To make the quadriceps perform more work and increase the efficiency of the exercise, Sean should minimize the amount of trunk flexion at the start of the concentric phase.
We can describe trunk flexion as forward pelvic tilt and flexion of the spine. This activity causes more pressure on the muscles of your quadriceps and hence helps in building them.
The quadriceps can be described as the muscles that are present in the front region of the thigh. These area has more muscle mass as compared to other areas of your brain and hence need to be worked on so that the muscle mass here can be reduced.
In this kind of population, the make up of the population's gene pool will remain virtually the same as long as these conditions hold. In this kind of situation, no evolution can take place, all thing will remain the same. For evolution to occur, competition must exist.