Physical fitness, injuries, and team performance in soccer

PURPOSE: To investigate the relationship between physical fitness and team success in soccer, and to test for differences in physical fitness between different player positions. METHODS: Participants were 306 male soccer players from 17 teams in the two highest divisions in Iceland. Just before the start of the 1999 soccer season, the following variables were tested: height and weight, body composition, flexibility, leg extension power, jump height, and peak O2 uptake. Injuries and player participation in matches and training were recorded through the 4-month competitive season. Team average physical fitness was compared with team success (final league standing) using a linear regression model. Physical fitness was also compared between players in different playing positions. RESULTS: A significant relationship was found between team average jump height (countermovement jump and standing jump) and team success (P = 0.009 and P = 0.012, respectively). The same trend was also found for leg extension power (P = 0.097), body composition (% body fat, P = 0.07), and the total number of injury days per team (P = 0.09). Goalkeepers demonstrated different fitness characteristics from outfield players. They were taller and heavier, more flexible in hip extension and knee flexion, and had higher leg extension power and a lower peak O2 uptake. However, only minor differences were observed between defenders, midfield players, and attackers. CONCLUSION: Coaches and medical support teams should pay more attention to jump and power training, as well as preventive measures and adequate rehabilitation of previous injuries to increase team success.     

Physiological adaptations to soccer specific endurance training in professional youth soccer players

Background: Improved oxygen uptake improves soccer performance as regards distance covered, involvements with the ball, and number of sprints. Large improvements in oxygen uptake have been shown using interval running. A similar physiological load arising from interval running could be obtained using the soccer ball in training.

Objectives: The main aim was to study physiological adaptations to a 10 week high intensity aerobic interval training program performed by professional youth soccer players, using a soccer specific ball dribbling track.

Methods: Eleven youth soccer players with a mean (SD) age of 16.9 (0.4) years performed high intensity aerobic interval training sessions twice per week for 10 weeks in addition to normal soccer training. The specific aerobic training consisted of four sets of 4 min work periods dribbling a soccer ball around a specially designed track at 90–95% of maximal heart frequency, with a 3 min recovery jog at 70% of maximal heart frequency between intervals.

Results: Mean Vo_2max improved significantly from 63.4 (5.6) to 69.8 (6.6) ml kg^–1 min^–1, or 183.3 (13.2) to 201.5 (16.2) ml kg^–0.75 min^–1 (p<0.001). Squat jump and counter movement jump height increased significantly from 37.7 (6.2) to 40.3 (6.1) cm and 52.0 (4.0) to 53.4 (4.2) cm, respectively (p<0.05). No significant changes in body mass, running economy, rate of force development, or 10 m sprint times occurred.

Conclusion: Performing high intensity 4 min intervals dribbling a soccer ball around a specially designed track together with regular soccer training is effective for improving the Vo_2max of soccer players, with no negative interference effects on strength, jumping ability, and sprinting performance.

     

Surface-related injuries in soccer

The review of the effects of artificial turf and natural grass on surface-related traumatic injuries in soccer suggests that surfaces with artificial turf produce more abrasion injuries than surfaces with natural grass. Most authors report no significant difference in injury frequencies for the number of traumatic injuries. However, some authors report fewer traumatic injuries on artificial turf, especially after a period of adaptation on the artificial turf. A difference in injury pattern and injury mechanism when playing on different types of surfaces has been suggested, as well as an increased injury risk for frequent alternating between different playing surfaces. The relationship between knee and ankle injuries and the fixation of the foot to the ground is not yet evaluated in soccer. In American football, the severity and incidence of knee and ankle injuries were reported to be significantly lower when using shoes with lower friction properties. However, in American football severe injuries typically occur in collision situations often independent of the surface. Soccer is characterised by sprinting, stopping, cutting and pivoting situations, where shoe-surface relations are essential and frictional resistance must be within an optimal range. Future research should address this compromise between performance and protection.     

Head injuries, heading, and the use of headgear in soccer

Soccer has more than 265 million players around the world and is the only contact sport with purposeful use of the head for controlling and advancing the ball. Head contact in soccer has the potential to cause acute traumatic brain injury including concussion or, potentially, a pattern of chronic brain injury. Although early retrospective research on the effects of soccer heading seemed to suggest that purposeful heading may contribute to long-term cognitive impairment, prospective controlled studies do not support this and, in fact, suggest that purposeful heading may not be a risk factor for cognitive impairment. Headgear has not been shown to be effective in reducing ball impact but may be helpful in reducing the force of non-ball-related impacts to the head. There are concerns that universal use of headgear may cause more aggressive heading and head challenges, leading to increased risk of injury.     

Applied physiology of soccer

Soccer is characterised as a high intensity, intermittent non-continuous exercise. Players cover approximately 10 km of ground per game, of which 8 to 18% is at the highest individual speed. In higher levels of competition there is a greater number of tackles and headings plus a greater percentage of the game is performed at maximum speed. The average aerobic energy yield during a national level game is around 80% of the individual maximum. Blood lactate concentration during a game averages 7 to 8 mmol/L. Because of a high energy yield most players have empty muscle glycogen stores at the end of the game, were hypohydrated and also have an increased body temperature. Soccer players of national and international standard have a maximal aerobic power of around 60 to 65 ml/kg/min, an above average anaerobic alactacid power, and a greater buffer capacity and muscle strength compared with untrained controls, yet seem to be less flexible.     

Postural stability decreases in elite young soccer players after a competitive soccer match

ObjectiveTo investigate the effects of an official soccer match on postural stability in youth elite soccer players.DesignSingle-group pre-post design.SettingCompetitive soccer match.ParticipantsTwenty elite U-19 male soccer players (mean age: 17.7 ± 1.0 years) of which 11 completed the full experimental set-up.Main outcome measuresPostural stability evaluated by unilateral stance tests for dominant and non-dominant lower limbs on a force plate under two visual conditions: eyes opened (EO) and eyes closed (EC).ResultsAfter the match, the centre of gravity (CoG) sway velocity with EO increased on the dominant and non-dominant limbs (median [interquartile range], 0.90°/s [0.60–1.10] vs. 1.10°/s [0.60–1.60]; and 0.70°/s [0.50–0.90] vs 1.00°/s [0.70–1.30]; respectively; p < 0.05). The CoG sway velocity with eyes closed did not change pre- to post-match.ConclusionsThe soccer match decreased the postural stability only when the assessment was conducted with eyes open.     

Fluid loss and body composition of elite Kuwaiti soccer players during a soccer match

AIM: The aim of this study was to assess the effect of the hot weather conditions of Kuwait on fluid loss (FL) and body composition of Kuwaiti soccer players. METHODS: During 5 preseason soccer games, 10 elite Kuwaiti soccer players participated in this study. The age and physical characteristics (mean+/-SD) of the subjects were: age 24+/-4.7 years; height 173.4+/-5.2 cm; mass 68.2+/-7 kg; and the percent body fat 12.3+/-3.7%, the mean temperature 45.4+/-2 degrees C, mean humidity was 23.6+/-4.2%. Measurements were taken at the beginning, half time, and the end of each game; FL was measured by body weight changes. Urine specific gravity was used to determine the state of hydration. Body composition was measured using Biodynamics Model 310e Body Composition Analyzer. RESULTS: There was a significant difference in body weight changes between 1st and 2nd half at P>0.05. The mean value of the FL at the end of the game was 3.1+/-1.4 L; indicating no significant difference in FL between 1st and 2nd half at P>0.05). The mean value urine specific gravity at the end game was 1.026+/-0.002; there was a significant difference between first, and second half for urine specific gravity (P>0.05). CONCLUSIONS: Results of this study indicated that the subjects did not consume enough fluid to offset FL. Players and coaches involved with activities in hot humid environments should pay closer attention to FL and body weight changes which occur during physical activity. Special care should always be taken to insure players consume extra water prior to each training session or game.     

Neuropsychological impairment in soccer athletes

BACKGROUND: Soccer reportedly places participants at risk for neuropsychological impairment, although it is unknown if the risk is associated primarily with concussion, subconcussive blows from heading the ball, or some combination thereof. Moreover, the extent to which younger versus older athletes are at risk for soccer-related cognitive impairment is unclear. We hypothesized that soccer athletes, especially older ones, would show poorer neuropsychological test performance than comparable swimmers. METHODS: Thirty-two soccer (26 college and 6 professional) and 29 swimmers (22 college and 7 masters level), all involved for at least 4 years in their sport at collegiate or national levels, participated. In a 2 X 2 (sport X age category) factorial design, all participants underwent 4 neuropsychological tests with 11 outcome measures assessing motor speed, attention, concentration, reaction time, and conceptual thinking. RESULTS: Soccer athletes performed worse than swimmers on measures of conceptual thinking. The older soccer group in particular performed poorly on measures of conceptual thinking, reaction time, and concentration. Among non-goaltender soccer athletes, estimates of career exposure to brain trauma (based on length of career and level of play) predicted significantly poorer test performance on 6 of 11 measures, even after statistically controlling for age. CONCLUSIONS: Results provide additional evidence that participation in soccer may be associated with poorer neuropsychological performance, although the observed pattern of findings does not specifically implicate heading as the cause. Although deficits were most apparent among older soccer players, serial neuropsychological testing for early detection of impairment is recommended for younger players as well.     

Accidental injuries in soccer]

Frequency and severity of football related injuries have been registered on 90 swiss championship players. A multifactorial evaluation was then done, taking into account age, duration of football practice and number of training hours. Analysis was made of type and place of the injury, its origin as well as the length of the recovery period. The highest injury rate occurs in August (start of the championship). In the national leagues, a team will be hit by 20 injuries on average every half season, 20% of which require a break in the sports activity. The incidence of injuries depends on the performance level. Its values varies between 2.1 and 10.7 per 1000 hours of football play, the highest frequency being seen in the lower leagues. 40% of the mishaps happen during training sessions and 70% of all injuries require a recovery period of more than one week. The best protection rests on a mix of thorough warming up, regular stretching sessions for the legs and a well applied taping, even for preventive purposes.     

Injuries in women's professional soccer

Objective: The injury data from the first two seasons of the Women's United Soccer Association (WUSA) were analysed to determine the injury incidence, anatomic location of injuries, and relation of player position.

Methods: Injury data on 202 players from eight teams during the first two seasons of the WUSA were prospectively collected and analysed.

Results: A total of 173 injuries occurred in 110 players with an overall injury incidence rate of 1.93 injuries per 1000 player hours. The incidence of injury during practice and games was 1.17 and 12.63 per 1000 player hours, respectively. Of the injuries 82% were acute and 16% were chronic. Most of the injuries (60%) were located in the lower extremities. Strains (30.7%), sprains (19.1%), contusions (16.2%), and fractures (11.6%) were the most common diagnoses and the knee (31.8%) and head (10.9%) were the most common sites of injury. Anterior cruciate ligament (ACL) injuries accounted for 4.6% of all injuries and the incidence of ACL tears was 0.09 per 1000 player hours (practice 0.04, game 0.90). Midfielders suffered the most injuries (p<0.007).

Conclusion: We conclude that the injury incidence in the WUSA is lower than the 6.2 injuries per 1000 player hours found in the corresponding male professional league (Major League Soccer); however, knee injuries predominate even in these elite female athletes.

     

Severe soccer injuries in amateurs

OBJECTIVES: To ascertain the number and type of severe soccer injuries admitted to King Edward Hospital in South Africa over 42 months. METHODS: This was a retrospective study of all patients admitted for treatment or observation to the orthopaedic unit only. Patients treated as outpatients, irrespective of severity, are also presented for comparison. RESULTS: Thirty two patients were admitted with severe injuries. The injuries included 18 fractures of the tibial and femoral shaft. Two tibial shaft fractures were compound. Four tibial plateau fractures and five epiphyseal injuries were identified. One patient had a fracture-dislocation of the hip. One patient with a popliteal artery injury presented 48 hours after the injury had occurred. He had an above knee amputation. In the same period 122 patients were treated as outpatients. The types of injury in this group were similar to soccer injuries reported in other countries. CONCLUSIONS: Very serious injuries are sustained by casual soccer players in South Africa. Urgent measures need to be taken to prevent such injuries.     

Injuries among young soccer players

We registered all new injuries among 496 male youth soccer players, aged 12 to 18 years, during the course of one year. The incidence of injury was 3.7 injuries per 1000 hours of soccer per player. The incidence increased with age, and at the higher ages within the youth players, approached the incidence rate of senior players (age greater than or equal to 18 years). Seventy percent of the injuries were located in the lower extremities, particularly the knee (26%) and ankle (23%). Back pain occurred in 14% of players. Fractures, which accounted for 4% of injuries, were most often in the upper extremities. We conclude that youth soccer is a relatively low-risk sport with an injury pattern that differs slightly from that of senior players.     

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.