## 4 Discussion
As suggested by [PERSON] et al. (2016), a possible explanation for the higher velocities during knee flexion is that curling the leg while seated is a much more common motor task than extending the hip with a fully extended knee while in the supine position. This represents an adaptive pattern to usual movements ([PERSON] et al., 2016). Knee flexion during a leg curl is a usual movement for athletes in a gymnasium, while hip extension starting from 80\({}^{\circ}\) in the supine position may be a less common exercise, which confirms our finding of the greater velocity observed despite less muscles being involved. An additional comment on higher velocities during curls is that hamstring muscles mainly contain quick contraction fibers (white fibers) ([PERSON] et al., 2016), whereas the agonist muscles (_gluteus maximus_, _adductor longus_, and _adductor magnus_) include slow contraction fibers. The combination of quick and slow fibers, reaching a greater torque, turns out to have a smaller peak velocity than the velocity of a curl when only the hamstring muscles are involved. The third important result refers to the combination of torque and velocity. Overall, the figures show that hip extension torque (MVHE) during a quick movement (2.42 Nm/kg) is more than twice the knee flexion torque (MVKF with 1.07 Nm/kg) due to the activation of the _gluteus maximus_ and other minor agonist muscles when the limb is extended. On the other hand, and in an inverse relationship, when the athlete sits and curls his or her leg, the maximum velocity is more than twice as large (MVKF: 452.56\({}^{\circ}\)/s) as the velocity in the supine position (MVHE: 215.96\({}^{\circ}\)/s), as shown in Table 2. We multiplied the peak velocity by the peak torque during both motor tasks, MVHE and MVKF. The result is an estimation of the maximum power deployed during the motor tasks. MVKF is quicker than MVHE, while MVHE involves a greater torque than MVKF. The product of peak velocity and peak torque favors MVHE as a more powerful motor task. At variable velocities with peak values of 215.96\({}^{\circ}\)/s and 452.56\({}^{\circ}\)/s for MVHE and MVKF, respectively, the power estimates are 452.56\({}^{\circ}\)Nm/s.kg and 542.13\({}^{\circ}\)Nm/s.kg, respectively. The difference, as shown in Table 3 to be in the order of 89.569\({}^{\circ}\)Nm/s.kg, is borderline significant (\(p\) = 0.051). This highlights the fact that during MVHE, agonists are recruited in addition to the hamstring muscles. Since the muscle fibers in both motor tasks, MVHE and MVKF, act from a similar fiber length, hip extension produces more torque but knee flexion produces more velocity, resulting in a small increase in power during hip extension, making use of a greater PCSA [42] active in hip extension. The similar length of fibers was mentioned in the comments on the first results of this research, and the fact that only quicker fibers are active as part of the second results. Incidentally, no real difference (\(-\)0.044 Nm/kg in 2.851 Nm/kg, about 1.5%) was found between men and women, which was expected because torque was normalized to body mass. The velocity is also the same for men and women, with differences below 2% (\(-\)5.494\({}^{\circ}\) in 314.245\({}^{\circ}\)/s, about 1.7%). Consequently, the maximum weight normalized power of men and women are also similar because of body mass normalization. Special care is necessary when prescribing a rehabilitation, prevention, or maintenance program, in the sense of adapting them to everyone [8; 45]. The MVHE motor task mimics the swing phase of running, which is when most injuries occur [1; 17]. For this reason, we suggest that the quantitative evaluation of parameters is of paramount importance during hamstring rehabilitation and training. A simple instrument, such as DINABANG, used together with an elastic resistance band, can be of great help in the sports field to closely monitor athletes' evolution, with little risk of either inefficient movements or overdose.