Effect of Functional Fatigue on Knee Force Sense in Amateur Adult Female Football Players

Background Intact proprioception (joint position sense, kinaesthesia, force sense (FS)) is critical for optimal neuromuscular control of knee functional joint stability. Fatigue impairs knee FS in adult male footballers. The effect of fatigue on knee FS and resulting implications for injury prevention practice have not been studied for adult female footballers. Aim Determine the effect of functional fatigue on knee flexion FS (KF-FS) in amateur adult female football players. Methods Twenty-one players participated (mean±SD: age 23.3±3.5yr; height 164.1±6.4cm; mass 62.6±6.4kg). Functional fatigue was defined/induced using the Functional Agility Short-Term Fatigue Protocol (FAST-FP). The FAST-FP incorporated acceleration-deceleration tasks typical of football training/match-play. Dominant leg (preferred stance leg) KF-FS was measured (Newtons (N)). Players sat on an isokinetic dynamometer in isometric mode, the knee flexed 45°. A knee flexion target trial-reproduction trial sequence was repeated three times, the difference between trials designated the absolute error (AE), the mean AE used for data analyses. Force sense measurements occurred before and immediately after the FAST-FP. Results Force sense AE did not significantly change following fatigue (pre-fatigue = 7.0±4.8N; post-fatigue = 10.1±6.8N; pre-/post-difference = 7.7±5.6N; P = 0.14; Cohen’s d = 0.34). Four players’ (19%) post-fatigue FS deteriorated by more than twice the group’s pre-/post-difference standard deviation. Conclusion Despite functional fatigue, group mean KF-FS did not significantly change. However, one-fifth of players’ KF-FS deteriorated substantially after functional fatigue was induced. Some players, therefore, may be more in need of fatigue-resistance training than others to maintain optimal KF-FS and neuromuscular control of knee functional joint stability.