups were measured and differences related to leg dominance were evaluated. A total of 44 healthy male soccer players (who had trained regularly at least for the last five years) and 44 sedentary people as their control counterparts were involved in this study. All participants were tested using a KT-1000 knee arthrometer for knee laxity. Isokinetic concentric knee peak torque and hamstring/quadriceps (H/Q) ratio were also measured at 60, 180, 300 degrees/s through a Cybex 2 - 340 dynamometer. Posterior laxity in the non-dominant side of soccer players was significantly higher than in the dominant side (p < 0.005) while there were no significant anterior and total anteroposterior (total AP) laxity differences in both groups. Soccer players had significantly lower anterior and total AP laxity values than controls (p < 0.0001) while there was no significant difference between posterior laxity values in both sides. Dominant extremity demonstrated significantly higher knee flexor peak torque and H/Q ratio at 180 degrees /s in soccer players (p < 0.05). Similarly in sedentary controls, H/Q ratio at 60 degrees /s of the dominant side was significantly higher than that in the non-dominant side (p < 0.05). Soccer players had significantly higher extensor and flexor peak torque values and H/Q ratios than sedentary subjects for both extremities. In both groups, there were no significant correlations between knee laxity and isokinetic knee extensor and flexor strength and H/Q ratios except weak negative correlation between posterior knee laxity and isokinetic extensor peak torque at 60, 180 and 300 degrees /s (p < 0.005, r = - 0.43, p < 0.05, r = - 0.39, p < 0.05, r = - 0.32 respectively) in the non-dominant side of soccer players and at 300 degrees /s (p < 0.05, r = - 0.32) in the non-dominant side of controls. Soccer players demonstrated significantly less sagittal knee laxity and higher isokinetic strength of the knee flexors and extensors compared to sedentary controls. Isokinetic strength difference was found to be higher for the flexor muscle group. Further prospective studies are needed to explain whether the increased H/Q ratio decreases the risk of ligamentous injury.     

The physiological demands of Gaelic football.

Match-lay demands of Gaelic football and fitness profiles were assessed at club competitive level. English Gaelic football club championship players (n = 11) were assessed for anthropometry, leg strength and time to exhaustion on a treadmill run. A similar test battery was administered to a reference group of University competitive soccer players (n = 12). Heart rate was recorded during match-play using radio telemetry and blood lactate concentrations were determined at half-time and after full-time. No differences (p > 0.05) were observed between the Gaelic and soccer players in: body mass (70.7 +/- 10.3 vs 76.6 +/- 10.3 kg); height (176 +/- 5.9 vs 177.7 +/- 6.4 cm); leg to trunk ratio (0.53 +/- 0.01 vs 0.54 +/- 0.03); adiposity (12.2 +/- 2.1 vs 13.5 +/- 3.2% body fat); mean somatotype (2.8 - 4.3-2.0 vs 2.4-4.2-2.4); leg strength measures; and performance on the treadmill. The percentage muscle mass values were lower for the Gaelic players compared to the soccer players (41.9 +/- 5.4 vs 47.3 +/- 5.2%; p > 0.005). For the Gaelic and soccer players, respectively, mean heart rate recorded during each half of match-play were (157 +/- 10 and 158 +/- 12 beats/min) and (164 +/- 10 and 157 +/- 11 beats/min), whilst blood lactates measured at the end of each half, were (4.3 +/- 1 and 3.4 +/- 1.6 mmol/l) and (4.4 +/- 1.2 and 4.5 +/- 2.1 mmol/l). Gaelic footballers at English club championship level seem to exhibit similar fitness profiles, and are subject to broadly similar physiological demands as University-level competitive soccer players.     

Quantitative evaluation of acute myocardial infarction by In-111 antimyosin Fab myocardial imaging]

For quantitative evaluation of acute myocardial infarction, In-111 antimyosin Fab myocardial imaging (InAM) was performed in 17 patients with myocardial infarction who underwent Tl-201 (TL) and Tc-99m pyrophosphate (PYP) myocardial imaging in acute phase. For calculating the infarct size, voxel counter method was used for analysis in PYP and InAM, and extent and severity score were used on bull's-eye polar map in TL. The most appropriate cut-off level ranged from 65 to 80% by the fundamental experiment using cardiac phantom. The cut-off level of 0.70 (InAM) and 0.65 (PYP) were used for clinical application of voxel counter analysis. The infarct size calculated by InAM and PYP was compared with wall motion abnormality index by echocardiography (WMAI), TL extent score, TL severity score, peak CK and sigma CK. Infarct size by InAM showed the following correlations with other indices. PYP: r = 0.26 (ns), TL extent score: r = 0.72 (p less than 0.01), TL severity score: r = 0.65 (p less than 0.05), WMAI: r = 0.69 (p less than 0.05). The infarct size by PYP did not show any correlations with these indices. Therefore, the infarct size by InAM showed better correlations with TL and WMAI than that of PYP. So InAM was considered superior to PYP for quantitative evaluation of acute myocardial infarction.     

Heart rate variability, training variation and performance in elite swimmers

The aim of the present study was to investigate the relationships between heart rate variability (HRV) changes and both training variations and performances in elite swimmers. A secondary purpose was to measure catecholamine urinary excretion in elite swimmers to validate the HRV indices of sympathetic activity during training. Thirteen swimmers (4 females and 9 males) were tested before and after 4 weeks of intense training (IT) and 3 weeks of reduced training (RT). At the end of each period, the swimmers participated in an official competition of their best event. Individual performances were expressed as percentage of the previous season's best performance. Spectral analysis was used to investigate RR interval variability. HRV indices failed to show any significant changes between the study periods (p>0.05). Pre-IT HF was correlated with performance (r=0.45; p=0.05) and HFnu (r=0.59; p<0.05) during RT. On the other hand, once RT was completed, HFnu was correlated positively to performance (r=0.81; p<0.01) and negatively to fatigue (r=- 0.63; p<0.03). Conversely, the indices of sympathetic activity, i.e., LFnu and LF/HF ratio were inversely related to performance (both r=- 0.81; p<0.01); total fatigue score was correlated to the changes in HFnu (r=- 0.63; p<0.03) and in the LF/HF ratio (r=0.58; p<0.05). Changes in the adrenaline/noradrenaline ratio over the follow-up period were related to the changes in the LF/HF ratio (r=0.45; p<0.03). In highly trained swimmers coping well with a training program, including 4 weeks of IT followed by 3 weeks of RT, HRV indices were unaltered. On the other hand, after the 3 weeks of RT, HFnu was positively related to performance and inversely related to the fatigue score. Thus, elevated initial HF levels could be important in the parasympathetic activity increases during taper and, hence, in swimming performance improvement.     

Are acceleration and cardiovascular capacities related to perceived load in professional soccer players?

ABSTRACT

This study aims at assessing physical fitness performance and its relationship with the differential ratings of perceived exertion of training load (dRPE TL) and match load (dRPE ML) in a Spanish professional soccer team at the beginning of several in-season periods: 1–4 weeks, 5–8 weeks and 1–8 weeks. Performance and mechanical variables over the acceleration phase, as well as cardiovascular performance variables were evaluated in 20 male professional soccer players of a team competing in the Spanish Second Division League. Moreover, dRPE TL and dRPE ML were quantified. The dRPE TL showed negative and large associations between both maximal aerobic speed (MAS) and maximal oxygen consumption (VO_2max) (from r = ?0.53; ± 0.06 to r = ?0.53; ± 0.05 95% CL, p = 0.035 to 0.036) and RPEres TL values throughout the 5–8 and 1–8 week periods. Furthermore, dRPE ML positive and large associations were found between players initial MAS or VO_2max (from r = 0.50; ± 0.17 to r = 0.56; ± 0.11 95% CL, p = 0.026 to 0.049) and RPEmus ML in 1–4 and 1–8 week periods. The current study suggests that a better cardiovascular capacity could be connected with a lower RPEres TL and higher RPEmus ML.     

Aerobic and anaerobic power characteristics of Saudi elite soccer players

BACKGROUND: To assess the aerobic and anaerobic characteristics of Saudi elite soccer players, and to examine the interrelationship between measures of aerobic and anaerobic power in the elite soccer players. METHODS. PARTICIPANT: Twenty-three outfield elite soccer players representing the Saudi national team participated. Their means (+/- SD) for age, body mass, height and estimated fat % were: 25.2 +/- 2.3 years; 73.1 +/- 6.8 kg; 177.2 +/- 5.9 cm; and 12.3 +/- 2.7%, respectively. MEASURES: Cardiorespiratory parameters, including maximal oxygen uptake (V O2 max), were assessed by open-circuit spirometry during graded treadmill running. Anaerobic power measures were obtained using Wingate anaerobic test, and included peak power (PP), and average power for 5 sec (AP 5), 10 sec (AP 10), 20 sec (AP 20) and 30 sec (AP 30). RESULTS: Mean (+/-SD) values for V O2max in absolute and relative to body mass were 4.16 +/- 0.34 l x min-1 and 56.8 +/- 4.8 ml x kg-1 x min-1, respectively. Such V O2max value was 118% and 80% of those reported for Saudi college males and distance runners, respectively. The ventilatory anaerobic thereshold (Tvent) averaged 43.6 ml x kg-1 x min-1. There were no significant differences in V O2max and Tvent between players based on positions, although the midfielders and the centre-backs had the highest and the lowest individual values for both measures, respectively. Values (+/- SD) of PP and AP 30 were 873.6 +/- 141.8 W (11.88 +/- 1.3 W x kg-1), and 587.7 +/-55.4 W (8.02 +/- 0.53 W x kg-1), respectively. Only in absolute PP & AP 30 were the centre-backs significantly superior to the other players. In addition, V O2max was inversely related to PP (r = - 0.54; p < 0.05) and positively related to AP 30 (r = 0.45; p < 0.05). CONCLUSIONS: The aerobic power, expressed relative to body mass, of Saudi elite soccer players was in the lower range of values normally reported in the literatures for elite soccer players. Both PP and AP 30 were somewhat lower than values previously reported for elite soccer players from other countries.     

Intensity demands and peak performance of elite soccer referees during match play

ObjectivesThis study examined the peak physical and physiological (heart rate) performance intensities andassociated decrements in elite soccer referees during match play.DesignLongitudinal study.MethodsPhysical performancevariables and heart rate were analyzed during 457 matches across two seasons. Differences between halves, and the rate ofdecline in peak performance intensities across moving average durations of 1–10 minutes were assessed using linear mixed models and power-law analysis, respectively.ResultsLarge significant differences were observed between halves for mean total distance, mean velocity, mean heart rate, and percentage of maximal heart rate (p ≤ 0.05; r = 0.51–0.64). Peak intensities (p ≤ 0.05; r = 0.15–0.17) and the rate of decline (p < 0.001; r = 0.17–0.37) were significantly higher in the 2^nd half compared to the 1^st half, for relative total distance, relative high-intensity running and mean velocity. The rate of decline was significantly greater in the 2^nd half than the 1^st half for relative distance covered by high-intensity acceleration (>2 m/s^–2/min), deceleration (<-2 m/s^–2/min), and relative mean heart rate (p < 0.001; r = 0.28–0.61). Elite soccer referees might have experienced transient fatigue during match play, as relative high-intensity running immediately following the most intense 5-minute period significantly declined by 61.2% ( p< 0.001; r = 0.94), and was 16.2% lower than the mean 5-minute period (p < 0.001; r = 0.34).ConclusionsIncreased physical and physiological demands during match play, with associated declines in the second half and transient signs of fatigue throughout the match, supports the inclusion of high-intensity interval and endurance training programs to prepare soccer referees for the intensity demands and peak performance outcomes of match play.     

Echocardiographic findings in professional league soccer players. Effect of the position of the players on the echocardiographic parameters

BACKGROUND: The purpose of the study was to compare the echocardiographic parameters of soccer players to healthy controls and to assess the effect of the position of the soccer players on the echocardiographic findings. METHODS: M Mode 2D and Doppler echocardiographic examination were carried out on 83 professional league soccer players and 52 healthy controls. RESULTS: Soccer players had increased interventricular septum (1.14+/-0.13 cm vs 0.99+/-0.17 cm, p<0.001) left ventricular posterior wall (1.08+/-0.16 cm vs 0.91+/-0.13 cm, p<0.001) thickness, increased left ventricular diastolic diameter (5.24+/-0.40 cm vs 4.88+/-0.43 cm, p<0.001), volume (133+/-23 ml vs 113+/-22 ml, p<0.001) and increased left ventricular mass index (142+/-28 g/m2 vs 103+/-23 g/m2, p<0.001) compared to controls. Soccer players had greater mitral E wave to A wave ratio (2.08+/-0.53 vs 1.65+/-0.43, p<0.001) compared to controls. Soccer players were subgrouped according to their position in the play as goal keepers, defensive, midfielder, and offensive players. Comparison among defensive, midfield and offensive players revealed subtle differences between defensive and midfield players. Right ventricular dimensions were higher in goal keepers compared to midfielders due to the greater body surface area of the goal keepers (2.8+/-0.4 cm vs 2.4+/-0.5 cm, p<0.05). Left ventricle end diastolic dimension were similar between groups but when these dimensions were corrected for the greater height of the defensive players the difference between midfields and defensive players became significant (3.05+/-0.18 vs 2.89+/-0.22, p=0.05). On Doppler flow parameters the ratio of peak E wave to A wave velocity (2.27+/-0.55 vs 1.84+/-0.36, p<0.05) was increased in midfield players compared to defensive players. CONCLUSIONS: It was concluded that soccer players had greater left ventricular wall thickness, volume and mass compared to controls. But the effect of the position of the players on the measured cardiac dimensions were minimal. These subtle findings were explained by the leveling effect of the playing system and training, and lack of physical training during the previous month.     

Injury risk is greater in physically mature versus biologically younger male soccer players from academies in different countries

ObjectivesTo investigate if maturity status was associated with injury risk in male academy soccer players.DesignProspective cohort surveillance study.SettingProfessional soccer academies.Participants501 players (aged 9–23 years) from eight academies in England, Spain, Uruguay and Brazil.Main outcome measuresPlayers were grouped by maturity offset as pre-peak height velocity (PHV), circa-PHV, post-PHV or adult. Injury prevalence proportion (IPP) and days missed were recorded for one season per player, with training/match exposure recorded in a sub-sample (n = 166).ResultsIPP for all injuries combined increased with advancing maturity, with circa-PHV (p = 0.032), post-PHV (p < 0.001) and adult (p < 0.001) higher than pre-PHV. IPP was higher in post-PHV and adult than pre-PHV for non-contact (p = 0.001 and p = 0.012), soft-tissue (both p < 0.001), non-contact soft-tissue (p < 0.001 and p = 0.005), muscle (both p < 0.001), thigh (both p < 0.001), ankle (p = 0.035 and p = 0.007) and hamstring injuries (p = 0.041 and p = 0.017). Ligament/tendon IPP was greater in adult versus pre-PHV (p = 0.002). IPP for growth-related injuries was lower in post-PHV than pre-PHV (p = 0.039). Injury incidence rates (n = 166) exhibited similar patterns to IPP in the full cohort.ConclusionsInjury patterns were similar between post-PHV and adult academy players but, crucially, relatively more of these groups suffered injuries compared to pre- and circa-PHV (except growth-related injuries).     

Hip adduction strength and provoked groin pain: A comparison of long-lever squeeze testing using the ForceFrame and the Copenhagen 5-Second-Squeeze test

ObjectivesTo compare long-lever squeeze testing using the ForceFrame and the Copenhagen 5-Second-Squeeze test (5SST) for assessment of hip adduction strength and provoked groin pain in elite male soccer players.DesignCross-sectional study.SettingPre-season testing at facilities of a Danish professional 1^st tier soccer club and academy.ParticipantsElite male soccer players (n = 83, mean age; 16 ± 2.7 years) from U13, U14, U15, U17, U19 and senior teams cleared for full training and match participation.Main outcome measuresMaximum isometric hip adduction strength (Nm/kg) and provoked groin pain (NRS 0–10).ResultsHip adduction strength was 16% lower in the ForceFrame. A Bland-Altman plot showed a systematic bias (−0.47 Nm/kg, 95% CI [-0.57; −0.38]) and lack of agreement (95% limits of agreement: -1.31; 0.39 Nm/kg). In the ForceFrame, provoked groin pain was less intense (median NRS 0 [IQR: 0–1] vs. 5SST: 1 [IQR: 0–3], p < 0.001) and reported by fewer players (NRS >0) (27% [n = 22] vs. 5SST: 61.4% [n = 51], p < 0.001).ConclusionsThe ForceFrame and the 5SST lack agreement and are not interchangeable methods. This may have implications when selecting a method for screening and detecting early groin problems in male soccer players.     

Validity of simple field tests as indicators of match-related physical performance in top-level professional soccer players

The aim of this study was to examine the construct validity of selected field tests as indicators of match-related physical performance. During the competitive season, eighteen professional soccer players (age 26.2 +/- 4.5 yrs, mass 80.8 +/- 7.8 kg, and height 181.9 +/- 3.7 cm) completed an incremental running field test to exhaustion, a vertical-jump and a repeated-sprint ability (RSA) test. Match physical performance was quantified during official matches using a video-computerized, semi-automatic, match analysis image recognition system, (ProZone, Leeds, UK). The selected measures of match physical performance were: total distance covered (TD), high intensity running (HIR: > 14.4 km . h (-1)), very high intensity running (VHIR:> 19.8 km . h (-1)), sprinting (> 25.2 km . h (-1)) and top running speed. Significant correlations were found between peak speed reached during the incremental field test and TD (r = 0.58, R (2) = 0.34; p < 0.05), HIR (r = 0.65, R (2) = 0.42; p < 0.01) and VHIR (r = 0.64, R (2) = 0.41; p < 0.01). Significant correlations were also found between RSA mean time and VHIR (r = - 0.60, R (2) = 0.36; p < 0.01) and sprinting distance (r = - 0.65, R (2) = 0.42; p < 0.01). Significant differences were found between the best and worst group as defined by the median split technique for peak speed (TD = 12 011 +/- 747 m vs. 10 712 +/- 669, HIR = 3192 +/- 482 m vs. 2314 +/- 347 m, and VHIR = 1014 +/- 120 vs. 779 +/- 122 m, respectively; p < 0.05) and RSA mean time (VHIR = 974 +/- 162 m vs. 819 +/- 144 m, and sprinting = 235 +/- 56 vs. 164 +/- 58 m, respectively; p < 0.05). In conclusion, this study gives empirical support to the construct validity of RSA and incremental running tests as measures of match-related physical performance in top-level professional soccer players.     

Changes in perceived stress and recovery in overreached young elite soccer players

The aim of this study was to prospectively monitor sport-specific performance and assess the stress-recovery balance in overreached (OR) soccer players and controls. During two competitive seasons, 94 players participated in the study. The stress-recovery balance (RESTQ-Sport) and sport-specific performance (Interval Shuttle Run Test) were assessed monthly. Seven players with performance decrement of at least a month were classified as OR. Stress and recovery measures were assessed between groups (OR vs healthy players) and at different times within the OR group. An unfavorable total recovery score appeared 2 months before diagnosis when compared with the reference values of the healthy group established at the start of the season (P=0.009) and also over the two seasons (P=0.028). The scales Emotional Stress (P=0.044), Physical Recovery (P=0.009), General Well-being (P=0.001) and Sleep Quality (P=0.045) were sensitive to OR compared with the average of the healthy group over the two seasons. Finally, Fatigue and Being in Shape demonstrated the largest changes in stress and recovery within the OR players (effect size=1.14 and 1.50). The longitudinal monitoring of performance and changes in stress and recovery may be useful for the detection of OR in its earliest stage. The information obtained from these tests can be used to optimize individual training and recovery programs.     

Left atrial remodelling in competitive adolescent soccer players

Left atrial (LA) enlargement and improved myocardial diastolic properties are a component of athlete's heart. We performed a longitudinal study involving adolescent athletes to investigate the impact of training on LA remodelling and diastolic function. 21 competitive adolescent soccer players were enrolled and engaged in an 8-month training program. Echocardiographic analysis was performed at baseline, after 4 and 8 months. We assessed diastolic function by Doppler tissue imaging and we analyzed LA adaptations by 2D speckle-tracking echocardiography. After 4 months, LA mean volume index significantly increased (Δ=5.47±4.38?mL/m2, p≤0.0001). After 8 months, a further increase occurred (Δ=8.95±4.47?mL/m2, p≤0.0001). A higher E velocity (p=0.001; p=0.001), a greater E/A ratio (p=0.002; p=0.0009), a higher e' peak (p= 0.005; p=0.001), and a greater e'/a' ratio (p=0.01; p=0.0006) were observed at 4 and at 8 months, respectively. E/e' ratio significantly decreased after 8 months (p≤0.005). Global peak atrial longitudinal strain and global peak atrial contraction strain values significantly decreased after 8 months (p=0.0004, p=0.01, respectively). An 8-month training program is associated with LA dimensional and functional training-specific adaptations in competitive adolescent soccer players. Myocardial diastolic properties can improve after training also in subjects already presenting with features of athlete's heart.     

Strength and speed characteristics of elite, subelite, and recreational young soccer players

The purpose of the present study was to compare maximal isometric force, force-time curve characteristics, pedaling rate, vertical jump, and sprint performance among young soccer players from different competition levels. Fifty-four (54) young soccer players were divided into three groups according to competition level: the elite group (n=18) consisted of soccer players from the national youth soccer team of Greece, the subelite group (n=18) consisted of youth soccer players who participated in the local championship, and the recreational group (n=18) consisted of recreational soccer players. All groups were evaluated for maximal isometric force, explosive force at 100 msec, peak force relative to body mass, rate of force development, squat and drop jump heights, 10 m sprint time, and pedaling rate. The elite group presented significantly (p < 0.05) higher maximal isometric force, vertical jump height, and pedaling rate, and lower 10 m sprint time in comparison with the subelite and recreational groups. No significant differences were observed in strength and speed characteristics between the subelite and recreational young soccer players. The findings of the present study suggest that the elite young soccer players can be distinguished from subelite and recreational young soccer players in strength and speed characteristics. These strength and speed measures can be used for strength and speed diagnosis, and for designing and evaluating training programs.     

Variation in top level soccer match performance

This study examined the influence of the opposing team, seasonal variations and the influence of first half activity on match performance in top-level soccer players. Physical performance measures were collected using the ProZone match analysis system from 20 professional soccer players from the same team and their opponents (n = 188) during a season. Match activities (standing, walking, jogging, running, high-speed running and sprinting), distances (total distance [TD], high-intensity running [HIR] and very high-intensity running [VHIR]) and other measures including involvement with the ball and peak running speed were collected. The influence of opponent team, the level of opposition, first half physical activities on second half activities, and playing position were analysed. The main finding was that TD (r = 0.62, p < 0.05), HIR (r = 0.51, p < 0.05), and VHIR (r = 0.65, p < 0.05) of the reference team was influenced by the activity profile of the opponent teams. The TD and HIR was higher against Best opponent teams compared to Worst opponent teams (p < 0.05), and the TD, HIR and VHIR travelled in the first half significantly influenced the distances covered in the second half. TD, HIR and VHIR were greater at the end of the season. These results may be used to interpret meaningful changes in match performance in top level soccer.