Rectus Femoris of the Quadriceps

The rectus femoris is located at the anterior central region of the upper leg, and is a muscle that is part of the collective group of muscles commonly known as the quadriceps (which are located at the front of the upper leg).

The rectus femoris is recruited during a knee extension action, along with the other quadriceps muscles. Exercises that involve knee extension will stimulate the rectus femoris effectively.

The squat is seen by many as the best overall exercise for lower body development. The exercise requires many muscles as stabilising and synergists to aid the execution of the lift. Because of this some people choose only to use the squat for quadriceps stimuli. The squat can be viewed in the exercise section to the right.

An alternative or addition to this is to incorporate an isolation exercise such as the leg extension that just requires the knee extension. The upside of this is that it is favoured by some as more stress is placed directly on the quadriceps, and not secondary muscle groups. This is beneficial to those who may have injuries in other areas, such as the lower back, or other areas that would feel discomfort during the execution of the Squat. The leg extension also allows for isolateral training.

6-12 reps will likely provide optimal time under tension for most the quadriceps muscles, providing adequate stimulation for sarcoplasmic hypertrophy, and acute response to anabolic hormone concentrations, compared to that of lower rep ranges.
If however strength is your primary goal then 1-5 reps with an exercise such as squats will likely lead to the best recruitment of the large motor units and type iiB fibres, and neural adaptations of the nervous system. One can also master the technique of the squat, which should in time lead to better execution of the lift, and therefore better poundages being shifted.