Any floor exercise in which the back leans backwards requires you to pay the maximum attention to avoiding excessive solicitations of your spinal column. To make sure you are really stressing only muscles, I’m proposing you exercises that will let you tone up your back while extending it and keeping abdominals always active.
How? Lie in the floor in prone position, keeping your legs straight and your feet about shoulder-width apart. It is advisable that something or someone holds our feet on the ground to ensure a correct execution. Keeping your hands below your chin or behind your head, slowly lift your chest without stressing the spines, but only thanks to your back’s strength.
Do at least 3 series of 15 repetitions, with 30 seconds pauses. At the end, keep the peak position for up to one minute.
Attention: make slow and controlled movements, avoiding sudden or abrupt ones. At the end, it is advisable to compensate you back’s effort: you can sit on your heels and lean forward to stretch your back’s muscles or do some abs.
Tip: you can slightly diminish the intensity of the exercise by keeping your feet further apart.
Variation: if already well trained, you can do the whole exercises without weights on your feet, only by using your strength.