The lying straight leg raise is an exercise that primarily works your abdomen and hips. It’s very simple to do and doesn’t require any equipment, but you can utilize an exercise mat too for comfort. Weights can also be attached to the ankles for added resistance, but if you perform the exercise carefully and concentrate on your form, your natural body weight should be enough for you to feel the burn.
Laying it Down
To perform a lying straight leg raise, lay flat on the floor or other stable surface such as a workout bench. Hold your stomach muscles in and place your arms out to your sides on the floor, palms down. If you're using a bench, grasp the sides. Make sure that your head, back, legs and butt are all in contact with the floor or bench. Lift your legs slowly to a 90-degree angle for one second. Keep your legs straight, taking care not to bend at the knees. Hold the position for one second, then lower your legs slowly back down for a further count of one second.
It's All in the Hips
The main muscles used in the lying leg raise are your hip flexors, specifically the iliacus, the pectineus in the front of your upper thighs and the adductor longus which runs from your pubic bone to your femur. The pectineus allows you to bring your thigh toward your body while your adductor longus allows you to flex and rotate your thigh to the side.
Defining the Thighs
Your thigh muscles work with your hip flexors to bring your legs up and down. The main muscle here is the sartorius, which extends down and across the top of your thigh in toward your knee. This muscle moves, flexes and rotates your thighs at the hip and allows you to bend at the knees. Other muscles included are the quadriceps femoris which are located in the fronts and sides of your thighs. These muscles are linked down to your knees, allowing them to bend.
Impressive Washboard Abs
The abdominal muscles help you to hold the weight of your legs as you lift them during the exercise. The rectus abdominis muscle covers your abdomen and is responsible for drawing your body toward your hips. The final muscles engaged are your obliques, which curve around your sides towards the front of your abdomen. These muscles work with your rectus abdominis to allow your body to bend, bringing your chest towards your hips and thighs.