This investigation is aimed to examine the effects of two different exercise-oriented protocols on the knee torque-angle relationship of the knee flexors.

Thirty two young soccer players were be randomly assigned to three groups: hamstring-eccentric (ECC, n=11), unstable-squatting (UNS, n=11) or control (C, n=10). The ECC and UNS groups performed eighteen sessions over 6 weeks of an injury prevention protocol, using only 3 hamstring-eccentric or unstable-squatting exercises. The angle-torque relationship was measured before and after the training intervention. Voluntary isometric torque was recorded at six test angles, with participants prone (35º-100º; 0º on full extension).

This study utilized a three parallel-groups randomized controlled design, where 3 between-participant conditions, ECC, UNS and C, were tested. Once considered eligible for the study, all participants were familiarized with the testing procedures. Participants attended the laboratory for a pre-training test session, where body mass, height and muscle functional parameters were recorded. Two days after their pre-test, participants including in ECC or UNS started a 6 weeks (18 sessions) training program while the control group did not perform any type of resistance training.

Nevertheless, during the 6 weeks intervention period all three groups continued with their normal recreationally physical activity consisting in 2 to 3 sessions per week of soccer training or friendly matches. Two days after the end of the intervention period muscle function was re-tested.

Inclusion Criteria:

• males, recreationally trained football players
• Read and sign the informed consent

Exclusion Criteria:

• Participants that has undertaken a lower body resistance-training program in the preceding 6 months,
• Reported a previous lower limb injury