Here’s a simple, yet sweaty, circuit for your legs utilizing the Smith Machine, Stability Ball And Bosu Ball. The workout balls really demand more stabilization from your body, so you will feel this in your core too.
Perform three rounds of each circuit.
Exercises:
Smith Machine Narrow Squat: Set the bar up on the smith machine so it’s at shoulder height. Load up your weights balanced on either side. With bar across back, like up and turn bar slightly to unhinge. Legs and feet should be near each other, if not touching. Squat your butt backwards, with torso upright and knees directly over ankles. This really works your booty and quads. The smith machine takes the balance almost out of the equation, so you should be able to focus on going lower in your squat and really hitting those leg muscles.
Bosu Ball Lunge to Knee Drive: start standing with one leg on the Bosu and another behind, in a normal Lunge position. Lower yourself into a Lunge with knees over ankles in front, torso upright, and back knee under butt. As you come up from the Lunge, put your weight into the front leg and balance while lifting your back leg bent up towards your chest. Slowly lower back down. This really tests your balance, not just in your abs, but the stability of your leg muscles too. It also works butt and quads.
Stability Ball Skier: start standing behind stability ball, lean your knees into it, set arms on the ground and walk out into a plank position with shins resting on ball. From plank (don’t let your butt sag), pull with lower abs and hip flexors as you turn hips sideways, Bending your legs, and Crunching with your abs to bring your knees towards stomach. Release back into a flat plank before crunching to the other side.
Smith Machine Straight Leg Deadlift: In this particular Smith Machine, I turned around so the angle of the machine worked with me as I pulled up. Set the bar low and load up weights. Grip bar, turning to unhinge. Feet should be hip width apart, with legs straight and back flat. Squeeze your hamstrings and butt as you lift the weight up, standing tall before resting back down. You will really feel this in butt and hamstrings, and since balance is taken out of the equation (thank you smith Machine) you might be able to lift a slightly heavier weight than normal.
Bosu Curtsy Lunge (Ball Up): start standing tall on the Bosu Ball. Reach one leg back and diagonal, bringing knee to ground. With all your weight in the front leg and working on balance, bring the back leg up to ball to rest. Repeat all reps on this side before switching to the next. This really tests core and ankle stability, all while working quads and booty.
Stability Ball Walkouts: Start behind the ball, lean knees into it and with arms on floor walk out into a plank position. This is really designed to work stability in your abdominal muscles, so make sure you keep them engaged. You don’t want your butt in the air or sagging down. Walk out so the ball is near your toes and hands are under shoulders. Then walk it back, keeping feet in air. That’s one rep. Continue to finish all.
Smith Machine Lunge: Set the bar up at shoulder height and load up weights. Stand with legs spread in a Lunge position. Lift bar up and twist to unhinge. Bend back leg first, then front leg as you lower body. Squeeze quads and butt as you come back up. Repeat all reps on one leg before re-racking and switching to the other side.
Bosu Ball One Leg Glute Bridge: lay down with butt close to ball, ball side up. Place one leg on ball and one leg straight up in the air. Squeeze butt and abs as you lift your torso so your body becomes a straight line from the bent knee to your shoulder on the ground. I dig my elbows into the ground to help steady the movement. Repeat all reps on one side before switching to the next.
Stability Ball Ab Pass: lay on back with ball between legs. Lift legs and arms simultaneously so they meet above abs. Pass ball to arms, lowering arms and legs to ground again. Lift all back up to meet in the middle to complete first rep. Keep switching until all reps are complete. This works lower abs and hip flexors. 
Amber Launstein 