With few exceptions muscles exert smaller tension at shorter lengths.

The rectus femoris muscles and wrist extensors are in deference to the above rule  in some populations.

The rectus femoris is one of the four powerful quadricep muscles of the upper thigh. The rectus can flex the thigh at the hip and extend the leg at the knee.

In a seated position since the hip is flexed and the muscle is at a shortened length the action of extending a leg is primarily driven by the other three muscles of the quadriceps, the vastus lateralis, vastus medialis and vastus intermedius and less by the rectus femoris.

Biomechanically, you would think that the strength of the shortened rectus in knee extension would be weaker for everyone. Not true.

There are the aforementioned exceptions, thus the relationship between muscular strength and the tension a muscle can produce is very complex, especially across groups of individuals.

Comparing cyclists with runners, you find the cyclist tend to be strong at a short compared to long rectus femoris length.

It has been argued that since cyclists have a shorter range of hip motion when cycling, compared to the range of motion of runners, that producing more tension at a shorter length is due to training. Other scientist argue that a strong rectus femoris in a shortened position is the result of genetics or of both genetics and training.

Whether the answer is training, inheritance or a combination of both, for the coach and athlete it raises an interesting conundrum about playing sports that require you to keep your knees bent.

When playing offensive line in football the position of choice is bending at the hip and knee. The lineman are also taught to slide their feet to keep an effective posture. They must be strong with their rectus femoris in a shortened position.

Knowing this, a leg press should be the tool of choice to agument strength.  Something for coaches and athletes to think about as they design their workout to Get Strong.