Adductor squeeze test and groin injuries in elite football players: A prospective study.

OBJECTIVE: To examining the relationship between hip adductor strength and groin injury incidence during the competitive season of professional football teams. DESIGN: Prospective Cohort study. SETTING: Controlled laboratory environment. PARTICIPANTS: Seventy-one players volunteered to participate. MAIN OUTCOME MEASURES: In the pre-season, maximal hip adductor strength was measured by means of the isometric adductor squeeze test. Hip adductor strength, normalized by body mass, was compared between players who suffered a groin injury (n = 18) vs uninjured players (n = 53). Risk ratios (RR) were used to evaluate the likelihood of players to suffer this type of injury. RESULTS: Most of the reported groin injuries occurred during competitive matches (5.5 per 1000 match hours). Maximal isometric hip adductor strength was lower in the groin-injured group compared with their uninjured counterparts (429.8 ±â€¯100 vs 564 ±â€¯58.7 N, d = -1.58 and 5.40 ±â€¯1.27 vs 7.71 ±â€¯0.89 N/kg, d = -1.88, respectively). Results revealed that values of maximal isometric adductor strength lower than 465.33 N increased the probability to suffer a groin injury by 72%. Furthermore, values of force relative to body mass lower than 6.971 N/kg increased the probability to suffer a groin injury by 83%. CONCLUSION: The assessment of Hip adductor strength, in addition to other measurements, might help practitioners to determine the probability of suffering an overuse groin injuries in elite football players.

In-season training periodization of professional soccer players.

The aim of this study was to quantify the seasonal perceived respiratory and muscular training loads (i.e., sRPEres-TL and sRPEmus-TL) completed by elite-oriented young professional soccer players. Twenty-four players (20.3 ± 2.0 years) belonging to the same reserve team of a Spanish La Liga club participated in this study. Only the players that were available to train for a whole week with the team and also to play the weekly game were considered: Starters, players that participated in the match for at least 45 min and Non-Starters, players that did not participate or played less than 45 minutes in the match. The competitive period was analysed after the division into 5x6-8 week blocks and 35x1 week microcycles. Data were also analysed with respect to number of days before the immediate match. Weekly TL variation across the in-season blocks was trivial-small for both groups except between Block 2 and Block 3 (ES= moderate). Substantial TL differences (ES= small-very likely) were found between training days, the TL pattern being a progressive increase up to MD-3 followed by a decrease until MD-1. Except for the match, sRPEres-/sRPEmus-TL was very similar between Starters and Non-Starters. In summary, perceived TL across the season displayed limited variation. Coaches periodized training contents to attain the highest weekly TL 72 hours before the match to progressively unload the players between MD-3 and the match day. The data revealed that the TL arising from the weekly game was solely responsible for the observed higher weekly TL of Starters in comparison with Non-Starters.

Individual Muscle use in Hamstring Exercises by Soccer Players Assessed using Functional MRI.

This study used functional magnetic resonance imaging (fMRI) to compare individual muscle use in exercises aimed at preventing hamstring injuries. Thirty-six professional soccer players were randomized into 4 groups, each performing either Nordic hamstring, flywheel leg curl, Russian belt or conic-pulley exercise. MRIs were performed before and immediately after a bout of 4 sets of 8 repetitions. Pre-post exercise differences in contrast shift (T2) were analyzed for the long (BFLh) and short head (BFSh) of biceps femoris, semitendinosus (ST), semimembranosus (SM) and gracilis (GR) muscles. Flywheel leg curl increased (P<0.001) T2 of GR (95%), ST (65%), BFSh (51%) and BFLh (14%). After the Nordic hamstring, GR (39%), ST (16%) and BFSh (14%) showed increased T2 (P<0.001). Russian belt and conic-pulley exercise produced subtle (P<0.02) T2 increases of ST (9 and 6%, respectively) and BFLh (7 and 6%, respectively). Russian belt increased T2 of SM (7%). Among exercises examined, flywheel leg curl showed the most substantial hamstring and GR muscle use. However, no single exercise executed was able to increase T2 of all hamstring and synergist muscles analyzed. It is therefore suggested that multiple exercises must be carried out to bring in, and fully activate all knee flexors and hip extensors.

Does small-sided-games' court area influence metabolic, perceptual, and physical performance parameters of young elite basketball players?

The purpose of this study was to investigate the effect of court size on physiological responses and physical performance of young elite basketball players. Twelve male basketball players (18.6 ± 0.5 years; 88.8 ± 14.5 kg; 192.6 ± 6.5 cm) from an under-19 team performed two small-sided games (matches) with different court areas (28x15 m and 28x9 m; 28x15 and 28x9 protocols). The number of players (3x3) was kept the same in each protocol. The players performed a repeated-sprint ability (RSA) test before and after each match. Blood lactate concentration was collected before (pre) and after (post) the matches, and the session rating of perceived exertion (session-RPE) was determined 30 minutes after the match. Best and mean time in the RSA test were not different between the 28x15 and the 28x9 match protocols (p > 0.05). A significant difference was observed for lactate concentration from pre- to post-match (p < 0.05) in both protocols (28x15 and 28x9); however, there was no significant interaction between protocols. A similar session-RPE mean score (28x15: 7.2 ± 1.4 and 28x9: 6.6 ± 1.4) was detected for both protocols (p > 0.05, ES=0.41). In summary, the results of the current study suggest that the different court areas induced similar responses. Although there was no significant difference in effort perception, players tended to perceive a greater effort in the larger court size.

Validity of the V-cut Test for Young Basketball Players.

The aim of the present study was to assess the reliability, usefulness, validity, age-related differences and responsiveness of a 25- m side-step cutting maneuver test (V-cut test). Fifty young male basketball players performed the V-cut test on 2 occasions separated by 5-7 days to assess test-retest reliability and determine a priori usefulness. Twenty subjects also completed both the L-Run and 505 test to analyze the possible relationships among these 3 tests. Furthermore, 33 players performed the V-cut test 4 times throughout the season to analyze responsiveness. Finally, 53 players (U-14 to U-20) were assessed in the V-cut test to examine the age-related differences. Reliability scores showed high intraclass correlation coefficient (ICC=0.90) and low coefficient of variation (CV=1.4%). The responsiveness of the V-cut test was good, as the typical short- (1.5-1.7%), mid- (1.6-3.1%) and long-term (3.3%) changes in V-cut performance were higher than the CV. Low (r=0.64; CL90%: 0.34; 0.82) to moderate (r=0.76; CL90%: 0.53; 0.88) relationships were found between the V-cut test with the 505 and L-Run test, respectively. Age-related differences analysis showed better V-cut test performance as age increased in adolescent basketball players. The V-cut test is reliable to assess change of direction ability (CODA) and it could be used to monitor CODA in adolescent basketball players.

Effects of hamstring-emphasized neuromuscular training on strength and sprinting mechanics in football players.

The objective of this study was to examine the effects of a neuromuscular training program combining eccentric hamstring muscle strength, plyometrics, and free/resisted sprinting exercises on knee extensor/flexor muscle strength, sprinting performance, and horizontal mechanical properties of sprint running in football (soccer) players. Sixty footballers were randomly assigned to an experimental group (EG) or a control group (CG). Twenty-seven players completed the EG and 24 players the CG. Both groups performed regular football training while the EG performed also a neuromuscular training during a 7-week period. The EG showed a small increases in concentric quadriceps strength (ES = 0.38/0.58), a moderate to large increase in concentric (ES = 0.70/0.74) and eccentric (ES = 0.66/0.87) hamstring strength, and a small improvement in 5-m sprint performance (ES = 0.32). By contrast, the CG presented lower magnitude changes in quadriceps (ES = 0.04/0.29) and hamstring (ES = 0.27/0.34) concentric muscle strength and no changes in hamstring eccentric muscle strength (ES = -0.02/0.11). Thus, in contrast to the CG (ES = -0.27/0.14), the EG showed an almost certain increase in the hamstring/quadriceps strength functional ratio (ES = 0.32/0.75). Moreover, the CG showed small magnitude impairments in sprinting performance (ES = -0.35/-0.11). Horizontal mechanical properties of sprint running remained typically unchanged in both groups. These results indicate that a neuromuscular training program can induce positive hamstring strength and maintain sprinting performance, which might help in preventing hamstring strains in football players.

Psychophysiological stress responses during training and competition in young female competitive tennis players.

This study sought to compare the psychophysiological stress responses during an actual competitive game and a training session in a group of high-level young female tennis players. 12 players were monitored during one match and a training day (i.e., simulated match play). Measurements included salivary cortisol (SC), the revised Competitive Sport Anxiety Inventory, heart rate (HR), and rate of perceived exertion (RPE). Match day elicited higher SC levels for losers at all points in time when compared to winners. All players showed significantly lower SC levels during training when compared to the match at all points in time except during the evening for winners. Winners of match and training situations had significantly higher self-confidence and lower cognitive anxiety and somatic anxiety scores than losers. Heart rate and RPE were significantly higher for losers only during the match (158.9±8.3 vs. 168±6.7 bpm; 12.9±1.2 vs. 15±0.8, for losers and winners, respectively). There were moderate to strong correlations between SC, self-confidence and anxiety scores, and match workload (i.e., HR and RPE) only during the match day. These results indicate that the interplay between psychophysiological responses, match workload and outcome was evident only under real competitive situations.

Progression of mechanical properties during on-field sprint running after returning to sports from a hamstring muscle injury in soccer players.

The objectives of this study were to examine the consequences of an acute hamstring injury on performance and mechanical properties of sprint-running at the time of returning to sports and after the subsequent ~2 months of regular soccer training after return. 28 semi-professional male soccer players, 14 with a recent history of unilateral hamstring injury and 14 without prior injury, participated in the study. All players performed two 50-m maximal sprints when cleared to return to play (Test 1), and 11 injured players performed the same sprint test about 2 months after returning to play (Test 2). Sprint performance (i. e., speed) was measured via a radar gun and used to derive linear horizontal force-velocity relationships from which the following variables obtained: theoretical maximal velocity (V(0)), horizontal force (F(H0)) and horizontal power (Pmax). Upon returning to sports the injured players were moderately slower compared to the uninjured players. F H0 and Pmax were also substantially lower in the injured players. At Test 2, the injured players showed a very likely increase in F(H0) and Pmax concomitant with improvements in early acceleration performance. Practitioners should consider assessing and training horizontal force production during sprint running after acute hamstring injuries in soccer players before they return to sports.

Locomotor performance in highly-trained young soccer players: does body size always matter?

To examine the effects of body size on locomotor performance, 807 15-year-old French and 64 Qatari soccer players participated in the present study. They performed a 40-m sprint and an incremental running test to assess maximal sprinting (MSS) and aerobic speeds, respectively. French players were advanced in maturity, taller, heavier, faster and fitter than their Qatari counterparts (e.g., Cohen's d=+1.3 and + 0.5 for body mass and MSS). However, when adjusted for body mass (BM), Qatari players had possibly greater MSS than French players (d=+0.2). A relative age effect was observed within both countries, with the players born in the first quarter of the year being taller, heavier and faster that those born during the fourth quarter (e.g., d=+0.2 for MSS in French players). When directly adjusted for BM, these MSS differences remained (d=+0.2). Finally, in both countries, players selected in National teams were taller, heavier, faster and fitter than their non-selected counterparts (e.g., d=+0.6 for MSS in French players), even after adjustments for body size (d=+0.5). Differences in locomotor performances between players with different phenotypes are likely mediated by differences in body size. However, when considering more homogeneous player groups, body dimensions are unlikely to substantially explain the superior locomotor performances of older and/or international players.

Adding heat to the live-high train-low altitude model: a practical insight from professional football.

OBJECTIVES: To examine with a parallel group study design the performance and physiological responses to a 14-day off-season 'live high-train low in the heat' training camp in elite football players. METHODS: Seventeen professional Australian Rules Football players participated in outdoor football-specific skills (32 ± 1°C, 11.5 h) and indoor strength (23 ± 1°C, 9.3 h) sessions and slept (12 nights) and cycled indoors (4.3 h) in either normal air (NORM, n=8) or normobaric hypoxia (14 ± 1 h/day, FiO2 15.2-14.3%, corresponding to a simulated altitude of 2500-3000 m, hypoxic (HYP), n=9). They completed the Yo-Yo Intermittent Recovery level 2 (Yo-YoIR2) in temperate conditions (23 ± 1°C, normal air) precamp (Pre) and postcamp (Post). Plasma volume (PV) and haemoglobin mass (Hb(mass)) were measured at similar times and 4 weeks postcamp (4WPost). Sweat sodium concentration ((Na(+))(sweat)) was measured Pre and Post during a heat-response test (44°C). RESULTS: Both groups showed very large improvements in Yo-YoIR2 at Post (+44%; 90% CL 38, 50), with no between-group differences in the changes (-1%; -9, 9). Postcamp, large changes in PV (+5.6%; -1.8, 5.6) and (Na(+))sweat (-29%; -37, -19) were observed in both groups, while Hb(mass) only moderately increased in HYP (+2.6%; 0.5, 4.5). At 4WPost, there was a likely slightly greater increase in Hb(mass) (+4.6%; 0.0, 9.3) and PV (+6%; -5, 18, unclear) in HYP than in NORM. CONCLUSIONS: The combination of heat and hypoxic exposure during sleep/training might offer a promising 'conditioning cocktail' in team sports.

Monitoring fitness, fatigue and running performance during a pre-season training camp in elite football players.

OBJECTIVES: To examine the usefulness of selected physiological and perceptual measures to monitor fitness, fatigue and running performance during a pre-season, 2-week training camp in eighteen professional Australian Rules Football players (21.9±2.0 years). DESIGN: Observational. METHODS: Training load, perceived ratings of wellness (e.g., fatigue, sleep quality) and salivary cortisol were collected daily. Submaximal exercise heart rate (HRex) and a vagal-related heart rate variability index (LnSD1) were also collected at the start of each training session. Yo-Yo Intermittent Recovery level 2 test (Yo-YoIR2, assessed pre-, mid- and post-camp, temperate conditions) and high-speed running distance during standardized drills (HSR, >14.4 km h(-1), 4 times throughout, outdoor) were used as performance measures. RESULTS: There were significant (P<0.001 for all) day-to-day variations in training load (coefficient of variation, CV: 66%), wellness measures (6-18%), HRex (3.3%), LnSD1 (19.0%), but not cortisol (20.0%, P=0.60). While the overall wellness (+0.06, 90% CL (-0.14; 0.02) AU day(-1)) did not change substantially throughout the camp, HRex decreased (-0.51 (-0.58; -0.45)% day(-1)), and cortisol (+0.31 (0.06; 0.57) nmol L(-1)day(-1)), LnSD1 (+0.1 (0.04; 0.06) ms day(-1)), Yo-YoIR2 performance (+23.7 (20.8; 26.6) m day(-1), P<0.001), and HSR (+4.1 (1.5; 6.6) m day(-1), P<0.001) increased. Day-to-day ΔHRex (r=0.80, 90% CL (0.75; 0.85)), ΔLnSD1 (0.51 (r=0.40; 0.62)) and all wellness measures (0.28 (-0.39; -0.17)

Repeated high-speed activities during youth soccer games in relation to changes in maximal sprinting and aerobic speeds.

The aim of this study was to examine in highly-trained young soccer players whether substantial changes in either maximal sprinting speed (MSS) or maximal aerobic speed (as inferred from peak incremental test speed, V(Vam-Eval)) can affect repeated high-intensity running during games. Data from 33 players (14.5±1.3 years), who presented substantial changes in either MSS or V(Vam-Eval) throughout 2 consecutive testing periods (~3 months) were included in the final analysis. For each player, time-motion analyses were performed using a global positioning system (1-Hz) during 2-10 international club games played within 1-2 months from/to each testing period of interest (n for game analyzed=109, player-games=393, games per player per period=4±2). Sprint activities were defined as at least a 1-s run at intensities higher than 61% of individual MSS. Repeated-sprint sequences (RSS) were defined as a minimum of 2 consecutive sprints interspersed with a maximum of 60 s of recovery. Improvements in both MSS and V(Vam-Eval) were likely associated with a decreased RSS occurrence, but in some positions only (e. g., - 24% vs. - 3% for improvements in MSS in strikers vs. midfielders, respectively). The changes in the number of sprints per RSS were less clear but also position-dependent, e. g., +7 to +12% for full-backs and wingers, - 5 to - 7% for centre-backs and midfielders. In developing soccer players, changes in repeated-sprint activity during games do not necessarily match those in physical fitness. Game tactical and strategic requirements are likely to modulate on-field players' activity patterns independently (at least partially) of players' physical capacities.

Match play intensity distribution in youth soccer.

The purpose of this study was to quantify match play intensity distribution in young soccer players in relation to age, playing position and physical fitness. Distance covered and heart rate were measured (global positioning system) on 103, highly-trained young players (Under13 to Under 18) during 42 international club games. Maximal sprinting speed (MSS), estimated maximal aerobic speed (MAS) and maximal heart rate (HRmax) were assessed via field test measures. Distance covered and heart rate (HR) were categorized into 5 intensity zones relative to MSS and MAS and HR(max), respectively. Intensity distribution was significantly influenced by both age and playing position with younger groups, wide-midfielders and strikers covering the greatest distance above the MAS. There was a significant, negative, large-to-very large correlation (r= -0.52-0.74) between MAS and the distance run at speeds above MAS for all positions except strikers. HR responses were not different across age groups and playing positions. Distance covered below MAS were lower in the second half for all positions (P<0.05; 0.08<η(2)<0.20), while distance covered at intensities above MAS were maintained (P>0.1; 0.00<η(2)<0.03). This reduction in distance covered below MAS was not related to a player's physical capacity. Except for strikers, a superior aerobic fitness level was unlikely to affect total distance covered but was associated with a reduced individual running demand during the game.

Monitoring changes in physical performance with heart rate measures in young soccer players.

The aim of the present study was to verify the validity of using exercise heart rate (HRex), HR recovery (HRR) and post-exercise HR variability (HRV) during and after a submaximal running test to predict changes in physical performance over an entire competitive season in highly trained young soccer players. Sixty-five complete data sets were analyzed comparing two consecutive testing sessions (3-4 months apart) collected on 46 players (age 15.1 ± 1.5 years). Physical performance tests included a 5-min run at 9 km h(-1) followed by a seated 5-min recovery period to measure HRex, HRR and HRV, a counter movement jump, acceleration and maximal sprinting speed obtained during a 40-m sprint with 10-m splits, repeated-sprint performance and an incremental running test to estimate maximal cardiorespiratory function (end test velocity V (Vam-Eval)). Possible changes in physical performance were examined for the players presenting a substantial change in HR measures over two consecutive testing sessions (greater than 3, 13 and 10% for HRex, HRR and HRV, respectively). A decrease in HRex or increase in HRV was associated with likely improvements in V (Vam-Eval); opposite changes led to unclear changes in V (Vam-Eval). Moderate relationships were also found between individual changes in HRR and sprint [r = 0.39, 90% CL (0.07;0.64)] and repeated-sprint performance [r = -0.38 (-0.05;-0.64)]. To conclude, while monitoring HRex and HRV was effective in tracking improvements in V (Vam-Eval), changes in HRR were moderately associated with changes in (repeated-)sprint performance. The present data also question the use of HRex and HRV as systematic markers of physical performance decrements in youth soccer players.

Match running performance and fitness in youth soccer.

The activity profiles of highly trained young soccer players were examined in relation to age, playing position and physical capacity. Time-motion analyses (global positioning system) were performed on 77 (U13-U18; fullbacks [FB], centre-backs [CB], midfielders [MD], wide midfielders [W], second strikers [2 (nd)S] and strikers [S]) during 42 international club games. Total distance covered (TD) and very high-intensity activities (VHIA; >16.1 km·h (-1)) were computed during 186 entire player-matches. Physical capacity was assessed via field test measures (e. g., peak running speed during an incremental field test, VVam-eval). Match running performance showed an increasing trend with age ( P<0.001, partial eta-squared (η (2)): 0.20-0.45). When adjusted for age and individual playing time, match running performance was position-dependent ( P<0.001, η (2): 0.13-0.40). MD covered the greater TD; CB the lowest ( P<0.05). Distance for VHIA was lower for CB compared with all other positions ( P<0.05); W and S displayed the highest VHIA ( P<0.05). Relationships between match running performance and physical capacities were position-dependent, with poor or non-significant correlations within FB, CB, MD and W (e. g., VHIA vs. VVam-eval: R=0.06 in FB) but large associations within 2 (nd)S and S positions (e. g., VHIA vs. VVam-eval: R=0.70 in 2 (nd)S). In highly trained young soccer players, the importance of fitness level as a determinant of match running performance should be regarded as a function of playing position.

Repeated-sprint sequences during youth soccer matches.

This study examined the occurrence and nature of repeated-sprint sequences (RSS) in highly-trained young soccer players, as a function of age, playing position and playing time. Time-motion analyses using a global positioning system (GPS) were performed on 99 highly-trained young soccer (U13, U14, U15, U16, U17 and U18) players during 42 international games. Sprint activities were defined as at least a 1-s run at intensities higher than 61% of the individual peak running velocity; RSS, as a minimum of 2 consecutive sprints interspersed with a maximum of 60 s. During the first half of games the younger teams had a greater number of RSS than the older teams (P<0.001): U13>U14>U16>U15>U18>U17. The younger players also performed more (e. g., U14 vs. U17: 2.8±0.3 vs. 2.6±0.3, P<0.05) and longer (e. g., U14 vs. U17: 2.8±0.5 vs. 2.6±0.5 s, P<0.05) sprints per sequence than the older players. RSS occurrence was also affected by playing position and decreased throughout the game in most age-groups (P<0.001). Both the occurrence and the nature of RSS are affected by age, position and playing time. Present results also question the importance of repeated-sprint ability as a crucial physical component of soccer performance in developing players.

Influence of rest duration on muscle activation during submaximal intermittent contractions with the elbow flexor muscles.

AIM: The purpose of the study was to compare the influence of two intervals between consecutive intermittent contractions with the elbow flexors on time to failure and the accompanying changes in electromyographic (EMG) activity and excitation-contraction coupling. METHODS: Subjects performed 6-s intermittent isometric contractions at 50% of the maximal voluntary contraction (MVC) force to task failure in two sessions. The recovery period between consecutive contractions was 4-s (short recovery protocol, SRP) in one and 14-s (long recovery protocol, LRP) in the other session. RESULTS: The number of contractions performed to task failure was greater for the LRP (99 + or - 24) compared with the SRP (46 + or - 18; P<0.05). The amplitude and duration of the maximal compound action potential (M-wave) did not change during either protocol. EMG activity (% peak MVC) for the elbow flexors and the force fluctuations increased more rapidly during the SRP compared with the LRP (P<0.05) and was greater at task failure for the SRP protocol (P<0.05). These changes were accompanied by a faster decline in twitch force. CONCLUSIONS: The results indicate that a briefer interval between consecutive contractions was associated with a more rapid impairment of the excitation-contraction coupling and a faster increase in muscle activation, despite a similar net muscle force for the two protocols.

Intensity of tennis match play.

This review focuses on the characteristics of tennis players during match play and provides a greater insight into the energy demands of tennis. A tennis match often lasts longer than an hour and in some cases more than five hours. During a match there is a combination of periods of maximal or near maximal work and longer periods of moderate and low intensity activity. Match intensity varies considerably depending on the players' level, style, and sex. It is also influenced by factors such as court surface and ball type. This has important implications for the training of tennis players, which should resemble match intensity and include interval training with appropriate work to rest ratios.

Upper body aerobic fitness comparison between two groups of competitive surfboard riders.

The aim of the present study was to evaluate and compare the upper-body aerobic fitness characteristics in 2 groups of competitive surfers with different performance levels. Thirteen male competitive surfers performed an incremental dry-land board paddling test to determine specific peak oxygen uptake (VO2peak), peak power output (Wpeak) and the exercise intensity (%VO2peak) that elicits a blood lactate concentration of 4 mmol x L(-1) (LT4). As a measure of surfing performance, surfers were ranked according to their competitive season performance (RANK) and divided into 2 groups based on their performance level; European top-level competitive surfers (ELS) (n = 7) and regional level competitive surfers (RLS) (n = 6). ELS reached significantly higher values than RLS for Wpeak (154.71 +/- 36.82 W vs. 117.70 +/- 27.14 W: P = 0.04) and LT4 (95.18 +/- 3.42 %VO2peak vs. 88.89 +/- 5.01 %VO2peak; P = 0.02) but not VO2peak (3.34 +/- 0.31 L x min(-1) vs. 3.40 +/- 0.37 L x min(-1); P = 0.77). Spearman-rank order correlation analysis revealed that RANK was inversely correlated with Wpeak (r = -0.65, P = 0.01) and LT4 (r = -0.58, P = 0.03). These findings identify that better surfers have higher upper body aerobic fitness scores.