Deep transverse friction massage group. Participants were taught by one of the examiners how to sit and perform pre-exercise self-massages on their tested leg musculotendinous junction (MTJ). The procedure consisted of applying friction massage by fingertips transversely to the hamstrings tendon, in a sitting position. The tendon was located over four finger widths proximal to the medial and lateral epicondyles of the femur. One examiner carefully monitored how the technique was performed to assure the precision of the application. This massage technique was applied over a duration of 30 seconds.

The dynamic stretching intervention was included for its positive effects on agility and muscle strength. Participants in this group, swung their tested leg actively into hip flexion while keeping their knee fully extended and their ankle fully plantar flexed until a stretch was felt in the posterior thigh. This was repeated over 30 seconds and included in the participant's warm-up phase.

In the static stretching intervention, all participants laid on the floor in a supine position with both feet pointing upwards, with the tested limb in full knee extension and the foot in a relaxed position. The tested limb was moved up passively to a point of slight pain or discomfort at the posterior aspect of the thigh. This technique puts the hamstrings muscle at its greatest possible length. This position should be held for 30 seconds and was performed three times for a total of one minute and 30 seconds, 15 minutes after a match or training. The contralateral leg was stabilized by means of another collaborator in order to prevent compensation by rotation or elevation of the pelvis.

The procedure consisted of applying friction massage by fingertips transversely to the hamstrings tendon, in a sitting position. The tendon was located over four finger widths proximal to the medial and lateral epicondyles of the femur

Straight leg raise (SLR) is a widely used outcome measure used to assess the extensibility of the hamstrings muscle. SLR was first applied to all participants across the groups. All football players laid supine and taught to relax during testing. The tested limb was raised by a volunteer therapist with the knee in full extension and the foot in a relaxed position. The other lower limb was stabilized in a neutral hip rotation and full knee extension by another volunteer. The test was stopped once the therapist felt a strong resistance, or when the pelvic rotation was noted. Then, the assessor placed the goniometer over the greater trochanter, with one arm aligning the lateral femoral condyle, and the other arm aligning parallel to the ground, in a direction to the mid-axillary line and recorded the hip angle. The scores were recorded as degrees of range of movement.

The T-Drill has been proven to be a highly reliable testing measurement. Footballers were instructed on how to perform the T-Drill and on the test procedures. Then, they were instructed to jog for 2 min to warm-up. The participants performed the T-drill twice and the trial with the best time was taken for analysis by the mean of an alert assessor with a stopwatch. Results were measured in seconds and scores were interpreted as (1) excellent, < 9.5; (2) good, 9.5-10.5; (3) average, 10.5-11.5; and (4) poor, > 11.5.

After a rest time of 5 min, participants were guided to the knee flexors strengthening machine (hamstrings curl machine) for one repetition maximum (1RM) testing. Resistance was placed just proximal to the posterior part of the calcaneus bone. Footballers performed first specific warm-up, consisting of a set of ten repetitions of knee flexion, with a light load. Afterwards, for safety reasons, an estimation of hamstring 1RM was calculated using Brzycki formula [Weight lifted ÷ (1.0278 - (0.0278 × Number of repetitions)]. This formula exhibited a relatively low level of bias (1.6 to 0 kg). Maximal voluntary strength was recorded in kilograms.

Measured by recording if any injury affected the players.