One Legged glute bridges
When you perform glute bridges with one leg, you increase the intensity without using extra weight. For this variation, simply stretch one leg straight in the air and do the exercise as usual. Do the same number of repetitions on each leg.
Glute bridges with elevated legs
To make the glute bridges more difficult, you can put your legs on an elevation (e.g. a bench or chair), so that you have to cover a greater distance before you are fully stretched.