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A Systematic Scoping Review of Isokinetic Testing in High-Level Female Soccer Players: Methodological Considerations: Comparison
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Please note this is a comparison between Version 2 by Dong Zhang and Version 1 by Antonio Cicchella.

There is a lack of clarity on the isokinetic testing of professional female soccer players (PFSPs) concerning the proper use of isokinetic testing, and the existing data, useful for rehabilitation purposes, are confusing. This review aims to highlight the main methodological issues and provide guidance for performing reliable isokinetic strength (IS) based on evidence data. Following the PRISMA guidelines, we selected 18 out of 98 papers dealing with healthy PFSPs surveying four databases. It emerged that there is a large difference between subjects even in comparable test conditions (e.g., usage of the same isokinetic device). The more reliable testing speed ranges from 60°/s to 180°/s. Employing lower or higher velocities does not add information to test results. Interlimb differences in healthy PFSP are confirmed to be approximately 10 percent. The H/Q ratio does not differ through the different calculation methods, considering eccentric values or not, in any considered menstrual cycle phase. It emerged that more methodological rigor is necessary in PFSP isokinetic testing.

  • isokinetic testing
  • professional female soccer players
  • H/Q ratio
  • methodology

1.1. Background of the Review

In recent years, the representation of female athletes in scientific research has gradually increased. Nevertheless, compared with the extensive body of literature on male athletes, female athletes remain underrepresented in sports science research [1]. Only about 20 percent of football studies focused on women, and only about 15 percent on professional women players (in earlier years) in one earlier bibliometric review [1]. For instance, women’s football has been severely neglected in the field of scientific research, especially in biomechanical studies [2]. Most existing biomechanical research mainly focuses on the male sports domain. The training guidance provided to female athletes is still based on data obtained only from male players [3], and these training guidelines ignore the significant differences in joint range of motion and flexibility [4], body composition [5], and muscle strength [6] between genders.
Previous studies have shown that sex-related differences in neuromuscular control, movement strategies, and fatigue responses may influence both athletic performance and injury susceptibility in female soccer players [7]. Compared with males, female athletes appear to rely more on hip and core stabilization strategies during dynamic tasks, while also exhibiting different neuromuscular responses under fatigue conditions [8]. These neuromuscular characteristics may contribute to altered lower-limb biomechanics, including increased dynamic knee valgus and a potentially greater risk of anterior cruciate ligament (ACL) injuries during high-intensity movements [9]. Strength is one of the fundamental physical characteristics that affects all athletic performance, and there are differences in strength levels and the indicators used for evaluating athletic performance between male and female athletes. Previous studies have shown that female athletes generally exhibit lower concentric peak torque values of the knee extensors and flexors compared with males, particularly at angular velocities between 60°/s and 180°/s, with reported normalized peak torque values commonly ranging between approximately 1.2 and 2.8 Nm/kg depending on muscle group and testing velocity [10]. Despite these sex-related neuromuscular differences, training strategies in female soccer are still frequently adapted from male-based protocols [3,11][3][11].
In addition, several studies reported lower H/Q ratios at low angular velocities in female soccer players [12], which may reflect reduced hamstring contribution during knee stabilization tasks and potentially increase susceptibility to ACL-related injury mechanisms during high-intensity movements. Most existing studies have small sample sizes and are limited to players from a single team, making it difficult to generalize the research results to athletes of different competitive levels or backgrounds [13]. Additionally, some studies only focus on static strength assessment and lack isokinetic or functional movement tests that better reflect actual athletic performance [14].
To address the limitations in the evaluation of female athletes, objective assessment tools are of vital importance. Isokinetic testing is widely used to evaluate neuromuscular characteristics such as peak torque, inter-limb asymmetry, and hamstring-to-quadriceps (H/Q) ratios in athletes [15]. The isokinetic test also plays a key role in diagnosing muscle imbalance between the quadriceps and hamstrings, as well as between the two legs [16].
In female soccer players, the interpretation of these measurements may be influenced by several sex-specific factors, including menstrual cycle phase, fatigue responses, and individual biomechanical characteristics. Previous studies have suggested that hormonal fluctuations across the menstrual cycle may affect muscle function, coordination, and perceived fatigue, potentially contributing to variability in isokinetic outcomes [17]. When assessing strength in women, in addition to the knowledge of menstrual cycle phase, it is also important to know iron status [18]. Additionally, due to anatomical differences, women are more prone to ACL injuries than men [19]. However, many studies did not adequately control or report these variables, limiting the comparability of findings across investigations [20]. In addition, differences in testing protocols, competitive level, and participant characteristics may further influence the interpretation of isokinetic data in female soccer populations.
In the relevant literature from the past decade (2015–2025), most studies did not adequately consider variables specific to women, such as the menstrual cycle, hormone levels, or physiological and psychological states [21]. Although some studies suggested that these factors had a limited impact on isokinetic strength (IS), they could still affect muscle status and the variability of the data. Even though some studies have taken into account the effects brought about by different phases of the menstrual cycle, their assessment methods usually lack biochemical verification of hormone levels and are merely based on calendar calculations [22].
In addition, the ratio of hamstring muscles to quadriceps muscles (H:Q ratio) can not only reflect the risk of injury but also predict functional performance. Among them, the eccentric strength of the hamstring muscles plays a crucial role in movement control [23]. In recent years, some scholars have proposed that the H/Q ratio based on the rate of torque development (RTD) should replace the traditional H/Q ratio as an indicator for evaluating dynamic knee joint stability and movement performance. Previous studies suggested that RTD-based H/Q ratios may be associated with deceleration capacity and dynamic knee stabilization during high-intensity movements [24], particularly during rapid braking tasks requiring eccentric hamstring activation.

1.2. Purpose of the Review

This systematic review aims to analyze the methodological approaches used in isokinetic testing among high-level female soccer players and to summarize the principal neuromuscular variables commonly assessed, including peak torque, inter-limb asymmetry, and hamstring-to-quadriceps (H/Q) ratios. In addition, this review examines how these variables have been associated with functional and performance-related outcomes reported in the literature, such as change-of-direction ability, deceleration capacity, and injury-related risk indicators. Finally, this review aims to identify methodological inconsistencies across studies and provide practical considerations for the standardization of isokinetic assessment protocols in female soccer players.

References

  1. Ventaja-Cruz, J.; Cuevas Rincón, J.M.; Tejada-Medina, V.; Martín-Moya, R. A Bibliometric Study on the Evolution of Women’s Football and Determinants Behind Its Growth over the Last 30 Years. Sports 2024, 12, 333.
  2. Okholm Kryger, K.; Wang, A.; Mehta, R.; Impellizzeri, F.M.; Massey, A.; McCall, A. Research on women’s football: A scoping review. Sci. Med. Footb. 2022, 6, 549–558.
  3. Sakamoto, K.; Asai, T. Comparison of Kicking Motion Characteristics at Ball Impact between Female and Male Soccer Players. Int. J. Sports Sci. Coach. 2013, 8, 63–76.
  4. Allison, K.F.; Keenan, K.A.; Sell, T.C.; Abt, J.P.; Nagai, T.; Deluzio, J.; McGrail, M.; Lephart, S.M. Musculoskeletal, biomechanical, and physiological gender differences in the US military. US Army Med. Dep. J. 2015, 22–32.
  5. Mascherini, G.; Castizo-Olier, J.; Irurtia, A.; Petri, C.; Galanti, G. Differences between the sexes in athletes’ body composition and lower limb bioimpedance values. Muscle Ligaments Tendons J. 2019, 7, 573.
  6. Miller, A.E.; MacDougall, J.D.; Tarnopolsky, M.A.; Sale, D.G. Gender differences in strength and muscle fiber characteristics. Eur. J. Appl. Physiol. Occup. Physiol. 1993, 66, 254–262.
  7. The Eternally Wounded Athlete: How Medical Professionals and Sports Injury Researchers Have Limited Female Athletes’ Sport Participation and Biased the Interpretation of Sports Injury Research|Current Epidemiology Reports. Available online: https://link.springer.com/article/10.1007/s40471-020-00255-0 (accessed on 30 October 2025).
  8. López-Valenciano, A.; Ayala, F.; De Ste Croix, M.; Barbado, D.; Vera-Garcia, F.J. Different neuromuscular parameters influence dynamic balance in male and female football players. Knee Surg. Sports Traumatol. Arthrosc. 2019, 27, 962–970.
  9. Hodel, S.; Imhoff, F.B.; Strutzenberger, G.; Fitze, D.; Obrist, S.; Vlachopoulos, L.; Scherr, J.; Fucentese, S.F.; Fröhlich, S.; Spörri, J. Greater hip internal rotation range of motion is associated with increased dynamic knee valgus during jump landing, both before and after fatigue. Knee Surg. Sports Traumatol. Arthrosc. 2025, 33, 1560–1568.
  10. Yilmaz, E.; Aydin, T.; Kiliç, S.; Toluk, Ö. Bilateral knee joint isokinetic muscle strength and angle specific balance ratio in soccer players. Dtsch. Z. Sportmed. 2023, 74, 234–241.
  11. Cicchella, A.; Zhang, C. Recommendations for the Isokinetic Test of Female’s Soccer Players Knee: A Systematic Review. Med. Pharmacol. 2024.
  12. Andrade, M.D.S.; De Lira, C.A.B.; Koffes, F.D.C.; Mascarin, N.C.; Benedito-Silva, A.A.; Da Silva, A.C. Isokinetic hamstrings-to-quadriceps peak torque ratio: The influence of sport modality, gender, and angular velocity. J. Sports Sci. 2012, 30, 547–553.
  13. Mariano, I.G.; Alves, L.E.M.; Rodrigues, E.L.; Azevedo, B.R.; Castro, A.L.O.; Mendonça, L.D. Analysis of musculoskeletal injuries in elite female soccer players: Cohort study in one Brazilian team. Phys. Ther. Sport 2025, 73, 25–33.
  14. Rusu, L.; Ungureanu Dobre, A.; Chivaran, A.G.; Marin, M.I. Relation between Muscle Force of Knee Extensors and Flexor Muscles and Sleep Quality of Women Soccer Players: A Pilot Study. Appl. Sci. 2023, 13, 2289.
  15. Wilk, K.E.; Arrigo, C.A.; Davies, G.J. Isokinetic Testing: Why it is More Important Today than Ever. Int. J. Sports Phys. Ther. 2024, 19, 374–380.
  16. Cvjetkovic, D.; Bijeljac, S.; Palija, S.; Talic, G.; Radulovic, T.; Kosanovic, M.; Manojlovic, S. Isokinetic Testing in Evaluation Rehabilitation Outcome After ACL Reconstruction. Med. Arch. 2015, 69, 21.
  17. Quigley, T.; Greig, M. The influence of menstrual cycle phase on isokinetic knee flexor and extensor strength in female soccer players: A pilot study. Res. Sports Med. 2025, 33, 87–96.
  18. Pengelly, M.; Pumpa, K.; Pyne, D.B.; Etxebarria, N. Iron deficiency, supplementation, and sports performance in female athletes: A systematic review. J. Sport Health Sci. 2024, 14, 101009.
  19. Zech, A.; Hollander, K.; Junge, A.; Steib, S.; Groll, A.; Heiner, J.; Nowak, F.; Pfeiffer, D.; Rahlf, A.L. Sex differences in injury rates in team-sport athletes: A systematic review and meta-regression analysis. J. Sport Health Sci. 2022, 11, 104–114.
  20. Harvey, W.F.; Niu, J.; Zhang, Y.; McCree, P.I.; Felson, D.T.; Nevitt, M.; Xu, L.; Aliabadi, P.; Hunter, D.J. Knee alignment differences between Chinese and Caucasian subjects without osteoarthritis. Ann. Rheum. Dis. 2008, 67, 1524–1528.
  21. Eustace, S.J.; Morris, R.; Tallis, J.; Page, R.M.; Greig, M. The influence of angle-specific torque of the knee flexors and extensors on the angle-specific dynamic control ratio in professional female soccer players. J. Sports Sci. 2022, 40, 1235–1242.
  22. Belamjahad, A.; Tourny, C.; Hackney, A.C.; Jebabli, N.; Chariba, N.; Laziri, F.; Saeidi, A.; Laher, I.; Granacher, U.; Zouhal, H. Preseason neuromuscular versus endurance training leads to greater improvements in isokinetic strength, muscle damage, and inflammation parameters in highly trained female soccer players. BMC Sports Sci. Med. Rehabil. 2025, 17, 107.
  23. Ogando, P.H.M.; Moura, I.G.d.; Ramos, G.P.; Wilke, C.F.; Coimbra, C.C.; Soares, D.D. Isokinetic Peak Torque Ratio Between Hamstring and Quadriceps Musculature Correlates With Game Performance in Elite and U-20 Players of the Brazilian Women’s Soccer Team. Women Sport Phys. Act. J. 2025, 33, wspaj.2024-0025.
  24. Zhang, Q.; Léam, A.; Fouré, A.; Wong, D.P.; Hautier, C.A. Relationship Between Explosive Strength Capacity of the Knee Muscles and Deceleration Performance in Female Professional Soccer Players. Front. Physiol. 2021, 12, 723041.
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