The quadriceps (quads) are a group of four muscles positioned on the anterior side of the legs. They function mainly to extend the knee. Aesthetically, well developed quads give a thicker, more three dimensional look to the legs, especially in a front pose. The 'outer sweep' and 'teardrop' are two areas in particular that give the lower body a more impressive appearance.
The obvious quad isolation exercise is, of course, the leg extension. The quads come into play in most lower body exercises however, from squats to lunges to the leg press. Look at splitting your leg training across two lower body days, one with a quad emphasis and one with a hamstring and glute emphasis (compounds for the second session might include RDLs or hip thrusts).
Before getting into any heavy quad work, you want to ensure that the knees and hips are warm. You might want to spend 5 minutes or so doing some steady movement on the spin bike or treadmill before getting start ned, followed by some warm up drills. Save any static stretching or foam rolling for after your session!
A great machine to warm and open the hips. Use a mid to high rep range and control the weight through the entire range of motion.
Single leg seated hamstring curl
Even though this is a quad focused session, starting with a small amount of hamstring work will not only allow you to get more hamstring volume in across the week, but can help prevent injury. Single leg variations can help establish a stronger mind to muscle connection and force us to use less ego.
The first 'big' movement of this session. Hack squats, when done correctly, are an incredible leg builder. Make sure to lock your back against the pad and find a foot positioning that is comfortable for you. Unlike a conventional barbell squat where the core and back take on a lot of work, this should be all lower body. Really focus on progressing weight over time on these while keeping form immaculate.
Leg press (feet low and narrow)
Everyone's favorite! For most,positioning the feet lower on the pad and at around shoulder width will result in the most quad recruitment. For a more glute focused press, widen the feet with toes pointing out.
DB split squat
Elevate the back foot on a bench or box and lower the back knee as far as comfortably possible. Experiment with leaning forwards or staying more upright to determine what helps you connect with your quads most. These should be difficult!
And finally, the leg extension. There should be plenty of blood in the quads by now already. Sets of 12-15 concentrating on fully locking the knees out at the top and keeping control of the weight as it is lowered to start position.
We're afraid you're not getting to skip out on this one! Calves are a relatively small muscle and tend to recover well. If you're struggling to grow them, up the frequency! Throw one calve exercise with 2-3 working sets at the end of every other session.