Incidence of injury in indoor soccer

Prevention of anterior cruciate ligament injuries in female team handball players: a prospective intervention study over three seasons

OBJECTIVE

To assess the effect of a neuromuscular training program on the incidence of anterior cruciate ligament injuries in female team handball players.

DESIGN

Prospective intervention study.

SETTING

Female team handball: Division I-III in Norway.

PARTICIPANTS

Players from the three top divisions: control season (1998-1999), 60 teams (942 players); first intervention season (1999-2000), 58 teams (855 players); second intervention season (2000-2001), 52 teams (850 players).

INTERVENTION

A five-phase program (duration, 15 min) with three different balance exercises focusing on neuromuscular control and planting/landing skills was developed and introduced to the players in the autumn of 1999 and revised before the start of the season in 2000. The teams were instructed in the program and supplied with an instructional video, poster, six balance mats, and six wobble boards. Additionally, a physical therapist was attached to each team to follow up with the intervention program during the second intervention period.

MAIN OUTCOME MEASURES

The number of anterior cruciate ligament injuries during the three seasons and compliance with the program.

RESULTS

There were 29 anterior cruciate ligament injuries during the control season, 23 injuries during the first intervention season (OR, 0.87; CI, 0.50-1.52; p = 0.62), and 17 injuries during the second intervention season (OR, 0.64; CI, 0.35-1.18; p = 0.15). In the elite division, there were 13 injuries during the control season, six injuries during the first intervention season (OR, 0.51; CI, 0.19-1.35; p = 0.17), and five injuries in the second intervention season (OR, 0.37; CI, 0.13-1.05; p = 0.06). For the entire cohort, there was no difference in injury rates during the second intervention season between those who complied and those who did not comply (OR, 0.52; CI, 0.15-1.82; p = 0.31). In the elite division, the risk of injury was reduced among those who completed the anterior cruciate ligament injury prevention program (OR, 0.06; CI, 0.01-0.54; p = 0.01) compared with those who did not.

CONCLUSIONS

This study shows that it is possible to prevent anterior cruciate ligament injuries with specific neuromuscular training.

Risk factors for lower extremity injury: a review of the literature

Prospective studies on risk factors for lower extremity injury are reviewed. Many intrinsic and extrinsic risk factors have been implicated; however, there is little agreement with respect to the findings. Future prospective studies are needed using sufficient sample sizes of males and females, including collection of exposure data, and using established methods for identifying and classifying injury severity to conclusively determine additional risk factors for lower extremity injury.

Recent advances in the rehabilitation of isolated and combined anterior cruciate ligament injuries

The rehabilitation process begins immediately following ACL injury, with emphasis on reducing swelling and inflammation; improving motion; regaining quadriceps control; allowing immediate weight-bearing; and restoring full passive knee extension and, gradually, flexion. The goal of preoperative rehabilitation is to prepare the patient mentally and physically for surgery. Once the ACL surgery is performed, it is important to alter the rehab program based on the type of graft used and any concomitant procedures performed. This will aid in preventing several postoperative complications, such as loss of motion, patellofemoral pain, graft failure, and muscular weakness. The goal of this article has been to provide an overview of the application and the scientific basis for formulating a rehabilitation protocol following ACL surgery. For an athlete to return to competition, it is imperative that he or she regain muscular strength and neuromuscular control in their injured leg while maintaining static stability. In the past, rehabilitation programs attempted to prepare the athlete for return to sports by using resistance exercise alone. Current rehabilitation programs focus not only on strengthening exercises, but also on proprioceptive and neuromuscular control drills in order to provide a neurologic stimulus so that the athlete can regain the dynamic stability needed in athletic competition. We believe that it is important to use this approach not only possible causes that might predispose the individual to future injury.

The differential effects of fatigue on reflex response timing and amplitude in males and females

We examined the effects of fatigue on patellar tendon reflex responses in males and females. A spring-loaded reflex hammer elicited a standardized tendon tap with the knee positioned in an isokinetic dynamometer and flexed to 85 degrees. We recorded vastus lateralis activity (SEMG) and knee extension force production at the distal tibia (force transducer). Reflex trials were performed before and after (immediate, 2, 4, and 6 min) an isokinetic fatigue protocol to 50% MVC (90 degrees /s). For each event, pre-motor time (PMT), electromechanical delay (EMD), and total motor time (TMT) were obtained, as well as EMG amplitude (EMG(amp)), time to peak EMG (EMG(tpk)), peak force amplitude (F(amp)), time to peak force (F(tpk)), EMG:force ratio (E:F), and rate of force production (F(rate)=N/ms). TMT increased significantly in females following fatigue, while males showed no change. The increased TMT was due to an increased EMD with fatigue, while PMT was unaffected. EMG(amp) and F(amp) were somewhat diminished in females yet significantly augmented in males following fatigue, likely accounting for the differential changes in EMD noted. Results suggest males and females may respond differently to isokinetic fatigue, with males having a greater capacity to compensate for contraction force failure when responding to mechanical perturbations.

Prevention of soccer injuries: a prospective intervention study in youth amateur players

BACKGROUND

Risk factors for soccer injuries and possibilities for prevention have been discussed by several authors, but only a few have investigated the effectiveness of preventive interventions.

PURPOSE

The aim of the present study was to evaluate the effects of a prevention program on the incidence of soccer injuries in male youth amateur players.

STUDY DESIGN

Prospective controlled intervention study.

METHODS

Seven soccer teams took part in a prevention program that focused on education and supervision of coaches and players, while seven other teams were instructed to train and play soccer as usual. Over 1 year all injuries were documented weekly by physicians. Complete weekly injury reports were available for 194 players.

RESULTS

The incidence of injury per 1000 hours of training and playing soccer was 6.7 in the intervention group and 8.5 in the control group, which equates to 21% fewer injuries in the intervention group. The greatest effects were observed for mild injuries, overuse injuries, and injuries incurred during training. The prevention program had greater effects in low-skill than in high-skill teams.

CONCLUSIONS

The incidence of soccer injuries can be reduced by preventive interventions, especially in low skill level youth teams. Coaches and players need better education regarding injury prevention strategies and should include such interventions as part of their regular training.

Gender differences in strength and lower extremity kinematics during landing

This study evaluated kinematic, vertical ground reaction forces, and strength variables in healthy collegiate female basketball, volleyball, and soccer players compared with matched male subjects. Thirty athletes did single-leg landing and forward hop tasks. An electromagnetic tracking device synchronized with a force plate provided kinematic data and vertical ground reaction force data, respectively. Maximum angular displacement and time to maximum angular displacement kinematic variables were calculated for hip flexion, abduction, rotation, knee flexion, and lower leg rotation. Vertical ground reaction force data normalized to body mass provided impulse, maximum force, time to maximum force, and stabilization time variables. An isokinetic device measured quadriceps and hamstring peak torque to body mass at 60 degrees /second. With both tasks, females had significantly less knee flexion and lower leg internal rotation maximum angular displacement, and less knee flexion time to maximum angular displacement than males. For the single-leg land, females had significantly more hip internal rotation maximum angular displacement, and less lower leg internal rotation time to maximum angular displacement than males. For the forward hop, females had significantly more hip rotation time to maximum angular displacement than males. Females also had significantly less peak torque to body mass for the quadriceps and hamstrings than males. Weaker thigh musculature may be related to the abrupt stiffening of the knee and lower leg on landing in females.

Major international sport profiles

Sports are part of the sociocultural fabric of all countries. Although different sports have their origins in different countries, many sports are now played worldwide. International sporting events bring athletes of many cultures together and provide the opportunity not only for athletic competition but also for sociocultural exchange and understanding among people. This article reviews five major sports with international appeal and participation: cricket, martial arts, field hockey, soccer, and tennis. For each sport, the major aspects of physiological and biomechanical demands, injuries, and prevention strategies are reviewed.

The relationship between serum relaxin and knee joint laxity in female athletes

Gravidity studies have intimated a relationship between serum relaxin levels and joint laxity. To assess its applicability to eumenorrheic athletes, weekly serum relaxin and knee arthrometry measurements were obtained in 57 collegiate women and 5 men for 4 consecutive weeks. The former included athletes, ACL-injured athletes, and nonathletes, while the latter formed an a priori hormonal control. Analysis of variance revealed a significant change in weekly serum relaxin levels in females but not in anterior translation. Regression analysis failed to disclose a relationship between these variables. Therefore, we conclude relaxin does not affect knee laxity.

Anterior cruciate ligament injuries in young females playing soccer at senior levels

The aim of this investigation was to study the consequences of anterior cruciate ligament injuries in female soccer players. Special interest was focused on young female soccer players (< 16 years) sustaining anterior cruciate ligament injuries when playing at a senior level, which means playing together with players 19 years or older. In Sweden, all players belonging to an organized soccer club are insured by the same insurance company, the Folksam Insurance Company. Data of all soccer-related knee injuries in females reported to the Folksam Insurance Company between 1994 and 1998 were collected. A questionnaire was sent to 978 females who were registered to have sustained a knee injury before the age of 20 years. The response rate was 79%. Three hundred and ninety-eight female soccer players who had sustained an anterior cruciate ligament injury before the age of 19 years were analysed. Most of their anterior cruciate ligament injuries had been diagnosed using arthroscopy or magnetic resonance imaging (84%). Thirty-eight percent of the players had been injured before the age of 16 years. Of these, 39% were injured when playing in senior teams. When playing in senior teams 59% of the players below the age of 16 years and 44% of the players 16 years or older sustained their ACL injuries during contact situations. At the time of this investigation (2-7 years after the anterior cruciate ligament injury), altogether 78% (n = 311) reported that they had stopped playing soccer. The most common reason (80%) was symptoms from their anterior cruciate ligament-injured knee. It appears that many young female soccer players injure their anterior cruciate ligament when playing at a senior level. Therefore, we suggest that female soccer players under the age of 16 years should be allowed to participate only in practice sessions but not games at a senior level.

Gender differences in active musculoskeletal stiffness. Part II. Quantification of leg stiffness during functional hopping tasks

Leg stiffness was compared between age-matched males and females during hopping at preferred and controlled frequencies. Stiffness was defined as the linear regression slope between the vertical center of mass (COM) displacement and ground-reaction forces recorded from a force plate during the stance phase of the hopping task. Results demonstrate that subjects modulated the vertical displacement of the COM during ground contact in relation to the square of hopping frequency. This supports the accuracy of the spring-mass oscillator as a representative model of hopping. It also maintained peak vertical ground-reaction load at approximately three times body weight. Leg stiffness values in males (33.9+/-8.7 kN/m) were significantly (p<0.01) greater than in females (26.3+/-6.5 kN/m) at each of three hopping frequencies, 3.0, 2.5 Hz, and a preferred hopping rate. In the spring-mass oscillator model leg stiffness and body mass are related to the frequency of motion. Thus male subjects necessarily recruited greater leg stiffness to drive their heavier body mass at the same frequency as the lighter female subjects during the controlled frequency trials. However, in the preferred hopping condition the stiffness was not constrained by the task because frequency was self-selected. Nonetheless, both male and female subjects hopped at statistically similar preferred frequencies (2.34+/-0.22 Hz), therefore, the females continued to demonstrate less leg stiffness. Recognizing the active muscle stiffness contributes to biomechanical stability as well as leg stiffness, these results may provide insight into the gender bias in risk of musculoskeletal knee injury.

Neuromuscular contributions to anterior cruciate ligament injuries in females

Although anterior cruciate ligament (ACL) injuries are not gender specific, they do occur at a significantly greater rate in females. Biomechanical and neuromuscular deficits in females have been documented as factors contributing to ACL injuries, however little research has been conducted in the area of preventative training programs to improve these deficits. This article will describe the biomechanical and neuromuscular factors that contribute to ACL injuries in females, and provide a foundation from which preventative training programs should be designed.

A gender-related difference in the contribution of the knee musculature to sagittal-plane shear stiffness in subjects with similar knee laxity

BACKGROUND

Women's susceptibility to injuries involving the anterior cruciate ligament remains unexplained. Volitional contraction of the knee musculature is known to increase the resistance of the knee to shear deformation, raising the possibility that muscles play a part in protecting the anterior cruciate ligament during hazardous activities. We therefore tested the hypothesis that a volitional co-contraction of the knee muscles increases the sagittal-plane shear stiffness (or resistance to anterior tibial translation) of the knee more in men than in women.

METHODS

Twenty-three volunteers (ten men and thirteen women; mean age, 24.7 +/- 5.4 years), all with anterior tibial translation of 6 mm, agreed to participate in the study. Each subject underwent a subjective evaluation of knee function and activity level, an arthrometric measurement of passive anterior tibial translation, and an isokinetic dynamometer strength test at 60 degrees/sec. A dynamic stress test was then performed to measure anterior tibial translation while simultaneously monitoring lower-extremity muscle response.

RESULTS

Maximum co-contraction of the knee musculature significantly decreased mean anterior tibial translation in both men and women (from 7.8 mm to 2.2 mm in men and from 6.5 mm to 3.1 mm in women). The corresponding percentage increase in shear stiffness of the knee was significantly greater (p = 0.003) in men (379%) than in women (212%).

CONCLUSIONS

The results suggested that women have a diminished potential for muscular protection of passive structures of the knee in anterior tibial translation.

CLINICAL RELEVANCE

Maximal muscular protection of the anterior cruciate ligament in women may be less than that in men. This may be one factor explaining why more women than men are apt to sustain injuries to the anterior cruciate ligament.

Immobilisation and functional treatment for acute lateral ankle ligament injuries in adults

BACKGROUND

Acute lateral ankle ligament injuries (ankle sprains) are common problems in acute medical care. The treatment variation observed for the acutely injured lateral ankle ligament complex suggests a lack of evidence-based management strategies for this problem.

OBJECTIVES

The objective of this review was to assess the effectiveness of methods of immobilisation for acute lateral ankle ligament injuries and to compare immobilisation with functional treatment methods.

SEARCH STRATEGY

We searched the Cochrane Musculoskeletal Injuries Group specialised register (December 2001); the Cochrane Controlled Trials Register (The Cochrane Library, Issue 4, 2001), MEDLINE (1966-May 2000), EMBASE (1988-May 2000), reference lists of articles, and contacted organisations and researchers in the field.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials comparing either different types of immobilisation or immobilisation versus functional treatments for injuries to the lateral ligament complex of the ankle in adults were included. Trials which investigated the treatment of chronic instability or post-surgical treatment were excluded.

DATA COLLECTION AND ANALYSIS

Data were independently extracted by two authors. Where appropriate, results of comparable studies were pooled using fixed effects models. Individual and pooled statistics were reported as relative risks with 95% confidence intervals for dichotomous outcomes and weighted (WMD) or standardised (SMD) mean differences and 95% confidence intervals for continuous outcome measures. Heterogeneity between trials was tested using a standard chi-squared test.

MAIN RESULTS

Twenty-one trials involving 2184 participants were included. The mean validity score of the included trials increased from 9.1 (SD 3.0) to 10 (SD 2.9) after retrieving further information (maximum 18 points). Statistically significant differences in favour of functional treatment when compared with immobilisation were found for seven outcome measures: more patients returned to sport in the long term (relative risk (RR) 1.86, 95% confidence interval (CI) 1.22 to 2.86); the time taken to return to sport was shorter (WMD 4.88 (days), 95% CI 1.50 to 8.25); more patients had returned to work at short term follow-up (RR 5.75, 95% CI 1.01 to 32.71); the time taken to return to work was shorter (WMD 8.23 days, 95% CI 6.31 to 10.16); fewer patients suffered from persistent swelling at short term follow-up (RR 1.74, 95% CI 1.17 to 2.59); fewer patients suffered from objective instability as tested by stress X-ray (WMD 2.60, 95% CI 1.24 to 3.96); and patients treated functionally were more satisfied with their treatment (RR 1.83, 95% CI 1.09 to 3.07). A separate analysis of trials that scored 50 per cent or more in quality assessment found a similar result for time to return to work only (WMD (days) 12.89, 95% CI 7.10 to 18.67). No significant differences between varying types of immobilisation, immobilisation and physiotherapy or no treatment were found, apart from one trial where patients returned to work sooner after treatment with a soft cast. In all analyses performed, no results were significantly in favour of immobilisation.

REVIEWER'S CONCLUSIONS

Functional treatment appears to be the favourable strategy for treating acute ankle sprains when compared with immobilisation. However, these results should be interpreted with caution, as most of the differences are not significant after exclusion of the low quality trials. Many trials were poorly reported and there was variety amongst the functional treatments evaluated.

Anterior cruciate ligament reconstruction in men and women: An outcome analysis comparing gender

PURPOSE

Recent studies have shown that female athletes suffer a higher incidence of anterior cruciate ligament (ACL) tears than comparable male athletes. The purpose of this study was to evaluate the effect gender has on outcome in ACL reconstruction using bone-patellar tendon-bone autograft.

TYPE OF STUDY

Retrospective case review and outcome study.

METHODS

A retrospective review of a single surgeon's practice revealed 279 ACL reconstructions that met our criteria for inclusion. Two-hundred forty-nine of these patients (91%) were contacted. Two-hundred (72%) were evaluated with physical examination, KT-1000 testing, functional testing, and radiographic evaluation. Outcome was assessed with Tegner, Lysholm, modified HSS, and Cincinnati Knee rating scales, as well as the SF-36 health survey and a self-administered questionnaire. There were 137 men and 63 women. Data were evaluated with Wilcoxon rank sum testing, analysis of variance testing, chi-square analysis, and the Student t test. The level of significance was set at P <.05.

RESULTS

Postoperatively, no differences were noted on Lachman, anterior drawer, pivot shift, or functional testing in either groups. Male patients had a significantly greater mean prone heel height difference (1.80 v 1.10 cm, P =.0018) and mean KT-1000 maximum manual side-to-side difference (0.76 v 1.73 mm, P =.014). However, no differences were noted in the percentage of patients with greater than 5-mm side-to-side difference, with 5 men (4%) and 2 women (3%) classified as arthrometric failures. No differences were noted in mean Tegner, Lysholm, Noyes Cincinnati, and modified HSS scores. Men had significantly lower HSS radiographic scores (24.98 v 26.22, P =.0016). Men and women were compared with gender-matched controls for SF-36 testing, and women scored higher compared with controls than did men in the Role Physical, Body Pain, and General Health categories. No differences were noted in either group regarding donor-site pain, patellofemoral crepitance, or problems with stair climbing. Ninety-six percent of men and 98% of women would have had the surgery over again given similar circumstances.

CONCLUSIONS

Objective criteria failed to detect clinically significant differences in physical examination and arthrometric results between men and women. Knee rating scale scores were similar. Comparable outcome with high satisfaction and equal success can be expected in both men and women undergoing ACL reconstruction using bone-patellar tendon-bone autograft. No basis exists for the inclusion of gender as a determining factor regarding the decision to perform ACL reconstructive surgery with bone-patellar tendon-bone autograft.

An examination of injuries in major league soccer. The inaugural season

We analyzed the injury data collected from the 10 teams (237 players) that constituted Major League Soccer during its inaugural season. The overall injury rate was 6.2 per 1000 hours of participation. An injury rate of 2.9 per 1000 hours was noted for practice and 35.3 per 1000 hours was found for games. The difference was statistically significant. With regard to severity, 36% of injuries (143 of 399) were categorized as an incident (no time lost from competition). Of the 256 injuries that caused the player to lose playing time, 59% were classified as minor (<7 days lost), 28% as moderate (7 to 29 days lost), and 13% as major (>30 days lost). Seventy-seven percent of the injuries (197 of 256) were to the lower extremity; most frequently affected were the knee (N = 54) and ankle (N = 46). Neither the player's age nor playing position was found to be associated with prevalence or severity of injury. We believe that this information serves to underscore the notion that soccer, as it is played at the professional level, is a sport with a relatively low incidence of injury.

Correlation of estradiol in pregnancy and anterior cruciate ligament laxity

The purpose of this study was to determine whether a correlation existed between estradiol in pregnancy and laxity of the anterior cruciate ligament by measuring anterior tibial translation. All patients underwent measurement of anterior tibial translation using KT-1000 knee arthrometer testing and serum estradiol determination during the third trimester of pregnancy and postpartum. Forty knees were studied. The average serum estradiol levels decreased from 10,755.0 ng/L to 50.3 ng/L. There was an average decrease anterior tibial translation with a manual maximum displacement of 3.0 mm (range, 1 mm-5 mm) from the first to second examinations. Average measurement of anterior tibial translation in pregnant women showed a statistically significant increase in laxity in the third trimester of pregnancy compared with the postpartum laxity. The results of this study show that high serum estradiol levels during the third trimester of pregnancy correlate with increased anterior tibial translation and that this anterior tibial translation decreases with the return of serum estradiol to nonpregnant levels.

A comparison of knee joint motion patterns between men and women in selected athletic tasks

BACKGROUND

Women have higher non-contact anterior cruciate ligament injury rate than men do in sport activities. Non-contact anterior cruciate ligament injuries frequently occur in sports requiring cutting tasks. Alternated motor control strategies have identified as a potential risk factor for the non-contact anterior cruciate ligament injuries. The purpose of this study was to compare the patterns of knee kinematics and electromyographic activities in running, side-cutting, and cross-cutting between men and women recreational athletes.

METHODS

Three-dimensional kinematic data of the knee and electromyographic data of selected muscles across the knee joint were collected for 11 men and 9 women recreational athletes in running, side-cutting, and cross-cutting. Regression analyses with dummy variables for comparison of knee motion patterns between men and women.

RESULTS

Women tend to have less knee flexion angles, more knee valgus angles, greater quadriceps activation, and lower hamstring activation in comparison to men during the stance phase of each of the three athletic tasks. Literatures suggest these alternated knee motion patterns of women tend to increase the load on the anterior cruciate ligament.

CONCLUSION

Women on average may have certain motor control strategies that may alter their knee motion patterns. Women's altered knee motion patterns may tend to increase the load on the anterior cruciate ligament in the selected athletic tasks, which may contribute to the increased anterior cruciate ligament injury rate among women.

RELEVANCE

Non-contact anterior cruciate ligament injuries frequently occur in sports. Altered motor control strategies and lower extremity motion patterns are likely to play an important role in non-contact anterior cruciate ligament injuries. Non-contact anterior cruciate ligament injuries may be prevented by correcting altered motor control strategies and associated lower extremity motion patterns through certain training programs.

Inversion and eversion strengths in the weightbearing ankle of young women. Effects of plantar flexion and basketball shoe height

Maximum isometric ankle inversion and eversion muscle strengths were measured under full unipedal weightbearing in 20 healthy young adult women. When the women wore a low-top shoe, the mean (standard deviation) maximum external eversion moments resisted with the foot in 0 degrees and 32 degrees of ankle plantar flexion were 24.1 (7.6) and 24.1 (8.1) N x m, respectively, while the corresponding values for maximum inversion moments resisted were 14.7 (6.8) and 17.4 (6.4) N x m, respectively. Both shoe height and ankle plantar flexion affected the overall inversion moment resisted by 17% (P = 0.03) at 0 degrees of ankle plantar flexion to 11.9% (P = 0.003) at 32 degrees of ankle plantar flexion. However, neither shoe height nor ankle plantar flexion significantly affected the maximum eversion moment resisted. Although eversion muscle strength of the young women averaged 39% less than the corresponding value found in young men, the sex difference was not significant when ankle strengths were normalized by body size (body weight x height). Thus, when data from healthy young men and women were averaged, eversion and inversion strengths averaged 1.6% and 2.7%, respectively, of body weight x height.

Correlation of anthropometric measurements, strength, anterior cruciate ligament size, and intercondylar notch characteristics to sex differences in anterior cruciate ligament tear rates

We performed a prospective study based on the hypothesis that physiologic differences exist between men and women in strength after adjustments for body weight; that the size of the anterior cruciate ligament is proportionate to the strength of its antagonists, the quadriceps muscles; and that women have a relatively small anterior cruciate ligament, thus predisposing them to a disproportionate number of anterior cruciate ligament injuries. One hundred matched high school basketball players, 50 male and 50 female, were evaluated with anthropometric measurements, body fat analysis, muscle strength evaluation, and magnetic resonance imaging measurements of the intercondylar notch and cross-sectional area of the anterior cruciate ligament at the outlet. The male players were taller and heavier than their female counterparts, although they had 11% less body fat. Male players had statistically greater quadriceps and hamstring muscle strength than female players, even when adjustments were made for body weight. With adjustments for body weight, the size of the anterior cruciate ligament in girls was found to be statistically smaller than in boys. There was no statistically significant difference in the notch width index between the sexes. The study data support our hypothesis that sex differences in anterior cruciate ligament tear rates are caused primarily by several interrelated intrinsic factors. Most importantly, stiffness and muscular strength increase stress on the anterior cruciate ligament in female athletes. The anterior cruciate ligament, when adjustments have been made for body weight, is smaller in female athletes, and therefore, probably does not compensate for the lack of stiffness and strength.

Clinical comparison of intraarticular anterior cruciate ligament reconstruction using autogenous semitendinosus and gracilis tendons in men versus women

Reconstruction of the anterior cruciate ligament using a hamstring tendon autograft has often been recommended for female athletes. We compared the results of acute, isolated, intraarticular anterior cruciate ligament reconstructions using quadruple-looped hamstring autografts in 39 female and 26 male patients. All reconstructions were performed by the same surgeon using a similar surgical technique and the same postoperative management. In each case, patients had Endobutton femoral fixation and either post or button fixation for the tibial side. The average follow-up was 40.9 months for women and 39.0 months for men. Objective analysis of results included examination for the presence of effusion and crepitus, Lachman and pivot shift testing, and KT-1000 arthrometer testing for side-to-side differences. Subjective analysis consisted of a 15-item visual analog scale completed by patients postoperatively, and pre- and postoperative Tegner and Lysholm scores. The clinical failure rate was 23% (9 of 39) for the female patients and 4% (1 of 26) for the male patients, which was statistically significant. There was also a trend toward increased laxity in female patients. Subjectively, the women also reported a higher frequency and intensity of pain. Based on Tegner activity levels, more of the men returned to their preinjury level of activity than did the women. When compared with the male patients, female patients had a significantly higher failure rate after reconstruction.

Epidemiology of women's recreational ice hockey injuries

INTRODUCTION

Participation in ice hockey by women is increasing in many parts of North America; however, research into injuries and the patterns of injury among female players associated with this activity is limited.

PURPOSE

The purpose of this research was to examine the incidence and nature of injuries suffered by female recreational ice hockey players.

METHODS

This prospective study followed 314 female players from 33 teams in Edmonton, Canada, during the 1997-1998 hockey season. Injury and game attendance data were collected using monthly telephone interviews throughout the season. Diagnostic information for individuals who received medical treatment was solicited from the attending health professional.

RESULTS

A total of 102 players reported a total of 125 injuries for a rate 7.5 injuries/1000 player exposures. The anatomic region most often injured was the lower extremity (31.2%), and the most common diagnosis was sprain/strain (52.0%). The predominant injury mechanism was player contact, either as a result of collision with another player or a body check (40.0%). Of all injuries, 65.6% occurred during league games, 27.2% during play-off, tournament, or exhibition games, and 7.2% during practices. Although less than 1% of injuries resulted in hospitalization, 17.6% of injuries resulted in an absence from hockey of 8 or more days.

CONCLUSION

The diagnostic and anatomic distribution of injury in the women's hockey league was similar to that in leagues where full facial protection is mandatory. The observed injury rate was lower than the rates reported for male recreational and collegiate ice hockey players. Female recreational ice hockey players are at risk for injuries and further research is required to identify areas for injury prevention.

A prospective study of high school wrestling injuries

We performed a prospective study to evaluate injury patterns in a large population of high school wrestlers during one season. Preseason screening was performed on 458 male wrestlers from 14 different high schools. Certified athletic trainers submitted detailed weekly team and individual injury reports. There were 219 injuries in 418 wrestlers followed throughout the season for an overall injury incidence of 52 injuries per 100 wrestlers per season and an injury rate of 6.0 injuries per 1,000 exposures. The most commonly injured areas were the shoulder (24%) and knee (17%). Injured wrestlers were an average of 5 months older and had a 32% higher experience level than noninjured wrestlers. Wrestlers with ligamentous laxity suffered fewer shoulder injuries than the other wrestlers. The majority of injuries occurred in practice (63%), although the injury rate was higher in match competitions. Sixty-eight percent of practice injuries occurred during hard wrestling, 23% during drills, and 9% during conditioning. The most common wrestling situation resulting in injury was the takedown position (68%). Our results show that the older and more experienced wrestler may be at greater risk of injury. Hard wrestling during practice and the takedown position resulted in the highest occurrence of injury.

Neuromuscular and hormonal factors associated with knee injuries in female athletes. Strategies for intervention

Female athletes who participate in jumping and cutting sports are 4 to 6 times more likely to sustain a serious knee injury than male athletes participating in the same sports. More than 30,000 serious knee injuries are projected to occur in female intercollegiate and high school athletics in the US each year. The majority of these injuries occur by non-contact mechanisms, most often during landing from a jump or making a lateral pivot while running. Knee instability, due possibly to decreased neuromuscular strength and coordination or increased ligamentous laxity, may underlie the increased incidence of knee injury in females. Neuromuscular training can significantly increase dynamic knee stability in female athletes. Female sex hormones (i.e. estrogen, progesterone and relaxin) fluctuate radically during the menstrual cycle and are reported to increase ligamentous laxity and decrease neuromuscular performance and, thus, are a possible cause of decreases in both passive and active knee stability in female athletes. Oral contraceptives stabilise hormone levels during the menstrual cycle and may function to either passively or actively stabilise the knee joint. The long term objective of clinicians and researchers should be to determine the factors that make women more susceptible than men to knee ligament injury and to develop treatment modalities to aid in the prevention of these injuries. The immediate objectives of this review are to examine how female and male athletes differ in neuromuscular and ligamentous control of the lower extremity. The review will examine the effects of neuromuscular training on knee stability. The effects of female hormone levels and oral contraceptives on neuromuscular control of the female athletes' knee will also be discussed.

Gender differences in noncontact anterior cruciate ligament injuries

Female athletes have an increased incidence of ACL rupture. The cause of this increased injury rate is unclear, but it is most likely from a complex interplay between multiple variables. The relative risk of incurring an ACL injury is still low. The increased risk of ACL injury in women compared with men should not discourage female participation in sports. Instead, the focus should be on strategies to prevent injuries. Intrinsic factors are difficult or impossible to change; modifiable risk factors need to identified and prevention strategies should be employed.

Anterior cruciate ligament injuries in the female athlete. Potential risk factors

In the general population, an estimated one in 3000 individuals sustains an anterior cruciate ligament injury per year in the United States, corresponding to an overall injury rate of approximately 100,000 injuries annually. This national estimate is low for women because anterior cruciate ligament injury rates are reported to be two to eight times higher in women than in men participating in the same sports, presenting a sizable health problem. With the growing participation of women in athletics and the debilitating nature of anterior cruciate ligament injuries, a better understanding of mechanisms of injury in women sustaining anterior cruciate ligament injuries is essential. Published studies strongly support noncontact mechanisms for anterior cruciate ligament tears in women, which make these injuries even more perplexing. Speculation on the possible etiology of anterior cruciate ligament injuries in women has centered on anatomic differences, joint laxity, hormones, and training techniques. Investigators have not agreed on causal factors for this injury, but they have started to profile the type of athlete who is at risk. In the current study the most recent scientific studies of intrinsic and extrinsic risk factors thought to be contributing to the high rate of female anterior cruciate ligament injuries will be reviewed, important differences will be highlighted, and recommendations proposed to alleviate or minimize these risk factors among female athletes will be reported where appropriate.

Comparison of soccer shin guards in preventing tibia fracture

The goal of this study was to evaluate the effectiveness of a number of shin guards in protecting against tibia fracture in soccer players. A secondary purpose was to determine the relationship between the material and structural differences in shin guard design and the protection provided. Twenty-three commercially available shin guards were tested on a model leg containing a synthetic tibia that had been calibrated against human cadaver specimens. Each guard was categorized into one of four material types: plastic (N = 9), fiberglass (N = 6), compressed air (N = 4), and Kevlar (N = 4). The maximum combined force at the ends of the tibia, the principal strain on the posterior side of the tibia, and the contact time of the impact were measured using a drop track impact simulation. Shin guards provided significant protection from tibia fracture at all drop heights. The average guard reduced force by 11% to 17% and strain by 45% to 51% compared with the unguarded leg. At the higher drop heights, material composition and structural characteristics of the shin guards showed significant differences in protective abilities. These findings indicate that all shin guards provide some measure of protection against tibia fracture, although the level of protection may vary significantly among the different guards.

The effect of neuromuscular training on the incidence of knee injury in female athletes. A prospective study

To prospectively evaluate the effect of neuromuscular training on the incidence of knee injury in female athletes, we monitored two groups of female athletes, one trained before sports participation and the other not trained, and a group of untrained male athletes throughout the high school soccer, volleyball, and basketball seasons. Weekly reports included the number of practice and competition exposures and mechanism of injury. There were 14 serious knee injuries in the 1263 athletes tracked through the study. Ten of 463 untrained female athletes sustained serious knee injuries (8 noncontact), 2 of 366 trained female athletes sustained serious knee injuries (0 noncontact), and 2 of 434 male athletes sustained serious knee injuries (1 noncontact). The knee injury incidence per 1000 athlete-exposures was 0.43 in untrained female athletes, 0.12 in trained female athletes, and 0.09 in male athletes (P = 0.02, chi-square analysis). Untrained female athletes had a 3.6 times higher incidence of knee injury than trained female athletes (P = 0.05) and 4.8 times higher than male athletes (P = 0.03). The incidence of knee injury in trained female athletes was not significantly different from that in untrained male athletes (P = 0.86). The difference in the incidence of noncontact injuries between the female groups was also significant (P = 0.01). This prospective study demonstrated a decreased incidence of knee injury in female athletes after a specific plyometric training program.

A comparison of results after arthroscopic anterior cruciate ligament reconstruction in female and male competitive athletes. A two- to five-year follow-up of 429 patients

The aim of this study was to compare the results after arthroscopic anterior cruciate ligament reconstruction in female and male competitive athletes who had a pre-injury Tegner activity level of > or =7 and a non-injured contralateral anterior cruciate ligament. One hundred and thirty-three female and 296 male patients were followed at 38 (21-68) months after the index operation. All the patients were operated on by experienced knee surgeons using patellar tendon autografts and interference screw fixation. At the index operation the median age of the female patients was 23 (1645) years and the median age of the male patients was 26 (16-47) years. The reconstruction was performed a median of 10 (0-141) and 10 (0-203) months after the injury in women and men respectively. The patients were re-examined by independent observers. At the follow-up, the median Lysholm score was 89 (38-100) points in the female group and 90 (22-100) points in the male group (P=0.015). The IKDC evaluation system, subjective anterior knee pain, subjective evaluation of the results, the knee-walking test and the KT-1000 tests revealed no differences between the groups. The mean (+/-2 SD) pre-injury Tegner activity level was 8.1 (+/-1.9) (median 8 (7-10)) in the female group and 8.4 (+/-1.8) (median 9 (7-10)) in the male group (P=0.003). At the follow-up, the Tegner activity level was 6.2 (+/-3.8) in the female group and 6.8 (+/-3.6) in the male group (P=0.012). At the follow-up, the Tegner activity level had decreased by 1.9 (+/-3.8) for the women and 1.6 (+/-3.3) for the men, as compared with the pre-injury level (n.s.). The difference between the performed and the desired activity level at the follow-up was 1.1 (+/-3.2) in the female group and 0.9 (+/-3.0) in the male group (n.s.). In the female group 53/133 (40%) and in the male group 115/296 (39%) returned to the pre-injury activity level (n.s.). The median one-leg-hop quotient was 93 (0-116)% in the female group and 96 (0-130)% in the male group (P=0.006). Concomitant meniscal injuries prior to the index operation, at the index operation or during the follow-up period were found in 64/133 (48%) women and in 185/ 296 (62%) men (P<0.01). The main conclusion was that the overall results in female and male athletes were comparable two to five years after the anterior cruciate ligament reconstruction. However, concomitant meniscal injuries were more common in male than females athletes after anterior cruciate ligament injuries.

Skiing injuries

Skiing is a winter sport enjoyed by approximately 200 million people worldwide. An overall injury rate of approximately 3 per 1000 skier-days means that skiing certainly is the riskiest sport undertaken by adults on a routine basis. However, the data suggest that one can anticipate years of enjoyable recreation free from injury. Many troubling injuries, particularly to the lower leg, have shown a steady decline over the past 20 to 30 years because of advances in boot design and binding capabilities. In addition, as information has been gathered regarding the importance of proper maintenance and adjustments, equipment now available can protect a skier more effectively than at any time in the past. Nevertheless, skiing continues to present inherent risks that can be minimized through the following strategies: 1. Enroll in a conditioning program before skiing that focuses on strength and endurance components particularly of the legs and back. 2. Have equipment that is compatible with the skier both from the standpoint of size and expertise. 3. Have equipment adjusted professionally. 4. Do routine testing of binding releases each day before beginning to ski. 5. Ski under control at speeds that are consistent with ability. 6. Stop skiing before fatigue becomes the limiting factor.

Knee joint laxity and neuromuscular characteristics of male and female soccer and basketball players

Anterior cruciate ligament injuries are occurring at a higher rate in female athletes compared with their male counterparts. Research in the area of anterior cruciate ligament injury has increasingly focused on the role of joint proprioception and muscle activity in promoting knee joint stability. We measured knee joint laxity, joint kinesthesia, lower extremity balance, the amount of time required to generate peak torque of the knee flexor and extensor musculature, and electromyographically assessed muscle activity in 34 healthy, collegiate-level athletes (average age, 19.6 +/- 1.5 years) who played soccer or basketball or both. Independent t-tests were used to determine significant sex differences. Results revealed that women inherently possess significantly greater knee joint laxity values, demonstrate a significantly longer time to detect the knee joint motion moving into extension, possess significantly superior single-legged balance ability, and produce significantly greater electromyographic peak amplitude and area of the lateral hamstring muscle subsequent to landing a jump. The excessive joint laxity of women appears to contribute to diminished joint proprioception, rendering the knee less sensitive to potentially damaging forces and possibly at risk for injury. Unable to rely on ligamentous structures, healthy female athletes appear to have adopted compensatory mechanisms of increased hamstring activity to achieve functional joint stabilization.

Youth soccer: an epidemiologic perspective

The youth soccer movement in the United States is developing at a tremendous rate. This article explores the epidemiology of youth soccer including trends in participation, injury data, and injury categories that are of specific concern to the young athlete. Finally, recommendations are made regarding possible future areas of study and research on youth soccer.

How can injuries be prevented in the World Cup soccer athlete?

In order to prevent soccer injuries, different risk factors have to be identified as intrinsic (e.g., joint stability or muscle imbalance) and extrinsic (e.g., equipment, turf, and rules risk factors). Some preventive measures are discussed in this article, such as shin guards, prophylactic braces and taping (or both), and proprioceptive training.

Association between the menstrual cycle and anterior cruciate ligament injuries in female athletes

Anterior cruciate ligament injury rates are four to eight times higher in women than in men. Because of estrogen's direct effect on collagen metabolism and behavior and because neuromuscular performance varies during the menstrual cycle, it is logical to question the menstrual cycle's effect on knee injury rates. Of 40 consecutive female athletes with acute anterior cruciate ligament injuries (less than 3 months), 28 (average age, 23 +/- 11 years) met the study criteria of regular menstrual periods and noncontact injury. Details concerning mechanism of injury, menstrual cycle, contraceptive use, and previous injury history were collected. A chi-square test was used to compute observed and expected frequencies of anterior cruciate ligament injury based on three different phases of the menstrual cycle: follicular (days 1 to 9), ovulatory (days 10 to 14), and luteal (day 15 to end of cycle). A significant statistical association was found between the stage of the menstrual cycle and the likelihood for an anterior cruciate ligament injury (P = 0.03). In particular, there were more injuries than expected in the ovulatory phase of the cycle. In contrast, significantly fewer injuries occurred in the follicular phase. These hormones may be a factor in the knee ligament injury dilemma in women.

Low back pain in college athletes. A prospective study correlating lower extremity overuse or acquired ligamentous laxity with low back pain

STUDY DESIGN

A prospective evaluation of the incidence of low back pain in college athletes was undertaken.

OBJECTIVES

To evaluate prospectively leg length discrepancy, hip flexor tightness, and lower extremity acquired laxity or overuse as predictive factors for low back pain in college athletes.

SUMMARY OF BACKGROUND DATA

A pilot study found an association between low back pain and the factors to be studied. Several allusions to the kinetic chain theory appear in the literature, but little prospective research has been done in examining the effects of lower extremity involvement on the back.

METHODS

Two-hundred fifty-seven college athletes representing nine varsity sports were screened during a preseason sports physical examination. Measures of flexibility, ligamentous stability, leg length discrepancy, and overuse syndromes were recorded. Athletes were observed throughout the ensuing year for low back pain requiring treatment by the athletic trainer. Those athletes with low back pain as the result of direct trauma to the region were excluded from the data.

RESULTS

Twenty-four athletes (9.3%) received treatment for low back pain. Thirteen of 87 women (15%) compared with 11 of 170 men (6%) required treatment for low back pain (P = 0.048). Of 57 athletes with lower extremity acquired laxity or overuse, low back pain developed in 14 (P < 0.001).

CONCLUSIONS

Athletes with lower extremity acquired ligamentous laxity or overuse may be at risk for the development of noncontact low back pain during athletic competition. Female athletes with lower extremity involvement appeared to have a higher incidence of low back pain treatment compared with their male counterparts. Inflexibility of the lower extremities or leg length discrepancy were not associated with future low back pain treatment.

Registration of cruciate ligament injuries in Norwegian top level team handball. A prospective study covering two seasons

All cruciate ligament injuries in the three upper divisions for men and women (3392 players) in Norwegian team handball in the 1989-90 and 1990-91 seasons were registered. A questionnaire was mailed to all injured players. Ninety-three cruciate ligament injuries were registered; 87 in the anterior cruciate ligament (ACL), and six in the posterior cruciate ligament (PCL). Among women, 1.8% were injured compared with 1.0% of the men. In the first division, the risk of being injured was considerably higher: 4.5% of the players had a cruciate ligament injury. There were 0.97 cruciate ligament injuries per 100 playing hours in the three divisions taken together. Seventy-five per cent of the injuries occurred during games. Ninety-five per cent involved no contact between players. Activities in which the friction between shoe and floor was significant caused 55% of the injuries. Injuries caused by running into another player contributed to only 5% of the injuries. No significant differences were observed in injury incidence during matches between different types of floors (parquet, Pulastic and other synthetic surfaces.)

A rigorous comparison between the sexes of results and complications after anterior cruciate ligament reconstruction

Although there is a higher relative incidence of anterior cruciate ligament injuries in female than in comparable male athletes according to the literature, the majority of populations studied after reconstruction are male-dominated. We wished to determine whether a selection bias for reconstruction based on sex is warranted according to complications and outcome. Ninety-four patients (47 of each sex) were matched for chronicity of injury, age, preoperative sports activity levels, articular cartilage condition, and months of followup. All had patellar tendon autogenous reconstruction and a similar program of immediate knee motion and early return to function. The results were rated with the Cincinnati Knee Rating System. At a mean of 26 months postoperatively, there were no significant differences for complications or outcome between men and women. Women required an average of six more rehabilitation visits than men; however, none required additional surgery for knee motion complications and the rate of patellofemoral crepitus conversion was only 7%, lower than that found for men (15%). The overall failure rate was low, only 6% for women and 4% for men. We concluded that the functional rehabilitation program was effective, postoperative complications were few, and no scientific basis exists to use sex alone as a selection criteria for anterior cruciate ligament reconstruction.

Changes in the flexibility characteristics of the ankle complex due to damage to the lateral collateral ligaments: an in vitro and in vivo study

This study was part of a long-term effort to develop a reliable diagnostic procedure for ankle ligament injuries. Earlier efforts led to the development and validation of a six-degrees-of-freedom instrumented linkage capable of measuring the flexibility characteristics of the ankle complex in vitro and in vivo. The major goal of the present study was to determine if these flexibility measurements are sufficiently sensitive to detect the presence of damage to the lateral collateral ligaments of the ankle joint both in vitro and in vivo. The in vitro testing was conducted on the legs from six fresh cadavers before and after serial sectioning of the anterior talofibular ligament and the calcaneofibular ligament. The flexibility in inversion-eversion, anterior drawer, and internal-external rotation was measured before and after resection of the ligaments. The in vivo testing was conducted on five patients with unilateral injuries to the ankle ligament. The flexibility evaluation used for in vitro specimens was also performed on both the injured and the intact ankles. For the in vitro testing, the data analysis was based on comparison of flexibility values before and after resection of the ligaments, whereas the data analysis for the in vivo testing was based on comparison of the flexibility of the injured joint with that of the intact contralateral joint. The results of the in vitro study indicated that both an isolated rupture of the anterior talofibular ligament and combined damage of the anterior talofibular and calcaneofibular ligaments produce statistically significant changes in flexibility. Furthermore, the most sensitive parameters to the presence of ligament injuries were found to be early flexibility in anterior drawer, early flexibility in inversion, and the amount of coupling between internal rotation and inversion. These parameters provided a basis for differentiating between an isolated injury to the anterior talofibular ligament and a combined anterior talofibular and calcaneofibular ligament injury. For an isolated anterior talofibular ligament injury, a significant increase in flexibility in anterior drawer was present, whereas the increase in inversion flexibility or in the amount of coupling was insignificant. However, the increases in inversion flexibility and the amount of coupling became significant when both ligaments were involved. The results of the in vivo study indicated that significant changes in flexibility can be detected in patients with lateral ankle injuries. Finally, both the in vitro and in vivo results suggest that development of a reliable diagnostic test for ankle ligament injury based on changes in passive flexibility may be possible.

Epidemiology of anterior cruciate ligament injuries in soccer

We did a retrospective study of all anterior cruciate ligament injuries (972) verified by arthroscopic evaluation at hospitals in the Hordaland region of Norway from 1982 to 1991. Our final study group comprised 176 patients who had participated in organized soccer and answered a questionnaire. The overall incidence rate was 0.063 injuries per 1000 game hours. Men incurred 75.6% (133) of the injuries. Women had an incidence rate of 0.10 injuries per 1000 game hours, significantly higher than that for men (0.057). The incidence rate was higher (0.41) for men in the top three divisions. Most of the injuries (124) occurred during games. Contact injuries from tackling was the injury mechanism in 46.0% of the cases. Players on the offensive team incurred 122 (69.3%) of the injuries. Reconstructive surgery was performed on 131 (74.4%) of the injured players and was found necessary for return to a high level of play. Half of the players (87) returned to soccer; men at high levels of play had the highest return rate (88.9%), and men over age 34 had the poorest return rate (22.9%). Nearly one-third of the injured athletes gave up soccer because of poor knee function or fear of new injury.

The effect of exercise, prewrap, and athletic tape on the maximal active and passive ankle resistance of ankle inversion

This investigation explored alternatives to the null hypotheses that maximal active and passive resistance to inversion developed by a near-maximally inverted and weightbearing ankle is not altered by 1) the use of prophylactic adhesive athletic tape, 2) the use of non-adhesive prewrap (underwrap), or 3) 40 minutes of vigorous exercise. Ten healthy men and 10 healthy women (mean age, 25 +/- 3 years) with no recent ankle injuries underwent testing to determine maximal ankle resistance to inversion under unipedal, weightbearing conditions. Tests were performed with and without the support of athletic tape, and before and after 40 minutes of exercise. Half the testing sessions were performed with prewrap under the tape. At 15 degrees of inversion, without any external ankle support, healthy young men and women could maximally resist a mean (SD) inversion moment of 52.9 (6.4) N-m and 28.3 (5.8) N-m, respectively. Although use of ankle tape provided a 10% increase in maximal resistance to inversion moments, this increase diminished to insignificant levels after 40 minutes of vigorous exercise. Use of prewrap improved maximal resistance to inversion by more than 10%.

Plyometric training in female athletes. Decreased impact forces and increased hamstring torques

The purpose of this study was to test the effect of a jump-training program on landing mechanics and lower extremity strength in female athletes involved in jumping sports. These parameters were compared before and after training with those of male athletes. The program was designed to decrease landing forces by teaching neuromuscular control of the lower limb during landing and to increase vertical jump height. After training, peak landing forces from a volleyball block jump decreased 22%, and knee adduction and abduction moments (medially and laterally directed torques) decreased approximately 50%. Multiple regression analysis revealed that these moments were significant predictors of peak landing forces. Female athletes demonstrated lower landing forces than male athletes and lower adduction and abduction moments after training. External knee extension moments (hamstring muscle-dominant) of male athletes were threefold higher than those of female athletes. Hamstring-to-quadriceps muscle peak torque ratios increased 26% on the nondominant side and 13% on the dominant side, correcting side-to-side imbalances. Hamstring muscle power increased 44% with training on the dominant side and 21% on the nondominant. Peak torque ratios of male athletes were significantly greater than those of untrained female athletes, but similar to those of trained females. Mean vertical jump height increased approximately 10%. This training may have a significant effect on knee stabilization and prevention of serious knee injury among female athletes.

Maximal contraction lessens impact response in a muscle contusion model

The effect of muscle contraction on a contusion injury model was studied in the gastrocnemius muscle of anesthetized rats. Both limbs of 18 rats received a contusion injury with a blunt non-penetrating impact. One hind limb was relaxed during impact and the other was electrically stimulated to tetanic contraction. The impact was produced using a drop-mass technique (mass = 171 g, height = 101 cm, spherical radius of impactor tip = 6.4 mm). The impact response was determined by sampling (10 kHz) the transmitted impact force and the displacement of the impactor. In a subgroup of nine rats, the severity of the contusion injury was measured by recording contractile tension in twitch and tetanus within two hours of injury. We found that the peak impact force was significantly less (p < 0.01), while the peak impact displacement was significantly greater (p < 0.01) in the contracted limb. Correspondingly, the impact stiffness of the contracted limb was significantly less (p < 0.01) than the impact stiffness in the relaxed limb. Both impacts produced significant injuries relative to an uninjured control group. The tetanic tension (31 +/- 4 N) generated by the muscles that were contracted during impact was significantly (p < 0.03) greater than that generated by the muscles that were relaxed during impact (27 +/- 4 N). The findings from this specific model indicate that the impact response of the limbs with relaxed muscle was dominated by the underlying bone, while maximally contracted muscle decreased the influence of the bone and lessened the impact response. Maximally contracted muscle was not more susceptible to injury and may act as protective mechanism against some impacts.

Injuries in elite volleyball

During the 1993-1994 volleyball season, injuries to players in the two Danish elite divisions were registered by means of a questionnaire survey. Eighty per cent of the players returned the questionnaire. A total of 70 female players reported 79 injuries and 67 male players reported 98 injuries, representing an overall incidence of 3.8 injuries per player per 1000 volleyball hours played. The injury incidence was the same for female and male players. Most injuries occurred in spiking (32%) and in blocking (28%). The injuries were predominantly either acute injuries to fingers (21%) and ankles (18%) or overuse injuries to shoulders (15%) and knees (16%). Shoulder injuries seemed to be a more serious problem in females. During the past 10 years the rate of overuse injuries has increased from 16% to 47% in male elite volleyball, corresponding to a significant increase in the incidence of these injuries from 0.5 to 1.8 injuries per player per 1000 played hours (P < 0.001). A possible explanation for this could be a 50% increase in training activity during this period.

Neuromuscular performance characteristics in elite female athletes

The purpose of this research was to identify possible predisposing neuromuscular factors for knee injuries, particularly anterior cruciate ligament tears in female athletes by investigating anterior knee laxity, lower extremity muscle strength, endurance, muscle reaction time, and muscle recruitment order in response to anterior tibial translation. We recruited four subject groups: elite female (N = 40) and male (N = 60) athletes and sex-matched nonathletic controls (N = 40). All participants underwent a subjective evaluation of knee function, arthrometer measurement of anterior tibial translation, isokinetic dynamometer strength and endurance tests at 60 and 240 deg/sec, and anterior tibial translation stress tests. Dynamic stress testing of muscles demonstrated less anterior tibial translation in the knees of the athletes (both men and women) compared with the nonathletic controls. Female athletes and controls demonstrated more anterior tibial laxity than their male counterparts and significantly less muscle strength and endurance. Compared with the male athletes, the female athletes took significantly longer to generate maximum hamstring muscle torque during isokinetic testing. Although no significant differences were found in either spinal or cortical muscle reaction times, the muscle recruitment order in some female athletes was markedly different. The female athletes appeared to rely more on their quadriceps muscles in response to anterior tibial translation; the three other test groups relied more on their hamstring muscles for initial knee stabilization.

Injuries in indoor soccer. The Lake Placid Dawn to Dark Soccer Tournament

We conducted a prospective study of soccer injuries during the Soccer America Dawn to Dark Indoor Soccer Tournament, which was organized by the Lake Placid Soccer Center, Lake Placid, New York, 1993. Eight hundred twenty-four players competed in open men's, open women's, over-30 men's, and mixed divisions. The overall rate of injury per 100 player hours was 4.44, with a rate of 5.79 in the open men's, 4.74 in the open women's, 2.73 in the over-30 men's, and 1.54 for the mixed divisions. The differences in injury rates for men versus women and men versus older men were not statistically significant. Twenty-five of the 38 injuries (65.8%) were mild, with 27 injuries (71.4%) occurring in the lower extremities. Ankle sprains were the most common injuries and combined ligamentous injuries to the knee were the most common severe injuries. As the injuries increased in severity, they were more likely to be noncontact injuries. The data demonstrate the low incidence of injury in male and female indoor soccer participants. The data also show the similarity in the types of injuries sustained by indoor and outdoor soccer players.

The incidence of ankle sprains in soccer

This study investigated the relationship between exposure time and ankle sprains in soccer. Forty-one teams (639 players) from four male senior soccer divisions at different levels of skill (divisions I-VI) were followed prospectively for 1 year. The exposure to soccer and the number of injuries per player were higher in higher divisions, but the injury incidence, percentage of ankle injuries and incidence of ankle injuries were the same at different levels of skill. Of all injuries 17 to 20% were ankle sprains and the incidence varied between 1.7 to 2.0 ankle injuries per 1,000 hours of exposure. Since players with previous ankle problems run an increased risk of reinjury we suggest that these players receive preventive advice.