The quadriceps consist of four heads (hence the name quadriceps). The heads are: the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius.
With the exception of the rectus femoris, all of the heads of the quadriceps have one function, which is extending the knee.
That means that the quadriceps are active every time you walk or stand up. Additionally, and in conjunction with the hamstrings, the quadriceps stabilizes the knee.
- Stand with your feet shoulder-width apart. Maintain the natural arch in your back, squeezing your shoulder blades and raising your chest.
- Grip the bar across your shoulders and support it on your upper back. Unwrack the bar by straightening your legs, and take a step back.
- Bend your knees as you lower the weight without altering the form of your back until your hips are below your knees.
- Raise the bar back to starting position, lift with your legs and exhale at the top.
- Place your legs on the platform with your feet at shoulder width.
- Release the weight and extend your legs fully, without locking your knees.
- Lower the weight until your legs are at a 90° angle (but DO NOT allow your butt and lower back to rise off of the pad. This will put your lower back in a rounded position, which is very dangerous.)
- Raise the weight back to starting position.
- Stand straight with your feet slightly apart and hold a kettlebell in one hand.
- Bring the same leg as the arm holding the kettlebell in front of you, squat down until your thigh is parallel to the ground, keeping your back straight.
- Return to the starting position and repeat.
- Hold the weight tucked into your upper chest area, keeping your elbows in. Your feet should be slightly wider than shoulder width.
- Sink down into the squat, keeping your elbows inside the track of your knees.
- Push through your heels while keeping your chest up and return to starting position.