Torque, power and fatigue ratio in knee flexors and extensors of soccer players

Abstract

Introduction: Soccer is the most popular and practiced sport in the world and is characterized by high intensity movements. This high demand induces several types of locomotor system injury, and one of the intrinsic factors responsible for triggering these injuries is muscle imbalances, which can occur between limbs or between muscles groups of the same limb. Objective: To evaluate the muscular performance between knee flexor/extensor groups of both limbs in professional soccer athletes.: Methods: Isokinetic assessments were performed in 18 professional soccer athletes, with mean age of 26.9 ± 3.6 years and mean body mass index (BMI) of 23.9 ± 1.7 kg/m2.. The test protocol consisted of five concentric contractions of knee flexion and extension at angular velocity of 60o/sec, 15 contractions at 180o/sec and 30 contractions at 300o/sec in both limbs. Test paired t-test was used to verify the torque, power, and fatigue ratio of flexors and extensors of the dominant and non-dominant knee. Results: There was no significant difference between the evaluated members related to dominance (p>0.05). Regarding the torque ratio between flexors and extensors, we observed values below what is considered normal for this population, besides a higher fatigue index in knee flexor group when compared with the extensor group. Conclusion: No better performance was observed in the dominant limb, suggesting that, although this limb is preferred, this does not necessarily characterizes the better performance. The data also revealed an imbalance in the torque production capacity between the knee flexor and extensor groups, with an unfavorable ratio for the hamstrings, as well as a higher fatigue index in this group, which would make these muscles more susceptible to injures. Level of Evidence II; Diagnostic studies - Investigating a diagnostic test.