Cassie "Badass Cass" Mason treats her legs the way other lifters treat their upper bodies.

"Your arms are usually getting three days a week, so why wouldn't you put as much time into your legs?" she asks.

To kick her butt (and quads and hams) into shape, and to keep her 1.4 million Instagram followers happy, Mason often performs a weekly full quad-focused day and a full hamstring-focused day—both of them heavy—followed by a full glute-focused finishing day of lighter, accessory work.

Not quite ready for three hard-and-heavy lower-body blasts? Start by at least having a couple of high-quality all-around leg workouts each week. This routine workout from Mason hits every lower-body muscle group—hard. It can be performed as one component of your two or three-pronged leg attack, or you could do it twice a week and call it good.

For this workout, Mason does 5 sets of six exercises for 8-12 reps per set, going near failure on the last set of every exercise. Within those 5 sets, she increases the weight 2-3 times—though it's fine for you to keep the weight consistent the first time you perform it. Her rest periods are always kept to a minimum (30 seconds to a minute) to keep her heart rate up. When she goes heavier, she rests longer, but not by much. Push yourself!

Technique Keys

Pulsing Smith Machine Squat

For this exercise, Mason does a slightly wider than shoulder-width squat, going all the way down, then coming only halfway up again—or "pulsing"—before returning down. Then, she rises to full extension. She repeats the pulse with each rep, generating a serious burn in the quads and glutes.

Leg Press

Perform the leg press with feet shoulder-width apart and a knees-to-chest lowering. This stance is ideal for activating the greatest amount of total leg musculature possible, and the full lowering makes sure the posterior muscles get hit just as hard as the quads. Just don't lower so far that your lower back comes off the pad.

Side Lunge

Mason does her side lunges with light weight on her shoulders, getting low but keeping good posture, with an upward head and chest. These are great using just your body weight, too.

Double Walking Lunge

The double walking lunge is another pulsing exercise. Stick with light weights and keep your form strict. These are burners with no weight at all! After you step forward with each rep, rise about halfway before pressing through your front heel up to full extension. Then, repeat with the opposite leg.  Warning: These will make you seriously sore!

Smith Machine Step-Up

Place a stable step at a height where your front leg is bent to around 90 degrees while stepping on it. Then, step up firmly through your front heel. Even with light weight, this is an awesome exercise that demands lots of booty work without putting stress on the back.

Pulsing Leg Extension

Get ready for yet another pulsing exercise to burn out your quads. A full repetition includes one extension plus one half extension. When that last rep is done, you will be, too.

I know, I know. It's not the most popular topic, but we need to talk about leg day—and what you can do to get your lagging legs back on track.

True, you wince at the thought of the muscle soreness you'll feel after working these four moves into your routine, but if you want serious results, you need to do serious work.

Think big, stay strong, and pump up those wheels!

Kettlebell Pistol Squat

Squatting with each leg separately means the muscles in each leg will have to work harder, but at the end of the day, both legs will be stronger.

Doing pistol squats with a kettlebell makes this move easier because you can hold the weight by the horns (sides of the handle) and keep it in the middle of your chest. This keeps the center of gravity where you want it.

Pro Tip: If you're not up to weighted pistol squats yet, use a body suspension strap to help you. Alternatively, practice with your own body weight to make sure your form is on point before adding extra weight. If you think you've got it down, do 3 sets of 10-12 reps per leg.

Good Morning

Most people think of good mornings as a lower-back strengthening exercise or an assistant for the deadlift, but it's a great stand-alone exercise to light up your hamstrings and glutes.

The key with the good mornings is to focus on sticking your butt out and keeping your chest high as you bend over. Simply bending over without maintaining a straight back could lead to a lower-back injury.

Once you've hinged over as far as you can with a straight back, concentrate on pulling in your hips and driving the bar straight up. Feel your hamstrings engage and squeeze your glutes when you stand.

Pro Tip: Warm up with a power band by placing one end of it around your shoulders behind your neck—exactly where you'll put the barbell—and standing on the other end. Or use a PVC pipe to practice the hip-hinging motion before you add weight. After 2-3 warm-up sets, do 3-4 working sets of 15 reps.

Donkey Calf Raise

Calves are a tricky muscle group to build, which is probably why they are all but forgotten on leg day. Everyone seems to have their own secret tricks for building calf muscles, but skipping calf exercises is a surefire way to sabotage your gains.

With donkey calf raises, your calves are isolated and work hard. Performing donkey calf raises on a machine saves time and keeps it simple. If you don't have access to a machine, use a weight belt, plate, or even a workout partner to help add weight.

Pro Tip: Your calves naturally do a lot of work every day, so if you want to see growth, slam them with volume and pump as much blood into the muscles as possible. Use 1-1/2 reps, where you perform a full rep, go halfway down, then lift again. Do 3 sets of 15 reps like this and the results will speak for themselves.

Side-To-Side Box Shuffle

Doing box shuffles at the end of your workout targets all the muscles when they are warmed up and full of blood. Since you'll be tired, stay focused for this exercise so you don't kick the box. You're not trying to set a speed record. Just take your time with each step.

The side-to-side box shuffle is both a great plyometric leg finisher and good extra cardio. Start with a low box or step and go higher as you improve.

Pro Tip: You can use this as a warm-up before you start training if you're too concerned about doing it after your training. Either way, go back and forth for 10 reps. Rest for a minute and repeat for 3-5 sets, depending on your fitness level.