Background: Anterior cruciate ligament (ACL) injury is more prevalent in young athletes and women. A deficit of knee flexor strength and a H/Q strength ratio below 0.6 in athletes are risk factors. Therefore, the main objective of this study is to determine if there are differences in the strength of the knee musculature, joint work, and H/Q ratio between professional and junior elite basketball players and sexes, since there are differences in the incidence of ACL injuries between these groups. Methods: Forty-three professional (27 male and 16 female) and 42 junior elite (28 male and 14 female) basketball players were evaluated. Dynamometric knee flexion and extension measurements were performed on both lower limbs at three angular velocities: 30°/s, 120°/s, and 180°/s. Concentric knee flexion and extension strength variables were measured in Newtons, the strength ratio between flexors and extensors in H/Q ratio, and muscle work (product of force times displacement) in Joules. Comparisons of the measured variables were made between categories and sexes. Results: Significant differences (p < 0.05) were found between categories (professional and junior) in all measured strength parameters as well as in joint work. No differences were found between categories in the H/Q ratios. Significant differences (p < 0.05) were found between sexes in most measured strengths and joint work. However, no differences were found in most of the H/Q ratios. Female basketball players have lower values of strength and muscle work than male players, however, in the H/Q ratio data there are no differences between the two groups. The same occurs between junior and professional athletes. Conclusions: The authors conclude that flexor and extensor strength values should be analyzed in isolation and not in terms of the H/Q ratio.

Hamstring muscle injuries account for 12% of all injuries in soccer players. Several studies claim that the hamstring/quadriceps (H/Q) strength ratio has the potential to predict hamstring injuries, although the current evidence is not robust enough to definitively support this claim. Therefore, the main objective of the present study is to analyze whether there are changes in the H/Q ratio at different knee flexion angles and establish a measurement protocol capable of reducing the high prevalence of hamstring injury. We performed an observational study with 24 third-division soccer players. The conventional isokinetic H/Q strength ratio and H/Q strength ratio were measured at different knee flexion angles (15°, 30°, 45°, 60°, and 75°) at 60°/s and 180°/s. The conventional H/Q ratio differs from the H/Q ratios at 15° and 30° knee flexion at 60°/s and from the H/Q ratios at 15°, 45°, 60°, and 75° at 180°/s (p < 0.05). Based on the results obtained in this study, we recommend calculating the H/Q ratios at 15° and 30° knee flexion in the protocol for measuring the flexor and extensor strength of the knee. This additional data will establish more specific cut-off points that could predict and prevent future hamstring muscle injuries.

Anterior cruciate ligament (ACL) injuries are highly prevalent in sports and occur more frequently in female athletes, potentially due to hormonal influences across the menstrual cycle. This study aimed to analyze static postural control across menstrual cycle phases under varying postural and sensory demands. A longitudinal repeated-measures design was conducted in 22 healthy women (18–30 years) with regular menstrual cycles and moderate physical activity levels. Static balance was assessed using a Zebris pressure platform across three menstrual phases (follicular, ovulatory, luteal), three stance conditions (bipedal, dominant and non-dominant single-leg), and two visual conditions (eyes open and closed). Center of pressure variables included confidence area, velocity, and anteroposterior and mediolateral displacement. Differences between phases were analyzed using the Friedman test with Wilcoxon post hoc comparisons and Kendall’s W effect size. No significant differences were observed in bipedal stance or under eyes-open conditions. However, under eyes-closed single-leg conditions, significant phase-dependent differences emerged. In dominant-leg stance, greater instability during the ovulatory phase was found for mediolateral displacement (p < 0.001; W = 0.321), anteroposterior displacement (p = 0.007; W = 0.223), confidence area (p < 0.001; W = 0.378), and velocity (p = 0.048; W = 0.138). Similar results were observed in the non-dominant leg for mediolateral displacement (p = 0.03; W = 0.159) and confidence area (p = 0.002; W = 0.287). These findings indicate that menstrual cycle phase influences postural control primarily under increased sensory and postural demands. The ovulatory phase appears to be associated with reduced stability when visual input is removed, suggesting a transient decrease in sensorimotor efficiency and a potential increase in neuromuscular vulnerability related to ACL injury risk.

Some knee strength measuring devices have an anterior cushioning area but relies on a belt for the posterior pad adjustment, creating an uneven force distribution. This study analyzed whether the distal pad position affects knee strength measurements. Eleven professional basketball players participated in this study, with a total of 22 knees evaluated. Knee flexion and extension dynamometric measurements were performed at different angular velocities: 30°/s, 120°/s, and 240°/s. For each angular velocity, two measurements were performed with varying positions of the measuring tool pad at the anterior and posterior aspects (AA and PA). The hamstring/quadriceps (H/Q) ratio was calculated by dividing the hamstring musculature’s maximum peak strength by the quadricep musculature’s maximum peak strength at each measurement. The knee work was extracted from the device after finishing the measurements. Significant differences were found between measurement positions in the knee flexion force at 30°/s (p < 0.001) and 120°/s (p = 0.027). No differences were found for the extension forces. As for the H/Q ratio, significant differences were found between positions at 30°/s (p < 0.001). Furthermore, significant differences between positions were found for the knee work at 120°/s (p = 0.019). These findings suggest that the positioning of the pad on the leg directly influences knee flexor strength measurements, which in turn impacts critical parameters, such as the H/Q ratio and knee work. Given the importance of these variables in injury prevention, particularly for conditions such as anterior cruciate ligament (ACL) injuries, ensuring precise and reliable measurement methods is essential. We recommend using the PA position because it increases knee flexion strength values, potentially leading to more accurate assessments of the muscle function and balance.