Lie on a mat, bend your knees and press your feet against the mat (at shoulder width). Bend your knee joints at an angle of about 90˚ and keep your knees and feet apart at shoulder width. Place your palms on your thighs.
From the starting position lift one leg up from the mat, not changing the knee angle, and as you are lifting the leg exert pressure with your hand against the working leg. Lift your leg up to a position where your thigh and trunk are at about a 90˚ angle. Go slowly back down the same way while keeping the pressure between the hand and the thigh. Alternate your legs. Inhale in the starting position, hold your breath briefly to fix your trunk, and exhale while returning to the starting position. Breathing in, make another repetition of the exercise.
Make sure you have the right body posture with a fixed trunk and your pelvis in a neutral position to avoid excessive lordosis at your waist.
Keep your legs in an equal position and keep the angle at your knees unchanged throughout the entire movement.
When overcoming the resistance, eliminate engaging of the chest and shoulder muscles. Try to keep your shoulders lying against the mat all the time.
Keep your head in a neutral position against the mat.
Take account of your breathing while doing the exercise and do not move dynamically.
To restrict over-bending at the lower back, bring your pelvis into a neutral position and try to press your lower back against the mat.