Abstract Background The assessment of the hamstrings-to-quadriceps (H:Q) strength ratio using an isokinetic dynamometer is commonly performed throughout the football season and is frequently used as an indicator of potential lower-limb injury risk. However, these evaluations are typically conducted under non-fatiguing conditions, even though most football-related lower-limb muscle injuries occur when players are already experiencing significant neuromuscular fatigue. Aims The aims of the present study were to (a) compare H:Q strength ratios across repetitions during a fatigue-inducing protocol in professional female football players and (b) evaluate the Fatigue Index (FI) of the knee flexors and extensors in response to the same fatigue-inducing protocol. Methods Fifteen professional football players (21.8 ± 5.3 years; 60.1 ± 8.7 kg; 163.6 ± 7.6 cm) performed a 30-repetition concentric isokinetic fatigue test protocol. Peak knee joint torques were computed for each repetition, and the conventional H:Q ratio (the ratio between the hamstrings and quadriceps concentric peak torque) was then calculated. Results The 30-repetition isokinetic fatigue test significantly reduced Peak Torque (PT) for both knee extensors (34%) and flexors (47%). This PT reduction began notably from the 7th and 8th repetitions, respectively ( P ≤ 0.001). FI was significantly greater for the knee flexors (47%) compared with the extensors (34%) ( P ≤ 0.001). Crucially, the H:Q ratio decreased significantly only after the 15th repetition, reaching its lowest value at the end of the test H:Q 27–30 (0.52 ± 0.10), P ≤ 0.001 vs. (H:Q 3–6 (0.64 ± 0.10). Conclusions These results show a reduction ( P ≤ 0.001) on H:Q ratio after fatigue-induced condition, and a greater reduction in the knee flexors (47% vs 34%). This fatigue-induced neuromuscular state may increase the potential risk of lower-limb injury in female football players. Considering the hamstrings’ susceptibility to fatigue, conditioning programs for female athletes should emphasize fatigue resistance to enhance performance and reduce the likelihood of injury.
Godinho et al. (Wed,) studied this question.