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

Effect of COVID-19 on Injury Incidence and Severity in Professional Female Football Players: A Cohort Prospective Study

BACKGROUND

Earlier statements suggested a negative impact of coronavirus disease 2019 (COVID-19) infection on sports performance and injury risk. With the COVID-19 pandemic under control and the dominance of a less-severe strain of the virus, there is a need to confirm whether these adverse effects still apply to the current situation.

HYPOTHESIS

Infected players would have a higher noncontact muscle injury incidence compared with noninfected counterparts.

STUDY DESIGN

Cohort observational study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Seven teams (n = 147 players) competing in the Spanish professional women's football league (Liga F) were prospectively monitored during the 2021-2022 season. Data from noncontact injuries were recorded and classified following the latest consensus statement from the International Olympic Committee. COVID-19 was certified by the medical staff by regular polymerase chain reaction analysis.

RESULTS

Ninety-two players suffered at least 1 noncontact muscle injury during the season. Injury incidence during the season was similar in players with COVID-19 (n = 83) and players without infection (5.1 ± 6.7 versus 4.9 ± 10.0 injuries/1000 h of play, respectively; P = 0.90). Players with COVID-19 were not more likely to suffer noncontact injuries compared with those players without infection (R2 = 0.02; odds ratio [OR] 95% confidence interval [95% CI] = 0.36-1.38; P = 0.31). There was no effect of COVID-19 on the days of absence due to injury (R2 = 0.01; OR 95% CI = 1.00-1.01; P = 0.44) or in the classification of the severity of the injury (P = 0.79).

CONCLUSION

COVID-19 has no significant effect on noncontact injury incidence and severity in professional female football players.

CLINICAL RELEVANCE

Currently, COVID-19 infection does not alter noncontact muscle injury risk in professional football and requires no further attention in terms of injury management. Usual return-to-play protocols apply to COVID-19 considering the particularities of each player since the severity of infection, period of inactivity, and effects on the player's health and performance.

Is hip adductor or abductor strength in healthy athletes associated with future groin pain? A systematic review and meta-analysis

OBJECTIVE

To systematically review the association between hip adduction and abduction strength, and adduction-to-abduction strength ratio in healthy athletes with the occurrence of future groin pain and time-loss groin injuries.

DESIGN

Systematic review with meta-analysis.

DATA SOURCES

PubMed, Web of Science, SPORTDiscus, PEDro, Embase, and Scopus.

ELIGIBILITY CRITERIA

Studies included had to (1) measure hip adductor or abductor strength in healthy athletes, (2) conduct a follow-up period to assess the occurrence of groin pain, (3) present strength data separately for participants who remained uninjured and those who suffered an injury and (4) use a prospective design. Risk of bias was assessed according to the Quality in Prognosis Studies tool. The certainty in the evidence appraised was measured using the Grading of Recommendations Assessment Development and Evaluation approach.

RESULTS

Thirteen prospective cohort studies met the inclusion criteria. Overall study risk of bias was rated as low. Players who remained uninjured had stronger adduction strength compared with players who subsequently suffered groin pain (standardised mean differences with 95% CIs (SMD=-0.5, 95% CI -0.92 to -0.09)) and time-loss groin pain (SMD=-0.68, 95% CI -1.31 to -0.06). Trivial effects were observed for abduction strength (groin pain SMD=0.03, 95% CI -0.11 to 0.17; time-loss SMD=-0.07, 95% CI -0.25 to 0.11) and adduction-to-abduction strength ratio (groin pain SMD=-0.02, 95% CI -0.55 to 0.51; time-loss SMD=-0.11, 95% CI -1.11 to 0.89). Age and diagnostic criteria were not significant moderators of the relationship between adductor strength and groin pain (p=0.72 and p=0.12).

CONCLUSION

There is a moderate effect of hip adductor strength on the occurrence of groin pain, while there is no relationship between either abductor strength or the ratio of adductor-to-abductor strength with the occurrence of groin pain.

PROSPERO REGISTRATION NUMBER

CRD42024548630.

Hip adduction and abduction strength values in NCAA Division I American football players: Strength values and a comparison across position groups

OBJECTIVES

To report hip adduction, abduction, and adduction:abduction strength ratio values in NCAA Division I American football players, and to compare strength values across position groups.

DESIGN

Cross-sectional study.

SETTING

University training facility.

PARTICIPANTS

85 male football players.

MAIN OUTCOME MEASURES

Isometric hip adduction and abduction strength values in the 0° hip-flexion long-lever and 0° hip-flexion short-lever testing positions, using a ForceFrame.

RESULTS

Hip strength values are presented across two testing positions. ANOVA revealed significant differences (p ≤ 0.05) in hip strength between position groups, with medium-to-large effect size (n2 = 0.116-0.284). Skill-position and mid-position players demonstrated significantly greater hip adduction and abduction relative strength in both testing positions, when compared to lineman-position players. In addition, skill-position and mid-position players demonstrated significantly greater hip adduction:abduction strength ratios (0.19-0.20, 24-25%) in the long-lever testing position, when compared to lineman-position players, with large effect size (n2 = 0.178). No significant differences in strength were observed between skill-position and mid-position players. Hip adduction:abduction strength ratios ranged from 0.68 to 0.88 in the long-lever testing position and 1.05 to 1.09 in the short-lever testing position.

CONCLUSION

Significant differences in relative strength exist between position groups of NCAA Division-I football players, in hip adduction, abduction and adduction:abduction ratio.

A comparison of force generation in isometric hip adductor strength exercises: Introducing the weighted isometric Copenhagen Adduction exercise

OBJECTIVES

To compare maximal isometric force generation between hip adductor long-lever squeeze, the Copenhagen Adduction (CA) exercise with body-mass only, and the weighted isometric CA exercise, in rugby union players.

DESIGN

Cross-sectional study.

SETTING

Club training facility.

PARTICIPANTS

Forty-four male, rugby union players.

MAIN OUTCOME MEASURES

Maximum isometric hip adduction squeeze strength in the long-lever testing position, in addition to maximum isometric force data in the isometric CA exercise, and the weighted isometric CA exercise with increasing load.

RESULTS

Significantly greater (p ≤ 0.05) torque (Nm/kg) was observed in athletes when performing a weighted isometric CA exercise with: 105% body-mass (0.22Nm/kg, +6.8%), 110% body-mass (0.44Nm/kg, +13.1%), 120% body-mass (0.80Nm/kg, +22.6%), 130% body-mass (1.16Nm/kg, +31.3%), 140% body-mass (1.58Nm/kg, +40.8%) and 150% body mass (1.96Nm/kg, +48.3%), in comparison to the isometric CA exercise, with large effect size (ES = 1.372-5.196). Significantly greater torque was also observed when compared to the isometric hip adduction long-lever squeeze exercise, with large effect size (ES = 2.022-4.091). Twenty-nine athletes reached one maximum isometric repetition in weighted isometric CAs at either 130% body-mass (n = 16) or 140% body-mass (n = 13).

CONCLUSIONS

The weighted isometric Copenhagen Adduction exercise demonstrates greater force output than the isometric CA and the long-lever squeeze.

Hip Adduction and Abduction Strength Reference Values of Gaelic Football and Rugby Union Players: A Cross-Sectional Study

PURPOSE

The purpose of this research was to report isometric hip adduction and abduction strength reference values of men's and women's Gaelic football and rugby union players and compare values between sexes and between sports.

METHODS

This cross-sectional cohort study consisted of 331 club-level athletes. Maximum isometric hip adduction squeeze and abduction press strength values were measured with a ForceFrame across several testing positions.

RESULTS

Hip adduction squeeze and abduction press strength reference values for men's and women's Gaelic and rugby union footballers were provided with mean and 1 SD. A 2-way analysis of variance demonstrated significant sport × sex interaction main effects for hip adduction squeeze (η2 = .159-.228), abduction press (η2 = .099-.144), and adduction:abduction ratio (η2 = .120). Men demonstrated significantly greater relative (Newtons per kilogram) maximum isometric hip adduction squeeze (15.5%-26.4%, 0.48-1.00 N/kg) and hip abduction press (9.6%-19.6%, 0.20-0.67 N/kg) strength across all testing positions when compared with women of the same sport. Male Gaelic football players demonstrated significantly greater hip adduction (8.7%-14.0%, 0.30-0.52 N/kg) and abduction (6.1%-8.6%, 0.16-0.31 N/kg) strength (Newtons per kilogram) than their rugby counterparts, while no significant between-sports differences in strength were observed between female athletes.

CONCLUSION

Reference values are provided with mean and 1 SD. Sport and sex interaction had significant main effects for hip adduction, abduction, and adduction:abduction ratio, with medium to large effect sizes. Male athletes demonstrate significantly greater hip strength than female athletes of the same sport, and male Gaelic players demonstrate greater hip strength than male rugby players.

Deceleration Capacity During Directional Change as a Time-Efficient (Ecological) Prescreening of Hip Adductor Force Status in Amateur Soccer Players

ABSTRACT

Miralles-Iborra, A, Del Coso, J, De Los Ríos-Calonge, J, Elvira, JLL, Barbado, D, Urban, T, and Moreno-Pérez, V. Deceleration capacity during directional change as a time-efficient (ecological) prescreening of hip adductor force status in amateur soccer players. J Strength Cond Res 38(12): 2114-2120, 2024-Reduced isometric adductor muscle strength has been identified as a modifiable risk factor contributing to injury in soccer players. However, the measurement of hip adductor muscle strength is habitually laboratory-based, with isolated hip movements that do not reflect soccer-specific movements that induce groin injury during match play. This study aimed to determine the usefulness of deceleration capacity during a change of direction (COD) as a time-efficient (ecological) prescreening of hip adductor force status in soccer players. Nineteen amateur soccer players completed unilateral isometric hip adductor strength assessments and a 180° COD test. Isometric hip strength assessment included the maximum peak torque (PT) and maximum rate of torque development (RTDmax) relative to players' body mass. Players' deceleration capacity during the COD test was determined for each leg through maximum deceleration normalized to the linear momentum. A linear regression analysis was performed to associate isometric hip strength variables with the deceleration capacity during the COD test at each leg. There was not a statistically significant association between deceleration capacity and hip isometric maximum PT of the dominant and nondominant legs ( r ≤ 0.14, p > 0.05). Nevertheless, a moderate association was found between deceleration capacity and RTDmax for both legs ( r ≥ 0.58, p < 0.05). The optimal linear regression model suggests that measuring deceleration capacity during a directional change test could explain RTDmax by 33 and 43% for the dominant and nondominant legs, respectively. During a 180° COD test, the deceleration capacity captured through GPS-accelerometer device was limited as a prescreening tool to evaluate hip adductor force status in soccer players.

Monitoring hip adductor strength in professional women's football players over a season: A prospective study

OBJECTIVES

To describe the changes in hip adductor strength of professional women's football players over a season.

DESIGN

One-season prospective study.

SETTING

Facilities of a national first division club.

PARTICIPANTS

Professional women's football players.

MAIN OUTCOME MEASURES

Maximum hip adductor isometric strength in the long-lever and short-lever positions at four timepoints: early preseason, early season, mid-season, and end-season.

RESULTS

Twenty-two players completed the study. Hip adductor strength values in early preseason (134 ± 29 N in the long-lever position and 317 ± 68 N in the short-lever position) were significantly lower than in the early season (171 ± 29 N and 363 ± 54 N) and mid-season (163 ± 23 N and 369 ± 53 N). By the end of the season (150 ± 19 N and 345 ± 39 N), strength values had significantly declined from both early and mid-season levels. Visual inspection of individual athletes' strength evolution over time reveals heterogeneous responses, with some players showing trajectories opposite to the group at specific time points.

CONCLUSIONS

Hip adductor strength increased from the preseason to the start of the women's football national league, remained stable during the first half of the league, but slightly declined in the second half. The heterogeneous responses among athletes underscore the importance of individualized monitoring throughout the season.

Hip adduction and abduction strength values in elite-level male and female youth soccer players: A comparison between sexes, and across age-groups

OBJECTIVES

To report isometric hip adduction squeeze and abduction press strength values of elite-level youth male and female soccer players and examine if differences exist between sexes, and age-groups.

DESIGN

Cross-sectional cohort study.

SETTING

Elite youth soccer academy.

PARTICIPANTS

102 soccer players (n = 64; male, n = 38 female) competing in the national youth soccer leagues from under (U) 14-19 years of age level (U-14, U-15, U-17, U-19).

MAIN OUTCOME MEASURES

Isometric hip adduction and abduction strength values were measured with a ForceFrame in various testing positions.

RESULTS

Isometric hip adduction and abduction strength values are presented. Male U-17 and U-19 players demonstrated significantly greater (p < 0.05) absolute(N) and relative (N/kg) hip adduction and abduction strength than their female counterparts, with large (η2 = 0.068-0.227) and medium-to-large (η2 = 0.049-0.234) effect size, respectively. Significant differences in absolute strength, but not relative strength, were observed for hip adduction and abduction between male age-groups (U-14, U-15, U-17, U-19), with hip abduction strength differences only existing between U-14 and U-17 groups. No significant differences in hip strength were observed between U-17 and U-19 groups for female players.

CONCLUSION

Male youth soccer players have higher absolute and relative hip adduction and abduction strength than females at the U-17 and U-19 level.

Non-contact lower limb injuries in Rugby Union: A two-year pattern recognition analysis of injury risk factors

The cause of sport injuries are multifactorial and necessitate sophisticated statistical approaches for accurate identification of risk factors predisposing athletes to injury. Pattern recognition analyses have been adopted across sporting disciplines due to their ability to account for repeated measures and non-linear interactions of datasets, however there are limited examples of their use in injury risk prediction. This study incorporated two-years of rigorous monitoring of athletes with 1740 individual weekly data points across domains of training load, performance testing, musculoskeletal screening, and injury history parameters, to be one of the first to employ a pattern recognition approach to predict the risk factors of specific non-contact lower limb injuries in Rugby Union. Predictive models (injured vs. non-injured) were generated for non-contact lower limb, non-contact ankle, and severe non-contact injuries using Bayesian pattern recognition from a pool of 36 Senior Academy Rugby Union athletes. Predictors for non-contact lower limb injuries included dorsiflexion angle, adductor strength, and previous injury history (area under the receiver operating characteristic (ROC) = 0.70) Dorsiflexion angle parameters were also predictive of non-contact ankle injuries, along with slower sprint times, greater body mass, previous concussion, and previous ankle injury (ROC = 0.76). Predictors of severe non-contact lower limb injuries included greater differences in mean training load, slower sprint times, reduced hamstring and adductor strength, reduced dorsiflexion angle, greater perceived muscle soreness, and playing as a forward (ROC = 0.72). The identification of specific injury risk factors and useable thresholds for non-contact injury risk detection in sport holds great potential for coaches and medical staff to modify training prescriptions and inform injury prevention strategies, ultimately increasing player availability, a key indicator of team success.

Assessment of Strength and Power Capacities in Elite Male Soccer: A Systematic Review of Test Protocols Used in Practice and Research

BACKGROUND

Strength and power represent two crucial physical qualities for the attainment of a high level of performance considering the frequency and the importance of explosive actions occurring during elite soccer match-play. Evaluation of strength and power is a multifaceted concept involving a vast array of tests and outcome variables. Nevertheless, a comprehensive and systematic search of strength and power assessment procedures in elite soccer has yet to be undertaken.

OBJECTIVES

The aims of this systematic review were to: (1) identify the tests and outcome variables used to assess strength and power of elite male soccer players; (2) provide normative values for the most common tests of strength and power across different playing levels; and (3) report the reliability values of these strength and power tests.

METHODS

A systematic review of the academic databases MEDLINE, CINAHL, SPORTDiscus, Web of Science and OVID for studies published until August 2023 was conducted, following the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were eligible for inclusion if they: (1) were original research studies, published in a peer-reviewed journal, and written in English language; (2) had the primary aim to assess strength and/or power; (3) players were male and older than 17 years of age (i.e., mean age of the group); and (4) their playing level was defined as "professional", "international" or "elite".

RESULTS

Regarding strength testing, 115 studies and 29 different tests were identified. The three most frequent strength tests were the knee extensor isokinetic strength test (58 studies), the knee flexor isokinetic strength test (55 studies) and the Nordic hamstring strength test (13 studies). In terms of power testing, 127 studies with 31 different tests were included. The three most frequent power tests were the countermovement jump with hands fixed on hips (99 studies), the squat jump (48 studies) and the vertical jump with arm swing (29 studies).

CONCLUSIONS

The wide range of different tests and outcome variables identified in this systematic review highlights the large diversity in the employed testing procedures. The establishment of a hybrid testing approach, combining standardised and widely accepted tests for establishing normative standards and enabling comparisons across different contexts, with flexible context-specific testing batteries, has the potential to maximise the impact of testing information for practitioners. In addition, the limited reporting of reliability data across studies highlights the need for practitioners to establish their own reliability measure within their specific contexts, informing the selection of certain tests and outcome variables.

Association between Hip/Groin Pain and Hip ROM and Strength in Elite Female Soccer Players

Background/Objectives: Hip strength and range of motion have been compared in soccer players with and without hip and groin pain but only in male footballers or gender-combined samples. In female soccer players, the biomechanics contributing to this injury remain poorly understood compared to other sporting injuries. The aim of the present study is to investigate whether differences exist in adductor and abductor isometric test values and hip joint range of motion between elite female soccer players with longstanding groin pain and injury-free controls. Methods: Ten female elite soccer players with current longstanding hip and groin pain and twenty-five injury-free controls from the same teams were included in the study. Hip adductor and abductor isometric strength were evaluated with a hand-held dynamometer. A bent knee fall-out test was also utilized to examine the hip joint range of motion. Results: A significant difference in abductor isometric test values was observed between the control group (2.29 ± 0.53 N/Kg) and the hip and groin pain group (2.77 ± 0.48 N/Kg; p = 0.018). Furthermore, the injured group showed a decreased adductor/abductor ratio compared to the control group (1.00 ± 0.33 vs. 1.27 ± 0.26; p = 0.013). No differences were observed in the bent knee fall-out test (p = 0.285). Conclusions: Female elite soccer players with current longstanding hip and groin pain exhibited higher abductor isometric strength and lower adductor/abductor ratio compared to non-injured women players. There were no differences in the BKFO test between groups.

Testing in Intermittent Sports-Importance for Training and Performance Optimization in Adult Athletes

ABSTRACT

Performance in intermittent sports relies on the interplay between multiple physiological systems determining the capacity to perform short explosive efforts as well as repeated intense actions with limited recovery over the course of an entire game. Testing should reflect these demands to allow for sport- and position-specific capacity analyses that eventually may translate into optimized training and improved performance. This may include individual load management and optimized training prescription, intensity targeting for specific positions or individual athletes, as well as benchmarking for monitoring of training progression and enhanced engagement of athletes. This review provides an overview of available tests in different exercise domains identified as relevant (from assessment of single explosive actions to intermittent endurance capacity), forming the basis for recommendations on how to compose a comprehensive yet feasible test battery that may be integrated into the seasonal competition and training plan. The test procedures should cover the performance spectrum of relevance for the individual athlete-also in team sports to account for positional differences. We emphasize the benefits of sport-specific tests, highlight parameters of importance for test standardization, and discuss how the applied test battery may be supplemented with secondary tests directed toward specific energy systems to allow for more in-depth analyses when required (e.g., in terms of an underperforming athlete). The synergy between testing and tracking of match performance (utilizing time-motion or global positioning systems) is highlighted, and although tracking cannot substitute for testing, combining the tools may provide a comprehensive overview of the physiological demands and performance during competition contextualized to the athletes' maximal exercise capacity.

Acute Effects of Ice Hockey on Hip Range of Motion, Strength, and Pelvic Tilt in Competitive Male Players

BACKGROUND

Ice hockey players are at high risk for hip and groin injury. Several risk factors have been identified or proposed, including lower hip rotation range of motion (ROM), lower hip adductor strength, lower ratio of hip adductor to abductor strength, and lower pelvic tilt angle. It is not known how these risk factors change acutely with ice hockey participation.

HYPOTHESIS

Acute exposure to ice hockey will result in a reduction in ROM, strength, and pelvic tilt angle in competitive male players.

STUDY DESIGN

Controlled cohort study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Risk factors for hip and groin injury, including isometric hip adductor strength at 0° of flexion, the ratio of hip adductor to abductor strength, total hip rotation passive ROM in supine, and the resting pelvic tilt angle, were assessed immediately before, immediately after, and 24 hours after an ice hockey exposure in 42 competitive male ice hockey players. Rating of perceived exertion (RPE) was collected to identify the intensity of the exposure.

RESULTS

There was a significant decrease in total hip rotation ROM (-7.32°, P < 0.01 (-3.91, -10.70)) and hip adductor strength (-4.41 kg, P < 0.01 (-2.81, -6.00) immediately after the exposure, and a significant decrease in total hip rotation ROM (-18.54°, P < 0.01 (-14.35, -22.73)), hip adductor strength (-6.56 kg, P < 0.01 (-4.58, -8.61)), and the ratio of hip adductor to abductor strength (-0.12, P < 0.01 (-0.21, -0.45)) 24 hours after. There was no significant change in pelvic tilt found in this study immediately after or 24 hours after. There was a moderate relationship between changes in hip adductor strength and changes in the ratio of hip adductor to abductor strength (r = 0.433, P < 0.01). RPE was not significantly correlated to any of the changes observed.

CONCLUSION

Risk factors for hip and groin injury in ice hockey players are modifiable after a single ice hockey exposure.

CLINICAL RELEVANCE

The identified fluctuation of injury risk factors for hip and groin injury in ice hockey players has implications for injury risk profiling, rehabilitation, and return-to-competition decision-making.

A survey into the current fitness testing practices of elite male soccer practitioners: from assessment to communicating results

This study provides insight into the current fitness testing practices in elite male soccer. One hundred and two practitioners from professional soccer leagues across 24 countries completed an online survey comprising 29 questions, with five sections: a) background information, b) testing selection, c) testing implementation, d) data analysis, and e) data reporting. Frequency analysis was used to evaluate the responses to fixed response questions and thematic analysis was used for open-ended questions to generate clear and distinct themes. Strength (85%) and aerobic capacity (82%) represent the most frequently assessed physical qualities. Scientific literature (80%) is the most influential factor in testing selection and practitioners conduct fitness testing less frequently than their perceived ideal frequency per season (3.6 ± 2 vs. 4.5 ± 2). Time and competitive schedule were the greatest barriers to fitness testing administration. Practitioners mostly used a 'hybrid' approach (45%) to fitness testing, blending 'traditional' (i.e., a day dedicated to testing) and 'integrated' (i.e., testing within regular training sessions) methods. Microsoft Excel is the most used software for data analysis (95%) and visualization (79%). An equal use of the combination of best and mean scores of multiple trials (44%) and the best score (42%) was reported. Comparing a player's test performance with previous scores (89%) was the most common method for interpreting test results. However, only 38% considered measurement error. Digital displays and verbal feedback are the most common data reporting methods, with different data reporting processes for coaches and players. Practitioners can use data and findings from this study to inform their current testing practices and researchers to further identify areas for investigation, with the overarching aim of developing the field of fitness testing in elite male soccer.

Hip adduction and abduction strength profiles in elite and sub-elite female soccer players according to players level and leg limb-dominance

BACKGROUND

Understanding the hip adduction and abduction strength in female soccer players is crucial for performance enhancement and injury prevention. This study compares the strength profiles in these muscle groups between elite and sub-elite female soccer players and assesses the impact of leg limb-dominance.

METHODS

A descriptive-comparative study was employed. Eighty-two female soccer players were evaluated. Isometric hip-adduction and abduction strength were measured using a handheld dynamometer.

RESULTS

Female elite and sub-elite soccer players displayed a mean and standard deviation (SD) on isometric hip-adductor strength for dominant (3.19 Nm/kg ± 0.69 vs. 2.40 Nm/kg ± 0.67) and non-dominant leg (3.32 Nm/kg ± 0.76 versus 2.42 Nm/kg ± 0.70), respectively. For isometric hip-abductor strength in elite and sub-elite players, a mean and SD of dominant (2.86 Nm/kg ± 0.56 vs. 2.07 Nm/kg ± 0.50) and non-dominant (2.80 Nm/kg ± 0.59 vs. 2.04 Nm/kg ± 0.43). In essence, elite players were stronger than sub-elite players on isometric hip-adduction (mean difference [MD] = 0.82 Nm/kg, CI95% = 0.42-1.12) and abduction (MD = 0.83 Nm/kg, CI95% = 0.54- 1.12) both in dominant and non-dominant, leg, whereas no differences existed for hip adduction:abduction ratios between groups and legs.

CONCLUSIONS

Elite female athletes exhibited greater strength than sub-elite female players in both hip adduction and abduction, whereas adduction:abduction ratio values did not differ between the two groups or between different legs.

Inter- and intra-session variability of compression strain gauge for the adductor groin squeeze test on soccer athletes

The importance of hip adductor strength for injury prevention and performance benefits is well documented. The purpose of this study was to establish the intra- and inter-day variability of peak force (PF) of a groin squeeze protocol using a custom-designed compression strain gauge device. Sixteen semi-professional soccer players completed three trials over three separate testing occasions with at least 24-h rest between each session. The main findings were that the compression strain gauge was a reliable device for measuring PF within and between days. All intraclass correlations were higher than 0.80 and coefficients of variations were below 10% across the different sessions and trials. Due to the information gained through the compression strain gauge, the higher sampling frequency utilized, portability, and the relatively affordable price, this device offers an effective alternative for measuring maximal strength for hip adduction.

Acute Adductor Muscle Injury: A Systematic Review on Diagnostic Imaging, Treatment, and Prevention

BACKGROUND

Controversies remain regarding the diagnosis, imaging, and treatment of acute adductor injuries in athletes.

PURPOSE

To investigate the diagnostic imaging, treatment, and prevention of acute adductor injuries based on the most recent and relevant scientific evidence.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

The PubMed and Web of Science databases were searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to identify articles studying acute adductor injury in athletes. Inclusion criteria were original publication on acute adductor injury in amateur or professional athletes, level 1 to 4 evidence, mean patient age >15 years, and results presented as return-to-sport, pain, or functional outcomes. Quality assessment was performed with the CONSORT (Consolidated Standards of Reporting Trials) statement or the methodological index for non-randomized studies criteria. Articles were grouped as imaging, treatment, prevention focused, or mixed.

RESULTS

A total of 30 studies published between 2001 and 2021 were selected, involving 594 male patients with a mean age 26.2 years (range, 16-68 years). The most frequent sports were soccer (62%), basketball (14%), futsal (6%), American football (3%), and ice hockey and handball (2%). Risk factors for acute adductor injury were previous acute groin injury, adductor weakness compared with the uninjured side, any injury in the previous season, and reduced rotational hip range of motion. The frequency of complete adductor muscle tears on magnetic resonance imaging was 21% to 25%. For complete adductor tears, the average time to return to play was 8.9 weeks in patients treated nonoperatively and 14.2 weeks for patients treated surgically. Greater stump retraction was observed in individuals treated surgically. Partial acute adductor tears were treated nonoperatively with physical therapy in all studies in the present systematic review. The average time to return to play was 1 to 6.9 weeks depending on the injury grade. The efficacy of adductor strengthening on preventing acute adductor tears has controversial results in the literature.

CONCLUSION

Athletes with partial adductor injuries returned to play 1 to 7 weeks after injury with physical therapy treatment. Nonoperative or surgical treatment is an acceptable option for complete adductor longus tendon tear.

Application of a Custom Device to Measure Isometric Knee Strength: Possible Injury Correlation in Professional Soccer (Football) Players

Injury in sports is an occurrence that prevents athletes from participating in training and competitions and has an incidence of 8.1 injuries/1000 h of practice. This translates into a cost and also into danger, especially if the event is repeated, for the health of the athlete; the injury certainly has a multifactorial causality. On the other hand, having instruments that can represent an alarm could be helpful for those involved in sports science. We used a specifically designed instrument, presented in a previous work, which shows excellent reliability and repeatability in measuring the strength of the knee flexors and extensors to test 107 players belonging to three different teams playing in the Italian Serie A. We took three measurements, beginning of the season, mid-season, and close to the end of the season. This retrospective study on 107 professional soccer players demonstrates that isometric force-related parameters of the knee extensors and flexors are associated with the risk of injury to lower limbs. Logistic regression evidenced a significant correlation between the parameter indicating the imbalance of the force between the flexors of the two limbs (p≤0.05, OR = 1.089) and the occurrence of injuries. Survival analyses (p≤0.001) evidenced a correlation between the population survival time and the injury incidence. We demonstrated that the analysis of the strength imbalance is correlated with injury occurrence, but it is well known that sports injuries are a multifactorial event; so, they cannot be predicted by only one parameter. However, the method proposed in this paper could represent a useful tool for sport scientists.

[Groin pain in sports games: a systematic review]

BACKGROUND

In sports games, epidemiological data show that groin pain is relatively common and can lead to repeated loss of time. Consequently, it is essential to be aware of the evidence-based prevention strategies. The aim of this systematic review was to examine risk factors and prevention strategies for groin pain and to rank them based on their evidence in sports games.

METHODS

The review was conducted according to the PRISMA guidelines, using a PICO-scheme in the PubMed, Web of Science and SPOLIT databases. We included all available intervention and observational studies on the influence of risk factors and prevention strategies on groin pain in sports games. The methodological quality and level of evidence was assessed using the PEDro-Scale and OCEBM model, respectively. Finally, the quantity, quality and level of evidence was used to rank each risk factor for its grade.

RESULTS

Moderate evidence was found for four risk factors that significantly influence the risk of groin pain: male sex, previous groin pain, hip adductor strength and not participating in the FIFA 11+ Kids. Moreover, moderate evidence was found for the following non-significant risk factors: older age, body height and weight, higher BMI, body fat percentage, playing position, leg dominance, training exposure, reduced hip abduction, adduction, extension, flexion, and internal rotation-ROM, hip flexor strength, hip abductor, adductor, flexor and core strengthening with balance exercises, clinical hip mobility tests and physical capacities.

CONCLUSION

The identified risk factors can be considered when developing prevention strategies to reduce the risk of groin pain in sports games. Thereby, not only the significant, but also the non-significant risk factors should be considered for prioritisation.

Weekly screening of youth male football players: a 14-week longitudinal investigation of interactions between groin pain and long lever adductor squeeze strength

OBJECTIVES

To explore relationships between groin pain and adductor squeeze strength in male academy football players over a 14-week period.

DESIGN

Longitudinal cohort study.

METHODS

Weekly monitoring of youth male football players consisted of reporting groin pain and testing long lever adductor squeeze strength. Players who reported groin pain at any time during the study period were stratified into the "groin pain" group while players who did not report pain remained in the "no groin pain" group. Baseline squeeze strength was retrospectively compared between groups. Players that developed groin pain were examined via repeated measures ANOVA at four timepoints: baseline, last squeeze before pain, pain onset, and return to pain-free.

RESULTS

53 players were included (age 14.4 ± 1.6 years). Baseline squeeze strength was not different between players in the "groin pain" (n = 29, 4.35 ± 0.89 N/kg) versus "no groin pain" group (n = 24, 4.33 ± 0.90 N/kg, p = 0.83). At a group level, players with no groin pain maintained similar adductor squeeze strength throughout 14 weeks (p > 0.05). Compared to baseline (4.33 ± 0.90 N/kg), players with groin pain had decreased adductor squeeze strength at the last squeeze before pain (3.91 ± 0.85 N/kg, p = 0.003) and at pain onset (3.58 ± 0.78 N/kg, p < 0.001). Adductor squeeze strength at the point where pain subsided (4.06 ± 0.95 N/kg) was not different from baseline (p = 0.14).

CONCLUSIONS

Decreases in adductor squeeze strength manifest one-week prior to groin pain onset and further decrease at pain onset. Weekly adductor squeeze strength may be an early detector for groin pain in youth male football players.

Reliability and validity of common hip adduction strength measures: The ForceFrame strength testing system versus the sphygmomanometer

OBJECTIVES

The criterion validity of the sphygmomanometer was evaluated, relative to the Force Frame strength testing system. Test-retest reliability was assessed for both hip adduction and abduction strength.

DESIGN

Test-retest reliability study and criterion validity study.

PARTICIPANTS

50 asymptomatic, field-sport athletes.

MAIN OUTCOME MEASURES

Maximal isometric hip adduction and abduction strength were measured. Interclass correlation coefficient(ICC_2,1) with confidence intervals were calculated to evaluate reliability of peak strength values. A Pearson product-moment correlation coefficient(r) was calculated to examine criterion validity of the sphygmomanometer as a measure of force when compared to the ForceFrame.

RESULTS

Intra-rater reliability for bilateral adduction testing using both ForceFrame and sphygmomanometer values revealed good-excellent reliability for both the 0° (ICC_2.1 = 0.87-0.90) and 45° (ICC_2.1 = 0.81-0.91) positions. ForceFrame values revealed good-excellent reliability for 0° abduction position and 45° abduction position. A good-moderate relationship (Pearson's r = 0.63) for 0° adduction position, and poor relationship (Pearson's r = 0.40) for 45° adduction position, were found between adduction squeeze values on ForceFrame and sphygmomanometer.

CONCLUSION

Excellent reliability in hip adduction squeeze strength testing for both modes. However, there exists a 'good to moderate'-'fair' relationship between the Force Frame and sphygmomanometer.

Strength and Power Performance Changes During an In-Season Resistance Training Program in Elite Futsal Players: A Case Study

In this study, we aimed to analyze (i) the strength and power changes after resistance training (RT) in elite futsal players, and (ii) the associations between the session rate of perceived exertion (sRPE) and perceived total quality recovery (TQR), and the sRPE and TQR with the volume load of the RT program. Ten elite futsal players (24.8 ± 5.4 years; 76.2 ± 7.1 kg; 1.77 ± 0.05 m) performed an in-season 8-week RT program twice per week. RT consisted of 2-3 sets x 3-6 reps at 45-65% of one-repetition maximum (1RM) with maximal velocities in the full squat and complementary exercises with the same volume. We assessed the TQR before every session, while the sRPE was calculated after each RT session. One week before and after the intervention, we measured the countermovement jump (CMJ) height, isometric hip adduction strength (IHAS), 1RM, and peak power (PP) in the full squat progressive loading test. After the 8-week training program, there was a significant improvement in most outcomes, yet the gains (%Δ) remained below the minimal detectable change (MDC), except for IHAS (CMJ: p < 0.05, %Δ = 6.7, MDC% = 7.2; IHAS: p < 0.001, %Δ = 19.1, MDC% = 14.6; 1RM: p > 0.05, %Δ = 9.2, MDC% = 21.5; PP: p < 0.05; %Δ = 14.4, MDC% = 22.4). We also found a significant negative correlation between TQR and the sRPE (r = -0.45, p < 0.001). Our data suggest that RT based on low-volume and low-to-moderate loads may not produce a sufficient stimulus to induce meaningful dynamic strength and power gains in elite futsal players, although it improves isometric strength. Furthermore, monitoring TQR before sessions may show coaches how the elite futsal player will perceive the session's intensity.

Hip adduction and abduction strength in youth male soccer and basketball players with and without groin pain in the past year

The objectives of this study were to 1) assess the differences between youth soccer and basketball players with and without past year groin pain (GP) in hip adduction and abduction strength and several training characteristics (age at the start of regular training, weekly training frequency, warm-up and training duration, use of stretching and/or stabilisation exercises during warm-up, use of resistance training); 2) present strength reference values for youth soccer and basketball players. 227 players participated (age 16.9 ± 1.4 years; height 184.2 ± 8.5 cm; mass 75.5 ± 11.9 kg). Hip adduction and abduction strength was measured in supine position (hip, knee and ankle in neutral position) using a MuscleBoard dynamometer. Interlimb asymmetries and hip adduction:abduction ratios were calculated. Past year GP and training characteristics were assessed with a retrospective questionnaire. 11.9% of players reported past year GP (16.9% in soccer and 6.4% in basketball). The only significant difference between the past year GP and the control groups was found in the age of the players at the start of regular training (7.2 ± 1.8 years for the GP group vs. 8.5 ± 2.6 years for the control group). Additionally, soccer players without past year GP have significantly higher hip adduction strength (1.1 ± 0.2 Nm/kg vs. 1.0 ± 0.2 Nm/kg) and adduction:abduction strength ratio (1.10 ± 0.18 vs. 1.03 ± 0.16) compared to basketball players. Our results show that hip adduction and abduction strength, interlimb asymmetry and hip adduction:abduction ratio do not differentiate between players with and without past year GP (p = 0.29-0.90), which means that their adduction or abduction strength can be analysed regardless of the GP presence in the past year. Additionally, players with past year GP started regularly training at significantly lower age, which could indicate the problematic nature of early/premature sports specialisation.

Etiology and Recovery of Neuromuscular Function Following Academy Soccer Training

Aim: To profile the etiology and recovery time-course of neuromuscular function in response to a mixed-content, standard training week in professional academy soccer players. We concurrently examined physical performance, cognitive function, and perceptual measures of mood and wellness states to identify a range of simple tests applied practitioners could use in the field as surrogate measures of neuromuscular function.

Methods: Sixteen professional academy soccer players completed a range of neuromuscular, physical, perceptual, mood, and cognitive function tests at baseline and after a strenuous training day (pitch and gym), with retest at 24, 48, and 72 h, and further pitch and gym sessions after 48 h post-baseline. Maximal voluntary contraction force (MVC) and twitch responses to electrical stimulation (femoral nerve) during isometric knee-extensor contractions and at rest were measured to assess central nervous system (voluntary activation, VA) and muscle contractile (potentiated twitch force, Q_tw,pot) function.

Results: Strenuous training elicited decrements in MVC force post-session (−11%, p = 0.001) that remained unresolved at 72 h (−6%, p = 0.03). Voluntary activation (motor nerve stimulation) was reduced immediately post-training only (−4%, p = 0.03). No change in muscle contractile function (Q_tw,pot) was observed post-training, though was reduced at 24 h (−13%, p = 0.01), and had not fully recovered 72 h after (−9%, p = 0.03). Perceptions of wellness were impaired post-training, and recovered by 24 h (sleepiness, energy) and 48 h (fatigue, muscle soreness, readiness to train). Countermovement jump performance declined at 24 h, while RSI (Reactive Strength Index) decrements persisted at 48 h. No changes were evident in adductor squeeze, mood, or cognitive function.

Conclusion: Elite youth soccer training elicits substantial decrements in neuromuscular function, which are still present 72 h post-strenuous exercise. Though central processes contribute to post-exercise neuromuscular alterations, the magnitude and prolonged presence of impairments in contractile function indicates it is the restitution of muscular function (peripheral mechanisms) that explains recovery from strenuous training in academy soccer players.

Validity and Reliability of the Smart Groin Trainer for Measuring Hip Adduction Strength

We analyzed the Smart Groin Trainer device's validity and reliability to measure the isometric hip adduction strength during the adductor squeeze strength test. Fifteen professional soccer players (25.33±4.06 years) and fifteen university students (21.60±1.76 years) participated in this study. All participants performed the squeeze strength test using two portable dynamometers: Smart Groin Trainer and Globus Ergometer. Three maximal isometric hip adduction contractions lasting 5s, interspersed by 3min rest intervals, were performed. Reliability was analyzed with intraclass correlation coefficients, standard error of measurements, and minimal detectable change. The absolute percent error and inter-device accuracy were also analyzed. Correlation analysis assessed the inter-device concurrent validity. The results found no significant differences (p>0.05) between devices in the squeeze strength test values in soccer players and university students. Inter-device comparisons revealed excellent levels of reliability and accuracy in soccer players. Concurrent validity measures revealed strong inter-device relationships in soccer players (r=0.89) and very strong relationships in university students (r=0.99). Intra-device analysis using the Smart Groin Trainer showed excellent relative and absolute reliability in tested soccer players. Our data demonstrated excellent levels of agreement between both dynamometers during the squeeze strength test, suggesting the Smart Groin Trainer as a valid, reliable, and accurate device to measure isometric hip adduction strength.

Knee and hip agonist-antagonist relationship in male under-19 soccer players

The purpose of this study was to evaluate the strength of the knee flexors and extensors and hip abductor and adductor muscles in young soccer players. Twenty-three male under-19 soccer players participated in this study (age: 17.7 ± 0.2 years; height: 173.0 ± 1.1 cm; body mass: 66.1 ± 1.3 kg). Body composition was measured using a bioelectrical impedance (InBody770), and the dynamometry was performed by an isokinetic dynamometer (Biodex System 3) for knee flexion and extension, and by an isometric dynamometer (Smart Groin Trainer), for hip adduction and abduction. Comparisons were made between dominant members (D) vs. non-dominant members (ND) and adductors vs. abductors (ADD:ABD) using the Wilcoxon test. There were statistically significant differences in the peak torques between the dominant and non-dominant members in the flexion function (Z = −4.198, p < 0.01) and in the extension function (Z = −4.197, p < 0.01) of the knee in concentric muscular action, and the flexion (Z = −4.198, p < 0.01) and in the extension (Z = −4.198, p < 0.01) of the knee in eccentric muscular action. No statistically significant differences were obtained in the conventional ratio (Z = −0.456, p = 0.648) nor the functional ratio (Z = −0.335, p = 0.738) between D and ND members. There were no statistically significant differences between adductors and abductors at the moment of strength for absolute values (N). The reference absolute and normalized to the weight values and the ADD:ABD can be used as a guideline for classifying players in screening and comparison in return tests to sports practice after an injury.

Effects of consecutive days of matchplay on maximal hip abductor and adductor strength in female field hockey players

Background

The purpose of this study was to examine the effects of two competitive field hockey matches, played on consecutive days, on maximal isometric hip adductor and abductor strength, wellness and fatigue.

Methods

Fourteen professional female field hockey players (age: 20.4 ± 5.4 years; body mass: 60.7 ± 7.2 kg; height: 167.0 ± 1.0 cm) volunteered to participate in this investigation. Maximal isometric hip adductor and abductor strength were obtained before (pre-match 1) and after the first match (post-match 1), after the second match (post-match 2), and 48 h after the second match. Locomotion patterns during the matches were obtained with portable Global Positioning System (GPS) and perceived exertion (RPE) was assessed after each match. In addition, Wellness Questionnaire (5-WQ) and the Total Quality Recovery Scale (TQR) were employed before the matches and 48 h after the second match.

Results

For the non-dominant limb, the maximal isometric hip adductor and abductor strength were lower after post-match 2 when compared to pre-match 1 (p = 0.011). Hip abductor strength in the non-dominant limb remained reduced 48 h after post-match 2 (p < 0.001). There were no differences in the total distance covered when comparing match 1 and match 2. Players reported more acute fatigue (5-WQ, p = 0.009) and increased muscle soreness on pre-match 2 compared to pre-match 1 (p = 0.015), while fatigue returned to pre-competition levels 48 h after post-match 2 (p = 0.027). No changes were observed in the TQR.

Conclusion

The assessment of maximal adductor and abductor strength before and after competitive matches, in addition to evaluating self-perceived fatigue by a wellness questionnaire can help to identify field hockey players with excessive fatigue responses during tournaments with a congested match program.

Factors Associated with Hip and Groin Pain in Elite Youth Football Players: A Cohort Study

BACKGROUND

Despite hip and groin pain being commonly reported in elite youth football players, little evidence on risk factors exists. Risk factors in adult football players include reduced hip adductor strength and hip adductor/abductor strength ratios, and lower Copenhagen Hip and Groin Outcome Score (HAGOS) subscale scores. It is unknown if these factors are also predictive of pain development in youth football players.

OBJECTIVE

To identify whether preseason hip adductor and abductor strength and HAGOS subscale scores of male and female elite youth football players are associated with in-season or historical (lifetime) hip and groin pain.

METHODS

Preseason hip adductor and abductor strength testing and the HAGOS were undertaken by 105 elite male (n = 58) and female (n = 47) football players aged 11-15 years. Medical staff documented both players' self-reported historical and in-season hip and groin pain. Univariate and multivariate logistic regression models were undertaken with main outcome measures in-season hip and groin pain and historical hip and groin pain and independent variables of hip muscle strength, hip muscle torque and HAGOS subscale scores.

RESULTS

Twenty-three players (21.9%) self-reported in-season hip and groin pain, while 19 players (18.1%) self-reported historical hip and groin pain. Pre-season hip adductor and abductor variables and HAGOS subscale scores failed to predict in-season hip and groin pain. However, a higher body mass index (odds ratio [OR] = 1.32; 95% CI 1.01, 1.73, p = .043) and being male (OR 5.71; 95% CI 1.65, 19.7) were associated with having in-season hip and groin pain (R2 = 0.211). There was also an association between historical hip and groin pain (R2 = 0.579) and both HAGOS subscale Quality of Life (odds ratio [OR] = 0.84; 95% CI 0.77, 0.91, p < .001) and mean abductor torque (OR = 11.85; 95% CI 1.52, 91.97; p = .018).

CONCLUSION

Pre-season hip adductor and abductor strength and HAGOS subscale scores did not predict subsequent in-season hip and groin pain in elite youth football players. However, pre-season higher hip abductor strength and lower HAGOS scores were retrospectively associated with historical hip and groin pain.

Effects of Whole-Season Training and Match-Play on Hip Adductor and Abductor Muscle Strength in Soccer Players: A Pilot Study

BACKGROUND

Previous investigations have associated weakness of hip muscles with a higher likelihood of developing hip groin injury. However, no previous investigation has examined the influence of soccer training and match-play during the season on maximal isometric hip adductor and abductor muscle strength.

HYPOTHESIS

Maximal hip adductor and abductor muscle strength would increase after the preseason, maintaining relatively constant levels across the soccer season.

DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 3.

METHODS

A total of 26 semiprofessional male soccer players underwent measurements of maximal isometric hip adductor and abductor muscle strength at 3 time points of the soccer season: preseason, midseason, and end-season to investigate the longitudinal effect of soccer training and competition during a complete season on maximal isometric hip adductor and abductor muscle strength in the semiprofessional Spanish soccer player.

RESULTS

Compared with preseason, hip abductor muscle strength increased in the midseason (14.2% and 17.1%, for dominant and nondominant limb, respectively; P < 0.001) and in the end-season (13.1%; P = 0.005, and 14.1%; P < 0.005). In contrast, hip adductor muscle strength remained unchanged across the season in both limbs. As a result, the adductor/abductor strength ratio in the nondominant limb was reduced at midseason and end-season time points (-14.6% and -18.4%, respectively; P < 0.001) with a corresponding tendency in the dominant limb (-9.3% and -15.0%, respectively; P > 0.05).

CONCLUSION

While maximal hip abductor muscle strength increased throughout the season, hip adductor muscle strength remained stable across the season. This produced a substantial deficit in hip adductor/abductor strength ratio at midseason and end-season.

CLINICAL RELEVANCE

The progressive imbalance in adductor/abductor strength across the soccer season may be an indicator of increased risk of groin injury and may reinforce the need for preventive rehabilitation activities focused on enhancing adductor muscle strength.

Alpha-Actinin-3 Deficiency Might Affect Recovery from Non-Contact Muscle Injuries: Preliminary Findings in a Top-Level Soccer Team

There are recent data suggesting an association between the R577X polymorphism (rs1815739) in the gene encoding α-actinin-3 (ACTN3) and the risk of musculoskeletal injuries. The purpose of this study was to analyze the association of rs1815739 with risk of, and recovery time from non-contact soft-tissue muscle injuries in professional soccer players. Forty-six (22 male and 24 female) players from a top-level professional soccer team were assessed during five consecutive seasons: the genotype distribution was: RR, 41.3%; RX, 47.8%; and XX, 10.9%. There was a trend towards a higher risk of muscle injury associated with the XX genotype (p = 0.092, with no injury-free XX player during the 5-year study period) and a significant genotype effect for the time needed to return to play (p = 0.044, with the highest value shown for the XX genotype, i.e., 36 ± 26 days, vs. 20 ± 10 and 17 ± 12 days for RR and RX, respectively). In conclusion, the XX genotype might be associated not only with a higher risk of non-contact muscle injuries, but also of recovery time from these conditions. However, more research in larger cohorts is needed to confirm this preliminary hypothesis.

Markers of muscle damage and strength performance in professional football (soccer) players during the competitive period

Background

The present study investigated the impact of competitive soccer on the short-term changes in isometric strength of the adductor muscle group during the competitive season.

Methods

In this cohort study we evaluated the association between a serum marker of muscle damage [creatine phosphokinase (CPK)] and isometric strength of the adductor muscles of the hip in 30 professional football players (age: 26.7±2.9 years) during two seasons of the national top-level championship. Serum CPK level was determined the day before the match, 12–20, 36–48, 60–72 h after the match. The maximum voluntary isometric contraction force of the adductor muscles complex was determined immediately after having taken blood samples.

Results

There was evidence of a statistically significant positive association between age, body mass index (BMI), percentage of body fat, and muscle strength, and between weight and muscle strength. There was evidence of a statistically significant negative association between the level of CPK and the maximum isometric strength of the adductors of soccer players. Changes in CPK levels were associated with the muscle strength recovery trend (P<0.001). The strength/CPK ratio at different time points had a U-shaped curve.

Conclusions

Exercise induced muscle damage significantly affects the strength of the adductor muscle group of professional soccer players during the competitive period. The lower the CPK level, the greater the athletes' strength at a given time point. Also, the greater the decrease in CPK level, the greater the rate of strength restoration.

Short and long lever adductor squeeze strength values in 100 elite youth soccer players: Does age and previous groin pain matter?

OBJECTIVE

To examine adductor squeeze strength in elite youth soccer players by investigating the relationship of age and previous one-year groin pain on adductor squeeze force outputs, and to provide reference values for youth players.

DESIGN

Cross-sectional study.

PARTICIPANTS

Elite youth soccer players (n = 100; age 14.5 ± 1.9 years; height 168.0 ± 10.7 cm; mass 60.7 ± 13.0 kg) participated.

MAIN OUTCOME MEASURES

Adductor squeeze tests were captured in short and long lever positions, and groin pain assessed via subjective retrospective questionnaire. Multiple linear regressions were computed to compare the effects of age and previous one-year groin pain on adductor squeeze strength.

RESULTS

Raw adductor squeeze force values (N) had a moderate positive relationship with age (short r = 0.517, p < 0.001; long r = 0.457, p < 0.001), but not when force is normalized to body mass (N/kg; short r = 0.014, p = 0.444; long r = -0.173, p = 0.043). Previous groin pain did not have an effect on short or long lever squeeze strength. Reference values for long lever adductor squeeze strength (3.59 ± 0.77 Nm/kg) are provided.

CONCLUSION

Age and previous groin pain do not have an effect on adductor squeeze strength values in elite youth soccer players, so comparing values to the present adolescent cohort can be quickly interpreted without adjustment for age or previous injury.

Clinical utility of measuring the size of the lumbar multifidus and quadratus lumborum muscles in the Australian football league setting: A prospective cohort study

OBJECTIVES

Test the odds of factors previously associated with lower limb injury (decreased size of the multifidus (MF) and increased size of the quadratus lumborum (QL) muscle) in an independent sample of Australian Rules Football (ARF) players.

DESIGN

Prospective cohort study.

SETTING

Professional ARF.

PARTICIPANTS

Forty-three male ARF players.

MAIN OUTCOME MEASURES

Cross-sectional areas (CSAs) of MF and QL muscles measured from pre-season ultrasound images. Playing season injuries were recorded by club personnel. A multivariable logistic regression model was used to evaluate the usefulness of MF and QL muscle size for predicting playing season lower limb injuries.

RESULTS

Fifteen players (35%) sustained a playing season lower limb injury. The multivariable model indicated that the odds of sustaining a lower limb injury during the season was 2.38 (95% CI: 1.18, 5.00; P = 0.017) times less likely for a one cm² increase from the mean value in MF muscle CSA at the L5 vertebral level after adjusting for CSA of the QL, age and BMI. The main effect and interaction models positively predicted 75% of players that sustained a lower limb injury during the season (sensitivity 80%, specificity 85%).

CONCLUSION

Future studies could examine the efficacy, feasibility and adherence of 'at risk' players to a pre-season training program aimed at increasing MF muscle size and monitor playing season injuries.

Adductor Muscles Strength and Strength Asymmetry as Risk Factors for Groin Injuries among Professional Soccer Players: A Prospective Study

The aim of this study was to prospectively examine the association between isometric hip adductor strength and between-limb strength asymmetry to groin injuries in male professional soccer players. Isometric hip adductor strength and between-limb strength asymmetry of 45 professional outfield soccer players from three First Division teams were tested during the 2017/2018 preseason. Players were then monitored throughout the 2017/2018 season for groin injuries. Ten groin injuries were recorded. When compared with uninjured players, players who sustained groin injury had significantly lower strength of respective muscle groups and significantly higher between-limb strength asymmetries (all p < 0.05; ES = 1.16 and 0.88; mean % difference = 26% and 51%). Isometric hip adductor strength had a significant inverse relationship with the incidence of occurring groin injuries (p = 0.016). No significant relationship between hip adductor strength asymmetry and the incidence of future groin injury was observed (p = 0.09). Finally, players' age and previous groin injury were not significantly associated with the incidence of future groin injuries (all p > 0.05). These results generally suggest that isometric adductor strength is a significant predictor of future groin injuries in men's professional football; however, due to the relatively low sample size, further studies are required.

The influence of a badminton competition with two matches in a day on muscle damage and physical performance in elite junior badminton players

To investigate the effects of a badminton competition with 2 matches in a day on hip strength and range of motion (ROM) and exercise-induced muscle damage in elite junior badminton players. Twenty players (age: 17±0.8 years; body mass: 62.9±6.5 kg, height: 173.8±8.9 cm) participated in this study. Passive hip internal (IR) and external rotation (ER), abduction (ABD) and adduction (ADD) hip ROM, isometric hip ADD and ABD muscle strength, countermovement vertical jump (CMJ) height and blood creatine kinase concentration (CK) were measured before and after a badminton competition during an international tournament. Blood samples were collected 24 h after the end of the last match. Compared to baseline values, hip IR and ER ROM were significantly decreased at post-competition in the dominant (IR=-9.0%; p=0.007 and ER=-15.2%; p=0.002) and non-dominant limbs (IR=-9.08%; p=0.004 and ER=-19.4%; p<0.001). In contrast, hip ADD (13.5%; p<0.001) and ABD (14.6%; p<0.001) strength increased significantly after the competition in the dominant limb and ABD strength increased significantly in the non-dominant limb (9.2%; p=0.001). From baseline values, CK increased after the competition (430.1%) and values remained elevated over baseline values 24 h later (160.4%). Although hip muscle strength increased, a badminton competition with two consecutive matches reduced hip ROM and increased blood CK concentration. This study suggests the necessity of investigating recovery strategies after a badminton competition to return hip ROM to basal values before the next day of the competition.