The split squat is among the easiest lower body exercises to perform. This gives you a good lower body option if you have access to little equipment. As a one-legged exercise, it allows the trainee to get more resistance from their bodyweight. This limits the additional resistance needed. This may reduce stress on the back due to the lower absolute load.
The split squat requires more balance and therefore works the stabilizers. Keep in mind this does not mean the split squat has an advantage over the two-limbed lower body exercises. Too much stabilization can reduce the strength stimulus.
Balance and coordination can surpass creating tension as the limiting factors of the exercise. Other athletic activities, such as sprinting, adequately work the stabilizers too. You also work the stabilizers to brace during movements that use both legs as well. This means that even if unilateral work seems more specific to athletics, you get the benefits by including athletic motions. You then perform a regular bilateral squat to best develop lower body strength.
The split squat works the hip, thigh, and leg regions. Joint motions include hip extension, knee extension, and plantarflexion. The core, upper back, and gripping muscles contract without movement along with many other muscles. The stabilizer muscles of the inner thighs and outer hips work harder to maintain balance as a unilateral movement. The lower back receives less work due to the position and less weight used.
This guide focuses on a variation of the split squat sometimes known as the Bulgarian split squat. I teach how to do it with dumbbells here. Although you can split squat with a barbell, I feel the dumbbell version works more safely. In the case that you do have access to a barbell, you should use the barbell squat instead.
Equipment
You will need a bench or something else to elevate the rear foot. You also need dumbbells and weight plates. The dumbbells lie beneath the body rather than on the upper back. The floor provides the safety mechanism, requiring no extra equipment. This improves the convenience and safety. The grip strength can limit the weight used, although you can use chalk if needed. This usually helps enough.
Safety
Split squats rank ahead of any lunge. The awkward position of the rear leg in both split squats and lunges pose a problem. This places awkward forces on the rear knee. Doing the split squat minimizes this effect. The split squat controls this by keeping the rear leg elevated. No forward movement occurs.
Starting Position
Stand facing away from the bench. Position your rear foot on the bench. Try to keep the front of your foot in contact with the bench. Using the tip of the toe instead of the front part of your foot can lead to ankle and knee stress for the rear leg.
Use a high enough elevation for the bench that the hip can line up or go slightly below the top of the knee when you perform the movement. Too low of a bench will prevent this, as your knee will hit the floor before achieving enough range of motion. Too high may bother the rear leg.
Make sure you have some distance between your feet from left to right. Some trainees make the mistake of lining up their rear foot with their lead leg. This makes it impossible to stay balanced. Keep some lateral distance between each limb.
Hold the dumbbells at your sides. You will have a more upright position compared with other squat variations. Stick out the chest and pull back the shoulder blades. Keep this position for the entire movement. This represents, by far, the most important tip to keep good form. Do not allow the chest to collapse during the movement. When the reps feel difficult, allowing this to happen will encourage bad form and may end the exercise prematurely.
The eyes should focus straight ahead or slightly toward the ground. Never look toward the ceiling. The neck should feel in a comfortable position. Do not tuck the chin or rotate the head. Pick a point to keep your eyes focused on during the movement.
Using a mirror can harm coordination and lead to an unbalanced stress. Rely instead on feel when learning the squat. Do not squat with your face too close to a wall or other object. This assists coordination.
The active front leg should extend far out enough in front of you. This serves two purposes. First, you must prevent the knee from extending too far out in front of the toes of the lead leg. Failing to do this overemphasizes the quadriceps, leading to knee stress. Secondly, you want to distribute the load across all the active muscles. You should strike a balance. Have the knee closely line up with the tip of the foot as you bend the knee when viewed from the side. This will distribute the load over the hip and knee muscles.
The toes should point outward between 10-30°. This angle increases with a wider lateral distance between the feet. Toes pointed straight can harm hip extension and irritate the knees.
Abdominal bracing, which involves an isometric co-contraction between the muscles on each side of the trunk with a neutral spine, occurs naturally during a squat. Abdominal hollowing is an unnatural activity. This increases the risk of injury. Do not suck in the stomach.
Action
Lowering (Negative) Phase:
Keep the dumbbells at your sides. Prevent them from drifting forward. Descend until achieving the range of motion. This means at least the hip in line or slightly below the top of the knee for most trainees. This works best if the endpoint comes with the knee touching the ground. A soft pad can blunt the effect of your knee striking the ground, especially as the exercise grows harder.
Any inflexibility of the hamstrings and other hip muscles can lead to rounding of the lower back. Tight calves can make it impossible to keep your heel on the floor. Make sure these muscles feel loose enough through a proper warm-up and stretching routine. Do not allow the heels to leave the floor.
Take in a deep breath before descending. Hold it until you begin the lifting phase. This protects the spine by providing support created by the column of air. This benefit makes up for any blood pressure risks for nearly all trainees. Relax the foot of the rear leg as you lower yourself.
Focus on directing the lead hip foremost. Push the hip of the lead leg back as you descend. Driving the hips too far back will cause a pelvic tilt that will prevent the hip muscles from activating properly. This prevents your hip from staying underneath your body, throwing off your mechanics. This also makes the range of motion hard to achieve. Prevent this by remembering to keep the chest up.
The knee will bend naturally and requires no focus. Do not confuse hip extension with spinal flexion. Pushing your hips back does not mean the back has rounded. A vertical torso does not represent the correct way to squat. A forward lean comes with a correct squat.
The knees should not travel much beyond the toes. Failure to properly use the hips and maintain tightness in the bottom position may allow this to happen. You may also have positioned your front leg too closely to the bench. Make sure the front foot plants far enough away from the bench.
The knees should never twist inward. Prevent this by shoving the knee outward by using a technique called spreading the floor. Spreading the floor also encourages rear and inner hip activation. It keeps you safe and tight.
Minimize time spent in the bottom position. Use the tightness at the bottom to quickly rebound. Avoid excessive bouncing or jerking out of the bottom position. Make a fast but smooth transition into the lifting phase.
Strive for the crease of the hip just below the top of the knee. Achieve at least a 90° bend at the knee. You should surpass this point when your knee touches the ground.
Lifting (Positive) Phase:
The same mechanics apply as the lowering phase. The hips and shoulders should rise from the bottom position at the same pace. Keep the arms and dumbbells stable. Prevent your body from drawing forward.
The load should feel distributed across the foot. The heel drive is simply a teaching method. You should distribute your weight across the whole foot and not just your heel.
Finish
You will likely fail when you can no longer rise. Allow the rear knee to touch the ground. Set the dumbbells on the floor. Remove the rear foot from the bench.
The Split Squat
I am reluctant to recommend any single limb exercise as the mainstay for developing strength. Stability afforded by two limbs makes strength training much more effective. Any benefits of single-limb exercise could come from adding some athletic motions into your program during interval training. Nonetheless, the split squat remains a good option for those lacking equipment. It represents the best option if otherwise not able to perform a barbell squat or a trap bar dead-lift safely.